CLASS 4
Central Air Conditioning System
Central air conditioning is used for cooling big buildings, houses, offices, entire
hotels, gyms, movie theatres, factories etc.
If the whole building is to be air conditioned, HVAC engineers find that putting
individual units in each of the rooms is very expensive making this a better option.
A central air conditioning system is comprised of a huge compressor that has the
capacity to produce hundreds of tons of air conditioning.
Cooling big halls, malls, huge spaces, galleries usually only feasible with central
conditioning units
central air conditioner unit is an energy moving or converted machines that are
designed to cool or heat the entire house.
It does not create heat or cool. It just removes heat from one area, where it is
undesirable, to an area where it is less significant.
Central air conditions has a centralized duct system.
It uses Ac refrigerant (we may know it as Freon) as a substance to absorb the heat
from indoor evaporator coils and rejects that heat to outdoor condenser coils or vice
verse.
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
AHU Sensor
What’s in an AHU?
Heating/Cooling Coil
Filter Fan
Damper
Air handling unit AHU
•Air handling units (AHU, sometimes referred to as ‘air handlers’) form part of the
heating, ventilating and air conditioning system (HVAC) that supplies, circulates
and extracts air from buildings.
•Air handling units can be supplied in a range of sizes, and with a variety of
capabilities, but typically they comprise an insulated box that forms the housing
for; filter racks or chambers, a fan (or blower), and sometimes heating elements,
cooling elements, sound attenuators and dampers (that can be operated manually
or automatically to regulate or prevent specific air flows). In some situations, such
as in swimming pools, air handling units might include dehumidification.
•Heating and / or cooling can be generated within the unit itself, or can be provided
by connection to the building’s boilers or chillers.
•Generally, air handling units will be connected to the ductwork within the building
that supplies air to and extracts air from the interior, but they can be used to supply
and extract air direct to a space, or they may be located on a roof (rooftop units or
RTU).
•Air handling units that consist of only a fan and a heating or cooling element,
located within the space they are serving, may be referred to as fan coil units
(FCU). no risk to public health.
•Air handling units can be used to re-circulate a proportion of ‘stale’ air within a
building, mixing this with fresh air to reduce the amount of air conditioning that is
required. They can also include heat recovery, recovering heat from return air and
using it to warm the supply air.
•Fans may be single speed, may have a range of set speeds, or may be variable
frequency drive. Flow rates may also be controlled by inlet vanes or outlet
dampers.
•Air handling units generate noise (and vibration) which can be disruptive, and
this can be compounded where ductwork passes between acoustically separate
spaces. In this case, acoustic attenuators might be used. In addition, vibration
can be generated. This vibration can be isolated by inserting flexible sections
between the unit and ductwork and by isolating the unit from the building
structure.
•Where air handling units are located outside buildings, they can be the source of
complaints by neighbours because of the noise and vibration they generate and
sometimes because of odours they expel (typically where they are serving
kitchens). It is important that these units are properly designed, installed and
maintained to minimise this disturbance.
•‘Wet’ systems, that include water evaporative cooling, can present a hazard to
health. Businesses using such systems are required to carry out a risk
assessment and put in place procedures.
THE COOLANT
Heat is removed by the coolant.
Functions as a heat absorber from the evaporator
Good coolant must have following features :
1. Non toxic
2. Not explosive
3. Non-corrosive components
4. Soluble in oil to lubricate effectively
5. Harmless when responding to oil even in the presence of moisture
6. Have a high resistance to electricity.
CAN YOU FIND WHERE TO
Type of coolant USED EACH OF THIS
COOLANT?
R-22
MONOKLORODIFLUOROMETANA
R-11
TRIKLOROMONOFLUROMETANA
R-12
DIKLORODIFLUOROMETANA
•Air conditioners are rated by the number of British
Thermal Units (Btu) of heat they can remove per hour.
Another common rating term for air conditioning size is the
"ton," which is 12,000 Btu per hour.
•Room air conditioners range from 5,500 Btu per hour to
14,000 Btu per hour.
A ton is the cooling capacity of an air conditioning
system.
One ton is equal to the amount of heat required (288,000
Btu) to melt one ton of ice in a 24-hour period. A one-ton
air conditioner is rated at 12,000 Btu per hour
(288,000/24). A two-ton unit would be rated at 24,000 Btu
per hour.
Chilled Water Central
Air Conditioning
Comfort and wellbeing.
Hotel guests have high expectations and very individual demands when it
comes to the room climate. Some like it cool and fresh; others prefer it warm
and cosy. All of them, however, want a quiet room. Every hotel has an array of
many different rooms and areas, each with different and often complex
requirements for ventilation and air conditioning. From the lobby to
restaurants, kitchen and bar, and from conference and meeting rooms to the
spa. The demands on the air in a hotel could hardly be more diverse.
The perfect air condition for hotels: invisible – inaudible – unnoticeable.
To provide flexible and adaptable solutions for hotels. Comfort, wellbeing and
safety of people are clearly main focus. This does not mean, however, that
sustainability and protection of the environment is compromised. With all these
factors in mind, innovative system solutions such as air water systems that
provide quiet and efficient service without being noticed by hotel guests.
• ZONING AND AIR DISTRIBUTION,
• HEATING SYSTEM,
• AIR HANDLING UNITS, BASICS OF DUCT SIZING AND ROUTING,
PREFERRED LOCATIONS OF EQUIPMENT AND ARCHITECTURAL
REQUIREMENTS OF VARIOUS EQUIPMENT.
• ILLUSTRATION OF DUCT LAYOUT THROUGH A SMALL EXAMPLE.
• SPECIALIZED AIR CONDITIONING SYSTEMS: CLEAN ROOMS,
SERVER, HUB & UPS ROOMS, OPERATION THEATRES ETC
If lighting is zoned why shouldn’t HVAC
equipment be zoned?
Why have one thermostat to control the
temperature in an entire house?
Why not have a thermostat in every
room, or zone, to provide individual
temperature control?
APPLICATION USE
A Zone Control System can solve comfort
problems:
Between different floors
In finished basements
In home additions
In added sun rooms
Between external and internal areas
In bonus rooms located over garages
APPLICATION USE
Zoning also allows unoccupied areas to be maintained
at lower heating or higher cooling temperatures which
reduces energy usage and utility costs.
With the use of programmable thermostats, individual
zones can be scheduled to automatically change the
heating and cooling set points based on an occupied
and unoccupied program.
When a bedroom zone is not being occupied, a lower
heating and higher cooling set point can be maintained.
APPLICATION USE
A home or commercial building not zoned typically
leaves someone uncomfortable. It is too much to
expect one thermostat to provide comfortable
conditions for every room.
Zoning divides a home or building into areas (these
areas are called zones) with common heating and
cooling requirements.
Each zone is controlled by its own thermostat, allowing
people to be comfortable no matter where they are in
the building.
HEATING SYSTEM
HEATING FOR COMFORT
• In cold region, it is necessary to keep warmth in
the building; therefore some artificial measures
need to be taken.
• The primary sources of heat for buildings
heating-systems are fossil fuels, natural gas, and
various grades of fuel oils and coal.
• Electricity is used under certain circumstances
for heating in commercial buildings including
perimeter zone heating and service water
heating.
Heating for Comfort
• The heating plant produces heat and
distribution systems like ducts, fans and
pumps, terminal devices and auxiliary
equipment distributed to the intended places.
The equipment that produces heat are
furnace, boilers and furnaces, heat pumps,
heat exchangers, etc.
Heating for Comfort
Furnaces
• Furnaces are used to heat air streams that are used
for heating the interior of buildings. Boiler are pressure
vessels used to transfer heat produced by burning a
fuel to a fluid. The most common fluid used for this
purpose in buildings is water liquid or vapor.
• The key distinction between furnace and boiler is
that air is heated in furnace and water is heated in the
boilers. The fuel used for producing heat in boilers
and furnace include natural gas (i.e.methane),
propane, fuel oil, wood, coal and other fuels.
Heating for Comfort
Boilers
• A boiler is a device made from copper, steel or Cast-Iron
to transfer heat from a combustion chamber to water in the
liquid phase, vapor phase or both.
• Boilers are classified both by the fuel used and by the
operating pressure. Fuels include fuel oils, woods, coal
refuse drive fuels, and electricity.
• Boilers produce either hot water or stream at various
pressures. Stream produces by boilers is used in buildings
for space heating, water heating and absorption cooling's.
DEHUMIDIFIER
Definition : Dehumidify or dehumidification – literally means “pulling out or
removing” the moisture/humidity from the air.
The dictionary defines dehumidification as the process of removing
atmospheric moisture.
Methods of Dehumidification:
Air Conditioning – Dehumidification by increasing the total pressure or
compressing the air
Desiccant Dehumidification (also known as Chemical Dehumidification) –
In this method a desiccant material or drying substance is introduced
into the airstream to remove moisture.
Mechanical Dehumidification (also known as Refrigerative
Dehumidification) – It is the method of removing humidity by cooling the
air to condense the water vapour.
DEHUMIDIFIER APPLICATION
Product Drying : Food Industry ,Pharmaceutical Industry, Engineering and
Mechanical Industry ,Leather ,Aviation Industry ,Miscellaneous Industries
Production and Processing : Food Industry, Pharmaceutical Industry,
Electronics Manufacturing , Special Rooms ,Power and Power Distribution
Industry ,Healthcare/Hospitals ,Glass Industry , Printing Industry ,Aviation
Industry ,Automobile Industry Etc.
Packaging : Food Industry ,Garment Industry ,Pharmaceutical Industry ,
Fertilizer Industry.
Storage : Museums and Libraries , Shipping and Marine, Leather, Food
Industry ,Pharmaceutical Industry, Manufacturing ,Aviation's Industry ,Power
Industry ,Electrical Manufacturing Industry ,Special Rooms ,Defence Industry
What Is HVAC Load Calculation And Why Is It Important?
When replacing an existing HVAC system:
– Is buying the newest model ‘good enough’?
No !
– It’s important to have an HVAC load calculation performed first !
What is a Load Calculation?
– A mathematical process to determine the best size, application and
style of HVAC system.
– Load calculations will:
• Verify the total square footage
• Count the windows, doors and entry ways
• Check the insulation
• Count the floors
• Check the landscaping
• Check window treatments
• Check the condition of the duct work
Why is a Load Calculation Critical?
– A load calculation will:
• Pick the right sized system
• Find a system that will consume less energy
• Help you consume less energy
• Help HVAC companies diagnose large-scale issues
• Save your money on common monthly expenses
When we talk about sizing an air conditioning appliance (tons of cooling,
BTU/h or KW), we are specifying the cooling capacity (power) that needs to
be moved by the appliance (air conditioner) from the indoor space to
outdoors. The actual electrical power used to operate the appliance is
considerably less than the cooling power it needs to move.
The enthalpy value gives us the amount of heat in a pound of air. To know the
total heat removed by the evaporator, we need to know the volume (CFM -
volume of airflow; cubic feet/minute.) of air that passes the evaporator and
circulates through the system.
Typically, volume flow (CFM) is measured or calculated based on duct area size.
This measurement of heat removal by the air conditioning system is independent
of the ambient temperature outside the building and independent of the actual
temperatures of the room itself.
Rough calculation for sizing an A/C system:
((House square footage times 25, divided by 12,000 BTU) – 0.5) = required tons.
So, as an example, a 1,500-square foot home would look something like this:
1. 1,500 ft2 x 25 = 37,500 ft2
2. 37,500 ft2 / 12,000 BTU = 3.1 tons
3. 3.1 – 0.5 = 2.6 tons, so you’d need between a 2.5 to 3.0 ton sized central air
conditioning unit
DUCTING
Duct design objectives:
1.To provide conditioned air to meet all rooms heating & cooling requirements.
2.Is properly sized so that the pressure drop across the air handler within the
manufacturer and design specifications.
3.Is properly sealed so that any leakage or entrance of any polluted air is
avoided.
4.Has balanced air supply and return air flow so as to maintain a neutral
pressure in house.
5.Minimizes duct air temperature gains or losses between the air handler and
supply outlets, and between the return register and air handler.
THE PROCESS
The basic steps to design a typical ducted central system for a home are:
1.Collect information about the house
2. Perform room--‐by--‐room load calculations
3. Select equipment to meet loads
4.Design distribution system We can use this table to size the ducts:
Air-conditioning Manufacturer
• Blue Star
• Voltas
• Mitsubishi
• Daikin
• Hitachi
• Carrier
• Sharp
• L.G
• Whirlpool
• Godrej
ASSIGNMENT:
Specialized air conditioning systems:
• Clean rooms,
• Server hub & ups rooms,
• Operation theatres etc
What is a clean room?
A clean room is a room in which environmental conditions can be
controlled, such as fine particles in the air, the necessary temperature and
humidity, pressure, minute gas components, static electricity, minute
vibrations, and electromagnetic wave. The basic configuration is as shown
in the diagram below.
Clean rooms are indispensable for manufacturing precision industrial products
such as semiconductors and display panels.
To build a industrial clean room described below, the following types of
equipment are needed: air conditioning and filtration equipment to maintain the
temperature and cleanliness in the room, utility equipment to supply the cooling
water, special gases, and pure water necessary for the production machines,
heat source equipment for cooling, heating, or humidifying this equipment, and
monitoring and control equipment for clean room environments, for starting and
stopping operations for the facilitates, and for identifying malfunctions.
