UNIT 1

AIR CONDITIONING – PRINCIPLES AND SYSTEMS

SYLLABUS

 THERMODYNAMICS
 TRANSFER OF HEAT
 REFRIGERATION CYCLE COMPONENTS
 VAPOR COMPRESSION CYCLE
 REFRIGERANT
 COMPRESSOR
 CONDENSER
 EVAPORATOR
 REFRIGERANT CONTROL DEVICES
 ELECTRIC MOTORS
 AIR HANDLING UNITS
 COOLING TOWERS
 AIR CONDITIONING SYSTEMS FOR BUILDINGS OF DIFFERENT SCALES AND THEIR
REQUIREMENTS
 WINDOW TYPE
 SPLIT SYSTEM
 PACKAGE UNIT
 DIRECT EXPANSION SYSTEM
 CHILLED WATER SYSTEM
 FAN COIL UNIT
 DISTRICT COOLING SYSTEMS
 ENERGY EFFICIENT SYSTEM
 ENVIRONMENTAL ASPECTS AND LATEST INNOVATIONS

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 PREREQUISITE
2nd Law of Thermodynamics
The second law of physics you need to know is the 2nd Law of Thermodynamics:
If you paid attention in school, you might remember that the second law of
thermodynamics states that heat flows from hotter to colder bodies naturally. You can only
transfer heat from a colder body to a warmer body through some kind of external work.

Air Conditioning : The Fundamentals

Air conditioners transfer heat from the indoors to the outdoors.

Although you may think that air conditioners create cold air, they actually extract heat from
the indoor air and send it outside.

When heat is removed from the indoor air, the air is cooled down. It’s best to think of the
air conditioning process as heat flowing from the indoors to the outdoors.

The Refrigeration Cycle

An air conditioner works using a thermodynamic cycle called the refrigeration cycle. It
does this by changing the pressure and state of the refrigerant to absorb or release heat.

The refrigerant absorbs heat from inside of your home and then pumps it outside.

Most air conditioners are air-source, split systems. What this means is that there is one unit
inside and one unit outside, which is why it is called a split system.

Here are the basic parts of the refrigeration cycle (the same process that your refrigerator
used to keep food cold):
1. Air flows over the indoor coils, which contain extremely cold refrigerant

When air flows over the cold coils, heat from the air gets transferred to the refrigerant
inside the coils. After the air flows over the coils, it gets cold, normally dropping around 20
degrees.

This process follows the 2nd law of thermodynamics, which says that heat naturally
(spontaneously) flows from a warmer body to a cooler body.
After the refrigerant absorbs the heat, its state changes from a liquid to a vapor. This
warmer refrigerant gas then gets transferred to the compressor (step 2 in the refrigeration
cycle).

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2. Warmer, vaporized refrigerant gets compressed (pressurized) to a hot temperature

Even though the refrigerant has absorbed heat from the indoor air, it is still fairly cool. The
still cool, but warmer vaporized gas enters the compressor (located in the outside unit) to
increase its pressure and temperature.
We increase the temperature of the refrigerant because it needs to be warmer than the
outdoor air. Remember the 2nd law of thermodynamics again—heat flows from warmer to
cooler bodies.
If the refrigerant is 120 degrees and the outdoor air is 90 degrees, the outdoor air is cooler,
which means the heat from the refrigerant will flow in the direction we want—outside. If
the temperature outside is 120 degrees, the compressor will have to work extra hard to
increase the temperature of the refrigerant to a higher temperature.

After the refrigerant’s temperature is increased above that of the outdoor air’s
temperature, it then flows into another set of coils, known as the condenser coils (also
located outside).

3. Very hot refrigerant flows into condenser coils where it loses heat to the outdoor air

Since the refrigerant has been compressed (pressurized), it is now hotter than the outdoor
air. A condenser fan blows hot outdoor air over the even hotter outdoor condenser coils.

As outdoor air flows over the outdoor coils, heat is removed from the refrigerant and
released into the outdoor air. Again, this is due to the 2nd law of thermodynamics.
After the refrigerant loses thermal energy to the outdoor air, it condenses back into a liquid
and gets pumped back inside.

4. The still warm refrigerant from the outdoor unit needs to get cold

When the refrigerant leaves your outdoor condenser unit, its temperature is still pretty
high. The refrigerant’s temperature will need to drop significantly before it can absorb
more heat from the indoor air.

The metering device, usually a thermostatic expansion valve, is a special device that
depressurizes the refrigerant, causing a drop in temperature. It does this by expanding the
refrigerant into a larger volume.

The refrigerant needs to be colder than the indoor air in order to absorb heat. Once the
refrigerant gets cooled down, it flows back into the evaporator coils where it begins the
refrigeration cycle again.

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Hopefully, this helps you understand the basic workings of an air conditioner. The
refrigeration cycle is basically the same for your freezer and refrigerator.

1.1 THERMODYNAMICS
Thermodynamics simply describes the movement of heat. Thermodynamics is derived
from thermo, meaning heat, and dynamics, (literally “power”), and is used to describe the
movement or change of a process due to heat flow.

Heat and temperature are often confused or used interchangeably. Heat is the flow of
energy from one object or system, to another object or system. Temperature is a measure
of the internal kinetic energy of an object. As an example, a frying pan has a high
temperature because the molecules of the metal are moving quickly. When an egg is
cracked into the pan, heat flows from the pan to the egg. Although not obvious, the
temperature of the pan will drop slightly as it transfers heat to the egg.

THERMODYNAMIC LAWS

First Law - Energy cannot be created or destroyed, but can change form, and location. For
instance, burning wood changes the internal energy in the wood into heat and light energy.

Second Law - The Second Law is the most understandable and useful in real world
applications, and makes heating, air conditioning, and refrigeration possible. Energy must
flow from a higher state to a lower state. That is, heat must always flow from the warmer
object to a cooler object and not from the cooler object to the warmer object.

The Second Law holds in our everyday visible world, but on the subatomic level the law is
constantly violated, but statistically the law holds true. Although beyond the scope of this
article, an interested reader will find fascinating theories in quantum mechanics. A search
of the “arrow of time” will yield interesting variations of the Second Law.

1.2 TRANSFER OF HEAT

Heat can move in three ways: conduction, convection, and radiation.

Conduction is the easiest and most familiar to anyone who has burned themselves on a
stove or a hot pot. It is the direct transfer of heat from one object to another, when they are
in contact. Since heat is the flow of energy, and it is driven by the temperature difference
between two objects, an iron at 300° and a piece of dry ice at -110° will both burn a finger
because the temperature difference between the finger and the iron or dry ice is about the
same. In one case the flow of heat is into the finger, in the other the flow of heat is out of the
finger, but in both the heat flow is high.
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Convection is based on the movement of a fluid to transfer heat from one object or area to
another. Weather is a convective process; hot air and warm water move from the tropics
toward the poles.

Radiation is heat transferred directly from a source to an object without using a medium
like air or water. Heat radiated from the sun will melt snow on the road, even on a cold day.
The radiant energy warms the road surface without directly warming the air.

Moving heat from one object or area to another allows comfort heating and air
conditioning, as well as refrigeration for food preservation and processes.

Change of State

 Most of the common substances can exist in three different forms, called states:
solid, liquid and gas.
 The state will change when the substance is heated.
 As a solid, a substance has a fixed volume and shape and is usually unable to flow,
except in the case of glaciers. For instance, an ice cube or snowflake is the solid state
of water.
 When a solid is heated, it turns into a liquid. As a liquid, a substance has a fixed
volume, but its shape changes to fill the shape of its container. For instance, a glass
of water is the liquid state of water.
 When a liquid is heated, it turns into a gas. As a gas, a substance does not have a
fixed volume or shape. Gas expands to fill the shape and volume of its container.
Sensible Heat

 Sensible heat is potential energy in the form of thermal energy or heat.

 The thermal body must have a temperature higher than its surroundings.
 The thermal energy can be transported via conduction, convection, radiation or by a
combination thereof. In many cases the reference temperature is inferred from
common knowledge, i.e. "room temperature“.

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Latent Heat

 latent heat is the amount of energy in the form of heat released or absorbed by a
substance during a change of phase (i.e. solid, liquid, or gas) Two latent heats are
typically described:
Latent heat of fusion (melting or freezing)

Latent heat of fusion is defined as the amount of heat required to convert a unit mass of the
substance from solid to liquid form at its melting point without any rise temperature.

Latent heat of evaporation (boiling or condensation)

Latent heat of vapourization is defined as the amount of heat required to convert a unit
mass of the substance from liquid into its vapor state at the same temperature.

Saturation temperature

 The condition of temperature and pressure at which both liquid and vapor can exist
simultaneously is termed saturation.
 Saturation temperature is nothing but the temp at which addition of heat result in
change of phase, for water the change of phase will result in vapor at saturation
temperature and for steam the addition of heat result in superheated steam.

1.3 REFRIGERATION CYCLE COMPONENTS

•The refrigerant comes into the COMPRESSOR as a low-pressure gas, it is compressed and
then moves out of the compressor as a high-pressure gas.

•The gas then flows to the CONDENSER. Here the gas condenses to a liquid, and gives off its
heat to the outside air.

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•The liquid then moves to the EXPANSION VALVE under high pressure. This valve restricts
the flow of the fluid, and lowers its pressure as it leaves the expansion valve.

•The low-pressure liquid then moves to the EVAPORATOR, where heat from the inside air
is absorbed and changes it from a liquid to a gas.

•As a hot low-pressure gas, the refrigerant moves to the compressor where the entire cycle
is repeated.

•The four-part cycle is divided at the centre into a high side and a low side. This refers to
the pressures of the refrigerant in each side of the system.

1.4 VAPOR-COMPRESSION CYCLE

 The Vapor Compression Cycle uses energy input to drive a compressor that
increases the pressure and pressure of the refrigerant which is in the vapor state.
 The refrigerant is then exposed to the hot section (termed the condenser) of the
system, its temperature being higher than the temperature of this section.
 As a result, heat is transferred from the refrigerant to the hot section (i.e. heat is
removed from the refrigerant) causing it to condense i.e. for its state to change from
the vapor phase to the liquid phase (hence the term condenser).
 The refrigerant then passes through the expansion valve across which its pressure
and temperature drop considerably.
 The refrigerant temperature is now below that existing in the cold or refrigerated
section (termed the evaporator) of the system, its temperature being lower than the
temperature in this section. As a result, heat is transferred from the refrigerated
section to the refrigerant (i.e. heat is absorbed by the refrigerant) causing it to pass
from the liquid or near-liquid state to the vapor state again (hence the term
evaporator).
 The refrigerant then again passes to the compressor in which its pressure is again
increased and the whole cycle is repeated.
The four basic components of the vapour compression refrigeration system are
thus:

1. Compressor: The function of the compressor is to compress the input refrigerant

of low pressure and low temperature. As a result the pressure and the temperature of the
refrigerant increases. Generally reciprocating compressors are used in refrigeration
system. An external motor is used to drive the compressor.

2. Condenser: The condenser is a coil of tubes, which are made of copper. This
issued to condense the refrigerant which is in the form of vapor. And convert into liquid.

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 3. Expansion Valve: This is otherwise called throttle valve. This valve is used to
control the flow rate of refrigerant and also to reduce the pressure of the refrigerant.

4. Evaporator: This is the part in which the cooling takes place. This is kept in the
space where cooling is required. It is a coil of tubes made up of copper.

1.5 REFRIGERANT
Pressure temperature relationships for Liquid Refrigerants

Choosing a Refrigerant
Each fluid has its own distinct boiling temperature - pressure characteristic. This is
called the Saturation Pressure Temperature relationship, or P-T data for short. The normal
boiling point is atmospheric pressure, which is approximately 1 bar(a).
R134a boils at -26°C
R22 boils at -40.8°C
R404A boils at -46°C
The curves show the evaporating or condensing temperature of each of these fluids
together with carbon dioxide, over the range of temperatures of interest to refrigeration
engineers. Normally it is necessary to choose a fluid which evaporates between, say, -50
and +10 °C and which condenses at 40 to 70 °C. The pressure for both processes should be
greater than atmospheric - but not too high. Generally the higher the saturation pressure
for a given temperature, the better the thermal capacity of the fluid. So less fluid is required
to do the job. Unfortunately carbon dioxide will not condense at pressures above 70bar
because this is the critical pressure.
 Temperature and pressure are directly proportional to each other.

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  This means that as the temperature decreases, the pressure also decreases, and as
the temperature increases, the pressure increases.
 One way to think of this is if you increase the speed of the molecules –by increasing
their temperature- the force of the molecules hitting their container increases and
this increases the pressure.
 The temperature at which a liquid boils is dependent on the pressure exerted on it.

1.6 COMPRESSOR
The purpose of the compressor is to circulate the refrigerant in the system under
pressure; this concentrates the heat it contains.

At the compressor, the low pressure gas is changed to high pressure gas.

 The compressor has reed valves to control the entrance and exit of refrigerant gas
during the pumping operation. These must be firmly seated.
 An improperly seated intake reed valve can result in gas leaking back into the low
side during the compression stroke, raising the low side pressure and impairing the
cooling effect.
 A badly seated discharge reed valve can allow condensing or head pressure to drop
as it leaks past the valve, lowering the efficiency of the compressor.
Two service valves are located near the compressor as an aid in servicing the
system. One services the high side, it is quickly identified by the smaller discharge hose
routed to the condenser. One is used for the low side, the low side comes from the
evaporator, and is larger than the discharge hose

The compressor is normally belt-driven from the engine crankshaft. Most

manufacturers use a magnetic-type clutch which provides a means of stopping the
pumping of the compressor when refrigeration is not desired.

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1.7 CONDENSER
 The purpose of the condenser is to receive the high-pressure gas from the
compressor and convert this gas to a liquid.
 It does it by heat transfer, or the principle that heat will always move from a
warmer to a cooler substance.
 Air passing over the condenser coils carries off the heat and the gas condenses.
The condenser often looks like an engine radiator.

 Condensers used on R-12 and R-134a systems are not interchangeable. Refrigerant-
134a has a different molecular structure and requires a large capacity condenser.
 As the compressor subjects the gas to increased pressure, the heat intensity of the
refrigerant is actually concentrated into a smaller area, thus raising the temperature
of the refrigerant higher than the ambient temperature of the air passing over the
condenser coils.
 Clogged condenser fins will result in poor condensing action and decreased
efficiency. A factor often overlooked is flooding of the condenser coils with
refrigerant oil. Flooding results from adding too much oil to the system.

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  Oil flooding is indicated by poor condensing action, causing increased head pressure
and high pressure on the low side. This will always cause poor cooling from the
evaporator.
Expansion valve

 The expansion valve removes pressure from the liquid refrigerant to allow
expansion or change of state from a liquid to a vapour in the evaporator.
 The high-pressure liquid refrigerant entering the expansion valve is quite warm.
This may be verified by feeling the liquid line at its connection to the expansion
valve. The liquid refrigerant leaving the expansion valve is quite cold.
 The orifice within the valve does not remove heat, but only reduces pressure. Heat
molecules contained in the liquid refrigerant are thus allowed to spread as the
refrigerant moves out of the orifice.
 Under a greatly reduced pressure the liquid refrigerant is at its coldest as it leaves
the expansion valve and enters the evaporator.
 Pressures at the inlet and outlet of the expansion valve will closely approximate
gauge pressures at the inlet and outlet of the compressor in most systems.
 The similarity of pressures is caused by the closeness of the components to each
other.
 The slight variation in pressure readings of a very few pounds is due to resistance,
causing a pressure drop in the lines and coils of the evaporator and condenser.

1.8 EVAPORATOR
 The evaporator works the opposite of the condenser; here refrigerant liquid is
converted to gas, absorbing heat from the air in the compartment.
 When the liquid refrigerant reaches the evaporator its pressure has been reduced,
dissipating its heat content and making it much cooler than the fan air flowing
around it.
 This causes the refrigerant to absorb heat from the warm air and reach its low
boiling point rapidly. The refrigerant then vaporizes, absorbing the maximum
amount of heat.
 This heat is then carried by the refrigerant from the evaporator as a low-pressure
gas through a hose or line to the low side of the compressor, where the whole
refrigeration cycle is repeated.
 The evaporator removes heat from the area that is to be cooled. The desired
temperature of cooling of the area will determine if refrigeration or air conditioning
is desired. For example, food preservation generally requires low refrigeration
temperatures, ranging from 40°F (4°C) to below 0°F (-18°C).
 A higher temperature is required for human comfort. A larger area is cooled, which
requires that large volumes of air be passed through the evaporator coil for heat
exchange.
 A blower becomes a necessary part of the evaporator in the air conditioning system.
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  The blower fans must not only draw heat-laden air into the evaporator, but must
also force this air over the evaporator fins and coils where it surrenders its heat to
the refrigerant and then forces the cooled air out of the evaporator into the space
being cooled.

1.9 REFRIGERANT CONTROL DEVICES (THERMOSTATIC EXPANSION VALVE)

 Thermostatic Expansion Valve.—before discussing the thermostatic expansion
valve, let’s explain the term SUPERHEAT.
 In an evaporator, as the gas vapor moves along the coils toward the suction line, the
gas may absorb additional heat and its temperature rises.
 The difference in degrees between the saturation temperature and the increased
temperature of the gas is called superheat.
 A thermostatic expansion valve (fig.) keeps a constant superheat in the refrigerant
vapor leaving the coil.
 The valve controls the liquid refrigerant, so the evaporator coils maintain the
correct amount of refrigerant at all times.
 The valve has a power element that is activated by a remote bulb located at the end
of the evaporator coils.
 The bulb senses the superheat at the suction line and adjusts the flow of refrigerant
into the evaporator. As the superheat increases (suction line), the temperature, and
therefore the pressure, in the remote bulb also increases.
 This increased pressure, applied to the top of the diaphragm, forces it down along
with the pin, which, in turn, opens the valve, admitting replacement refrigerant from
the receiver to flow into the evaporator. This replacement has three effects. First, it
provides additional liquid refrigerant to absorb heat from the evaporator.
 Second, it applies higher pressure to the bottom of the diaphragm, forcing it upward,
tending to close the valve. And third, it reduces the degree of superheat by forcing
more refrigerant through the suction line.

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1.10 AIR HANDLING UNIT

Fan

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Centrifugal fan is used to circulate the air to the various parts of the sections in the
building. The typical types of fan available are Backward Inclined, Backward Curved,
Forward Curved and Airfoil.

The selection of the fan will depend on the air volume and the static pressure required of
the system. Usually, the designer of the system will use a specialized software to do this
selection.

In order to reduce the effect of vibration on the panel, the motor and the fan are usually
installed on the vibration isolator except when the drive assembly is external to the fan
casing.

In recent years, the use of variable air volume (VAV) system is becoming more popular as
the volume of the air being discharged can be varied depending on the load condition. If the
load is high, the fan speed will be higher and if the load is lower, the speed of the fan will be
lower.

The speed of the fan is varied by using frequency inverter instead of conventional motor
such as PSC motor. Frequency inverter provides better control of the fan speed as a whole
range of fan speed from super low to super high can now be utilized based on the load
conditions required.

This technology has enabled better use of energy and is in tandem with the move to go for
greener energy.

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Cooling Coil

Cooling Coil is used to cool and dehumidify the air. Both DX (direct expansion) cooling and
CW (chilled water) cooling coils are available for use depending on the system design.

These coils are arranged in rows with different fin spacing. Aluminium fins and copper
tubes are used in the design of the coils. The corrosion resistance hydrophilic fins are also
used due to its lower cost and lower resistance to the air velocity.

Filters

Filters are to remove particles and contaminants of various sizes from the air. The type of
air filter being used will very much depend on the application of the system.

Panel Filter is a flat and rectangular in shape and provides a minimum low efficiency
filtration which is acceptable to the air conditioning industry. The high velocity filter is
arranged vertically whereas the low velocity filter is arranged in V shape. Typical air
velocity that moves through the filters is in the range of 2-3 m/s.

HEPA Filter is very efficient and is able to achieve efficiencies up to 99.97%, removing
minute particles and airborne bacteria from the air. It is usually used in clean room
applications such as semiconductor production floor, operating theaters and critical
processes.

Electrostatic Filter is used to remove particles from the air by using highly charged
electrodes that ionized the air. Bag Filter is able to remove dust particles and is thrown
away after use. Roll Filter is used for high velocity filtration where the used part is rolled up
automatically/manually.

Humidifiers

During winter, the humidity level of the air can be low hence causing discomfort to the
occupants. The humidity of the air is increased by using the humidifiers. Here are the
commonly used humidifiers:

Spray Type has a header and spray nozzles that spray water with a pressure of 15 psi or
more.

Steam Pan Type has a pan and a heating coil to heat up the water of the pan. The
evaporation of water caused by the heating will increase the humidity level of the
surrounding air.

Steam Grid Type has tiny holes on the pipe to distribute the steam that flows through it. In
this case, the water that is heated up to produce the steam to be supplied to the grid is
conditioned to prevent odor being discharged to the room.

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Mixing Box

This box has air inlets that is attached to the dampers. This is the place where the outside
air and the return air are mixed to provide the correct proportion of air to be distributed to
the space that is to be conditioned.

1.11 ELECTRIC MOTORS

Split-Phase AC Motor

This is the simplest design where the RUN winding and START winding are connected in
parallel and 90° electrically apart. It is usually used in small pumps, fans and blowers
where the capacity is below 1 horsepower. It has a low starting torque but high starting
current. Since the torque is low, the ability to start the motor is only practical for low load
condition.

The RUN winding is make from bigger diameter wire and shorter turn for lower resistance
and high inductance properties. The START winding is make from smaller diameter wire
for higher resistance and low inductance properties.

When power is connected to the motor, both the windings will be energized with the
current in the RUN winding lags the current in the START winding by about 30° electrically.
This out-of-phase effect on the stator produces a starting torque and causes the rotor to
start rotating.

Typically the speed of the motor is 1800 rpm or 3600 rpm when running without any load.
When the load is connected, the speed can go down to 1725 rpm and 3450 rpm
respectively.

The no-load speed of the motor is given by:

Speed(rpm) = (Frequency of AC power X 120)/number of poles

For example, if your supply is 60 Hz and the motor is using two-pole, the synchronous
speed = (60X120)/2
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 = 3600 rpm

There is a switch known as centrifugal switch which is connected in series with the START
winding. This mechanical switch will open when the motor speed reaches 75% of the rated
speed typically within 2 seconds. Once the switch opened, the START winding in circuit is
disconnected.

This is to protect the START winding from overheating. When the motor is powered off, the
switch will close the circuit to get ready for the next starting of the motor.

These days, electronic relay is also being widely used to disconnect the START winding.

Single Phase Induction Motor

 Single phase induction motor is an AC motor were electrical energy is converted to
mechanical energy to perform some physical task. This induction motor requires
only one power phase for their proper operation.
 They are commonly used in low power applications, in domestic and industrial use.
Simple construction, cheap cost, better reliability, eases to repair and better
maintenance are some of its markable advantages.

Construction of Single Phase Induction Motor

 The main components of the Single Phase induction motor are stator and
rotor. Stator is known to be the stationary part.
 Usually, the single phase alternating supply is given to the stator winding. Rotor is
the rotating part of the motor. Rotor is connected to the mechanical load with the
help of a shaft. A squirrel cage rotor is used here.
 It has a laminated iron core with many slots. Rotor slots are closed or semi-closed
type. The rotor windings are symmetrical and at the same type it is short circuited.
An air gap is there between the rotor and the stator.
 The most practical applications of this motor are in refrigerators, clocks, drills,
pumps, washing machines etc. The stator winding in the 1Ø induction motor has
two parts: Main Winding and Auxiliary Winding.
 Usually, the Auxiliary winding is perpendicular to the main winding. In 1Ø induction
motor the winding with more turns is known as main winding. While the other wire
is called as auxiliary winding.

Principle of Operation

 When the stator of a single phase motor is fed with single phase supply, it produces
alternating flux in the stator winding. The alternating current flowing through stator
winding causes induced current in the rotor bars (of the squirrel cage rotor)
according to Faraday's law of electromagnetic induction.This induced current in the
rotor will also produce alternating flux. Even after both alternating fluxes are set up,
the motor fails to start. However, if the rotor is given a initial start by external force

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 in either direction, then motor accelerates to its final speed and keeps running with
its rated speed.

1.12 COOLING TOWERS

The purpose of a cooling tower is to cool down water that gets heated up by industrial
equipment and processes. Water comes in the cooling tower hot (from industrial process)
and goes out of the cooling tower cold.

The hot water is usually caused by air conditioning condensers or other industrial
processes. That water is pumped through pipes directly into the cooling tower. Cooling
tower nozzles are used to spray the water onto to the “fill media”, which slows the water
flow down and exposes the maximum amount of water surface area possible for the best
air-water contact. The water is exposed to air as it flows throughout the cooling tower. The
air is being pulled by a motor-driven electric “cooling tower fan”.

When the air and water come together, a small volume of water evaporates, creating an
action of cooling. The colder water gets pumped back to the process/equipment that
absorbs heat or the condenser. It repeats the loop over and over again to constantly cool
down the heated equipment or condensers.

Cooling Tower Applications

Traditional HVAC heating and cooling systems are used in schools, large office buildings,
and hospital. On the other hand, Cooling towers are much larger than traditional HVAC
systems and are used to remove heat from cooling tower water systems in petroleum
refineries, plants, natural gas processing plants, petrochemical plants, and other industrial
processes.

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Most cooling towers work based on the principle of “evaporative cooling“.

Evaporative Cooling

Evaporative cooling is the process where warm water from an industrial process is
pumped up to the top of the cooling tower where the water distribution system is. The
water then gets distributed by cooling tower nozzles to the wet deck. At the same time, air

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is being drawn through the air-inlet louvers forcing water to evaporate. Evaporation causes
the heat to be removed from the makeup water.

Cross flow Cooling Towers Flow Diagram

In cross flow cooling tower systems the water vertically flows through the fill media while
the air horizontally flows across the falling water. That’s why they call it “cross flow”
because the air and water cross paths or flows. Because of the crossing of flows, the air
doesn’t need to pass through the distribution system. This permits the use of hot water
flow via gravity and distribution basins on the top of the tower right above the fill media.
The basins are a standard of cross flow cooling towers and are applied on all units.

Counterflow Cooling Tower

In counter flow cooling tower system processes, the air vertically flows upwards,
counter to the water flow in the fill media. Due to the air owing vertically, it’s not possible
to use the basin’s gravity flow like in cross flow towers. As a substitute, these towers use
pressurized spray systems, usually pipe-type, to spray the water on top of the fill media.
The pipes and cooling tower nozzles are usually spread farther apart so they will not
restrict any air flow.

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A.H.U. (AIR HANDLING UNIT)

Air handling units, which usually have the acronym of A.H.U are found in medium to
large commercial and industrial buildings.

They are usually located in the basement, on the roof or on the floors of a building.
AHU’s will serve a specified area or zone within a building such as the east side, or
floors 1 – 10 or perhaps a single purpose such as just the buildings toilets. Therefore,
it’s very common to find multiple AHU’s around a building.

Some buildings, particularly old high rise building, will have just one large AHU, usually
located on the roof. These will supply the entire building. They might not have a return
duct, some older designs rely on the air just leaking out of the building. This design isn’t
so common anymore in new buildings because it’s very inefficient, now its most
common to have multiple smaller AHU’s supplying different zones. The buildings are
also more air tight so we need to have a return duct to regulate the pressure inside the
building.

So, what is the purpose of an air handling unit?

Air handling units’ condition and distribute air within a building. They take fresh
ambient air from outside, clean it, heat it or cool it, maybe humidify it and then force it
through some ductwork around to the designed areas within a building. Most units will
have an additional duct run to then pull the used dirty air out of the rooms, back to the
AHU, where a fan will discharge it back to atmosphere. Some of this return air might be
recirculated back into the fresh air supply to save energy, we’ll have a look at that later
in the article. Otherwise, where that isn’t possible, thermal energy can extracted and fed
into the fresh air intake. Again we’ll look at that later in more detail.

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DAMPERS

At the inlet of the fresh air housing and the discharge of the return air housing we
have some dampers. The dampers are multiple sheets of metal which can rotate. They can
close to prevent air from entering or exiting, they can open to fully allow air in or out, and it
can also vary their position somewhere in between to restrict the amount of air that can
enter or exit.

FILTERS

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 After the dampers we’ll have some filters. These are there to try and catch all the
dirt and dust etc from entering the ahu and the building. If we don’t have these filters
the dust is going to build up inside the ductwork and within the mechanical equipment,
it’s also going to enter the building and be breathed in by the occupants as well as make
the building dirty. So, we want to remove as much of this as possible. Across each bank
of filters, we’ll have a pressure sensor. This will measure how dirty the filters are and
warn the engineers when it’s time to replace the filters. As the filters pickup dirt, the
amount of air that can flow through is restricted and this causes a pressure drop across
the filters. Typically, we have some panel filters or pre-filters to catch the largest dust
particles. Then we have some bag filters to catch the smaller dust particles.

COOLING AND HEATING COILS

The next thing we’ll find are the cooling and heating coils. These are there to heat or cool
the air. The air temperature of the supply air is measured as it leaves the AHU and enters
the ductwork. This needs to be at a designed temperature to keep the people inside the
building comfortable, this designed temperature is called the set point temperature. If the
air temperature is below this value the heating coil will add heat to increase the air
temperature and bring it up to setpoint. If the air is too hot then the cooling coil will
remove heat to lower the air temperature and reach the setpoint. The coils are heat
exchangers, inside the coil is a hot or cold fluid, usually something like heated or chilled
water, refrigerant or steam.

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FAN

Next we’ll have a fan. This is going to pull the air in from outside and then through
the dampers, filters and coils and then push this out into the ductwork around the building.
Centrifugal fans are very common in old and existing AHU’s but EC fans are now being
installed and also retro fitted for increased energy efficiency. Across the fan we’ll also have
a pressure sensor, this will sense if the fan is running. If it is running then it will create a
pressure difference, we can use this to detect a failure in the equipment and warn the
engineers of the problem. We’ll also likely have a duct pressure sensor shortly after the fan,
this will read the static pressure and in some ahu’s the speed of the fan is controlled as a
result of the pressure in the duct, so we’ll also very often find a variable speed drive
connected to the fan for variable volume systems.

Then we have the ductwork which will send the air around the building to the designed
areas. We’ll also have some ductwork coming back which is brining all the used air from
the building back to a separate part of the AHU. This return AHU is usually located near the
supply, but it doesn’t have to be, it can be located elsewhere.

The return AHU in its simplest form has just a fan and damper inside. The fan is pulling the
air in from around the building and then pushing it out of the building. The damper is
located at the exit of the AHU housing and will close when the AHU turns off.

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HUMIDIFIER

Some buildings need to control the humidity of the air they supply into the building.
We’ll find a humidity sensor at the outlet of the supply AHU to measure the moisture in the
supply air, this will also have a setpoint for how much moisture should be in the air by
design.

If the airs moisture content is below this value then we need to introduce moisture
into the air using a humidifier, this is usually one of the last things in the AHU. This device
will usually either add steam or spray a water mist into the air. Many standard office type
building in northern Europe and north America have turned off their humidity units or
uninstalled them to save energy. Although they’re still crucial for places like document
stores and computer rooms.

If the air is too humid then this can be reduced through the cooling coil. As the air hits the
cooling coil the cold surface will cause the moisture within the air to condense and flow
away, you’ll find a drain pan under the cooling coil to catch the water and drain this away.
The cooling coil can be used to further reduce the moisture content by removing more heat,
but of course this will decrease the air temperature below the supply setpoint, if this occurs
then the heating coil can also be turned on to bring the temperature back up, this will work
although it is very energy intensive.

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Another very common version we’ll come across is to have a duct sit in between the
exhaust and the fresh air intake. This allows some of the exhaust air to be recirculated back
into the fresh air intake, to offset the heating or cooling demand. This is safe and healthy to
do but you will need to ensure the exhaust air has a low Co2 count so we need some Co2
sensors to monitor that. If the Co2 level is too high then the air can’t be re-used, the mixing
damper will close and the all the return air will be rejected from the building. When in
recirculation mode, the main inlet and outlet dampers will not fully close in this setup
because we still need a minimum amount of fresh air to enter the building. We can use this
in winter if the return air is warmer than the outside air and we can use this in summer if
the return air is cooler than the outside air, respective to the supply setpoint air
temperature, so we’ll also need some temperature sensors at the intake, return and just
after the mixing region. Some buildings require 100% fresh air so this strategy can’t be
used everywhere, local laws and regulations will dictate this.

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1.13Air conditioning systems for buildings of different scales and their requirements

52
AIR CONDITIONING SYSTEM FOR SMALL BUILDINGS

The choice of which air conditioner system to use depends upon a number of factors
including how large the area is to be cooled, the total heat generated inside the enclosed
area, etc. An HVAC designer would consider all the related parameters and suggest the
system most suitable for your space.

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1.14 WINDOW AIR CONDITIONER

 Window air conditioner is the most commonly used air conditioner for single
rooms. In this air conditioner all the components, namely the compressor,
condenser, expansion valve or coil, evaporator and cooling coil are enclosed in a
single box.
 This unit is fitted in a slot made in the wall of the room, or more commonly a
window sill.
 Window air conditioners are one of the most popular types of air conditioners being
used. Whether it’s your study room, bedroom, or hall, the window air conditioner
can be used for almost all types of spaces.
 To fit the window air conditioner in your room, you need to make a slot in one of the
walls of the room that is to be cooled.
 This system extends around two feet beyond the wall in the back side; hence behind
the wall some free space should be available so that the hot air can be thrown easily
from the condenser.
 The dew collected from the room is also thrown from the back of the air conditioner.
Thus window air conditioners can be used only if there is place available in the wall
to make the slot, and there is free space behind the wall for dissipating the heat and
dripping water.
 Window air conditioners are comprised of components like the compressor,
condenser, expansion valve or expansion coil, and the evaporator or the cooling coil,
all housed in a single box.
 There is also a motor which has shafts on both sides. On one side of the shaft the
blower is connected, which sucks hot air from the room and blows it over the
cooling coil, thus cooling it and sending it to the room.
 On the other shaft the fan is connected, which blows the air over Freon gas passing
through the condenser.
 The window air conditioner is the cheapest of all air conditioning systems. If your
room or office size is about less than 100 sq. ft. a window air conditioner of about
0.8 ton can be good enough.
 If the size of room is more than this but less than 200 sq. ft. your HVAC designer will
recommend a window air conditioner of about 1 ton. For rooms of bigger sizes but
less than 300 sq. ft. the system of about 1.5 ton is advisable.
 However, these sizes may change depending upon the number of people occupying
the space, its alignment with respect to sun, and other sources of heat generation
inside the room.
 It is better to consult your HVAC designer to find out the exact size of window air
conditioner suitable for your space.

54
  One of the complaints that window air conditioners have had is that they tend to
make noise inside the room. But this problem has been greatly overcome by the
present day efficient and less noisy rotary compressors, which also consume less
electricity.
 Today a number of fancy and elegant looking models of window air conditioners are
available that enhance the beauty of your rooms.
 Split air conditioners are used for small rooms and halls, usually in places where
window air conditioners cannot be installed. However, these days many people
prefer split air conditioner units even for places where window air conditioners can
be fitted.
EVAPORATIVE COOLER

As the name indicates, evaporative cooling is the process of reducing the temperature of
a system by evaporation of water. Human beings perspire and dissipate their metabolic
heat by evaporative cooling if the ambient temperature is more than skin temperature.
Animals such as the hippopotamus and buffalo coat themselves with mud for
evaporative cooling.
Direct evaporative cooling (open circuit) is used to lower the temperature of air by
usinglatent heat of evaporation, changing liquid water to water vapor. In this process,

55
 the energy in the air does not change. Warm dry air is changed to cool moist air. The heat
of the outside air is used to evaporate water.

Indirect evaporative cooling (closed circuit) is similar to direct evaporative cooling,

butuses some type of heat exchanger. The cooled moist air never comes in direct contact
with the conditioned environment.

Advantages and disadvantages of evaporative cooling systems:

Compared to the conventional refrigeration based air conditioning systems, the
evaporative cooling systems offer the following advantages:

 Lower equipment and installation costs

 Substantially lower operating and power costs. Energy savings can be as high as
75%
 Ease of fabrication and installation
 Lower maintenance costs
 Ensures a very good ventilation due to the large air flow rates involved, hence, are
very good especially in 100 % outdoor air applications
 Better air distribution in the conditioned space due to higher flow rates
 The fans/blowers create positive pressures in the conditioned space, so that
infiltration of outside air is prevented
 Very environment friendly as no harmful chemicals are used
Compared to the conventional systems, the evaporative cooling systems suffer from the
following disadvantages:

 The moisture level in the conditioned space could be higher, hence, direct
evaporative coolers are not good when low humidity levels in the conditioned
space is required. However, the indirect evaporative cooler can be used without
increasing humidity
 Since the required air flow rates are much larger, this may create draft and/or high
noise levels in the conditioned space

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  Precise control of temperature and humidity in the conditioned space is not
possible
 May lead to health problems due to micro-organisms if the water used is not clean
or the wetted surfaces are not maintained properly.

1.15 PACKAGED AIR CONDITIONERS

 The window and split air conditioners are usually used for the small air conditioning
capacities up to 5 tons.
 The central air conditioning systems are used for where the cooling loads extend
beyond 20 tons.
 The packaged air conditioners are used for the cooling capacities in between these
two extremes. The packaged air conditioners are available in the fixed rated
capacities of 3, 5, 7, 10 and 15 tons.
 These units are used commonly in places like restaurants, telephone exchanges,
homes, small halls, etc.
 As the name implies, in the packaged air conditioners all the important components
of the air conditioners are enclosed in a single casing like window AC.
 Thus the compressor, cooling coil, air handling unit and the air filter are all housed
in a single casing and assembled at the factory location.

 Depending on the type of the cooling system used in these systems, the packaged air
conditioners are divided into two types:
1) one with water cooled condenser and
2) one with air cooled condensers.

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Both these systems have been described below:

Packaged Air Conditioners with Water Cooled Condenser

 In these packaged air conditions the condenser is cooled by the water. The
condenser is of shell and tube type, with refrigerant flowing along the tube side and
the cooling water flowing along the shell side.
 The water has to be supplied continuously in these systems to maintain functioning
of the air conditioning system.
 The shell and tube type of condenser is compact in shape and it is enclosed in a
single casing along with the compressor, expansion valve, and the air handling unit
including the cooling coil or the evaporator.
 This whole packaged air conditioning unit externally looks like a box with the
control panel located externally.

1.16 SPLIT AIR CONDITIONER

The split air conditioner comprises of two parts: the outdoor unit and the indoor
unit. The outdoor unit, fitted outside the room, houses components like the compressor,
condenser and expansion valve. The indoor unit comprises the evaporator or cooling coil
and the cooling fan. For this unit you don’t have to make any slot in the wall of the room.
Further, present day split units have aesthetic appeal and do not take up as much space as a
window unit. A split air conditioner can be used to cool one or two rooms.
There are two main parts of the split air conditioner. These are:
1) Outdoor unit: This unit houses important components of the air conditioner like the
compressor, condenser coil and also the expansion coil or capillary tubing. This unit
is installed outside the room or office space which is to be cooled. The compressor is
the maximum noise making part of the air conditioner, and since in the split air
conditioner, it is located outside the room, the major source of noise is eliminated.
In the outdoor unit there is a fan that blows air over the condenser thus cooling the
compressed Freon gas in it. This gas passes through the expansion coil and gets
converted into low pressure, low temperature partial gas and partial liquid Freon
fluid.

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59
 2) Indoor unit:
 It is the indoor unit that produces the cooling effect inside the room or the office.
This is a beautiful looking tall unit usually white in color, though these days a
number of stylish models of the indoor unit are being launched.
 The indoor unit houses the evaporator coil or the cooling coil, a long blower and
the filter. After passing from the expansion coil, the chilled Freon fluid enters the
cooling coil.
 The blower sucks the hot, humid and filtered air from the room and it blows it
over the cooling coil. As the air passes over cooling coil its temperature reduces
drastically and also loses the excess moisture.
 The cool and dry air enters the room and maintains comfortable conditions of
around 25-27 degree Celsius as per the requirements.
 The temperature inside the space can be maintained by thermostat setting. The
setting should be such that comfortable conditions are maintained inside the
room, and there is also chance for the compressor to trip at regular intervals. If
the compressor keeps running continuously without break, its life will reduce.
 These days multi-split air conditioners are also being used commonly. In units
for one outdoor unit there are two indoor units which can be placed in two
different rooms or at two different locations inside a large room.
 Since there is long distance between the indoor and the outdoor unit, there is
always loss of some cooling effect; hence for the same tonnage, split air
conditioners produce somewhat less cooling effect than window air
conditioners.
 However, with modern insulation material this gap has been reducing between
the two. In any case, there are number of instances where there is just no
alternative to the split air conditioners.

CENTRALIZED AIR CONDITIONING

 Central air conditioning plants are used for applications like big hotels, large
buildings having multiple floors, hospitals, etc, where very high cooling loads are
required.
 The article describes various possible arrangements of central air conditioning
plants.
 The central air conditioning plants or the systems are used when large buildings,
hotels, theaters, airports, shopping malls etc are to be air conditioned completely.
 The window and split air conditioners are used for single rooms or small office
spaces. If the whole building is to be cooled it is not economically viable to put
window or split air conditioner in each and every room.
 Further, these small units cannot satisfactorily cool the large halls, auditoriums,
receptions areas etc.
 In the central air conditioning systems there is a plant room where large
compressor, condenser, thermostatic expansion valve and the evaporator are kept
in the large plant room.
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  They perform all the functions as usual similar to a typical refrigeration system.
However, all these parts are larger in size and have higher capacities.
 The compressor is of open reciprocating type with multiple cylinders and is cooled
by the water just like the automobile engine. The compressor and the condenser are
of shell and tube type.
 While in the small air conditioning system capillary is used as the expansion valve,
in the central air conditioning systems thermostatic expansion valve is used.
 The chilled air is passed via the ducts to all the rooms, halls and other spaces that
are to be air conditioned.
 Thus in all the rooms there is only the duct passing the chilled air and there are no
individual cooling coils, and other parts of the refrigeration system in the rooms.
What is we get in each room is the completely silent and highly effective air
conditions system in the room.
Further, the amount of chilled air that is needed in the room can be controlled by the
openings depending on the total heat load inside the room.
The central air conditioning systems are highly sophisticated applications of the air
conditioning systems and many a times they tend to be complicated. It is due to this reason
that there are very few companies in the world that specialize in these systems. In the
modern era of computerization a number of additional electronic utilities have been added
to the central conditioning systems.
i. Direct expansion or DX central air conditioning plant: In this system the huge
compressor, and the condenser are housed in the plant room, while the expansion
valve and the evaporator or the cooling coil and the air handling unit are housed in
separate room. The cooling coil is fixed in the air handling unit, which also has large
blower housed in it. The blower sucks the hot return air from the room via ducts
and blows it over the cooling coil. The cooled air is then supplied through various
ducts and into the spaces which are to be cooled. This type of system is useful for
small buildings.
ii. Chilled water central air conditioning plant: This type of system is more useful for
large buildings comprising of a number of floors. It has the plant room where all the
important units like the compressor, condenser, throttling valve and the evaporator
are housed. The evaporator is a shell and tube. On the tube side the Freon fluid
passes at extremely low temperature, while on the shell side the brine solution is
passed. After passing through the evaporator, the brine solution gets chilled and is
pumped to the various air handling units installed at different floors of the building.
The air handling units comprise the cooling coil through which the chilled brine
flows, and the blower. The blower sucks hot return air from the room via ducts and
blows it over the cooling coil. The cool air is then supplied to the space to be cooled
through the ducts. The brine solution which has absorbed the room heat comes back
to the evaporator, gets chilled and is again pumped back to the air handling unit.

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Introduction
 There are two types of central air conditioning systems: Direct Expansion (DX) type
of central air condition plants and Chilled Water type of the central air conditioning
plants.
 In the DX system the air used for cooling the room or space is directly passed over
the cooling coil of the refrigeration plant. In case of the chilled water system the
refrigeration system is used to first chill the water, which is then used to chill the air
used for cooling the rooms or spaces.
Both these systems have been discussed in details; this article discusses DX system, while
the next one describes chilled water system.
1.17 DIRECT EXPANSION (DX) TYPE OF CENTRAL AIR CONDITIONING PLANT
 In the direct expansion or DX types of air central conditioning plants the air used for
cooling space is directly chilled by the refrigerant in the cooling coil of the air
handling unit.
 Since the air is cooled directly by the refrigerant the cooling efficiency of the DX
plants is higher.
 However, it is not always feasible to carry the refrigerant piping to the large
distances hence, direct expansion or the DX type of central air conditioning system
is usually used for cooling the small buildings or the rooms on the single floor.
There are three main compartments of the DX type of central conditioning systems:

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 Figure: DX Central Air Conditioning Plant

1) The Plant Room:

 The plant room comprises of the important parts of the refrigeration system, the
compressor and the condenser.
 The compressor can be either semi-hermetically sealed or open type. The semi-
hermetically sealed compressors are cooled by the air, which is blown by the fan,
while open type compressor is water cooled.
 The open compressor can be driven directly by motor shaft by coupling or by the
belt via pulley arrangement.
 The condenser is of shell and tube type and is cooled by the water. The refrigerant
flows along the tube side of the condenser and water along the shell side, which
enables faster cooling of the refrigerant.

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  The water used for cooling the compressor and the condenser is cooled in the
cooling tower kept at the top of the plant room, though it can be kept at other
convenient location also.
2) The Air Handling Unit Room:

 The refrigerant leaving the condenser in the plant room enters the thermostatic
expansion valve and then the air handling unit, which is kept in the separate room.
 The air handling unit is a large box type of unit that comprises of the evaporator or
the cooling coil, air filter and the large blower.
 After leaving the thermostatic expansion valve the refrigerant enters the cooling coil
where it cools the air that enters the room to be air conditioned.
 The evaporator in the air handling unit of the DX central air conditioning system is
of coil type covered with the fins to increasing the heat transfer efficiency from the
refrigerant to the air.
 There are two types of ducts connected to the air handling unit: for absorbing the
hot return air from the rooms and for sending the chilled air to the rooms to be air
conditioned.
 The blower of the air handling unit enables absorbing the hot return air that has
absorbed the heat from the room via the ducts. This air is then passed through the
filters and then over the cooling coil.
 The blower then passes the chilled air through ducts to the rooms that are to be air
conditioned.
 The DX expansion system runs more efficiently at higher loads. Even in case of the
breakdown of the plants, the other plants can be used for the cooling purpose.
 The DX types of central air conditioner plants are less popular than the chilled water
type of central conditioning plants.

3) Air Conditioned Room:

 This is the space that is to be actually cooled. It can be residential room, room of the
hotel, part of the office or any other suitable application.
 The ducts from the air handling room are passed to all the rooms that are to be
cooled. The ducts are connected to the grills or diffusers that supply the chilled air
to the room.
 The air absorbs the heat and gets heated and it passes through another set of the
grill and into the return air duct that ends into the air handling unit room. This air is
then re-circulated by the air handling unit.
 Though the efficiency of the DX plants is higher, the air handling units and the
refrigerant piping cannot be kept at very long distance since there will be lots of
drop in pressure of the refrigerant along the way and there will also be cooling
losses.
 Further, for the long piping, large amounts of refrigerant will be needed which
makes the system very expensive and also prone to the ma instance problems like
the leakage of the refrigerant.

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  Due to these reasons the DX type central air conditioning systems are used for small
air conditioning systems of about 5 to 15 tons in small buildings or the number of
rooms on a single floor.
 If there are large air conditioning loads, then multiple direct expansion systems can
be installed. In such cases, when there is lesser heat load one of the plants can be
shut down and the other can run at full load.
 The DX expansion system runs more efficiently at higher loads. Even in case of the
breakdown of the plants, the other plants can be used for the cooling purpose.
 The DX types of central air conditioning plants are less popular than the chilled
water type of central conditioning plants.

Chilled Water Central Air Conditioning Systems

Chilled Water Central Air Conditioning Plants

 The chilled water types of central air conditioning plants are installed in the place
where whole large buildings, shopping mall, airport, hotel, etc, comprising of several
floors are to be air conditioned.
 While in the direct expansion type of central air conditioning plants, refrigerant is
directly used to cool the room air; in the chilled water plants the refrigerant first
chills the water, which in turn chills the room air.
 In chilled water plants, the ordinary water or brine solution is chilled to very low
temperatures of about 6 to 8 degree Celsius by the refrigeration plant. This chilled
water is pumped to various floors of the building and its different parts.
 In each of these parts the air handling units are installed, which comprise of the
cooling coil, blower and the ducts.
 The chilled water flows through the cooling coil. The blower absorbs return air from
the air conditioned rooms that are to be cooled via the ducts. This air passes over
the cooling coil and gets cooled and is then passed to the air conditioned space.

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66
Various Parts of the Chilled Water Air Conditioning Plant
All the important parts of the chilled water air conditioning plant are shown in the above
figure and described in detail below:

1) Central Air Conditioning Plant Room:

 The plant room comprises of all the important components of the chilled water air
conditioning plant. These include the compressor, condenser, thermostatic
expansion valve and the evaporator or the chiller.
 The compressor is of open type and can be driven by the motor directly or by the
belt via pulley arrangement connected to the motor. It is cooled by the water just
like the automotive engine.
 The condenser and the evaporator are of shell and tube type. The condenser is
cooled by the water, with water flowing along the shell side and refrigerant along
the tube side.The thermostatic expansion valve is operated automatically by the
solenoid valve.
 The evaporator is also called as the chiller, because it chills the water. If the water
flows along the shell side and refrigerant on the tube side, it is called as the dry
expansion type of chiller.
 If the water flows along tube side and the refrigerant along the shell side, it is called
as the flooded chiller.

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  The water chilled in the chiller is pumped to various parts of the building that are to
be air conditioned. It enters the air handling unit, cools the air in cooling coil,
absorbs the heat and returns back to the plant room to get chilled again.
 The amount of water passing into the chiller is controlled by the flow switch.
 In the central air conditioning plant room all the components, the compressor,
condenser, thermostatic expansion valve, and the chiller are assembled in the
structural steel framework making a complete compact refrigeration plant, known
as the chiller package.
 Piping required to connect these parts is also enclosed in this unit making a highly
compact central air conditioning plant.
 The air handling units are installed in the various parts of the building that are to be
air conditioned, in the place called air handling unit rooms. The air handling units
comprise of the cooling coil, air filter, the blower and the supply and return air
ducts. The chilled water flows through the cooling coil.
 The blower absorbs the return hot air from the air conditioned space and blows it
over the cooling coil thus cooling the air.
 This cooled air passes over the air filter and is passed by the supply air ducts into
the space which is to be air conditioned. The air handling unit and the ducts passing
through it are insulated to reduce the loss of the cooling effect.

2) Air Handling Unit Rooms:

 The air handling units are installed in the various parts of the building that are to be
air conditioned, in the place called air handling unit rooms.
 The air handling units comprise of the cooling coil, air filter, the blower and the
supply and return air ducts.
 The chilled water flows through the cooling coil. The blower absorbs the return hot
air from the air conditioned space and blows it over the cooling coil thus cooling the
air.
 This cooled air passes over the air filter and is passed by the supply air ducts into
the space which is to be air conditioned. The air handling unit and the ducts passing
through it are insulated to reduce the loss of the cooling effect.

3) Air Conditioned Rooms:

 These are the rooms or spaces that are to be air conditioned. These can be
residential or hotel rooms, halls, shops, offices, complete theater, various parts of
the airport etc.
 At the top of these rooms the supply and the return air ducts are laid. The supply air
ducts supply the cool air to the room via one set of the diffusers, while the return air
ducts absorbs the hot return air from the room by another set of the diffusers.
 The hot return air enters the air handling unit, gets cooled and again enters the
room via supply duct to produce air conditioning effect.

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4) Cooling Tower:
 The cooling tower is used to cool the water that absorbs heat from the compressor
and the condenser.
 When water flows through these components some water gets evaporated, to make
up this loss some water is also added in the cooling tower.
 The cooling tower is of evaporative type. Here the water is cooled by the
atmospheric air and is re-circulated through the compressor and the condenser.
1.19 FAN COIL UNIT
Fan-coil units Fan-coil unit is considerably small unit used for heating and cooling
coils, circulation fan, and proper control system, as shown in Figure. The unit can be
vertically or horizontally installed. The fan-coil unit can be placed in the room or exposed
to occupants, so it is essential to have appropriate finishes and styling. For central systems,
the fan-coil units are connected to boilers to produce heating and to water chillers to
produce cooling to the conditioned space. The desired temperature of a zone is detected by
a thermostat which controls the water.

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 1.20 DISTRICT COOLING SYSTEM
What is District Cooling?
Basically, a district cooling system (DCS) distributes cooling capacity in the form of chilled
water or other medium from a central source to multiple buildings through a network of
underground pipes for use in space and process cooling. Individual user purchases chilled
water for their building from the district cooling system operator and do not need to install
their own chiller plants. For this system, a central chiller plant, a pump house and a
distribution pipeline network are required.

The DCS is an energy-efficient air-conditioning system as it consumes 35% and 20% less
electricity as compared with traditional air-cooled air-conditioning systems and individual
water-cooled air-conditioning systems using cooling towers respectively. In some countries
that have substantial heating demand, the plant can also be designed to supply hot water to
form a District Heating and Cooling System (DHCS).

A typical DCS comprises the following components:

 Central Chiller Plant - generate chilled water for cooling purposes.

 Distribution Network - distribute chilled water to buildings
 User Station - interface with buildings' own air-conditioning circuits.

Central Chiller Plant

Chilled water is typically generated at the central chiller plant by compressor driven
chillers, absorption chillers or other sources like ambient cooling or “free cooling” from
deep lakes, rivers, aquifers or oceans.

Groups of large and energy-efficient water-cooled chillers are usually installed in a central
chiller plant to take advantage of the economy of scale and the cooling demand diversity
between different buildings within a district. Sea water condensers or fresh water cooling
towers can be utilized to reject waste heat from the central chillers.

Distribution Network
District chilled water is distributed from the cooling source(s) to the user stations through
supply pipes and is returned after extracting heat from the building’s secondary chilled
water systems. Pumps distribute the chilled water by creating a pressure differential
between the supply and return lines.

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User Station
The interface between the district cooling system and the building cooling system is
commonly referred to as user station. The user station would usually comprise of air
handling units, heat exchanger and chilled water piping in the building. A user station is
required in each user's building to connect the DCS distributed chilled water pipe to the
building. Inside the user station, devices called heat exchangers are installed to transfer
heat between the chilled water supply of DCS and the air-conditioning system of the user
building. The user station could be designed for direct or indirect connection to the district
cooling distribution system. With direct connection, the district cooling water is distributed
within the building directly to terminal equipment such as air handling and fan coil units,
induction units, etc. An indirect connection utilizes one or multiple heat exchangers in
between the district system and the building system.

1.21 ENERGY EFFICIENT SYSTEMS

Each air conditioner has an energy-efficiency rating that lists how many Btu per
hour are removed for each watt of power it draws. For room air conditioners, this
efficiency rating is the Energy Efficiency Ratio (EER), while for central air conditioners, it is
the Seasonal Energy Efficiency Ratio (SEER). As explained in EnergyStar, the EER is a
measure of how efficiently a cooling system will operate when the outdoor temperature is
at a specific level (95oF). In normal terms, the higher the EER, the more efficient the system
is. In technical terms, EER is the steady-state rate of heat energy removal (i.e. cooling
capacity) by the product measured in Btuh divided by the steady-state rate of energy input
to the product measured in watts. This ratio is expressed in Btuh/watt. The SEER measures
how efficiently a cooling system will operate over an entire season, and the higher the SEER
the more efficient the system is. In technical terms, SEER is a measure of equipment the

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total cooling of a central air conditioner or heat pump (in Btu) during the normal cooling
season as compared to the total electric energy input (in watt-hours) consumed during the
same period. An important direct measure of efficiency is the coefficient of performance
(COP), which demonstrates the cooling power of an air conditioning system divided by fan
and compressor power.

Room air conditioners generally range from 5,500 Btu per hour to 14,000 Btu per hour.
There are several appliance standards worldwide, which require a minimum EER for room
air conditioners (for instance in the USA these must be 8.0 or greater). For milder climates
an efficient air conditioning system could have a minimum 9 EER, while for hotter climates
this should be over 10. As far as the smaller portable air conditioning units are concerned,
the least efficient unit has an EER of less than 1.5.

1.22 ENVIRONMENTAL IMPACT OF AIR CONDITIONERS

CFCs/ HFCs
Air conditioners are complex machines that are made up of many different parts which
work in several ways. CFCs and HFCs are both cooling agents that are in the air
conditioners which, when released, increases the holes in the ozone over time.

Older air conditioners rely on CFC and HCFC and contribute to global warming in a major
way. Even newer models, which rely more on HFCs and HFOs play a large role in ozone
depletion.

Energy use
Air conditioners require lots of energy to function properly. It consumes so much
electricity and therefore releases pollution. When fossil fuel is burned, carbon dioxide is
also released into the air, more commonly known as a greenhouse gas, which is a major
contribution to ozone depletion.
The average and typical air conditioner will consume about 3000 to 5000 watts of
electricity every hour, depending on the season – the warmer, the more power used. This is
clearly very harmful to the environment, as well as extremely expensive.

Unclean ducts
It is important to note that air conditioners do not only affect the environment in a global
way, it also affects it on a small scale as well. The ducts in each air conditioner, over
time, collect dust and bacteria and every time the air conditioner is turned on, both are
released, and are toxic for humans, especially children.
There are ductless mini-split brands though that focus more on the environment and
safety of people. Ductless mini-split brands are actually more durable and work in warmer
climates such as Middle East, Asia and Central and South America.

Materials used

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 In the past air conditioners were mainly made out of metals. Though over the years,
people decided that metal is too expensive and too heavy, so they opted for
plastic. Although metal and plastic are both harmful to the environment, plastic is
completely non-biodegradable, which makes it an enemy of the environment. The
production of plastic alone is extremely detrimental, as it too releases carbon dioxide into
the air and causes what we now know as the greenhouse effect.
It is important to note that air conditioners can sometimes be vital for mere survival.
There are places, due to global warming, that are extremely warm and need the presence of
coolant. Though this turn into a cycle since ACs contribute to global warming, we
undoubtedly still need them in order to survive the rising temperatures, whether it’s at
home or in our working spaces. However, all is not lost as we still have the option of going
with more eco-friendly air conditioners can be both beneficial for your health as well as the
world’s health, and as technology advances, so do the efforts to make them less harmful to
our environment.

1.23 LATEST INNOVATIONS IN AIR CONDITIONER

INVERTER TECHNOLOGY

An inverter is a device for converting frequency. The technology is used in many home
appliances and controls electric voltage, current and frequency. Inverter air-conditioners
vary their cooling/heating capacity by adjusting the power supply frequency of their
compressors.

An inverter type air-conditioner adjusts the speed of the compressor to control the
refrigerant (gas) flow rate, thereby consuming less current and power. An inverter has
precise temperature control and as the set temperature is attained, the unit adjusts its
capacity to eliminate any temperature fluctuations.

In contrast, non-inverter air conditioners have a fixed cooling/ heating capacity and can
only control the indoor temperature by starting or stopping their compressors.

Non-inverter air-conditioners stops and starts repeatedly. The power consumption and
current goes down when the operation stops, but it goes up sharply at the time of restart
and thus it has high average power consumption and temperature variations. As a result,
inverter air conditioners are more energy-saving and comfortable than non-inverter air-
conditioners.

Let’s take an example of 1.5 Ton AC. Inverter AC can work from. 3 to 1.7 ton based on
cooling requirement. Non-inverter AC can work at 1.5 ton only (fixed capacity).

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Inverter power control

Non-inverter type air-conditioner

Inverter air-conditioners are able to vary their operating capacity. Non-inverter air-
conditioners can only operate at a fixed capacity.

Figure: Inverter AC (Scenario: Indoor Temperature: 22 Degree, Set Temperature: 22 Degree

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Figure: Non Inverter AC

Benefits of inverter AC

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 UNIT 2
DESIGN ASPECTS OF AIR CONDITIONING SYSTEMS

SYLLABUS

 Design criteria for selection of air conditioning.

 Configuring/ sizing of mechanical equipment, equipment and spaces for them.
 Horizontal and vertical distribution of services for large buildings.

2.1 SELECTION CRITERIA FOR AIR CONDITIONING SYSTEMS:

Selection of a suitable air conditioning system depends on:

 Capacity, performance and spatial requirements

 Initial and running costs
 Required system reliability and flexibility
 Maintainability
 Architectural constraints
 The relative importance of the above factors varies from building owner to
owner and may vary from project to project.
 The typical space requirement for large air conditioning systems may vary from
about 4 percent to about 9 percent of the gross building area, depending upon
the type of the system.
 Normally based on the selection criteria, the choice is narrowed down to 2 to 3
systems, out of which one will be selected finally.
 Architectural Constraints Designing air conditioning for different building
applications and occupancies requires a consideration of different design
criteria, operating hours, and different system characteristics.
 Specific design criteria usually dictate the type of air conditioning system that
should be selected.
 A good example is the design of an air conditioning system for a class 10 clean
room for fabrication of semiconductor wafer. In this case a constant-volume
central system is always the preferred option.
 When the clean room is in operation, adequate clean air must be provided to
maintain unidirectional flow to prevent the contamination of semiconductor
wafers by sub micrometer-size particulates.
 It should be noted that a constant-volume system with electric terminal reheat is
always preferable to a VAV system in places requiring high precision constant
temperature to be maintained in the conditioned space.

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  For guest rooms in luxury hotels, a four-pipe fan-coil system is the most widely
used air conditioning system as in addition to the systems ease of maintenance,
the four-pipe fan-coil system provides individual temperature and fan speed
controls as well as a positive supply of adequate outdoor ventilation air. When
the room is not occupied, the fan coil unit (in the room) can be turned off
conveniently.
 Space limitations specified by the architect or facility owner also influence the
selection of the air conditioning system.
 For example where the design for a high-rise building provides no Rooftop space
for AHUs and other mechanical equipment, or if there is not enough space for
supply and return duct shafts, a floor-by-floor AHU central system may be the
practical choice.
 Capacity and Performance Requirements Another vital consideration for the
selection of air conditioning system is the system capacity.
 For a single-story small retail shop, a constant-volume packaged system is often
chosen. If the conditioned space is a large indoor stadium with a seating capacity
of up to 70,000 spectators, a single-zone VAV central system is often selected.
This system also guarantees the provision of minimum ventilation controls for
required indoor air quality regulation.
 Maintenance Considerations It is worth mentioning here that a central system
with AHUs, a few water-cooled centrifugal chillers, and cooling towers needs less
maintenance work than a packaged system with many rooftop air-cooled units.
 A VAV reheat central system needs less maintenance work in the fan and plant
rooms than fan-coil system, which often requires much maintenance work in the
ceiling space directly above the conditioned space.
 Cost Considerations Initial cost and operating costs (mainly energy cost) are
always primary factors that affect the selection of an air conditioning system.
ENERGY CONSERVATION IN AIR- CONDITIONING SYSTEMS
 Balance air and water systems that are out of balance
 repair variable-air-volume boxes that are not working properly
 tighten loose fan belts
 repair leaking control valves
 replace leaking damper seals
 repair or replace malfunctioning variable-speed drives
 seal ductwork to minimize leaks
 Reduce excessive air-change rates.
 Building Envelope
(1)repair door and window seals to prevent excessive infiltration of unconditioned
outdoor air and excessive exfiltration of conditioned air replace inefficient glazing or install

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solar-control film provide internal or external shading devices to control solar-heat gain
Install additional thermal insulation where needed to reduce heat gain and loss.

(2)Two-speed cooling tower fans and variable-speed drives on fans and pumps and energy
management systems (or direct digital control systems) will allow for the modulating of
HVAC equipment. This controls the system so that it works only to meet the space
conditioning and ventilation requirements of the building spaces, and not just at full output
capacity at all times. For example, demand-controlled ventilation modulates ventilated air
to keep CO2 levels below a set point (for example, 1000 parts per million), thereby
allowing ventilation rates to be adjusted to the number of people occupying the space and
other variables. This strategy for reducing building ventilation saves energy without
compromising indoor air quality, and modern CO2 sensors are both reliable and
inexpensive.

(3)The cost-effectiveness of installing direct digital controls (DDCs) on an HVAC system

varies widely with the specific site and application. DDC systems save energy if they are
used to turn building systems off when they are not needed. In office buildings, DDC
systems can modulate HVAC and lighting equipment to achieve energy savings as well as
to trim demand during peak periods, thereby lowering energy bills for months to come.

(4)Using occupancy sensors in conjunction with digital controls can limit energy waste in
unoccupied hotel and motel rooms and similar spaces, including offices. Guest room
occupancy sensors or central control systems can reduce energy requirements without
inconveniencing guests. For example, a central switching system at the front desk can turn
on heating or air conditioning as the guest checks in or manually adjust thermostat settings
if the room is unoccupied. Heat sensing (infrared) detectors can activate HVAC and lighting
systems based on human presence in the room. Turn-off time delays of 10 to 30 minutes
can acommodate a guest’s departure from the room for short periods of time.

(5)Variable air volume (VAV) air-handling systems with variable-speed drives (VSDs) can
save considerable fan energy over constant volume systems. Incorporating a VSD on a VAV
fan allows it to slow down as load decreases. Because reducing fan speed by one-half will
reduce power consumption by seveneighths, a VSD on a VAV fan system offers compound
energy savings that can provide a payback of three to five years. Typical VSD installation
costs are $200 to $250 per horsepower of the motor driven. VAV can save energy
costeffectively in systems whose fans are 20 hp or more.

(6)Variable-speed drives are also useful in a number of other commercial and industrial
applications, from moving water from boilers or chillers to local heat exchangers to
adjusting patterns of irrigation to optimize crop growth while minimizing water use.
Motors used in pumping fluids like water or high-pressure air can match pumping rates to
instantaneous demands, thereby saving both energy and demand costs.
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(7)VSD’s are also useful in adjusting ventilation rates to ensure good indoor air quality
while controlling fan energy use. Instead of operating at fixed fan rates on a predetermined
schedule, ventilation rates can be varied to maintain CO2 levels below a given threshold,
for example, 1100 parts per million. Inserting a CO2 sensor in the return air stream to give
feedback to a simple control algorithm can optimize fan use while safeguarding air quality.

2.2 CONFIGURING / SIZING OF MECHANICAL EQUIPMENT:

A method and system of managing a configuration of mechanical equipment provides a
structured procedure.

It helps to manage various parameters of the mechanical equipment to facilitate the

maintenance of safety, performance and reliability of the mechanical equipment.

Correct sizing of mechanical equipment is important for several reasons.

Mechanical equipment larger than needed results in inefficiencies of the system.

TYPE OF EQUIPMENT COMMONLY AVAILABLE RATINGS

Window and Split AC Min : 1 TR – Max : 2 TR

Packaged Air-conditioners Min : 5.5 TR – Max : 22 TR

Ductable Air-conditioners Min : 5.5 TR – Max : 22 TR

DX-System - Min : 12 TR – Max : 90 TR

EQUIPMENT SPACING :

While planning for the space requirements of AC Equipment rooms the following
guidelines may be used.

TYPE OF EQUIPMENT SPACE REQUIREMENT

 Packaged unit room 3m x 2m – Single unit

 3m x 4 m – Two units
 3 m x 5 m – Three units
 AHU Rooms 4m x 3m – up to 30 TR
 4m x 5 m – up to 60 TR
 Water Cooled chiller plants 6m x 6m for each plant and pumps. 3m x 3m open space
for cooling tower.
 Air cooled chiller plants 10 m x 8 m open space for one plant and pumps.
Note the following:

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  Height of packaged unit room or the AHU room should be the same as that of the
area to be air conditioned.
 Ductable split units require minimum 600 mm clear space above false Ceiling to
locate the indoor units and to run the ducts.
 Equipment placing should be done with an eye on maintenance. Packaged unit
should have 1 m space in front of the unit for unit servicing.
 If it is water cooled 2 m at the side also required for condenser tube cleaning.
 Shafts should be sized properly for installing the pipes based on site conditions.
2.3 HORIZONTAL & VERTICAL DISTRIBUTION OF SERVICES FOR LARGE BUILDINGS

 Under-floor distribution Air-conditioning system distribution and terminal

equipment is generally located overhead in the ceiling void with the cool supply air
entering the room from ceiling diffusers.
 However, the supply of conditioned air from under the floor is a design option. In
this case, the air or water distribution and terminal devices are located in the floor
void, and hence the overhead services are reduced to only lighting and sprinklers.
 By making the floor void deep enough, the power, telecommunications and
computer wire ways may be incorporated into the one plenum, all being easily
accessible by merely opening up the raised floor.
 Under-floor cooling is particularly beneficial for spaces such computer rooms, as air
velocities from floor grilles and resultant noise levels are both much higher for
cooling of equipment than those which would be acceptable for people.

1. Raised floor
2. Fan-coil unit
3. Ducting and insulation
4. Lighting and Ceiling

Services located below composite beams

 Internal distribution of services For many reasons, there is pressure to minimise the
space allocated to the building services. Therefore, it is necessary to ensure an
efficient use of space for the service distribution system in the vertical and
horizontal directions and in the plant rooms.
 The following sections review the spatial aspects of the vertical and horizontal
service distribution.
 Conventionally, the horizontal distribution of services is arranged within a
horizontal layer which is generally located below the structure and above the
suspended ceiling.

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  This layer accommodates the distribution system (ducts, pipes, etc), the terminal
units and lighting units. The raised floor is placed on the floor slab and
accommodates the electrical and communication cabling. The lighting units are
often located within the ceiling depth. To determine the spatial allowance for these
elements, three design cases may be envisaged corresponding to different structural
configurations:
1. A flat slab with flexibility of service routing.

2. A slab and down stand beam arrangement.

3. A long span beam system with facility for service integration in the structural
depth.

1. Power/communications/dat
a outlet
2. Floor void
3. Ceiling void
4. Supply duct
5. Air outlet

Example of integrated services Case 2 – Slab and downstand beam arrangement

1. Raised floor
2. Fan coil unit
3. Ducting and insulation
4. Lighting and Ceiling
Services located below composite beams

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 1. Power/communic
ations/data outlet
2. Floor void
3. Ceiling void
4. Supply duct
5. Air outlet

Example of integrated services Case 3 – Long span beam with web openings

In case 1, the ducts pass below the floor within the depth allowed for the terminal
units. However, cross-overs of ducts must be avoided in order to minimize this depth. In
cases 2 and 3, the terminal units may be located between the beams, which means that
additional space below the beams is required only for the major ducts, ceiling and lighting
units. In case 3, the ducts are located entirely within the structural zone as they pass
through large openings in the deep beams. Typically, the diameter of these openings is
400mm, and the duct size is 300 or 350mm allowing for insulation etc. Vertical distribution
of services

Case 2
Case 1 Downstand Case 3
Vertical dimensions for the Flat soffit beams Long span beams
following components (mm) (mm) (mm)
Allowance - deflection & fire
protection 30 50 50 to 75
Lighting units and ceiling 100 to 150 100 100
Nil Nil
VAV box and attachments 400 (boxes between beams)
<400 , but
no 400 (inc. Nil- 400mm dia.
Ducts and insulation cross-overs insulation) openings
Total (below structure) 550 500 150 to 175
Raised floor 150 150 150
Structural depth (typical) 300 to 400 550 800 to 900
1,000 to
Total (ceiling-floor) 1,100 1,200 1,100 to 1,200

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 Typical vertical dimensions between ceiling and floor

The following recommendations apply to the vertical distribution of services:

 Provide continuous and uninterrupted vertical service routes

 Maintain a constant cross-section of the service route
 Position the plant room so that it is as close as possible to the centre of the
plan area it serves
 Consider the connection between horizontal services and vertical services
routes
 Provide separate routes for different services. The minimum is two; one for
electrics and one for water pipes, etc., although most buildings require more
service routes
 Horizontal distribution should ideally not extend more than 25 m from a
vertical service route. Longer distances will impose penalties on the system
design and increase the depth of horizontal service ducts
 Position plant rooms at no more than 10 storeys apart vertically.
The figure shows typical arrangements of vertical service routes. Vertical ducts which
transfer air from the roof-top plant to each floor can often be concentrated in a relatively
small riser, as shown below

Type Plant Notes

Small building One plant room, one riser. Location

(up to four of riser not important, due to small
storeys and up size of building (central location
to 2500 m2 total preferred). Plant room must be
floor area) adjacent to the riser

Large plan Several plant rooms adjacent to

building (4000 areas served. Some central plant,
m2 total floor for example for gas intake and
area) boilers, may be required

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Large, tall Plant room floors at basement and
building (over roof level. Intermediate plant
15 storeys) rooms may be required. Vertical
distribution within central core

L-shaped Several plant rooms, several risers.

building (1000 Risers and air plant rooms
m2 to 3000 adjacent to cores. Separate room
m2 per floor), (3 located at ground/basement level
-10 storeys) for new electric supply

Building with Four roof air plant rooms, one

atrium (typically basement plant room. Four risers
2000 m2 per related to cores. Basement plant
floor), (5 – 10 below atrium gives best
storeys) connection to risers

Typical arrangements of plant rooms and vertical service routes

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HORIZONTAL DISTRIBUTION OF SERVICES THROUGH CENTRAL CORRIDOR

 The horizontal distribution system for mechanical and electrical services should be planned
simultaneously with the structural frame and the interior finish systems, because the three
are strongly interrelated.
 The floor to floor height of a building is determined in part by the vertical dimension
needed at every story for horizontal runs of duct work and piping.
 The selection of finish ceiling, partition and floor systems is often based on their ability to
contain the necessary electrical and mechanical services and to adjust to future changes in
these services. All these strategies involve close cooperation among the architect and the
structural and mechanical engineers.
 Plumbing walls, they will not interfere with other services. Sprinkler heads which have the
next highest priority in the layout of horizontal services are served from the fire stand pipe
by horizontal piping that seldom exceeds 4 in. (100mm) in outside diameter.
 The spacing of the heads is coordinated with the placement of walls and partitions the
maximum coverage per head is about 200 sq. ft. (18.6 m2) in light hazard buildings such as
churches, schools, hospitals, office buildings, museums and auditoriums. Coverage in
industrial and storage buildings ranges from 130 to 90 sq. ft. (12.1 to 8.4 m2) per head,
depending on the substances handled in the building.

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  Air conditioning ducts, the next priority branch out from a local fan room or from a vertical
ducts in supply and return ducts. Return ducts are often very short and confined to the
interior areas of the building.
 Supply ducts extend through low velocity secondary ducts to air diffusers throughout the
occupied area of the floor. Diffusers are generally required at the rate of four to seven
diffusers per 1000 sq. ft. (100m2).

Figure: Plan of VAV Duct

GROUPED HORIZONTAL DISTRIBUTION OVER CENTRAL CORRIDORS:

 Sometimes the major runs of duct work, piping and wiring can be grouped in the ceiling
area above the central corridor of each floor of a building, leaving the ceilings of the
surrounding rooms essentially clean.
 This works especially well in hotels and apartment buildings that rely on above ceiling all
water or electric equipment adjacent to corridor for heating, cooling and ventilating.
 A low corridor ceiling is readily accepted in exchange for high, unobstructed space in the
occupied rooms, where the structure may be left exposed as the finish ceiling, saving cost
and floor to floor height.
 If the building has a two way flat plate or hollow core precast slab floor structure, the
overall thickness of the ceiling floor structure can be reduced to as little as 8 in. (200 mm)
Conduits containing wiring for the lighting fixtures may be cast into the floor slabs or
exposed on the surface of the ceilings.

86
 Figure: Grouped Horizontal Distribution over a Central Corridor

IN FLOOR AND RAISED ACCESS FLOOR DISTRIBUTION OF MECHANICAL SERVICES:

 Underfloor air distribution (UFAD) is an air distribution strategy for

providing ventilation and space conditioning in buildings as part of the design of
an HVAC system.
 UFAD systems use an underfloor supply plenum located between the structural concrete
slab and a raised floor system to supply conditioned air through floor diffusers directly into
the occupied zone of the building.
 Thermal stratification is one of the featured characteristic of UFAD system, which allows
higher thermostat setpoints compared to the traditional overhead systems (OH).
 UFAD cooling load profile is different from a traditional OH system due to the impact
of raised floor, particularly UFAD may has higher peak cooling load than OH systems.
 UFAD has several potential advantages over traditional overhead systems, including layout
flexibility, improved thermal comfort, improved ventilation efficiency, improved energy
efficiency in suitable climates and reduced life cycle costs.
 UFAD is often used in office buildings, particularly highly-reconfigurable and open plan
offices where raised floors are desirable for cable management.
 UFAD is appropriate for a number of different building types including commercials,
schools, churches, airports, museums, libraries etc.
 Careful considerations need to be paid in the construction phase of UFAD systems to ensure
a well-sealed plenum to avoid air leakage in UFAD supply plenum.

DISTRIBUTION ABOVE STRUCTURAL FLOOR:

 A raised access floor system allows maximum flexibility in running services because it can
accommodate piping, ductwork, and wiring with equal ease.
 It is especially useful in industrial or office areas where large number of computers or
computer terminals are used and where frequent wiring changes are likely.
 Through floors can be raised to any desired height above the structural deck, heights of 4 to
8 in. (100 to 200 mm) are most common. Less costly lower profile systems ranging from
21/2 to 3 in. (65 to 75 mm) in height are also available

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88
 UNIT 3
FIRE AND SAFETY
SYLLABUS

 Causes of fire in buildings.

 Stages of fire and how it spreads.
 Fire drill.
 Heat/ fire/ smoke detection.
 Alarm and extinguisher systems.
 Fire safety standards.
 General guidelines for egress design for multistorey buildings.

3.1 CAUSES OF FIRE IN BUILDINGS

Fire is a chemical process requiring three things to occur: oxygen, fuel and an
ignition source. Without one of these factors, a fire can’t start or will burn itself out.

Figure: Fire Triangle

 In all chemical processes, molecules rearrange themselves and energy is either

absorbed or expelled.
 When a fire burns, a process called oxidation occurs, the same process that
causes metal to rust.
 Oxidation is when oxygen atoms combine with carbon and hydrogen to form
carbon dioxide and water.
 When metal rusts, the process happens very slowly, but when a fire burns, heat
and energy is released very quickly.
 The rate of oxidation is especially fast with fuel sources such as paper and wood.
When heat can’t release faster than it’s created, combustion occurs. This is what
creates the flame and heat we call fire.

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1. Cooking equipment
Pots and pans can overheat and cause a fire very easily if the person cooking gets
distracted and leaves cooking unattended. Always stay in the room, or ask someone to
watch your food, when cooking on hotplates.

2. Heating
Keep portable heaters at least one metre away from anything that could easily catch fire
such as furniture, curtains, laundry, clothes and even yourself. If you have a furnace, get it
inspected once a year to make sure it is working to safety standards.

3. Smoking in bedrooms
Bedrooms are best to be kept off limits for smoking. A cigarette that is not put out properly
can cause a flame, as the butt may stay alit for a few hours. It could burst into flames if it
came into contact with flammable materials, such as furniture. Did you know that fires
started in the bedroom or lounge make up 73% of all house fire fatalities?1

4. Electrical equipment
An electrical appliance, such as a toaster can start a fire if it is faulty or has a frayed cord. A
power point that is overloaded with double adapter plugs can cause a fire from an overuse
of electricity. A power point extension cord can also be a fire hazard if not used
appropriately. Double check the appliances and power points in your home.

5. Candles
Candles look and smell pretty, but if left unattended they can cause a room to easily burst
into flames. Keep candles away from any obviously flammable items such as books and
tissue boxes. Always blow a candle out before leaving a room. Did you know that in Perth
last year 34 house fires started as a result of candles?2

6. Curious children
Kids can cause a fire out of curiosity, to see what would happen if they set fire to an object.
Keep any matches or lighters out of reach of children, to avoid any curiosity turned
disaster. Install a smoke alarm in your child’s room and practice a home escape plan with
your children and family in case there was a fire. Teach kids understand the “stop, drop,
cover and roll” drill as well as knowing their address if they needed to call 000.

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7. Faulty wiring
Homes with inadequate wiring can cause fires from electrical hazards.
3.2 STAGES OF FIRE
By most standards including the International Fire Service Training Association (IFSTA)
there are 4 stages of a fire. These stages are incipient, growth, fully developed, and decay.
The following is a brief overview of each stage.

Incipient – This first stage begins when heat, oxygen and a fuel source combine and have a
chemical reaction resulting in fire. This is also known as “ignition” and is usually
represented by a very small fire which often (and hopefully) goes out on its own, before the
following stages are reached. Recognizing a fire in this stage provides your best chance at
suppression or escape.

Growth – The growth stage is where the structures fire load and oxygen are used as fuel for
the fire. There are numerous factors affecting the growth stage including where the fire
started, what combustibles are near it, ceiling height and the potential for “thermal
layering”. It is during this shortest of the 4 stages when a deadly “flashover” can occur;
potentially trapping, injuring or killing firefighters.

Fully Developed – When the growth stage has reached its max and all combustible
materials have been ignited, a fire is considered fully developed. This is the hottest phase of
a fire and the most dangerous for anybody trapped within.

Decay – Usually the longest stage of a fire, the decay stage is characterized a significant
decrease in oxygen or fuel, putting an end to the fire. Two common dangers during this
stage are first – the existence of non-flaming combustibles, which can potentially start a
new fire if not fully extinguished. Second, there is the danger of a backdraft when oxygen is
reintroduced to a volatile, confined space.

How does Fire Spread?

Once started, a building fire is likely to spread until all fuel has been used up. This could
have devastating consequences for your home or business. By understanding how fire
spreads, you may be better equipped to extinguish it.

 Chemicals and combustibles: When fire comes in contact with lab chemicals,
household cleaners, paint and other chemicals, the fire burns hotter and more
aggressively, encouraging it to spread. Other combustibles commonly found in the
home include mattresses, sofa cushions, magazines, newspapers and various
textiles.

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  Open space: A building with limited interior structure burns much faster than one
with hallways and closed doors. Walls and doors trap the fire and prevent the
flames and smoke from spreading. While the fire will eventually burn through the
structure and continue to spread if left to its own devices, a fire fighting team has a
much easier time dousing the flames in a building with more walls and doors,
especially if those structures are built to withstand the heat and damage of a fire.
 Construction materials: While a fire can burn through just about any modern
building, fire resistive buildings made of concrete and steel curb the spread of fire
better than wood frame homes.
 Ventilation: Buildings with central heating or air conditioning have ductwork,
which provides a way for flames and smoke to spread between floors of a building,
even when the structure is comprised primarily of concrete and steel.
 Water: In some cases, water is not the best fire extinguisher. Grease fires, for
example, can actually spread faster when doused with water. A special fire
extinguisher or baking soda should be used to suffocate and stop the spread of
grease fires in the kitchen.

3.3 FIRE DRILL

A fire drill is a method of practicing how a building would be evacuated in the event
of a fire or other emergencies. In most cases, the building's existing fire alarm system is
activated and the building is evacuated by means of the nearest available exit as if an
emergency had actually occurred. Fire drill procedures may vary depending on the building
type, such as hospitals or high rise buildings, where occupants may simply be relocated
within the building as opposed to evacuating the building. Generally, the evacuation is
timed to ensure that it is fast enough, and problems with the emergency system or
evacuation procedures are identified to be remedied. In addition to fire drills, most
buildings have their fire alarm systems checked on a regular basis to ensure that the
system is working. Fire alarm tests are often done outside normal business hours so as to
minimize disruption of building functions and in schools they are often done during a time
when students and staff aren't around or during the holidays where specialist fire alarm
engineers will test the alarms in the building and repair or upgrade the system if needed.

Class A
Class A fires are fires in ordinary combustibles such
as wood, paper, cloth, rubber, and many plastics.

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Class B
Class B fires are fires in flammable liquids such as gasoline,
petroleum greases, tars, oils, oil-based paints, solvents,
alcohols. Class B fires also include flammable gases such
as propane and butane. Class B fires do not include fires
involving cooking oils and grease.

Class C
Class C fires are fires involving energized electical
equipment such as computers, servers, motors,
transformers, and appliances. Remove the power and the
Class C fire becomes one of the other classes of fire.

Class D
Class D fires are fires in combustible metals such
as magnesium, titanium, zirconium, sodium, lithium, and
potassium.

Class K
Class K fires are fires in cooking oils and greases such
as animal and vegetable fats.

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3.4 HEAT DETECTORS

A heat detector is a fire alarm device designed to respond when the convected thermal
energy of a fire increases the temperature of a heat sensitive element. Heat detectors have
two main classifications of operation, “rate-of-rise” and “fixed temperature”. The heat
detector is used to help in the reduction of damaged property. It is triggered when
temperature increases. Fixed Temperature Heat Detector works when the heat exceeds a
pre-determined temperature, the bi-metal deflects and closes the contact, triggering the
fire signal.
Fixed Temperature Heat / Thermal Detectors can respond to:
 Fixed temperature limit
 Rapid rate of change of the temperature in the protected area
 Combination of these types of detection
Typical fixed temperature spot-type detectors contain a bimetallic switch element that
closes at a specified temperature limit. The switch is normally composed of two metals,
each having a different temperature coefficient of expansion.

As this bimetallic element heats the metal with higher coefficient of expansion, it causes the
switch to bend or curve, closing the switch; thus indicating an alarm condition.
Line type thermal detectors are cables that detect heat along their entire length. A line type
thermal detector may consist of two wires that are separated by an insulator.

After the heat builds to a certain level the insulation melts, allowing the wires to touch and
current to flow, initiating an alarm.

Heat smoke detectors

• This system is concerned with the detection of fire in an area and giving alarming alert to
take further action.
• The system generally consists of sensor, alarm and an alerting circuit.
• The main function is to rapidly extinguish the fire which may be due to short circuit or
other faults in the equipment.

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• The types of sensors used in purely based on the application.

Figure: Shows the ionization smoke detector.

 It consists of a small chamber with a battery connected to two wires. The wires are left
separated.
 To make electricity flow from one wire to the other, gap must be closed.
 The chamber contains a radioactive isotope.
 The radioactive isotope charges the air in the gap makes the electric current to flow.
 A current detector detects the current flow and normally the alarm will be quiet.
 If there is a smoke the charged ions in the air gap gets absorbed by the smoke and the
current flow gets reduced.
 When the current flow stops the alarm gets operated.
 Ionization-type smoke alarms have a small amount of radioactive material between two
electrically charged plates, which ionizes the air and causes current to flow between the
plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the
flow of current and activating the alarm.

Photo electric smoke detector:

 The photo electric smoke detector consists of a light source and receiver.
 In normal conditions the light is not received by the sensor.
 When there is high concentration of smoke in the air the smoke particles interrupt
the light beam and act like mirrors, reflecting the light so that the light is received by
the sensor and it triggers the alarm.

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 Figure: Photo electric smoke detector

3.5 FIRE ALARM SYSTEM

A fire alarm system has a number of devices working together to detect and warn
people through visual and audio appliances when smoke, fire, carbon monoxide or other
emergencies are present. These alarms may be activated automatically from smoke
detectors, and heat detectors or may also be activated via manual fire alarm activation
devices such as manual call points or pull stations. Alarms can be either motorized bells or
wall mountable sounders or horns. They can also be speaker strobes which sound an alarm,
followed by a voice evacuation message which warns people inside the building not to use
the elevators.
• Fire alarm control panel (FACP) OR fire alarm control unit (FACU); This
component, the hub of the system, monitors inputs and system integrity, controls outputs
and relays information.
• Primary power supply: Commonly the non-switched 120 or 240-volt alternating
current source supplied from a commercial power utility. In non-residential applications, a
branch circuit is dedicated to the fire alarm system and its constituents. "Dedicated branch
circuits" should not be confused with "Individual branch circuits" which supply energy to a
single appliance.
• Secondary (backup) power supplies: This component, commonly consisting of
sealed lead-acid storage batteries or other emergency sources including generators, is used
to supply energy in the event of a primary power failure. The batteries can be either inside
the bottom of the panel or inside a separate battery box installed near the panel.
• Initiating devices: These components act as inputs to the fire alarm control unit
and are either manually or automatically activated. Examples would be devices such as pull

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stations, heat detectors, and smoke detectors. Heat and smoke detectors have different
categories of both kinds. Some categories are beam, photoelectric, ionization, aspiration,
and duct.

 Notification appliances: This component uses energy supplied from the fire alarm
system or other stored energy source, to inform the proximate persons of the need
to take action, usually to evacuate. This is done by means of a pulsing incandescent
light, flashing strobe light, electromechanical horn, electronic horn, chime, bell,
speaker, or a combination of these devices. Strobes are either made of a xenon tube
(most common) or recently LEDs.
 Building safety interfaces: This interface allows the fire alarm system to control
aspects of the built environment and to prepare the building for fire, and to control
the spread of smoke fumes and fire by influencing air movement, lighting, process
control, human transport and exit
 Automatic fire detection and alarm systems are designed to warn building
occupants of a fire situation, they do not generally intervene in the fire growth
process except where interfaced with a fire suppression or other fire control system.

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These systems generally use smoke, heat or flame detectors to detect the outbreak of fire
and to alert building occupants and the fire service. Manual call points which allow an
occupant who discovers fire to raise the alarm may also be included in the system.
Single station residential smoke alarms, as installed in most homes, are the simplest system
for detecting a fire and warning the building occupants.
The time between the outbreak of fire and the commencement of firefighting is the single
most important factor in fire control and can be effectively reduced by having the system
monitored directly by the fire service.
Fire alarm systems must be heard by the building occupants in all parts of the building. To
achieve this, they are often connected to occupant evacuation warning and
intercommunication systems which sound a defined ‘beep - beep – beep’ throughout the
building when the detection system has been activated.
Sometimes these systems automatically close smoke and fire doors, operate flashing
warning lights, stop air-conditioning systems.

Types of Fire Extinguishers

Water and Foam

Water and Foam fire extinguishers extinguish the fire by
taking away the heat element of the fire triangle. Foam agents
also separate the oxygen element from the other elements.
Water extinguishers are for Class A fires only - they should not
be used on Class B or C fires. The discharge stream could
spread the flammable liquid in a Class B fire or could create a
shock hazard on a Class C fire.

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Carbon Dioxide
Carbon Dioxide fire extinguishers extinguish fire by taking
away the oxygen element of the fire triangle and also be
removing the heat with a very cold discharge.
Carbon dioxide can be used on Class B & C fires. They are
usually ineffective on Class A fires.

Dry Chemical
Dry Chemical fire extinguishers extinguish the fire primarily
by interrupting the chemical reaction of the fire triangle.
Today's most widely used type of fire extinguisher is the
multipurpose dry chemical that is effective on Class A, B, and C
fires. This agent also works by creating a barrier between
the oxygen element and the fuel element on Class A fires.
Ordinary dry chemical is for Class B & C fires only. It is
important to use the correct extinguisher for the type of fuel!
Using the incorrect agent can allow the fire to re-ignite after
apparently being extinguished succesfully.

Wet Chemical
Wet Chemical is a new agent that extinguishes the fire by
removing the heat of the fire triangle and prevents re-ignition
by creating a barrier between the oxygen and fuel elements.
Wet chemical of Class K extinguishers were developed for
modern, high efficiency deep fat fryers in commercial cooking
operations. Some may also be used on Class A fires in
commercial kitchens.

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Clean Agent
Halogenated or Clean Agent extinguishers include the halon
agents as well as the newer and less ozone depleting
halocarbon agents. They extinguish the fire by interrupting
the chemical reaction and/or removing heat from the fire
triangle.
Clean agent extinguishers are effective on Class A, B and C
fires. Smaller sized handheld extinguishers are not large
enough to obtain a 1A rating and may carry only a Class B and
C rating.

Dry Powder
Dry Powder extinguishers are similar to dry chemical except
that they extinguish the fire by separating the fuel from
the oxygen element or by removing the heat element of the
fire triangle.
However, dry powder extinguishers are for Class D or
combustible metal fires, only. They are ineffective on all other
classes of fires.

Water Mist
Water Mist extinguishers are a recent development that
extinguish the fire by taking away the heat element of the fire
triangle. They are an alternative to the clean agent
extinguishers where contamination is a concern.
Water mist extinguishers are primarily for Class A fires,
although they are safe for use on Class C fires as well.

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 Cartridge Operated Dry Chemical
Cartridge Operated Dry Chemical fire extinguishers
extinguish the fire primarily by interrupting the chemical
reaction of the fire triangle.
Like the stored pressure dry chemical extinguishers, the
multipurpose dry chemical is effective on Class A, B, and C
fires. This agent also works by creating a barrier between the
oxygen element and the fuel element on Class A fires.
Ordinary dry chemical is for Class B & C fires only. It is
important to use the correct extinguisher for the type of fuel!
Using the incorrect agent can allow the fire to re-ignite after
apparently being extinguished successfully.

Types of Extinguishers:
(a) Portable fire extinguishers can be divided into 5 categories according to the
extinguishing agent they contain:
(i) Water type extinguishers;
(ii) Foam extinguishers;
(iii)Dry powder extinguishers;
(iv)CO2 extinguishers; and
(v) Halon / Halon alternative type extinguishers.
(i) Water type extinguishers;
CONSTRUCTION
 These extinguishers are identical in appearance and construction to SODA
ACID type of extinguishers.
 The only exception is that instead of acid phial these extinguishers are provided
withC02 cartridge which is screwed to the cap of the extinguisher.
 The C02 cartridge has a sealing disc. The plunger has a piercing type nail attached to
it in such a way that it will puncture the sealing disc of CO2, cartridge
when pushed down.
There are two types of this extinguishers based on their position for operation.
- Upright type: These are provided with a dip pipe (siphon tube) attached to the oudet
point with or without a discharge hose pipe.

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- Invertible type : There is no dip pipe in this type of extinguishers and no discharge pipe is
provided
TYPES:
Water (gas cartridge) type extinguisher:

(i) In this pressure is released from a cartridge which is stored inside the body of
the extinguisher. The cartridge is pressurised with CO2 gas (to a pressure of
approx. 35 bars). On puncturing the cartridge, by striking the knob on the top,
the gas is released, and on coming out of the cartridge, it expels the water from
the body of the extinguisher. The expelled water comes out through the nozzle of
the extinguisher in the form of a small jet, which can be projected on to the fire.

(ii) The liquid capacity of the extinguisher, when filled to the specified level, is 9
litres.

(iii) The gas cartridge is screwed on to a holder which is fitted on to the cap of the
extinguisher. The maximum size of the gas cartridge is 60 g for a 9 litre
extinguisher.

(iv) On operation, the water jet should give an effective throw of not less than 6m for
a minimum period of 60 sec., and at least 95 % of water in the extinguisher
should be discharged.

Water (Stored Pressure) Extinguisher:

(i) The extinguisher is filled with water and dry air pressurized up to 10 bars. The air can
be supplied by compressed air cylinders or by certain type of pump.
(ii) Operation is performed by withdrawing the safety pin, depressing the valve lever and
directing the water jet by means of the hose.
(iii) As this type of extinguisher is permanently pressurised, it can only be opened for
inspection after discharged.
(iv) The normal capacity of this extinguisher is also 9 litres.

102
Figure: Water type extinguishers

103
(ii) DRY CHEMICAL POWDER EXTINGUISHER (Gas Cartridge Type)

The extinguisher is cylindrical in shape, made of solid drawn steel cylinder.

-It has a removable internal shell having gas pores and is protected with thin rubber rings
and rubber washer at its neck.
- The extinguisher is fitted with a siphon tube connected to the body with a small length of
high pressure flexible hose terminating into a squeeze grip type nozzle attached to its end.
- The nozzle is protected with a rubber cap against entry of moisture.
- The expellant is C02 gas in a cartridge which is sealed.
- The C02 gas cartrigde is screwed to the operating head which is' fixed with a piercing
mechanism.
- Dry chemical powder is filled in the body in quantitie's as per capacity.
(i) Various types of dry powder extinguishers are available in the market. Some of them are
filled with dry powders suitable for class B & C fires, and some suitable for class A B C fires.
(ii) Dry chemical powders have excellent fire knocking down properties. However, for
permanent extinguishment, more often, their use will have to be followed with discharge of
extinguishing media like foam or water.
(iii) Dry Powder Extinguisher (stored pressure type): The construction of this type of
extinguisher is Similar to that of water (stored pressure type). The pressure maintained
inside the extinguisher is about 10 bars. It is normally fitted with a pressure gauge and a
fan-shaped nozzle.
(iv) Dry Powder Extinguisher (Gas Cartridge) type: 4 sizes of extinguishers of this type are
available in the market - 1kg, 2kg, 5kg & 10 kg capacities. The sizes of the gas cartridges
also vary according to the extinguisher size. This type of extinguisher is quite common as a
requirement for various type of occupancies.

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 Figure: Dry Chemical powder type fire Extinguisher

(iii) Mechanical Foam extinguisher

The construction of this type of extinguisher is same as that of C02 Gas expelled type of
water type extinguisher. Instead of water, it contains foam compound mixed in water in the
ratio mentioned by the supplier.

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 Figure: Mechanical foam fire Extinguisher
Halon Extinguishers:
 In India Halon 1211 extinguishers are still available although they are- getting
phased out;
 The standard capacities of these extinguishers are 1.25 kg, 2.5 kg, 4 kg, 5 kg & 6.5 kg;
 They are quite effective on fires in electrical / electronic equipment;
They are getting replaced gradually by other extinguishers containing Halon alternatives

CO2 AND HALON SYSTEMS

 Carbon Dioxide constitutes a colourless, odorless and inert gas.

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  During usage, no damage is provoked (contrary to water or dry powder, the use of
which can cause important damage to equipment), it is a safe agent for the majority
of materials, non-hazardous for food, non-corrosive and nonconductive.
 It evaporates completely in a few seconds after the extinguishing procedure and
leaves no traces.
 Consequently, it can be used with no risk to various spaces containing electrical and
electronic devises, precious artworks, paintings or manuscripts, or to flammable
liquid warehouses, electric substations, kilns and ovens.
 The use of CO2 must be avoided to spaces where humans or animals are, because of
its provoking suffocating conditions. The three-dimension use of CO2 means that it
can extinguish fires in vertical and horizontal direction.
 Its fast diffusion constitutes the key to a successful extinguishment, since it can
penetrate through a break on a wall to all secret and remote places regardless of the
obstacles that may exist.
 Carbon Dioxide constitutes a stable commercial product with many other
applications and it is widely used all over the world. Permanent CO2 Systems can be
automatically or manually activated, while the activation can be effected
mechanically and pneumatically or electronically or from another combination of
the above depending on existing conditions.
 Carbon Dioxide is stored in normal temperature conditions in high pressure steel
cylinders. Pressure changes depending on the temperature (at 21o C it is about
59bar).
SYSTEM DESCRIPTION
 Single-Cylinder or multi-Cylinder systems can be applied according mainly to the
volume of the under protection areas.
 In multi-cylinder systems a Pilot Cylinder is used for activating the rest cylinders of
the system.
 The Pilot Cylinder can be activated automatically by use of detonator which gets
activated by a Detection System (Smoke & Rate-of-rise Heat Detectors and Control
Panel).
 It can also get activated manually by a Remote «System-Activation» Button. The
valve of Pilot Cylinder is connected through a High Pressure EPDM Flexible Hose to
the valve of the 1st cylinder of the system.
 When the detonator gets activated the valve of the Pilot Cylinder opens and the
propellant gas activates pneumatically at first the valve of the 1st cylinder of the
system and then the valves of the rest cylinders, which are connected through High
Pressure EPDM Flexible Hoses to each other.
 The Carbon Dioxide Gas of the Cylinders of the system is leaded to through High
Pressure EPDM Flexible Hoses to the Manifold System.
 The Manifold System consists of Manifold Pipes, Manifold Tee Pieces, Manifold
Blind Caps and Non-Return Valves.

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  At the end, the Carbon Dioxide Gas passes through the Pipe Network (Red Color
SCH40 or SCH80 tubes and 3.000lbs Spare Parts) and heads to the Local or Total
Flooding Nozzles from where it is discharged over the under-Protection Area.
 The Detection Equipment consists of Rate-of-rise Heat Detectors and Smoke
Detectors, which must be installed in pairs over the under Protection Area.
 A Three-Zone Fire Alarm-Detection Control Panel gets the signal from the detectors
incase of fire and an Optical-Sound Siren warns the user that the system will get
activated.
 The panel has the essential Time-Delay Option. When the time delay ends, the
control panel sends electrical current to the Detonator of the Pilot Cylinder which
explodes and the System gets activated.
 In parallel a STOP GAS Security Sign gets activated and warns the user not to enter
in the under-Protection Area.

HALON FIRE EXTINGUISHING SYSTEM

HALON
 Halon is a "Clean Agent." The National Fire Protection Association defines, a "Clean
Agent" as "an electrically non-conducting, volatile, or gaseous fire extinguishant that
does not leave a residue upon evaporation.
 Halon is a liquefied, compressed gas that stops the spread of fire by chemically
disrupting combustion. Halon 1211 (a liquid streaming agent) and Halon 1301 (a
gaseous flooding agent) leave no residue and are remarkably safe for human
exposure.
 Halon is rated for class "B" (flammable liquids) and "C" (electrical fires), but it is
also effective on class "A" (common combustibles) fires. Halon 1211 and Halon
1301 are low-toxicity, chemically stable compounds that, as long as they remain
contained in cylinders, are easily recyclable.

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  Halon is an extraordinarily effective fire extinguishing agent, even at low
concentrations.
 According to the Halon Alternative Research Corporation: "Three things must come
together at the same time to start a fire.
 The first ingredient is fuel (anything that can burn), the second is oxygen (normal
breathing air is ample) and the last is an ignition source (high heat can cause a fire
even without a spark or open flame).
 Traditionally, to stop a fire you need to remove one side of the triangle - the ignition,
the fuel or the oxygen. Halon adds a fourth dimension to fire fighting - breaking the
chain reaction.
 It stops the fuel, the ignition and the oxygen from dancing together by chemically
reacting with them."
 A key benefit of Halon, as a clean agent, is its ability to extinguish fire without the
production of residues that could damage the assets being protected.
 Halon has been used for fire and explosion protection throughout the 20th century,
and remains an integral part of the safety plans in many of today's manufacturing,
electronic and aviation companies.
 Halon protects computer and communication rooms throughout the electronics
industry; it has numerous military applications on ships, aircraft and tanks and
helps ensure safety on all commercial aircraft.
 Because Halon is a CFC, production of new Halon ceased in 1994. There is no cost
effective means of safely and effectively disposing of the Halon.
 Therefore, recycling and reusing the existing supply intelligently and responsibly to
protect lives and property is the wisest solution.

3.6 FIRE SAFETY STANDARDS

MAXIMUM TRAVEL DISTANCE

GROUP OF MAXIMUM TRAVEL DISTANCE MAXIMUM TRAVEL DISTANCE

OCCUPANCY (m) (m)
TYPE 1 & 2 CONSTRUCTION TYPE 3 & 4 CONSTRUCTION
RESIDENTIAL(A) 30 22.2

EDUCATIONAL(B) 30 22.5

INSTITUTIONAL(C) 30 22.5

ASSEMBLY(D) 30 30

BUSINESS (E) 30 30
MERCANTILE (F) 30 30

INDUSTRIAL (G) 45 30

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STORAGE (H) 30 30

HAZARDOUS (J) 22.5 30

DOOR WAYS
• No exit doorway shall be less than 1000 mm in width except assembly buildings
where door width shall be not less than 2000 mm.
• Doorways shall be not less than 2000 mm in height.
CORRIDORS AND PASSAGEWAYS
• Exit corridors and passageways shall be of width not less than the aggregate
required width of exit doorways leading from them in the direction of travel to the
exterior
WIDTH OF STAIRCASES
Residential buildings (dwellings) 1.0 m
b) Residential hotel buildings 1.5 m
c) Assembly buildings like auditorium, theatres and cinemas 2.0 m
d) Educational buildings up to 30 m in height 1.5 m
e) Institutional buildings like hospitals 2.0 m
f) All other buildings 1.5 m
WIDTH OF TREAD
• The minimum width of tread without nosing shall be 250 mm for internal staircase
of residential buildings.
• This shall be 300 mm for assembly, hotels, educational, institutional, business and
other buildings.
RISER
• The maximum height of riser shall be 190 mm for residential buildings and 150 mm
for other buildings and the number shall be limited to 15 per flight.
• Handrails shall be provided at a height of 1000 mm to be measured from the base of
the middle of the treads to the top of the handrails.

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AIR CONDITIONING
• Air -Conditioning systems circulating air to more than one floor area should be
provided with dampers designed to close automatically in case of fire and thereby
prevent spread of fire or smoke.
• Such a system should also be provided with automatic controls to stop fans in case
of fire.
• Escape routes like staircase, common corridors, lift lobbies; etc should not be used
as return air passage.
LOCATION OF FIRE DAMPERS
i) At the fire separation wall.
ii) Where ducts/passages enter the central vertical shaft.
iii) Where the ducts pass through floors.
iv) At the inlet of supply air duct and the return air duct of each compartment on every
floor.
The dampers shall operate automatically and shall simultaneously switch off the air-
handling fans. Manual operation facilities shall also be provided.

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 Figure: Fire Lift
a) To enable fire service personnel to reach the upper floors with the minimum delay, one
or more of the lifts shall be so designed so as to be available for the exclusive use of the
fireman in an emergency and be directly accessible to every dwelling/lettable floor space
on each floor.
b) The lift shall have a floor area of not less than 1.4 sq.mt. It shall have a loading capacity
of not less than 545 kg. (8 persons lift) with automatic closing doors.
c) The electric supply shall be on a separate service from electric supply mains in a building
and the cables run in a route safe from fire that is within a lift shaft. Lights and fans in the
elevator having wooden paneling or sheet steel construction shall be operated on 24-volt
supply.
d) In case of failure of normal electric supply, it shall automatically switch over to the
alternate supply. For apartment houses, this changeover of supply could be done through
manually operated changeover switch. Alternatively, the lift should be so wired that in case
of power failure, it comes down at the ground level and comes to stand still with door open.
Lift Enclosure/lift
General requirements shall be as follows
a) Walls of lift enclosures shall have a fire rating of two hours.
b) Lift motor room shall be located preferably on top of the shaft and separated from the
shaft by the floor of the room.
c) Landing door in lift enclosures shall have a fire resistance of not less than one hour.
d) The number of lifts in one lift bank shall not exceed four. A wall of two hours fire rating
shall separate individual shafts in a bank.
e) Lift car door shall have a fire resistance rating of 1 hour.
f) For buildings 15.0 m. and above in height, collapsible gates shall not be permitted for lifts
and solid doors with fire resistance of at least one hour shall be provided.
3.7 EGRESS SYSTEMS
A continuous and unobstructed path of travel from any point in a building or structure to a
public way that consists of the following three separate and distinct parts:
• Exit access: The travel path or area that leads from where a person is located to the
entrance to an exit.
• Exit: That portion of a means of egress that is separated by construction or
equipment from other areas of the building. Exit components include walls, floor, doors, or
other means that provide the protected path necessary for the occupants to proceed with

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reasonable safety to the exterior of the building. An exit may comprise vertical or
horizontal means of travel such as doorways, stairways, ramps, corridors, and
passageways. Types of permissible exits are doors leading directly outside or through a
protected passageway to the outside, smoke-proof towers, interior and outside stairs,
ramps, and escalators in existing buildings. Elevators are not accepted as exits.
• Exit discharge: That portion of a means of egress between the end of the exit and a
public way or other safe place.
Arrangement of means of egress
Location
At least two exits should be provided for all areas. These exits must be remotely located
from each other and arranged and constructed to minimize the possibility that more than
one may be blocked by any one fire or other emergency condition. For all new construction,
the “diagonal” rule requires exits to be separated by at least half of the diagonal distance of
the area served.
Number of means of egress
The minimum number of exits from any balcony, mezzanine, or other area must be two.
The minimum number of exits must be increased as follows:
• Occupant load of more than 49 but fewer than 500
• Occupant load of more than 500 but fewer than 1,000
• Occupant load of more than 1,000
• Exceptions are granted for existing buildings as provided by the specific occupancy
sections of various Building or Life Safety codes.

The minimum occupant load or number of people expected in a building at any time is
determined by dividing the gross or net floor area of a specific portion of the building by a
factor projected for each person. The factor projected for each person and the choice of
gross or net floor area varies with the type of occupancy. Specific requirements also exist
for fixed seating arrangements. These values are minimums and, if the occupancy level will
be higher, then additional existing capacity must be provided. In addition, the exit capacity
provided must meet the highest occupancy level expected and should not be designed to an
average.
Access to an exit (Maximum Travel Distance)
The codes specify the travel distance allowed to reach an exit. This is an extremely
important feature since a person could be exposed to fire or smoke conditions during the
time it takes to reach an exit. A general rule is the maximum travel distance to at least one

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exit shall not exceed 150 feet in buildings not sprinklered or exceed 200 feet in buildings
protected throughout by an approved supervised sprinkler system. Depending on the
occupancy, additional limitations on dead-end corridors and common pathways are
required in the travel distances to an exit.
Impediments to egress
In no case shall access to an exit be through kitchens, storerooms, restrooms, workrooms,
closets, bedrooms, or similar spaces, and exit access doors leading to exits must be
designed and arranged to be clearly recognizable. Hangings or draperies should not be
placed over exit doors or otherwise located so as to conceal or obscure any exits.
Discharge of an exit
Exits should discharge directly to the outside or equivalent safe area. NFPA highlights
circumstances where alternatives such as areas of refuge and exiting through lobby areas
can be used.
Means of egress components
Doors, stairs, ramps, and exit passageways are the most common means of egress
components. The code also permits fire escape, ladder, alternating tread devices, and slide
escapes in certain occupancies. Where safe exiting is not possible, the code also permits
“area of refuge” in specific cases.
Egress capacity
Egress capacity for each means of egress component is based on clear width of the
component and the type of occupancy. Egress capacity for an exit route is determined by
figuring egress capacity for each egress component and determining the most restrictive
component in the exit tour. In general, the egress capacity feet factor for stairs is 0.3 inches
per person and for ramps and level components is 0.2 inches per person.
Doors
In determining the egress width for a doorway for purposes of calculating capacity, only
the clear width of the doorway when the door is in the full open position should be
measured. Clear width is the unobstructed width of the door opening.
No door opening in the means of egress should be less than 32 inches clear width opening.
This width will allow passage of wheelchairs. For rooms with less than 70 square feet, the
width may be reduced to 28 inches provided that wheelchair use is not allowed in the
room. For existing structures, the minimum width is 28 inches. The maximum door leaf
width is 48 inches to facilitate use in an emergency.

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External Corridors
The minimum width of an exit access shall be 36 inches for new buildings and 28 inches for
existing. These minimums may be increased by individual occupancy chapter
requirements.
Limit displaying combustible wall hangings such as crafts and artwork in school on the
corridor walls. The corridor should not be used to store materials and equipment that will
restrict its use for safe exiting.
Stairs - dimensional criteria

Stairs must be of sufficient width so two persons can descend side by side to
maintain a reasonable rate of evacuation. Minimum width clear of all obstructions
must be 44 inches.
Stair treads must be wide enough to give good footing.. Stair treads must be
uniformly slip resistant and must be free of projections or lips that could trip stair
users.
Landings are required every 12 feet of stair height. Stairs that continue beyond the
level of exit discharge must be interrupted at the level of exit discharge by partitions
or other effective means.
The variance in tread and riser dimensions should not exceed 3/16 of an inch for
adjacent treads or risers of 3/8 of an inch from the largest to smallest tread/riser.
Handrails should be provided with stairs and shall not be more than 37 inches nor
less than 30 inches from the upper surface of the handrail to the surface of the tread,
in line with the face of the riser at the forward edge of the tread.
New handrails on open sides of stairs must have intermediate rails or an
ornamental pattern through, which a sphere of 4-inches in diameter cannot pass.
Any means of egress that are more than 30 inches above the floor or grade below
must be provided with guards to prevent falls over the open side.
Guards must be no less than 42 inches high and new railings should prevent a 4-inch
sphere from passing through.
Ramps
 The code permits use of inclined ramps. A new ramp in a public occupancy must
have a clear width of 44 inches and typically will have a 1-in-12 slope for a 6-inch or
greater rise.
 Steeper but shorter ramps are permitted. Maximum single rise for a ramp is limited
to 30 inches.
 The code also requires guards and handrails for ramps. Due to accessibility
considerations for the physically challenged, the ramp should be designed with
proper slope, width, and slip resistant surfaces.

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WINDOW EGRESS
 Although the height of a window above the floor surface can pose a challenge for
emergency escape, there is no set maximum sill height for bedroom, windows in the
NBC.
 Therefore, it is possible to install a window that satisfies the requirements, but
defeats the intent when the sill is so high that it cannot be reached for escape
purposes.
 It is recommended that the sills of windows intended for use as emergency escape
be not higher than 1.5 m (5 ft) above the floor.
 When it is unavoidable to have a sill height higher than 1.5 m, access to the window
should be improved by some means, such as built-in furniture installed below the
window.

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 UNIT 4
MECHANICAL TRANSPORTATION SYSTEMS IN BUILDINGS

SYLLABUS

 Lifts and escalators - types and applications.

 Round trip time for lifts.
 Design of lift lobby and vertical transportation core.
 Conveyors, travelators, dumb waiters. Standards for all.
 Latest technologies in vertical transport systems.
 Integration of lifts and escalators with building automation systems.

LIFTS OR ELEVATORS (TYPES & APPLICATIONS)

• In any multistory commercial or residential buildings, the vertical transportation
system typically composed of elevators and escalators.
• The elevators or lift is a type of vertical transport equipment that efficiently moves
people or goods between floors of a building.
• Elevators are generally powered by electric motors that drive traction cables or
counterweight systems like a host or to pump a hydraulic fluid to raise the cylindrical
piston in a hydraulic elevator.
Types of elevators:
Elevators used in modern buildings are of four types
(i) Hydraulic elevators
(ii) Geared traction elevators
(iii) Machine room-less traction elevators
(iv) Gearless traction elevators.
(i) HYDRAULIC ELEVATOR:
 Hydraulic elevators are commonly used in low rise buildings of two to five stories.
 They typically operate at a maximum speed of 150 feet per minute (Fpm)
 Hydraulic elevators are supported by a piston at the bottom of the elevator that pushes
the elevator up. The main elevator components are:
a. Machine drive system
b. Safety system

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Machine/ drive system:
 The machine/ drive system consists of piston or plunger. The cylinder shall be
constructed of steel pipe of sufficient thickness.
 The top of the cylinder shall be equipped with cylinder head with an internal guide ring
and self-adjusting packing.
 The plunger will be welded at the bottom of the cylinder to present the plunger from
leaving the cylinder.

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119
Hydraulic power unit:
The hydraulic power unit consists of:
 Tank
 Motor/ pump
 Valve
 Actuator
 Safety system

Tank:
 The tank shall have the sufficient capacity to provide an adequate reserve to prevent the
entrance of air or other gas into the system.
 An oil level monitoring device shall be provided for checking the oil level and the
minimum oil level mark shall be clearly indicated.
 The main function of the tank is to hold the liquid into the system.

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Motor/ pump:
 The main function of the motor/ pump in a hydraulic elevator is to constantly push the
liquid into the cylinder to lift the elevator.
 The pump or motor shall be a squirrel cage or slip ring induction motor and it shall run
with minimum noise and vibration.

Valve:
The main functions of valve are:
 Allows the liquid out of tank
 Keeps the pressure low when open
 Increases pressure when closed

The valve also has some additional features:

 Up and down acceleration and deceleration speed adjustment.
 Smooth stop at each landing shall be an inherent feature of the valve.
Actuator:
 Actuator is the device that transfers fluid or electrical energy to mechanical energy. The
actuator could be a piston because it moved up and down.

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Safety system
 The elevator shall be equipped with a final limit switch to cut off all power to the
elevator if the upper normal terminal stopping device fails.

MACHINE ROOM LESS TRACTION ELEVATORS:

 Geared traction elevators achieve their vertical motion from shaft. The gear in turn
rotates a ring gear been replaced with machine room less elevators.
 Geared traction is used for large capacity service and freight elevators.
 A drive pulley is attached to the ring gear. Steel cables run from the top of the elevator
car over the drive pulley to the top of the counterweight.
 As the drive pulley rotates, the elevator car is raised or lowered.
 The passenger elevators that have been provided with a geared traction have now been
replaced with machine room less elevators.
 Machine room less traction elevator use compact gearless traction hoist machine that
are mounted above the top floor.
 Manually operating ‘DOWN’ valve to lower elevator in an emergency.

(ii) GEARED TRACTION ELEVATORS:

 Geared traction elevators are used in mid-rise buildings of 5 to 15 stories and typically
operate at seeds of 200 to 500 fpm in passenger, service and freight elevator
applications.
 Typical speeds are 200 fpm, 350 fpm and 500 fpm.
 The primary difference between a geared traction hoist machine and a compact gearless
machine room less traction elevators is that the drive shear or pulley is directly
connected to motor shaft.

(iv) GEARLESS TRACTION ELEVATORS:

 Gearless traction elevators utilizing traditional full size gearless traction hoist machines
are used in high rise buildings of 12 to 100 stories and generally operates at the speed of
500 fpm to 18 fpm.
 The drive sheave of gearless hoist machine is directly connected to the motor shaft.
 Faster speeds are possible with traditional gearless elevators because of their large size
and they provide optimum performance.

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123
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TYPES OF LIFT BASED ON APPLICATIONS:

Passenger Lift: A lift designed for the transport of passengers.

Goods Lift: A lift designed primarily for the transport of goods but which may carry a lift
attendant or other person necessary for the unloading and loading of goods.

Service Lift (Dumb-Waiter) : A lift with a car which moves in guides in a vertical direction;
has net floor area of 1 m2, total inside height of 1.25 m; and capacity not exceeding 250 kg;
and is exclusively used for carrying materials and shall not carry any person.

Hospital Lift: A lift normally installed in a hospital/dispensary/clinic and designed to

accommodate one number bed/stretcher along its depth, with sufficient space around to
carry a minimum of three attendants in addition to the lift operator.

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DESIGN CRITERIA OF A LIFT OR ELEVATOR:
 In design of lift there are two basic considerations:
 The quality of service required
 The quality of service
 The above two determines the type of lift to be provided in a particular building.
 Quantity of service gives the passenger handling capacity of the lifts during the peak
hours.
 Quality of service is measured in terms of waiting time of passengers at various floors.
 The above things can be determined by proper study into the character of the building,
duration of peak hours, type and method of control, type of landing doors, tec.

The number of passengers and their capabilities:

 The load and speed for a lift required for a given building depends on the characteristics
of the building.
a) The number of floor to be served by the lift.
b) The population of each floor to be served
c) The maximum peak demand.

Population:
 The average population density can vary form one person per 4m2 to one person per

20m2
 The population density should be obtained from the building owner.
 If no indication is possible, 5m2 per person is normally assumed for office buildings.

QUALITY OF SERVICE:
The quality of service is measured by passage waiting time at the various floors.

Quality of service
20-25 seconds – Excellent
30-35 seconds – Good
35-40 seconds – Fair
45 seconds – Poor
Over 45 sec – Unsatisfied

Note: For residential buildings, longer interval should be permissible

CAPACITY:
 The minimum size of a car recommended for a single purpose building is that it should
have a capacity for a duty load of 884kg
 For larger buildings, cars with capacities upto 2040kg are recommended according to
the requirement.
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SPEED:
 It is dependent upon the quality of service desired. There is no set formula for
calculating the speed. The general recommendations are
No. of floors Speed
4 to 5 0.5 - 0.75 m/s
6 to 12 0.75 – 1.5m/s
13 to 20 Above 1.5 m/s

DETERMINATION OF CAPACITY:
During the morning peak hour,
The handling capacity is calculated by the formula
H = 300 x Q x 100
TxP

Where,
H Handling capacity as the percentage of the peak population handling during 5
minutes period
Q Average number of passengers carried in a car
T Waiting time
P Total population to be handled during peak morning period
The value of Q depends on the dimensions of the car.
It is noted that the car is not loaded always to its maximum capacity during each tip and
therefore for calculating H, the value of Q is taken as 80% of the maximum carrying
capacity of the car.
The waiting interval formula is:
T = RTT
N
N Number of lifts
RTT Round Trip Time (it is the average time required by each lift in taking load of
passengers from ground floor, discharging them in various upper floors and carrying back
to ground floor to take fresh passengers for next trip)
RTT is the sum of the time required in the following process:
a) Entry of passengers on the ground floor
b) Exit of the passengers on each floor for discharge
c) Door closing time on each start operation
d) Door opening time on each discharging operation
e) Acceleration periods
f) Stopping periods
g) Periods of full rated speeds between stops while going up
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 h) Periods of full rated speeds between shops while going down.

 The RTT (Round Trip Time) can be decreased by Increasing the speed of the lift
 By improving the design of lift related to opening and closing of the car, acceleration and
deceleration also the RTT can be reduced.
 The most important factor is shortening the time consumed between the entry and exit
of passengers with proper design of car door width.
 The utilization of centre opening doors also favors the door opening and closing time
periods. The centre opening door is much faster than the side opening type.

Lift Pits

 A lift pit shall be provided at the bottom of every lift. Pits shall be maintained in a
dry and clean condition. Where necessary, provision shall be made for
permanent drainage and where the pit depth exceeds 1.5 m suitable descending
arrangement shall be provided to reach the lift pit. And a suitable fixed ladder
or other descending facility in the form of permanent brackets grouted in the wall
extending to a height of 0.75 m above the lowest floor level shall be provided.
 A light point with a switch shall also be provided for facility of maintenance and
repair work.
Machine Room Details

 The lift machine, controller and all other apparatus and equipment of a lift
installation, accepting such apparatus and equipment as function in the lift well or
other positions, shall be placed in the machine room which shall be adequately
lighted and rendered fire-proof and weather-proof.
 The machine room shall have sufficient floor area as well as permit free access to all
parts of the machines and equipment located therein for purposes of
inspection, maintenance or repair. The room shall be kept closed, except to
those who are concerned with the operation and maintenance of the equipment.
When the electrical voltage exceeds 220/230 V ac, a danger notice plate shall be
displayed permanently on the outside of the door or near the machinery.
 Where standby generator is provided, it is necessary to connect fireman lift to
the standby generator. Depending upon the capacity of the standby generator one or
more other lifts may also be connected to the supply.
 The height of the machine room shall be sufficient to allow any portion of
equipment to be accessible and removable for repair and replacement and shall be
not less than 2 m clear from the floor or the platform of machine whichever is
higher.

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129
ESCALATORS (TYPES &APPLICATIONS)
Escalators are moving stairs used to convey people between floor levels. They are
usually arranged in pairs for opposing directional travel to transport up to 12 000 persons
per hour between them. The maximum carrying capacity depends on the step width and
conveyor speed. Standard steps widths are 600, 800 and 1000 mm, with speeds of 0.5 and
0.65 m/s. Control gear is less complex than that required for lifts as the motor runs
continuously with less load variations.

Landing platform:
 The platforms contain a floor plate and a comb plate.
 The floor plate provides space for the passengers to stand before they step on to the moving
stairs.
 The comb plate is the space between the stationary floor plate and the moving step. It is so
named because its edge has a series of cleats that resemble the teeth of a comb.
Major components of landing platforms are
a. Comb plate
b. Access cover
c. Comb lights

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Access cover:
 The access cover is used to access the pit area for inspection, maintenance and repairs, the
lower landing access cover plates provide access to the reversing station and step removal.
 The upper landing access cover may provide access to the driving machine and controller.
Comb lights:
 The comb lights are safety devices used to illuminate the area where the steps and comb
segments meet.
 They are provided at the upper and lower landing above the comb segments.
 The lights will be on always even if the escalator is not working.
Truss:
 The escalator truss is the structural frame of the escalator. It consists of three sections.
a. Lower section
b. Inclined section
c. Upper section
 It is a hollow metal structure that bridges the lower and upper landings.
 The ends of the trusses are attached to the top and bottom landing platforms through steel
or concrete supports.
 The front and back edges of the steps are each connected to two wheels.
 The rear (back) wheels are set further apart to fit into the back track and front wheels have
shorter axles to fit into the narrow front track.
Handrail:
 The handrail provides a convenient handhold for the passengers while they are riding on
the escalator.
Balustrade:
 The balustrade consists of the handrail and the exterior supporting structure of the
escalator.
 It is the escalator exterior components extending above the step and it supports the
handrail.
Steps:
 The steps are made of aluminium or steel.
 The steps are linked by a continuous metal chain that forms a closed loop.
Tracks:

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  The track system is built into the truss to guide the step chain, which continuously pulls the
steps from the bottom platform and books to the top in an endless loop
 There are actually two tracks:
a) One for the front wheel of the steps
b) One for the back wheel of the steps
 The track assembly is bolted but not welded on the truss for easy removal.
 The tracks are used to guide step wheels and step chains in their travel around the escalator
truss.
Newel:
 Newel is the balustrade termination at the upper and lower landing of the escalator in a
semi-circle shape.
 It contains the following switches.
a. Emergency stop
b. On / Off
c. Up / down directional indicator lighting
Emergency stop button:
 Emergency stop button is located at the newel so that anyone can stop the escalator if there
is a need.
 When the button is pressed, power to the electrical drive motor is shutoff and the escalator
brake is applied.
Key operated switches:
 Located on each newel and they are used to control the “ON” and “OFF” operation and the
direction of escalator travels.

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TYPES OF ESCALATORS
Escalator arrangements or configuration of escalators:
1. Single unit:
The single unit is used to connect two levels. It is suitable for buildings with passenger
traffic flow mainly in one direction. Flexible adjustment to traffic flow.
Example: Upward direction in the morning and downward direction in the evening is

possible.

2. Double unit:
This arrangement is used in the places in which persons travel in two opposite directions.

3.
Crissc
ross

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arrangement (Two way traffic)
 This type of installation is the one used more frequently as it allows customer to travel
quickly to the upper floors without any waiting time.
 Commonly used in big departmental stores and office buildings.

4. Single unit continuous (One way traffic)

The escalator that connects subsequent levels in one-way traffic is used mainly in small
department stores and commercial buildings.

5. Single unit non-continuous (One way traffic)

 The escalator that connects subsequent levels in a non-continuous one-way traffic is
not too comfortable for persons who want travel quickly through subsequent floors.
 However, this operation arrangement is attractive for owners of department stores
because it encourages visiting around. The escalator is used mainly in small
departmental stores and in commercial centres.

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Parallel arrangement:
 This arrangement is mainly used in departmental stores and public buildings with heavy
traffic.
 When there are three or more escalators or moving walks, it should be possible to
reverse the direction of travel depending on traffic flow.

6. Double non-continuous (Two way traffic)

 The escalator that connects subsequent levels in a non-continuous two way traffic is
used in office buildings and public transport buildings.
 The direction can be changed depending on the time.

7. Crisscross arrangement (Two way traffic)

This arrangement is used mainly in big department stores, office buildings and public
transport where efficient travel of person between floors is of high importance.

ESCALATORS AND HORIZONTAL MOVING WALKWAYS (DESIGN):

(i) An escalator is a moving staircase – a conveyor transport device for carrying people
between floors of a building.

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(ii) Escalators are powered by constant speed AC motors and more approximately at a
speed of (0.30 – 0.65 m) per second
(iii) Modern escalators have steel steps that move on a system of tracks in a continuous
loop.
(iv) Direction of movement up or down can be permanently the same or be controlled by
personnel according to the time of the day.

Benefits of escalators:
(i) They have the capacity to move large number of people.
(ii) They have no waiting interval
(iii) They can help in controlling traffic flow of people.
(iv) They can be weather proofed for outdoor use.

INCLINATION OF ESCALATORS AND MOVING WALKWAYS:

Escalators Moving walkways

 Inclination of 300 and 350 are the  Inclination of 100, 110, 120 are the
common international standards for common international standards for
escalators inclined moving walkways
 30 inclination:
0  100 inclination provides the most
This inclination provides the highest comfortable ride.
travelling comfort and maximum safety  Horizontal moving walkways can
for the user. generally be provided for inclinations
 350 inclination: between 00 and 60
The 350 inclination is the most efficient
solution as it requires less space and can
be implemented more cost effectively

Escalator capacity:
 Most escalators are designed with 1000mm wide steps which allows passengers to
move comfortably when carrying luggage and shopping bags.
 600mm and 800mm wide are also available and generally used in low traffic areas.
 Speed ranges between 0.5 to 0.65 m/s
 For a speed of 0.5 m/s the theoretical capacity is
600mm step width – 4500 persons/ hour
800mm step width – 6750 persons/ hour
1000mm step width – 9000 persons/ hour
The following formula can be used to calculate the capacity,
N= 3600 x P x V x COS θ
L
Where, N Number of persons moved/ hour
P Number of persons/ step

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 V Escalator speed (m/s)
L Length of step (m)
θ Angle of inclination
Example:
An escalator of 300 incline, one passenger/ step, a speed of 0.5 m/s and 400mm step length
N = 3600 x 1 x 0.5 x COS 300
0.4
= 3897 number of persons moved per hour

MOVING WALKWAYS (step width)

 For inclined moving walkway (100 to 120) pallets are available in width of 800 and
1000mm
 The most popular width is 1000mm. the moving walkways with this pallet width are
also suitable for transporting, shopping. They are mainly used in shopping centres and
railway stations.
 For horizontal moving walks with an inclination of (00 to 60) pallets are available in
width of 800mm, 1000mm, 1200mm and 1400mm.
 In airports, 1200 or 1400mm wide moving walks are to be installed in a continuous
arrangement. The same step and pallet width should be selected for all units.

OPTIMAL SPEED FOR ESCALATORS AND MOVING WALKWAYS:

The speed not only has a considerable impact on the potential transportation capacity of
escalators and moving walkways but also it influences the space requirements.
0.5 m/s 0.6 m/s 0.75 m/s
 This is the standard speed  Used in railway stations  Although speeds upto
of escalator and moving  Longer horizontal runs 0.75 m/s (escalators) and
walkways in commercial are required to ensure upto 0.9 m/s (moving
sector. safety of the escalator/ walkways) are possible,
 Safety, minimum space moving walkways. there is increased danger
requirement makes this of children or elder
speed the worldwide people falling in the
standards. landing area

Transportation of disabled persons and baby carriages:

 Escalators and moving walkways are not suitable for transporting wheel chairs and
baby carriages.
 It is recommended to post an alert near the escalator and moving walkways.

Free space:
 To ensure safety use of the escalators and moving walkways, sufficiently larger free
spaces must be provided at the upper and lower landings.
 For moving walkways the free spaces should have a length of atleast 5m.

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Balustrade height:
 Balustrades are available in heights of 900, 1000 and 1100mm. the advantage of 900mm
balustrade is that even small children can easily reach the handrail.
 For greater fall heights balustrade with a continuous height of 1000mm is
recommended.

Overhead clearance:
 The free overhead clearance at every point along the step/ pallet must be atleast 2.3m.

MOVING WALKWAYS OR TRAVELATORS

Travelators also known as autowalks, passenger conveyors and moving pavements. They
provide horizontal conveyance for people, luggage trolleys, wheelchairs and small vehicles
for distances up to about 300 metres. Slight inclines of up to 12 degree are also possible.
Applications range from retail, commercial and store environments to exhibition centres,
railway and airport terminals. Speeds range between 0.5 and 0.75 m/s, any faster would
prove difficult for entry and exit.
A slow moving conveyor mechanism that transports people across a horizontal or inclined
plane over a short to medium distance.
•can be used by standing or walking on them. They are often installed in pairs, one for each
direction.
•are built in one of two basic styles:
Pallet type — a continuous series of flat metal plates join together to form a walkway. Most
have a metal surface.
Moving belt — these are generally built with mesh metal belts or rubber walking surfaces
over metal rollers.
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High speed walkways
•Using the high-speed walkway is like using any other moving walkway, except that for
safety there are special procedures to follow when joining or leaving.
•riders must have at least one hand free to hold the handrail, those carrying bags, shopping,
etc., or must use the ordinary walkway nearby.
•Riders stand still with both feet on the metal rollers and let it pull them so that they glide
over the rollers.
Inclined moving walkways
•is used to move people to another floor so that people can take along their suitcase trolley
or shopping cart, or baby carriage.
•The carts have either a brake that is automatically applied, strong magnets in the wheels
to stay adhered to the floor, or specially designed wheels that secure the cart within the
grooves of the ramp, so that wheeled items travel alongside the riders and do not slip away.

Detailing for comfort, convenience of users

● Directional indication of location of the lift lobby for people unfamiliar with the building.
● Call buttons at landings and in the car positioned for ease of use with unambiguous definition for
up and down directions.
● Call buttons to be at a level appropriate for use by people with disabilities and small children.
● Call display/car location display at landings to be favorably positioned for a group of people to
watch the position of all cars and for them to move efficiently to the first car arriving.

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● Call lights and indicators with an audible facility to show which car is first available and in which
direction it is travelling.
● Lobby space of sufficient area to avoid congestion by lift users and general pedestrian traffic in
the vicinity.

ROUND TRIP TIME FOR LIFTS

RTT Round Trip Time (it is the average time required by each lift in taking load of
passengers from ground floor, discharging them in various upper floors and carrying back
to ground floor to take fresh passengers for next trip)
RTT is the sum of the time required in the following process:
i) Entry of passengers on the ground floor
j) Exit of the passengers on each floor for discharge
k) Door closing time on each start operation
l) Door opening time on each discharging operation
m) Acceleration periods
n) Stopping periods
o) Periods of full rated speeds between stops while going up
p) Periods of full rated speeds between shops while going down.

 The RTT (Round Trip Time) can be decreased by Increasing the speed of the lift
 By improving the design of lift related to opening and closing of the car, acceleration and
deceleration also the RTT can be reduced.
 The most important factor is shortening the time consumed between the entry and exit
of passengers with proper design of car door width.
 The utilization of centre opening doors also favors the door opening and closing time
periods. The centre opening door is much faster than the side opening type.

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DESIGN OF LIFT LOBBY AND VERTICAL TRANSPORTATION CORE

LAYOUT OF BANKS OF ELEVATORS

Figure: Four Car Arrangement

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Figure: Four Car Arrangement

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Figure: Four Car Arrangement

143
Figure: Six Car Arrangement

Figure: Six Car Arrangement

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 Figure: Six Car Arrangement

Figure: Eight Car Arrangement

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A thorough investigation shall be carried out for assessing the most suitable location for
lifts while planning the building. It shall take into account future expansions, if any.

The lifts shall be easily accessible from all entrances to the building. For maximum
efficiency, they shall be grouped near the centre of the building. Walking distance from the
lift to the farthest office or suite shall not exceed 60 m.

Arrangement of Lifts

(a) When more than one lifts are installed in a group, they shall be arranged side by side or
in two rows facing each other. Separation of lifts in the group shall be avoided.

(b) The lift lobby in front of lifts shall be wide enough to allow sufficient space for waiting
passengers and proper vision of hall button and hall lanterns. Above Figures give
acceptable arrangements of lifts in a group with acceptable space for waiting passengers.
More space shall be allowed in front of the lifts in the main floor than in the upper floors.

(c) It is preferable that the lift lobby is not used as a thoroughfare, but when absolutely
needed the lift lobby shall be wider enough to take into account of the space for people who
are moving.

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147
PLANNING AND LOCATING SERVICE CORES IN BUILDINGS
To function efficiently and to provide access for the elderly and disabled, modern
offices and public buildings are provided with suitably designed lift installations. Planning
(as with all services) should commence early in the design programme. Priority must be
given to locating lifts centrally within a building to minimise horizontal travel distance.
Consideration must also be given to position, relative to entrances and stairs. Where the
building size justifies several passenger lifts, they should be grouped together. In large
buildings it is usual to provide a group of lifts near the main entrance and single lifts at the
ends of the building. The lift lobby must be wide enough to allow pedestrian traffic to
circulate and pass through the lift area without causing congestion. For tall buildings in
excess of 15 storeys, high speed express lifts may be used which by-pass the lower floors.

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 Core is one of the most important structural and functional elements of the high rise
building. The core of a building is the area reserved for elevators, stairs, mechanical equipments
and the vertical shafts that are necessary for ducts, pipes and wires. Its wall are also the most
common location for the vertical wind bracing. The placement of the service core stems from four
generic types which are : - Central core - Split core - End core - Atrium core

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CONVEYORS

Conveyor Systems are mechanical devices or assemblies that transport material with
minimal effort. While there are many different kinds of conveyor systems, they usually
consist of a frame that supports either rollers, wheels, or a belt, upon which materials move
from one place to another. They may be powered by a motor, by gravity, or manually.
These material handling systems come in many different varieties to suit the different
products or materials that need to be transported.

Important Conveyor Systems Specifications

Load Capacity per Unit Length

Manufacturers will offer this attribute in cases where the conveyor will be built to a custom
length to permit users to determine loading margins.

Maximum Load Capacity

Associated with Load Capacity per Unit Length, this value can be stated for fixed length,
purpose-built conveyors. This can also be known as flow rate.

Conveyor Belt System Speed/Rated Speed

Belt conveyors are typically rated in terms of belt speed in ft/min. while powered roller
conveyors described the linear velocity in similar units to a package, carton, etc. moving
over the powered rollers. Rated speed applies to apron/slat conveyors and drag/chain/tow
conveyors as well.

Throughput

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Throughput measures the capacity of conveyors that handle powdered materials and
similar bulk products. It is often given as a volume per unit time, for instance, as cubic feet
per minute. This attribute applies to bucket, pneumatic/vacuum, screw, vibrating, and
walking beam conveyors.

Frame Configuration

Frame configuration refers to the shape of the conveyor frame. Frames can be straight,
curved, z-frames, or other shapes.

Drive Location

Drives can be located in different places on conveyor systems. A head or end drive is found
on the discharge side of the conveyor and is the most common type. Center drives are not
always at the actual center of the conveyor, but somewhere along its length, and are
mounted underneath the system. They’re used for reversing the direction of a conveyor.

Types of Conveyors

Belt

Roller

Powered Roller

Slat/Apron

Ball Transfer

Magnetic

Bucket

Chute

Drag/Chain/Tow

Overhead

Pneumatic/Vacuum

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Screw/Auger

Vertical

Vibrating

Walking Beam

Wheel

Belt

Belt Conveyors are material handling systems that use continuous belts to convey products
or material. The belt is extended in an endless loop between two end-pulleys. Usually, one
or both ends have a roll underneath. The conveyor belting is supported by either a metal
slider pan for light loads where no friction would be applied to the belt to cause drag or on
rollers. Power is provided by motors that use either variable or constant speed reduction
gears.

The belts themselves can be made from numerous materials, which should correspond to
the conditions under which the belt will be operating. Common conveyor belting materials
include rubber, plastic, leather, fabric, and metal. Transporting a heavier load means a
thicker and stronger construction of conveyor belting material is required. Belt conveyors
are typically powered and can be operated at various speeds depending on the throughput
required. The conveyors can be operated horizontally or can be inclined as well. Belt
conveyors can be troughed for bulk or large materials.

Roller Conveyor Systems

Roller Conveyors use parallel rollers mounted in frames to convey product either by
gravity or manually. Key specifications include the roller diameter and axle center
dimensions. Roller conveyors are used primarily in material handling applications such as
on loading docks, for baggage handling, or on assembly lines among many others. The
rollers are not powered and use gravity, if inclined, to move the product, or manually if
mounted horizontally. The conveyors can be straight or curved depending on the
application and available floor space.

Powered Roller

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Powered Roller Conveyors use powered rollers mounted in frames to convey products. Key
specifications include the drive type, roller diameter and material, and the axle center
dimension. Powered roller conveyors are used primarily in material handling applications
that require the powered conveyance of the product. Various drive types include belts,
chains/sprockets, and motorized rollers. Some of the uses of powered roller conveyors are
food handling, steelmaking and, packaging.

Slat Belt Conveyor/Apron

Apron/Slat Conveyors use slats or plates made of steel, wood, or other materials typically
mounted on roller chains to convey product. The slats are not interlocked or overlapping.
Apron/slat conveyors are used primarily in material handling applications for moving
large, heavy objects including crates, drums, or pallets in heavy-industry settings such as
foundries and steel mills. The use of slats in heavy duty use cases prolongs the service life
of the conveyor over other conveyor types that employ belts, which would wear out
quicker under the exposure to heavy loads. These conveyor systems are usually powered
and come in many sizes and load capacities.

Ball Transfer Conveyor

Ball Transfer tables or conveyors use a series of mounted ball casters to allow for
unpowered, multi-directional conveyance of the product. Key specifications include the ball
material and size. Ball transfer conveyors are used in material handling applications such
as assembly lines and packaging lines, among others. When positioned where multiple
conveyor lines meet, they are used to transfer products from one line to another and are
often used in sorting systems. Many sizes and load carrying capacities are available. Ball
transfer conveyors are not powered and rely on external forces to move the product along
the conveyor.

Magnetic

Magnetic Conveyors use moving magnets mounted beneath stationary plates, tables, or
other kinds of non-magnetic slider beds, to move magnetic (ferrous) materials, often in the
form of machining scrap. Magnetic conveyors are commonly used as chip conveyors to
remove ferrous chips from machining centers. Systems can be configured to use horizontal
motion, vertical motion, or combinations. They can be beltless or may use a conveying belt
instead of a slider bed. Underneath the conveying belt, a rail containing an electromagnet is

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used to attract ferrous materials to the belt. Because of the magnetic attraction of the
product to the conveyor, these systems can also be used upside down.

Bucket

Bucket Conveyors or bucket elevators use multi-sided containers attached to cables, belts,
or chains to convey products or materials. The containers remain upright along the system
and are tipped to release material. Bucket conveyors are used in applications such as parts,
bulk material, or food processing and handling. The conveyed material can be in liquid
form or dry such as sludge, sand, manure, sugar, and grain. The systems can be used
horizontally or can be inclined or vertical to change levels of the delivered products. Many
sizes and load carrying capacities are available depending on the application.

Chute

Chute or Trough Conveyors are material handling systems that use gravity to convey
product along smooth surfaces from one level to another. Key specifications include the
chute material and the physical dimensions such as length and chute width. Chute
conveyors are used for scrap handling, packaging, postal service package or mail handling,
etc. Chutes are designed to have a low coefficient of dynamic friction, allowing the product
or material to slide easily, and can be straight or curved depending on the needs of the
application.

Chain/Tow/Drag Line Conveyor

Drag/Chain/Tow Conveyors use mechanical devices attached to moving members, usually

chains or cables, to drag or tow products. Drag conveyors are used for moving bulk
materials in bins, flights, or other attachments and can have multiple discharge or loading
points. Tubular drag conveyors use a fully enclosed system of chains to convey product in
any direction. Chain conveyors use a chain, or multiple chains to move pallets or other
hard-to-convey products. Tow conveyors use a towline such as cables or chains, usually in
the floor or just above it, to tow product directly or to tow wheeled carts or dollies.

Overhead

Overhead Conveyors are mounted from ceilings that use trolleys or carriers moved by
chains, cables, or similar connections. Overhead conveyors are primarily used in material
handling applications where the product needs to be hung, such as dry-cleaning garment

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lines, paint lines, or parts handling systems, or for cooling and curing. Various types of
overhead conveyor systems configurations are available including electric track, monorail,
trolley, as well as inclined or ramped. Depending on the application, the load-carrying
capacity may be critical. Most overhead conveyors systems are powered and controlled,
while others are hand-operated conveyor belts.

Pneumatic/Vacuum

Pneumatic/Vacuum Conveyors use air pressure or vacuum to transport materials or items

in or through closed tubes or ducts or along surfaces. Pneumatic/vacuum conveyors are
used primarily in materials handling applications such as dust collection, paper handling,
ticket delivery, etc. and in processes such as chemical, mineral, scrap, and food. Materials
for the conveyors can be metallic or non-metallic depending on the media being conveyed.
Various sizes are available depending on the load and throughput requirements.

Horizontal Belt Conveyors

A conveyor system is a mechanical handling equipment that moves materials from

one location to another. Conveyors are especially useful in applications involving the
transportation of heavy or bulky materials. Conveyor systems allow quick and efficient
transportation for a wide variety of materials, which make them very popular in
the material handling and packaging industries.

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DUMB WAITER
A dumbwaiter elevator is a very small freight elevator that’s intended to carry objects
instead of people. Commercially, you’ll often find them in hospitals, restaurants, hotels, and
schools. They’re now also a popular addition to the home, with dumbwaiter installation
making it easier to move things upstairs and downstairs.

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157
LATEST INNOVATIONS
The Compass system speed the passenger on his/her way with efficient, personalized
service. It helps them avoid the crowds, skip stops, and get where they are going without
the extra wait. The system ensures an easy trip for every passenger, such as featuring
standard Braille keypads, voice instructions and floor announcements, interactive
directories, and additional time to enter and exit the elevator for passengers with
disabilities. It also has the ability to designate specific elevators for deliveries or other
building needs. Otis Compass can be applied in multiple elevator banks and either single or
double deck elevators.

In 2013, Otis launched a new generation of the Compass destination dispatch system called
CompassPlus. It replaces the traditional up and down push-button elevator system with an
array of customizable touch-capable fixtures in the elevator lobbies. A passenger enters his
or her destination from the hallway, rather than from inside the elevator, using a keypad or

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touchscreen device; receives an elevator assignment, which is shown on the touchscreen;
follows directions to the assigned elevator; and proceeds to his or her destination

INTEGRATION OF LIFTS AND ESCALATORS WITH BUILDING

AUTOMATION SYSTEMS.

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 UNIT
160
5
INTEGRATION OF SERVICES INTO ARCHITECTURAL DESIGN
Principles of grouping and integrating of horizontal and vertical distribution of all
services in a multi- storeyed building/ large building. (ELECTRICAL)

 In large buildings the type of distribution depends on the building type, dimension,
the length of supply cables, and the loads.
 The distribution system can be divided in to:
The vertical supply system (rising mains).
The horizontal supply (distribution at each floor level).
 In most cases a high voltage supply and transformer substation is required.
Normally HV switchgear and substation transformers are installed at ground floor
(or basement ).
 However, often there are appliances with large power demand installed on the top
floors (converters and motors for lifts, air conditioning equipment and electric
kitchens).
 As it is desirable to brining the high voltage supply as close as possible to the load
centers, transformers are installed at the top floor, or if required, additional ones
are installed on one of the intermediate floors.
 In such cases transformers with non-inflammable insulation and cooling are used.
The arrangement of the rising mains depends on the size and shape of the building
and suitable size of shafts for installing cables and bus ducts must be provided in
coordination with the building architect.
 The vertical supply system are implemented in several ways, some of which are :
Single Rising main:

Applications :-

 Where high supply security is not important.

Advantages :-

 a) The different loads of individual floors are balanced out.

 b) Only a small main L.V board is required.
 c) Simple in construction and operation.
Disadvantages :-

 Low supply security (a fault in the rising mains effect all floors).

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Grouped supply

Applications :-

High rise building with high load concentration.

Advantages :-

 Easier mounting.
 Smaller size for rising mains.

Disadvantages :-

162
 A fault in any rising mains effect several floors (relatively low security).
 Loads are balanced only within each group.
 Larger power distribution board.

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Applications :-

 In high rise buildings were stories are let separately (metering is at central point at
ground floor).
Advantages :-

a) Smaller size of cables can be used (easy installation).

b) In the case of a fault in arising main, only one story is effected.

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Disadvantages:-

a) Different loading of the individual floors can not be balanced out.

b) The rising main must be rated for the peak load of each floor.

c) Uneconomical – large number of cables and the size of the rising main shaft is quite
large.

d) Large low voltage distribution board with numerous circuits.

Principles of grouping and integrating of horizontal and vertical distribution of all services
in a multi- storeyed building/ large building( VERTICAL TRANSPORTATION )

 Several numbers of passenger elevators are usually required in most buildings

in order to cope with the traffic density and choosing the right elevator
configuration can be a critical decision.
 In the interest of economy as well as even utilization, every effort should be
made to achieve a layout where elevators can be combined into a group with
an appropriate group control system.
 For Office buildings, one elevator group can generally serve all floors in
buildings up to 15 to 20 floors depending on the building population. When
there are more than 20 floors, single grouping is not efficient and would
normally result in long travel times and congestion in the elevator lobbies
during peak periods.
 The passenger elevators for buildings with more than 20 floors (up to about
35 floors), should be separated into low rise service and high rise service.
Elevators in the low rise group should serve the lower half of the building while
elevators in the high rise group travel directly from the main stop to the
upper half of the building.
 Such a zoning arrangement would cut down on the number of stops per
elevator, thus reducing round trip times and increasing the handling capacity of
each group. Furthermore, the low rise group would then not require high speed
elevators, thus providing an economical solution as well as more efficient
distribution of the building population during peak periods.
 The same zoning principle is also applied in buildings with even greater
number of floors where 3 or more elevator zones can and should be deployed.
Efficiency of the passenger elevator service in a building is usually measured
by the "5-minute handling capacity" and the "average destination time" which
can be defined as the waiting time in the elevator lobby plus the travelling
time inside the elevator. As a guide, the following are the guidelines for 5-
minute handling capacity for different types of buildings:

165
Residential Apartments / buildings: 7 to 9%.

Premises without specific distribution traffic, such as mixed-tenancy Office buildings with
different working hours: 12 to 16%.

Premises with excessive distribution traffic, such as single tenancy Office buildings
with the same working hours: 16 to 25%.

Planning Requirements

General Considerations

The design team will need to consider a whole spectrum of diverse factors, for example:

• The arrival rate of passengers into the building

- How close are rail and bus stations?

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- Are the parking facilities self-contained or adjacent?

- How many building entrances are there?

- What is the mail distribution system in the building?

• The investment interests of the developer

- Is the building speculative?

- Is the owner a landlord or an occupant?

• The quality of the adjacent buildings

- Will new or existing tenants be attracted?

- Are there high-quality tenants looking to trade up or down in the neighboring area?

- Are the elevators in the adjacent buildings doing their job efficiently?

There could be over a hundred different possible configurations for your building's
elevators, and each will have its advantages and disadvantages compared with the
others. The professional team working to find that optimum solution will need expert
advice, both in conceptualizing alternative schemes and in providing the multiple
traffic calculations and simulations that will form the basis for the final design.

Individual Needs

The elevator requirements of both Commercial and Residential building can rarely be
planned on the basis of brochures alone. Each building is unique, and the optimum
solution will usually require individual variations from routine standards. For example:

- Very high buildings require extra hoist way clearance to allow for additional
construction tolerances.

- Individual national regulations will need to be accommodated.

- Innovations in architectural styling or structure may necessitate a radical approach to the

layout.

- Escalators may be more appropriate than elevators between adjacent floors. Frequently,
interchange floors or main lobbies with public spaces above them(such as retail) will
be better served by escalators, freeing the elevators for longer-distance travelers.

- High rise buildings needs fireman’s lift which serves every floor according to
national code requirements.

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GENERAL PLANNING FOR ESCALATORS AND PASSENGER CONVEYORS

Applications for escalators and passenger conveyors

Escalators and passenger conveyors enable a constant stream of passengers, even at

a high transport volume. In the commercial sector, consumers get to become familiar with
all sales levels. This gives escalators the potential to boost sales. In public transport,
escalators can transport passengers quickly at high traffic volumes.

Speeds and transport capacities

Speeds of between 0.45 and 0.5 m/s are the common international standard.
Speeds of 0.65 and 0.75 m/s are only recommended for higher rises or in public
transport. Increasing the speed does not lead to a proportional rise in transport
capacity, since users hesitate longer before stepping on the unit. Depending on the given
situation (location, application), the effective transport capacity may measure up to
80% of the theoretical values. The transport of baggage carts reduces transport capacity
significantly. In addition to a group of two or more escalators, a passenger elevator
should be provided for the transport of strollers and wheelchairs.

HORIZONTAL& VERTICAL DISTRIBUTION OF SERVICES FOR LARGE BUILDINGS (HVAC)

 Under-floor distribution Air-conditioning system distribution and terminal

equipment is generally located overhead in the ceiling void with the cool supply air
entering the room from ceiling diffusers.
 However, the supply of conditioned air from under the floor is a design option. In
this case, the air or water distribution and terminal devices are located in the floor
void, and hence the overhead services are reduced to only lighting and sprinklers.
 By making the floor void deep enough, the power, telecommunications and
computer wire ways may be incorporated into the one plenum, all being easily
accessible by merely opening up the raised floor.

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  Under-floor cooling is particularly beneficial for spaces such computer rooms, as air
velocities from floor grilles and resultant noise levels are both much higher for
cooling of equipment than those which would be acceptable for people.

5. Raised floor
6. Fan-coil unit
7. Ducting and insulation
8. Lighting and Ceiling

Services located below composite beams

 Internal distribution of services For many reasons, there is pressure to minimise the
space allocated to the building services. Therefore, it is necessary to ensure an
efficient use of space for the service distribution system in the vertical and
horizontal directions and in the plant rooms.
 The following sections review the spatial aspects of the vertical and horizontal
service distribution.
 Conventionally, the horizontal distribution of services is arranged within a
horizontal layer which is generally located below the structure and above the
suspended ceiling.
 This layer accommodates the distribution system (ducts, pipes, etc), the terminal
units and lighting units. The raised floor is placed on the floor slab and
accommodates the electrical and communication cabling. The lighting units are
often located within the ceiling depth. To determine the spatial allowance for these
elements, three design cases may be envisaged corresponding to different structural
configurations:
1. A flat slab with flexibility of service routing.

2. A slab and down stand beam arrangement.

3. A long span beam system with facility for service integration in the structural
depth.

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 6. Power/communications/dat
a outlet
7. Floor void
8. Ceiling void
9. Supply duct
10. Air outlet

Example of integrated services Case 2 – Slab and downstand beam arrangement

5. Raised floor
6. Fan coil unit
7. Ducting and insulation
8. Lighting and Ceiling
Services located below composite beams

6. Power/communic
ations/data outlet
7. Floor void
8. Ceiling void
9. Supply duct
10. Air outlet

Example of integrated services Case 3 – Long span beam with web openings

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 In case 1, the ducts pass below the floor within the depth allowed for the terminal
units. However, cross-overs of ducts must be avoided in order to minimize this depth. In
cases 2 and 3, the terminal units may be located between the beams, which means that
additional space below the beams is required only for the major ducts, ceiling and lighting
units. In case 3, the ducts are located entirely within the structural zone as they pass
through large openings in the deep beams. Typically, the diameter of these openings is
400mm, and the duct size is 300 or 350mm allowing for insulation etc. Vertical distribution
of services

Case 2
Case 1 Downstand Case 3
Vertical dimensions for the Flat soffit beams Long span beams
following components (mm) (mm) (mm)
Allowance - deflection & fire
protection 30 50 50 to 75
Lighting units and ceiling 100 to 150 100 100
Nil Nil
VAV box and attachments 400 (boxes between beams)
<400 , but
no 400 (inc. Nil- 400mm dia.
Ducts and insulation cross-overs insulation) openings
Total (below structure) 550 500 150 to 175
Raised floor 150 150 150
Structural depth (typical) 300 to 400 550 800 to 900
1,000 to
Total (ceiling-floor) 1,100 1,200 1,100 to 1,200
Typical vertical dimensions between ceiling and floor

The following recommendations apply to the vertical distribution of services:

 Provide continuous and uninterrupted vertical service routes

 Maintain a constant cross-section of the service route
 Position the plant room so that it is as close as possible to the centre of the
plan area it serves
 Consider the connection between horizontal services and vertical services
routes
 Provide separate routes for different services. The minimum is two; one for
electrics and one for water pipes, etc., although most buildings require more
service routes

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  Horizontal distribution should ideally not extend more than 25 m from a
vertical service route. Longer distances will impose penalties on the system
design and increase the depth of horizontal service ducts
 Position plant rooms at no more than 10 storeys apart vertically.
The figure shows typical arrangements of vertical service routes. Vertical ducts which
transfer air from the roof-top plant to each floor can often be concentrated in a relatively
small riser, as shown below

Type Plant Notes

Small building One plant room, one riser. Location

(up to four of riser not important, due to small
storeys and up size of building (central location
to 2500 m2 total preferred). Plant room must be
floor area) adjacent to the riser

Large plan Several plant rooms adjacent to

building (4000 areas served. Some central plant,
m2 total floor for example for gas intake and
area) boilers, may be required

Large, tall Plant room floors at basement and

building (over roof level. Intermediate plant
15 storeys) rooms may be required. Vertical
distribution within central core

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L-shaped Several plant rooms, several risers.
building (1000 Risers and air plant rooms
m2 to 3000 adjacent to cores. Separate room
m2 per floor), (3 located at ground/basement level
-10 storeys) for new electric supply

Building with Four roof air plant rooms, one

atrium (typically basement plant room. Four risers
2000 m2 per related to cores. Basement plant
floor), (5 – 10 below atrium gives best
storeys) connection to risers

Typical arrangements of plant rooms and vertical service routes

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HORIZONTAL DISTRIBUTION OF SERVICES THROUGH CENTRAL CORRIDOR

 The horizontal distribution system for mechanical and electrical services should be
planned simultaneously with the structural frame and the interior finish systems,
because the three are strongly interrelated.
 The floor to floor height of a building is determined in part by the vertical dimension
needed at every story for horizontal runs of duct work and piping.
 The selection of finish ceiling, partition and floor systems is often based on their
ability to contain the necessary electrical and mechanical services and to adjust to
future changes in these services. All these strategies involve close cooperation
among the architect and the structural and mechanical engineers.
 Plumbing walls, they will not interfere with other services. Sprinkler heads which
have the next highest priority in the layout of horizontal services are served from
the fire stand pipe by horizontal piping that seldom exceeds 4 in. (100mm) in
outside diameter.
 The spacing of the heads is coordinated with the placement of walls and partitions
the maximum coverage per head is about 200 sq. ft. (18.6 m2) in light hazard
buildings such as churches, schools, hospitals, office buildings, museums and

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 auditoriums. Coverage in industrial and storage buildings ranges from 130 to 90 sq.
ft. (12.1 to 8.4 m2) per head, depending on the substances handled in the building.
 Air conditioning ducts, the next priority branch out from a local fan room or from a
vertical ducts in supply and return ducts. Return ducts are often very short and
confined to the interior areas of the building.
 Supply ducts extend through low velocity secondary ducts to air diffusers
throughout the occupied area of the floor. Diffusers are generally required at the
rate of four to seven diffusers per 1000 sq. ft. (100m2).

Figure: Plan of VAV Duct

GROUPED HORIZONTAL DISTRIBUTION OVER CENTRAL CORRIDORS:

 Sometimes the major runs of duct work, piping and wiring can be grouped in the
ceiling area above the central corridor of each floor of a building, leaving the ceilings
of the surrounding rooms essentially clean.
 This works especially well in hotels and apartment buildings that rely on above
ceiling all water or electric equipment adjacent to corridor for heating, cooling and
ventilating.
 A low corridor ceiling is readily accepted in exchange for high, unobstructed space
in the occupied rooms, where the structure may be left exposed as the finish ceiling,
saving cost and floor to floor height.
 If the building has a two way flat plate or hollow core precast slab floor structure,
the overall thickness of the ceiling floor structure can be reduced to as little as 8 in.
(200 mm) Conduits containing wiring for the lighting fixtures may be cast into the
floor slabs or exposed on the surface of the ceilings.

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 Figure: Grouped Horizontal Distribution over a Central Corridor

IN FLOOR AND RAISED ACCESS FLOOR DISTRIBUTION OF MECHANICAL SERVICES:

 Underfloor air distribution (UFAD) is an air distribution strategy for

providing ventilation and space conditioning in buildings as part of the design of
an HVAC system.
 UFAD systems use an underfloor supply plenum located between the structural
concrete slab and a raised floor system to supply conditioned air through
floor diffusers directly into the occupied zone of the building.
 Thermal stratification is one of the featured characteristic of UFAD system, which
allows higher thermostat setpoints compared to the traditional overhead systems
(OH).
 UFAD cooling load profile is different from a traditional OH system due to the
impact of raised floor, particularly UFAD may has higher peak cooling load than OH
systems.
 UFAD has several potential advantages over traditional overhead systems, including
layout flexibility, improved thermal comfort, improved ventilation efficiency,
improved energy efficiency in suitable climates and reduced life cycle costs.
 UFAD is often used in office buildings, particularly highly-reconfigurable and open
plan offices where raised floors are desirable for cable management.
 UFAD is appropriate for a number of different building types including commercials,
schools, churches, airports, museums, libraries etc.
 Careful considerations need to be paid in the construction phase of UFAD systems to
ensure a well-sealed plenum to avoid air leakage in UFAD supply plenum.

DISTRIBUTION ABOVE STRUCTURAL FLOOR:

 A raised access floor system allows maximum flexibility in running services because
it can accommodate piping, ductwork, and wiring with equal ease.
 It is especially useful in industrial or office areas where large number of computers
or computer terminals are used and where frequent wiring changes are likely.

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 Through floors can be raised to any desired height above the structural deck,
heights of 4 to 8 in. (100 to 200 mm) are most common. Less costly lower profile
systems ranging from 21/2 to 3 in. (65 to 75 mm) in height are also available

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Principles of grouping and integrating of horizontal and vertical distribution of all
services in a multi- storeyed building/ large building. (FIRE SAFETY)

FIRE FIGHTING SYSTEMS

A fire fighting system is probably the most important of the building services, as its aim is
to protect human life and property.

It consists of three basic parts:

• a large store of water in tanks, either underground or on top of the building, called
fire storage tanks

• a specialised pumping system,

• a large network of pipes ending in either hydrants or sprinklers (nearly all buildings
require both of these systems)

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  A fire hydrant is a vertical steel pipe with an outlet, close to which two fire hoses are
stored (A fire hydrant is called a standpipe in America). During a fire, firefighters
will go to the outlet, break open the hoses, attach one to the outlet, and manually
open it so that water rushes out of the nozzle of the hose.
 The quantity and speed of the water is so great that it can knock over the firefighter
holding the hose if he is not standing in the correct way.
 As soon as the fire fighter opens the hydrant, water will gush out, and sensors will
detect a drop in pressure in the system. This drop in pressure will trigger the fire
pumps to turn on and start pumping water at a tremendous flowrate.
 A sprinkler is a nozzle attached to a network of pipes, and installed just below the
ceiling of a room. Every sprinkler has a small glass bulb with a liquid in it. This bulb
normally blocks the flow of water.
 In a fire, the liquid in the bulb will become hot. It will then expand, and shatter the
glass bulb, removing the obstacle and causing water to spray from the sprinkler. The
main difference between a hydrant and a sprinkler is that a sprinkler will come on
automatically in a fire.
 A fire hydrant has to be operated manually by trained firefighters - it cannot be
operated by laymen.
 A sprinkler will usually be activated very quickly in a fire - possibly before the fire
station has been informed of the fire - and therefore is very effective at putting out a
fire in the early stages, before it grows into a large fire. For this reason, a sprinkler
system is considered very good at putting out fires before they spread and become
unmanageable.
 General sprinklers are devices for a distributing water upon a fire in sufficient
quantity to extinguish it completely or to prevent its spread, by keeping the fire
under control, by the water discharged from the sprinklers.
 The water for firefighting is fed to the sprinklers through a system piping, normally
suspended from the ceiling, with the sprinklers installed at intervals along the pipes.
 The orifice of the sprinkler head, incorporating the fusible link or fusible bulb of the
automatic sprinkler, is normally kept closed, which is thrown open on the actuation
of the temperature sensitive fusible link or fusible bulb.
FIRE STORAGE TANKS

 The amount of water in the fire storage tanks is determined by the hazard level of
the project under consideration.
 Most building codes have at least three levels, namely, Light Hazard (such as
schools, residential buildings and offices), Ordinary Hazard (such as most factories
and warehouses), and High Hazard (places which store or use flammable materials
like foam factories, aircraft hangars, paint factories, fireworks factories).
 The relevant building code lists which type of structure falls in each category. The
quantity of water to be stored is usually given in hours of pumping capacity.

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  In system with a capacity of one hour, the tanks are made large enough to supply the
fire with water for a period of one hour when the fire pumps are switched on. For
example, building codes may require light hazard systems to have one hour’s
capacity and high hazard 3 or 4 hours capacity.
 The water is usually stored in concrete underground tanks. It is essential to ensure
that this store of water always remains full, so it must have no outlets apart from the
ones that lead to the fire pumps.
 These tanks are separate from the tanks used to supply water to occupants, which
are usually called domestic water tanks. Designers will also try and ensure that the
water in the fire tanks does not get stagnant and develop algae, which could clog the
pipes and pumps, rendering the system useless in a fire.
FIRE PUMPING SYSTEM

 Fire pumps are usually housed in a pump room very close to the fire tanks. The key
thing is that the pumps should be located at a level just below the bottom of the fire
tank, so that all the water in the tanks can flow into the pumps by gravity.
 Like all important systems, there must be backup pumps in case the main pump
fails. There is a main pump that is electric, a backup pump that is electric, and a
second backup pump that is diesel-powered, in case the electricity fails, which is
common. Each of these pumps is capable of pumping the required amount of water
individually - they are identical in capacity.
 There is also a fourth type of pump called a jockey pump. This is a small pump
attached to the system that continually switches on to maintain the correct pressure
in the distribution systems, which is normally 7 Kg/cm2 or 100 psi. If there is a
small leakage somewhere in the system, the jockey pump will switch on to
compensate for it. Each jockey pump will also have a backup.
 The pumps are controlled by pressure sensors. When a fire fighter opens a hydrant,
or when a sprinkler comes on, water gushes out of the system and the pressure
drops.
 The pressure sensors will detect this drop and switch the fire pumps on. But the
only way to switch off a fire pump is for a fire fighter to do this manually in the
pump room. This is an international code of practice that is designed to avoid the
pumps switching off due to any malfunction in the control system.
The capacity of the pumps is decided by considering a number of factors, some of which
are:

• The area covered by hydrants / standpipes and sprinklers

• The number of hydrants and sprinklers

• The assumed area of operation of the sprinklers

•The type and layout of the building

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THE DISTRIBUTION SYSTEM

 The distribution system consists of steel or galvanised steel pipes that are painted
red. These can be welded together to make secure joints, or attached with special
clamps.
 When running underground, they are wrapped with a special coating that prevents
corrosion and protects the pipe.
There are basically two types of distribution systems

Automatic Wet systems are networks of pipes filled with water connected to the pumps
and storage tanks, as described so far.

 Automatic Dry systems are networks of pipes filled with pressurized air instead of
water. When a fire fighter opens a hydrant, the pressurized air will first rush out.
 The pressure sensors in the pump room will detect a drop in pressure, and start the
water pumps, which will pump water to the system, reaching the hydrant that the
fire fighter is holding after a gap of some seconds.
 This is done wherever there is a risk of the fire pipes freezing if filled with water,
which would make them useless in a fire.
 Some building codes also allow manual distribution systems that are not connected
to fire pumps and fire tanks. These systems have an inlet for fire engines to pump
water into the system.
 Once the fire engines are pumping water into the distribution system, fire fighters
can then open hydrants at the right locations and start to direct water to the fire. In
high-rise buildings it is mandatory that each staircase have a wet riser, a vertical fire
fighting pipe with a hydrant at every floor.
 It is important that the distribution system be designed with a ring main, a primary
loop that is connected to the pumps so that there are two routes for water to flow in
case one side gets blocked.
 In more complex and dangerous installations, high and medium velocity water-
spray systems and foam systems (for hazardous chemicals) are used. The foam acts
like an insulating blanket over the top of a burning liquid, cutting off its oxygen.
 Special areas such as server rooms, the contents of which would be damaged by
water, usegas suppression systems. In these an inert gas is pumped into the room to
cut off the oxygen supply of the fire.
When you design a firefighting system, remember the following:

Underground tanks:

 water must flow from the municipal supply first to the firefighting tanks and then to
the domestic water tanks. This is to prevent stagnation in the water.

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  The overflow from the firefighting to the domestic tanks must be at the top, so that
the firefighting tanks remain full at all times.
 Normally, the firefighting water should be segregated into two tanks, so that if one is
cleaned there is some water in the other tank should a fire occur.
 It is also possible to have a system in which the firefighting and the domestic water
are in a common tank. In this case, the outlets to the fire pumps are located at the
bottom of the tank and the outlets to the domestic pumps must be located at a
sufficient height from the tank floor to ensure that the full quantity of water
required for firefighting purposes is never drained away by the domestic pumps.
 The connection between the two tanks is through the suction header, a large
diameter pipe that connects the all the fire pumps in the pump room. Therefore
there is no need to provide any sleeve in the common wall between the two
firefighting tanks.
 The connection from each tank to the suction header should be placed in a sump; if
the connection is placed say 300mm above the tank bottom without a sump, then a
300mm high pool of water will remain in the tank, meaning that the entire volume
of the tank water will not be useable, to which the Fire Officer will object.
 Ideally the bottom of the firefighting pump room should be about 1m below the
bottom of the tank. This arrangement ensures positive suction for the pumps,
meaning that they will always have some water in them.
 All pump rooms should without fail have an arrangement for floor drainage; pumps
always leak. The best way to do this is to slope the floor towards a sump, and install
a de-watering pump if the water cannot flow out by gravity.
 In cases where there is an extreme shortage of space, one may use submersible
pumps for firefighting. This will eliminate the need for a firefighting pump room.
 Create a special shaft for wet risers next to each staircase. About 800 x 1500 mm
should suffice. It is better to provide this on the main landing rather than the mid
landing, as the hoses will reach further onto the floor.
 Automatic sprinkler systems are quite effective for ensuring life safety, since they
give early warning of the existence of fire and simultaneously start application of
water on to the fire which will help control and extinguishment of the fire.
DRY RISERS

• Dry Riser Systems are installed in buildings for firefighting purposes by trained personnel
and which are normally dry and are capable of being charged with water by pumping from
Fire Service Appliances

• Dry Riser Systems are installed complete with an inlet breeching connector at Ground
Floor or at Fire Service Access Level and with Landing Valves at specified points on each
floor

• Dry Riser Systems are installed up to 50m above the Fire Service Access Level

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• Wet Riser Systems are installed in a buildings for firefighting purposes by trained
personnel and which are permanently charged with water from a pumped source

• Wet Riser Systems are installed complete with Landing Valves at specified points on each
floor

• Wet Riser Systems are installed up to and above 50m subject to the system being
designed to provide adequate flow and pressure at the upper floors

Dry Riser System

Dry fire main water supply pipe installed in a building for fire-fighting purposes, fitted with
inlet connections at fire service access level and landing valves at specified points, which is
normally dry but is capable of being charged with water usually by pumping from fire and
rescue service appliances.

WET RISERS

Wet fire main water supply pipe installed in a building for fire-fighting purposes and
permanently charged with water from a pressurized supply, and fitted with landing valves
at specified points.

Where fire mains are installed and there are no floors higher than 50 m above fire service
access level, wet or dry fire mains may be installed.

Where there are floors higher than 50 m above fire service access level, wet fire mains
should be installed owing to the pressures required to provide adequate fire-fighting water
supplies at the landing valves at upper floors and also to ensure that water is immediately
available at all floor levels.

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Figure: Dry Riser

Figure: Wet Riser

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SPRINKLER SYSTEM:

 Each sprinkler head is made up of steel cage fitted with a water deflector. A
quartzoid bulb, which contains a highly expansible liquid, is retained by the cage.
 The upper end of the bulb presses against a valve assembly which incorporates a
soft metal seal. Refer to the diagram below.

Figure: sprinkler head for sprinkler system

 When quartzoid bulbs are manufactured, a small gas space is left inside the bulb so
that, if the bulb is subjected to heat, the liquid expands and the gas space diminishes.
 This will generate pressure inside the bulb and the bulb will shatter once a
predetermined temperature is reached.
 Once the bulb shatters the valve assembly falls permitting water to be discharged
from the head which strikes the deflector plate and sprays over a considerable area.
 Generally the operating temperature range of quartzoid bulbs is 68 °C to 93 °C but
the upper limit of temperature can be increased. Quartzoid bulbs are manufactured
in different colours which indicate the temperature rating of the bulb.

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Communication
* Telecommunications Spaces keep telecommunications equipment and terminations
of telecommunications cables.
* Telecommunications pathways transport the cables.
* There is at least a telecommunications room (TR) at each floor.
* The pathways carries telecommunications cables from the TR to the vicinity of the
area served

Horizontal cabling of the telecommunication cabling system consists of two or more

cables that are connect to each work area from a Telecommunication room.
* Each cable is terminated at the cross-connection field in the TR.
* It can transmit both voice and data applications.

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VOICE AND DATA COMMUNICATION:
Data Compression
 If a typical message were statistically analyzed, it would be found that certain
characters are used much more frequently than others.
 By analyzing a message before it is transmitted, short binary codes may be assigned
to frequently used characters and longer codes to rarely used characters.
 In doing so, it is possible to reduce the total number of characters sent without
altering the information in the message.
 Appropriate decoding at the receiver will restore the message to its original form.
This procedure, known as data compression, may result in a 50 percent or greater
savings in the amount of data transmitted.
Data Encryption:
 Privacy is a great concern in data communications. The important messages that are
send can hacked without the knowledge of sender and receiver.
 To increase the security for data communications including digitized telephone
conversations, the data will be encoded and send to the receiver.

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 Authorized receiver stations will be equipped with a decoder that enables the
message to be restored. The process of encoding, transmitting, and decoding is
known as encryption.

COMPUTER LABS/ SERVER ROOMS:

Virtually every modern business needs servers to run their website, manage email, or
deploy cloud applications.
The first aspect to consider when setting up a server room in your office is where the
servers will be located. Finding suitable space within a company’s existing property for
an onsite server room can be an expensive proposition, often requiring significant
remodelling and potentially the construction of a custom space.
The location must be suitable for the installation of bulky power, air conditioning, and
networking equipment. It must be able to bear the weight of heavy equipment. Tight
spaces aren’t suitable because effective cooling requires the constant circulation of air.
It’s also inadvisable to build a server room in a windowed space or a space with an
external wall, both of which can make it difficult to control and secure the environment
within the server room.
Ideally, the space’s ceilings should be at least nine feet from the ground, and raised
ceilings are preferred to allow for the running of air ducts and installation of heat
exhausts and other equipment. Raised floors that allow for cable runs are also a bonus,
but not necessary for smaller server rooms.
Above all, a server room must be secure, with monitored and controlled access from
within the building and from external areas.
Server Room Equipment
Once a location has been selected, it’s time to consider the equipment that is to be
purchased and fitted. Much of the expense associated with building a server room is
generated by the equipment needed to support servers, rather than the servers
themselves.
Air Conditioning
Air conditioning for server rooms has three main tasks:

Maintenance of stable temperatures in the server room.

Humidity control: servers don’t do well in humid environments.
Air filtration: dust and other airborne particles can reduce the lifespan and reliability of
computing equipment.
Typically, smaller server rooms will use wall-mounted air conditioners. For larger
rooms under-ceiling units are preferable.
Temperatures within a server room should be approximately 71°F (22°C). Modern
servers will function at higher temperatures, but with an increased likelihood of
component failure.

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Fire Suppression

Servers represent a significant capital investment even before the data stored on them is
taken into account. Server room fire suppression equipment uses gas or chemical
suppression techniques to automatically extinguish fires. Most fire suppression systems
require pressure relief venting to be fitted to server rooms to mitigate pressure changes
during discharge.

Racks

Modern servers are designed to be mounted in racks. Servers are available in a wide range
of sizes, expressed as multiples of a rack unit (or “U”). The smallest server rooms will
require at least one cabinet or rack, which will contain space for servers. The larger the
server deployment, the more racks and cages you’ll need.

Networking

Depending on the number of servers the server room will house, you can expect to require:
 core routers
 switches
 appropriate cabling

Networking equipment should be housed in a secure equipment rack within the server
room. The type of networking equipment needed depends on the number of servers, the
desired levels of redundancy, and a number of other factors.

Larger server rooms require dedicated routers; Cisco and Juniper are the leading
manufacturers of networking equipment. Businesses that depend on the reliability of their
server room should choose to double-up on networking equipment for redundancy.

Power

Your server room requires a reliable power supply. At minimum the server room requires
a utility power source, but plugging servers directly into utility power is not a good idea.

For reliability, an Uninterruptible Power Supply (UPS) is required. A UPS provides

emergency power for short periods in the event of a mains power failure. Servers need a
consistent supply of power and mains power is prone to occasional brownouts or
blackouts. Without a UPS, servers are at risk of data corruption, equipment damage, and
availability issues.

The UPS typically provides power to a power distribution unit (PDU) mounted within the
server rack that houses the servers they power.

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Once again, redundancy is an important concern here. A UPS is only a temporary solution
to power outages, and for optimal reliability, multiple power sources that include an on-
site generator are preferred.

Security

Security should be a core priority, especially if an organization stores and processes

sensitive data. Server room security is a major component of most regulatory frameworks
governing data storage, including HIPAA for private medical data and PCI DSS for credit
card data.

Physical security equipment required might include:

 Heavy duty doors with electronic locks.

 CCTV monitoring of the server room and adjacent areas.

 Biometric or security card access controls.

Server rooms should not be accessible from the outside of the building and should not have
windows. Only authorized personnel should have access to the server room and all access
should be monitored and logged.

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