1

HVAC NOTES
1. HVAC- (HEAT VENTILATING AND AIR-CONDITIONING) IS A FIELD OF ENGINEERING WHICH DEALS WITH
THE HUMAN COMFORT BY MAINTAINING THE TEMPRATURE, HUMIDITY AND IN ADDITION TO THAT IT
ALSO DEAL WITH THE AIR EXCHANGE, AIR PURITY, DUST REMOVAL, BACTERIA REMOVAL AND OTHER
CONTAMINATES OF AIR.
2. AIR-CONDITIONING- treating the air according to the need of human comfort is called as air
conditioning.
3. Refrigeration- It is the process of maintaining an enclosed area temperature lower than the
surrounding environment.
4. Summer design condition- 75F DBT,63f WBT, 50% humidity
5. Project- It is the set of objective having definite life span, done by team work by using the people
from different area to meet an order. When objective meet project get closed.
6. Chiller- the main function of chiller is to cool the water. A chiller is a machine that removes
heat from a liquid via a vapor-compression or absorption refrigeration cycle. This liquid
can then be circulated through a heat exchanger to cool air or equipment as required. As
a necessary byproduct, refrigeration creates waste heat that must be exhausted to
ambient or, for greater efficiency, recovered for heating purposes. Concerns in design
and selection of chillers include performance, efficiency, maintenance, and product life
cycle environmental impact

7. Refrigerants-A refrigerant is a substance or mixture, usually a fluid, used in a heat pump

and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to
a gas and back again.
8. Air handling unit-An Air Handling Unit (most of the times abbreviated to AHU), or Air Handler, is
a central air conditioner station that handles the air that, usually, will be supplied into the
buildings by the ventilation ductwork (connected to the AHU).
Handling the air means that the air will be delivered into the building spaces with thermo-
hygrometric and IAQ (Indoor Air
 2

Quality)
The air handling unit is an integrated piece of equipment consisting of fans, heating and cooling coils, air-control
dampers, filters and silencers. Air Handling Units are often called AHU.The purpose of this equipment is to collect and
mix outdoor air with that returning from the building space. The air mixture is then cooled or heated,
9.
10. Refrigeration cycle-

Refri
geration cycle includes the compression, expansion, condensation and eva[poration.

11. Equipments of refrigeration-

A) compressor:- An air compressor is a device that converts power (using an electric motor,
diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed
air). By one of several methods, an air compressor forces more and more air into a storage
tank, increasing the pressure. When tank pressure reaches its upper limit the air compressor
shuts off. The compressed air, then, is held in the tank until called into use. The energy
contained in the compressed air can be used for a variety of applications, utilizing the kinetic
energy of the air as it is released and the tank depressurizes. When tank pressure reaches its
 3

lower limit, the air compressor turns on again and re-pressurizes the tankcondensorc

B) condenser:- a condenser is a device or unit used to condense a substance from

its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the
substance, and will transfer to the condenser coolant. Condensers are typicallyheat
exchangers

There are three condensers used in HVAC systems

 Water-cooled

 Air-cooled

 Evaporative

Applications:

 Air cooled – If the condenser is located on the outside of the unit, the air cooled condenser can
provide the easiest arrangement. These types of condensers eject heat to the outdoors and are
simple to install.

Most common uses for this condenser are domestic refrigerators, upright freezers and in residential
packaged air conditioning units. A great feature of the air cooled condenser is they are very easy to clean.
Since dirt can cause serious issues with the condensers performance, it is highly recommended that
these be kept clear of dirt.

 Water cooled – Although a little more pricey to install, these condensers are the more efficient
type. Commonly used for swimming pools and condensers piped for city water flow, these
condensers require regular service and maintenance.
 4

They also require a cooling tower to conserve water. To prevent corrosion and the forming of algae,
water cooled condensers require a constant supply of makeup water along with water treatment.

Depending on the application you can choose from tube in tube, shell and coil or shell and tube
condensers. All are essentially made to produce the same outcome, but each in a different way.

 Evaporative – While these remain the least popular choice, evaporative condensers can be used
inside or outside of a building and under typical conditions, operate at a low condensing temperature.

Typically these are used in large commercial air-conditioning units. Although effective, they are not
necessarily the most efficient.

Prior to beginning your install, make sure you choose a condenser that will provide you with the most
efficient use.

C) Evaporator:- An evaporator is a device used to turn the liquid form of a chemical into its
gaseous form. The liquid is evaporated, or vaporized, into a gas.
Drier:- Filter-driers play a pivotal role in the operation of air conditioning and refrigeration
systems. At the heart of the unit is the desiccant held in its cylindrical metal container. As
important as the filter-drier is, many actually do not understand how it works. Here are some
details.

The word desiccate means to dry out completely and a desiccant is a material or substance
that accomplishes the moisture removal. Moisture in the mechanical refrigeration cycle is
detrimental to the operation and life of the system. The filter-drier is an accessory that
performs the functions of filtering out particles and removing and holding moisture to
prevent it from circulating through the system

Accumulator:- Accumulators are used on fixed orifice tube systems to collect excess liquid that
may leave the evaporator’s outlet tube. Compressors are incapable of compressing liquid. To
prevent this, the accumulator is designed to allow only a regulated amount of oil and liquid
refrigerant to enter the compressor for lubrication and cooling.
 5

Expantion valve:- A thermal expansion valve (often abbreviated as TEV, TXV, or TX valve) is a
component in refrigeration and air conditioning systems that controls the amount of refrigerant flow
into the evaporator thereby controlling the superheating at the outlet of the evaporator. Flow control,
or metering, of the refrigerant is accomplished by use of a temperature sensing bulb, filled with a
similar gas as in the system, that causes the valve to open against the spring pressure in the valve
body as the temperature on the bulb increases.

12. Unit of refrigerant:- (tone)- A ton of ice melting over 24 hrs. provides a ton of
refrigeration each hour. 2,000 lbs. of ice at 144 BTUs per pound = 288,000 BTUs 288,000 ÷ 24

hrs. = 12,000 BTUs per hour, or 1 ton of refrigeration.

13. 1 BTU- A BTU is the amount of heat required to raise the temperature of 1 avoirdupois pound of
liquid water by 1 degree Fahrenheit at a constant pressure of one atmosphere.[1] As with

the calorie,

14. Cooling tower:- A cooling tower is a heat rejection device which rejects waste heat to
the atmosphere through the cooling of a water stream to a lower temperature. Cooling
towers may either use the evaporation of water to remove process heat and cool the working
fluid to near the wet-bulb air temperature ( use to remove the heat from circulating water)
 6

15. Type of a.c :-

AC Parameters Window AC Split AC Cassette AC

Suitable For Small rooms with a window Any room with or without a Large indoor spaces
sill window

Noise Relatively on the higher side Minimal noise Silent operation

Capacity range 0.75 ton to 2 ton 0.8 to 2 ton 1 ton to 4 ton

Advanced features Humidity control, dust filter Humidity control, dust filter, Humidity control, dust
bacteria filter filter, bacteria filter

Interference with Slight possibility to interfere Designer indoor units blend well Barely interferes with
home decor with window curtains and with wall decor interior decor
drapes

Ease of installation Minimal effort required Indoor and outdoor units need Needs specialised false
some amount of effort for ceiling
installation
Fan coil unit:- A Fan Coil Unit (FCU) is a simple device consisting of a heating and or cooling heat
exchanger or 'coil' and fan. It is part of an HVACsystem found in residential, commercial, and industrial
buildings. A fan coil unit is a diverse device sometimes using ductwork, and is used to control the
temperature in the space where it is installed, or serve multiple spaces. It is controlled either by a manual
on/off switch or by thermostat, this in turn controls the throughput of water to the heat exchanger using
a control valve and/or the fan speed.

Package unit:- 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.

16. Enthalpy is a measure of energy in a thermodynamic system. It includes the internal energy,
which is the energy required to create a system, and the amount of energy required to make
room for it by displacing its environment and establishing its volume and pressure.
17. entropy (usual symbol S) is a measure of the number of specific realizations or microstates that
may realize a thermodynamic system in a defined state specified by macroscopic variables. Most
understand entropy as a measure of molecular disorder within a macroscopic system.
18. Sensible heat:- Sensible heat is heat exchanged by a body or thermodynamic system that
changes the temperature, and some macroscopic variables of the body, but leaves unchanged
certain other macroscopic variables, such as volume or pressure
19. Latent heat:- Latent heat is energy released or absorbed, by a body or a thermodynamic
system, during a constant-temperature process that is specified in some way. An example
is latent heat of fusion for a phase change, melting, at a specified temperature and pressure
 7

20. Psychrometry :- Psychrometry is the science of studying the thermodynamic properties of

moist air and the use of these properties to analyze conditions and processes involving moist air.
Moist air is a mixture of dry air and water vapour.
Dry bulb temp- The dry-bulb temperature is the temperature indicated by a thermometer
exposed to the air in a place sheltered from direct solar radiation

Wet bulb temp- The thermodynamic wet-bulb temperature is a thermodynamic property of a

mixture of air and water vapor.

Humidity

Specific Humidity[

Specific humidity is defined as the proportion of the mass of water vapor per unit mass of the moist air
sample (dry air plus the water vapor); it is closely related to humidity ratio and always lower in value.

Absolute humidity

The mass of water vapor per unit volume of air containing the water vapor. This quantity is also known as
the water vapor density.[5]
Specific enthalpy

Analogous to the specific enthalpy of a pure substance. In psychrometrics, the term quantifies the total
energy of both the dry air and water vapour per kilogram of dry air.
Specific volume

Analogous to the specific volume of a pure substance. In psychrometrics, the term quantifies the total
volume of both the dry air and water vapour per kilogram of dry air.
Psychrometric ratio

The psychrometric ratio is the ratio of the heat transfer coefficient to the product of mass transfer
coefficient and humid heat at a wetted surface. It may be evaluated with the following equation: [6][7]

where:

 = Psychrometric ratio, dimensionless

 = convective heat transfer coefficient, W m −2 K−1

 = convective mass transfer coefficient, kg m−2 s−1

 = humid heat, J kg−1 K−1

 8

The psychrometric ratio is an important property in the area of psychrometrics, as it relates the
absolute humidity and saturation humidity to the difference between the dry bulb temperature
and the adiabatic saturation temperature.

Mixtures of air and water vapor are the most common systems encountered in psychrometry.
The psychrometric ratio of air-water vapor mixtures is approximately unity, which implies that the
difference between the adiabatic saturation temperature and wet bulb temperature of air-water
vapor mixtures is small. This property of air-water vapor systems simplifies drying and cooling
calculations often performed using psychrometic relationships.
21. A psychrometric chart is a graphical representation of the psychrometric processes of
air. Psychrometric processes include physical and thermodynamic properties such as dry bulb
temperature, wet bulb temperature, humidity, enthalpy, and air density.

Dry bulb temperature: These lines are drawn straight, not always parallel to each other, and
slightly inclined from the vertical position. This is the t–axis, the abscissa (horizontal) axis. Each
line represents a constant temperature.

Dew point temperature: From the state point follow the horizontal line of constant humidity ratio
to the intercept of 100% RH, also known as the saturation curve. The dew point temperature is
equal to the fully saturated dry bulb or wet bulb temperatures.

Wet bulb temperature: These lines are oblique lines that differ slightly from the enthalpy lines.
They are identically straight but are not exactly parallel to each other. These intersect the
saturation curve at DBT point.

Relative humidity: These hyperbolic lines are shown in intervals of 10%. The saturation curve
is at 100% RH, while dry air is at 0% RH.

Humidity ratio: These are the horizontal lines on the chart. Humidity ratio is usually expressed
as mass of moisture per mass of dry air (pounds or kilograms of moisture per pound or kilogram
of dry air, respectively). The range is from 0 for dry air up to 0.03 (lbmw/lbma) on the right
hand ω-axis, the ordinate or vertical axis of the chart.

Specific enthalpy: These are oblique lines drawn diagonally downward from left to right across
the chart that are parallel to each other. These are not parallel to wet bulb temperature lines.

22.Duct:- Ducts are used in heating, ventilation, and air conditioning (HVAC) to deliver and remove
air. The needed airflows include, for example, supply air, return air, and exhaust air.[1]Ducts commonly
also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring
acceptable indoor air quality as well as thermal comfort.

23. Ducting:-
 9

Fabrication- as per the size of the duct we select the thickness of the sheet i.e gauge of the sheet,
then cutting the sheet according to the size given is called as the fabrication.

Assembling:- after fabrication we take the duct according to the drawing and routing it is called
assembling.

Errection:- the duct which is fabricated and assembled is erected to the roof with proper support as
per the routing shown on drawing is called erecting.

24. Type of duct:-

Rectangular duct

Square duct

Round duct

Oval duct

Flexible duct

Note:- the round duct is the best duct according to the aspect ratio have less friction for air
and contribute positively towards the laminar flow of air inside duct. But we use round or
rectangular duct because the making of the rectangular duct and sqare duct is easy as
compare to the round one and oval one. (friction in the rectangular duct is high due to the air
void at the corners of the duct.

Flexible Duct- Flexible ducts are typically tube-shaped, made of a wire coil covered with a bendable,
durable plastic, and surrounded by insulation. This kind of ducting is best in tricky spaces where rigid
ducts are just not possible to install, or used to attach non-flexible ductwork to an air supply outlet.
Like most central air conditioning parts, flexible ducts have specific installation requirements. For
example, flexible ductwork needs to be secured and supported properly, ensuring little sagging or
snaking. Kinks, bends, and turns also need to be minimized – these reduce air flow and could hamper
the efficiency and effectiveness of the air conditioner. The advantages of flexible ducts are that they
are fairly quick and easy to install, and often cost less than rigid ductwork

25. Duct material:-

a. GI- galvanized iron sheet( mostly used)

b. s.s sheet- stainless steel sheet

c- pvc sheet

d. frp sheets- fibre glass reinforced plastic.(exhaust purpose)

 10

25. we are using metel sheet according to the SMACNA( sheet metal air conditioning contractor
national association) and BIS ( bureau of indian standard)

26. The duct size varies

GAUGE THICKNESS MAXM SIZE

26 0.5MM UPTO 450 MM

24 0.65MM 450-750MM

22 0.85MM 750-1500MM

20 0.95MM 1500-2250MM

18 1.2MM ABOVE 2250MM

27. INSULATION:-

THERMAL INSULATION:- To avoid the heat leakage .we use

A) Thermocol /board

B) Fibre glass wool ( all foil forced )

C) Nitrile rubber

D) Phenotherm

E) A flex insulation

F) Arma flex insulation

G) Trocilane rubber insulation

H) Adhesive elastomeric rubber

ACOUSTIC INSULATION:-

Rigid board glass wool perforated all sheet. . acoustic insulation is up to few meters only after the
duct from the AHU.

28. Duct Support:-

a) Threaded rod

b) anchor fastner

c) connector
 11

d) L & C channel

e) slotted C- change

f) G.I wire

note:- for small scale work we use the flanges but for the high scale load we use the L & c angle.

28. Aspect ratio:- Ratio of the maximum width to the min length is called a.r

A.R- max length (w/h)/min length (w/h)

To decrease the cost of the ducting we have to maintain the aspect raio of the duct as 1 if the aspect ratio
is more then one then the cost will increase and it will also lead to the increment in the to tal cost of the
project.

Note:- aspect ratio must lie in between 1:1 to 6:1 must not increase then 8:1.

29. hvac conversions

Cº=5/9(Fº-32), Fº=9/5Cº+32/ 1 USGPM=3.8 L 1 UKGPM=4.5 L

1m=3.281ft , 1ft=0.3048m

1kj=0.9478BTU, 1KW=1.341H.P , 1 watt=3.415BTU/HR

1cal/sec=14.286BTU/HR

1Kpa=4.0186 inches of H2O= 0.3349ftH2O=0.145 Psi= 0.01 bar

1m²=10.764ft²=35.346ft³

1m/sec=196.85fpm(foot per min)(velocity), 1 m³/sec=2119cfm(vol occupaid)

1m³/hr=0.5886cfm(ft³/m)

1lt/sec=2.119cfm

1lit/se=15.85gpm(gallon per million), 1kg=2.205 lb(pounds)

1TR=12000 btu/hr= 3.517 KW

1TR=3024 kcal/hr= 400 cfm

1 TR=50kcal/min=1.2kg=3.7 HP

1TR:- 2.4 USGPM= 3 UKGPM

 12

NOTE=technically- if aspect ratio increases friction increases, heat loss increases, turbulence
increase, noise increases, vibration increases , insulation cost increase, static pressure
increases, demand more power of the blower and the ahu.

Ducting- perimeter increases, no of sheet increases, handling problem increases, fabrication

problem increases, man power increases, installation and the errection problem inc. no of the
fixtures increases, maintenance problem increases.

Cost wise- lead to the increases in the cost of equipment, insulation, maintenance, technical ,
fixtuere, fabrication handling,power charges, operational cost.

30. CLASSIFICATION OF DUCT

A/C TO ASHRAE A/C TO SMACNA

BASED ON THE VELOCITY= LOW VELOCITY BASED ON VELOCITY. LOW VELOCITY-

DUCT< 2500 FPM, HIGH VELOCITY DUCT> 2500 UPTO 1500 FPM MIDEUM VELOCITY DUCT-
FPM 1500 TO 2500 FPM, HIGH VELOCITY- 2500 TO
5400 FPM

GI SHEET= M/C SELECTION- I.S-277, BASED ON PRESSURE = CLASS 1- UPTO

3.5”WC/100’, CLASS II- 3.5-6.25” WC/100’,
CLASS III- 6.25-12.5 WC/100’

DUCT WORK= I.S-655

31. ELEMENTS OF DUCT:-

BIRDS SCREEN- Used as a first filter it is used before the ahu to eliminate the big particles to reach in
the ahu look like a chicken mesh.

LOUVER:- it is used to pave the path for the air to the ahu. Plenium box:- used for the collection of

return air.

Canvas:- used after the ahu to eliminate the sound after the duct.

Flanges :- it is used to connect the two duct.

BDD:- (back draft damper)- it is used to protect the element of ahu by protecting the returning of air.
 13

Gasket:- used in b/w two element of the duct for the proper sealing (not allow the air to leak).

Cleats:- used to collect the two flanges.

Slotted c channel:- used as a support used as the bottom of the duct provide rigid support.

Flexible duct- used at the starting of the duct after the ahu, at the end of the ahu, used to connect the
duct to the diffuser and grill, used where it is difficult to deal with the metal duct at the sharp turn.

Thermal insulation:- to cope with the heating or cooling effect leakage from the duct.

Acoustic insulation:- use to cope with the sound.

Turning vanes:- it is very important to maintain the cosy flow of the air to deny the turbulence at the turns

and maintain the laminarity of the air at the sharp turn turning vanes.

Offset :- when it is needed to take the duct at different altitude or when we have to cross the columb or
any obstacle we use the offset. .

Taper:- used in between two different dia duct.

Dummy/ end cap:- it is used at the end of the duct.

V.C.D:- (VOLUME CONTROL DAMPER):- A Volume Control Damper (VCD) is a valve that stops or regulates the
flow of air inside a duct, VAV box, air
 14

handler units, or other air handling equipment. A VCD may be used to cut off central air conditioning to an
unused room, or to regulate it for room-by-room temperature and climate control

32. Elements of HVAC:-

T.F.A:- (treated fresh air unit):- it only deal with the air exchange only.

Treated Fresh Air Units incorporating Heating/Cooling Coils: These systems are generally used where
large volume of fresh is bought in. Most commercial applications need temperature and relative
humidity control for comfort for which fresh air needs to be treated. ( used for fan coil unit).

Note:- Do not deal with the cooling of the air like ahu.

FAN:-

Axial fan

Centrifugal fan Exaust fan

Propeller fan

Cabinet fans:- small fan for exhaust

Bifurcated fans:- belt driven fan

Smoke spill air fans:- to get the room of the smoke out of room.

Air separator:- use to eliminate the air lock.( seperate the air fom the water in the pipes.)

Expansion tank:- when there is the pressure drop due to leakage expansion of tank will manage it

Booster pump:- put water in the expansion tank.

Note:- the expansion tank is used to expand the water when there is pressure drop by help of booster
tank from up tank.

Heating pump:- it is in the boilers to boil.

Scrubber:- it is used for the kitchen exhaust, installed over the head of the cook.
 15

PAC:- is use to cool the electronic area it provide high cooling effect, direct cooling and high pressure.

AIR WASHER:- filter dry air and supply it to the room divide dirt from the atmospheric air.

Silicon sealent:- its function is to close the gap in the duct.

Shoe piece duct:- used when we are arranging the branch in the main duct.( used to divide the cfm for
the branching purpose)

Humidifier:- use to humidify the air by the help of the sprinkler.

fire damper:- it is used for the purpose of saving the hvac system at the time of fire.

D.P sensor :- dp sensor is use to see the pressure diff in the duct , we use this sensor to test that
pressure according to the design is coming inside the duct or not.

CROSS TALK ATTENUATORS:-use for the small offices when the rooms are parted into the small
officesCTS is installed over small false ceiling it will transfer air with each other & it will exit yhe
return air.

V.A.U: - (ventilation air units) provide fresh air to specified area.

jet fan:- it is the large size fan use in basement ventilation and in the parking areas.

Exhaust air units:- Toilet exhaust units(TEU), STP exhaust air unit (STPEAU), WTP exhaust air
unit(WTPEAU) , kitchen exhaust unit, pantry exhaust unit, plant room exhaust unit, pump room
exhaust air unit.

Size of copper pipe:- ¾”, 3/8”, 5/4”, 5/8”, ½”, 1”.(inches)

REDUCERS:- it is used to connect two diffuser of different size it is of two type concentric and eccentric
diffuser( eccentric one is more better b’cos concentric one leds to friction and also the scrap loss.

33. GRILLs:- use to supply the air

I) 0ºgrills:- spot sooling

ii) 30º grills:- side throw

iii) 60º grills:- side throw

iiii) egg carate grills:- used in floor & where PAC is installed.

34. DIFFUSER:- it is used to diffuse the air in the room.

a) 1 way diffuser
 16

b) 2 way diffuser

c) three way diffuser

d) 4 way diffuser

e) slotted diffuser( single slotted, double slotted, 3 slotted, 4 slotted

f) jet nozzle diffuser

g) disc valve diffuser

h) round diffuser( these diffusers will be controlled by damper name callerd HIT &MIX damper), (used in
malls )

35. various height in duct design and reading.

BOS= bottom of slab

BOB= bottom of beam.

BOD= bottom of ceiling

BOC= bottom of false ceiling

BOF= bottom of false ceiling

FFC= finished floor level

SSL= structured slab level.

36. SELECTION OF DIFFUSE SIZE ACC. TO CFM.

CFM SAD/RAD CFM

UPTO 150 6”*6”
150TO 300 9”*9”
301 TO 500 12”*12”
501 TO 700 15”*15”
701 TO 1000 18”*18”
1001 TO 1400 24”*24”

DATA REQUIRED FOR SELECTION

A) Total air flow(cfm) for the area served

B) Suggested location
C) Ceiling height
D) Type of ceiling
 17

E) Type of application

37. SELECTION OF GRILLS ACCORDING TO THE CFM

CFM SAG/RAG SIZE

50 TO 150 10”*6”
175 TO 350 20”*6” OR 16”*8”
400 TO 500 24”*6” OR 20”*8”
505 TO 600 30”*6” OR 24”*8”
605 TO 750 40”*6” OR 30”*8”
755 TO 900 48”*6” OR 36”*8”
905 TO 1000 40”*8”
1025 TO 1200 48”*8”

38. PIPE

PIPE MATERIAL

A) MS PIPES
B) GI PIPES
C) CARBON STEEL
D) STAINLESS STEEL
E) COPPER

CLASSIFICATION OF PIPE-

I) CLASS A PIPES- UPTO 1.5 MM

II) CLASS B PIPES – UPTO 3.5 MM

III) CLASS C PIPES- UPTO 5.56 MM

PIPE FITTINGS

1) Connecting flanges
2) Dead end flanges
3) V- groove is done, for quality work, to avoid leakage,
4) Elbow, reducers, t-pipe
5) Flanges
6) Nipples (small dia tubes use to connect guage to the pipe)
7) Coupling (threaded pipes ,groove pipes)

39. Pipe support

 18

A) Threaded rod

B) L&c angle

C) u- clamp

D) PUF saddle support ( poly utherene foam)

40. Valves- is use to control and to access the flow

Butterfly valves:- A butterfly valve is a valve which can be used for isolating or regulating flow. The
closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for
quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve designs
as well as being lighter in weight, meaning less support is required. The disc is positioned in the center of
the pipe; passing through the disc is a rod connected to an actuator on the outside of the valve. Rotating
the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is
always present within the flow, so a pressure drop is always induced in the flow, regardless of valve
position.

Gate valve:- A gate valve, also known as a sluice valve, is a valve that opens by lifting a round or
rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing
surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of
fluid and minimum restriction is desired. The gate faces can form a wedge shape or they can be parallel.
Gate valves are primarily used to permit or prevent the flow of liquids, but typical gate valves shouldn't be
used for regulating flow, unless they are specifically designed for that purpose.

Note:- butterfly and gate valves are of normally open or normally closed type.

Globe valve:- A globe valve, different from ball valve, is a type of valve used for regulating flow in
a pipeline, consisting of a movable disk-type element and a stationary ring seat in a
generally spherical body.[1]

Globe valves are named for their spherical body shape with the two halves of the body being separated
by an internal baffle. This has an opening that forms a seat onto which a movable plug[2] can be screwed

in to close (or shut) the valve. The plug is also called a disc ordisk.[3][4] In
globe valves, the plug is connected to a stem which is operated by screw action using a handwheel in
manual valves. Typically, automated globe valves use smooth stems rather than threaded and are
opened and closed by an actuator assembly.
 19

Ball valve:- A ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball
(called a "floating ball") to control flow through it. It is open when the ball's hole is in line with the flow and
closed when it is pivoted 90-degrees by the valve handle. [1] The handle lies flat in alignment with the flow
when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve's
status.[2]

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long
periods of disuse. These qualities make them an excellent choice for shutoff applications, where they are
often preferred to gates and globe valves, but they lack their fine control in throttling applications.

NOTE:- GLOBE VALVE AND BALL VALVE IS TYPE OF BALANCING VALVE.

NRV VALVES:- (CHECK VALVES) A check valve, clack valve, non-return valve or one-way valve is
a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.

Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and
the other for fluid to leave. There are various types of check valves used in a wide variety of applications.

PRESSURE GAUGE:- Many techniques have been developed for the measurement
of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum
gauges.

A manometer is an instrument that uses a column of liquid to measure pressure, although the term is
currently often used to mean any pressure measuring instrument.

Temperature gauge:- use to check the temperature at appoint.

FLOW SWITCH:- A flow sensor is a device for sensing the rate of fluid flow. Typically a flow sensor is
the sensing element used in a flow meter, or flow logger, to record the flow of fluids. As is true for all
sensors, absolute accuracy of a measurement requires a functionality for calibration.
 20

STRAINER:- strainer is used to clean the liquid.

BTU metre:- BTU meters measure the energy content of liquid flow in British thermal units (BTU), a basic
measure of thermal energy.

41.Definations and theory are :-

 ASHRAE:- American society of heating refrigeration and air conditioning

 The drain pipes are used in the ahu to release the water accumulated as sweat due to the
condensation of water vapour.

 HEPA FILTERS:- High-efficiency particulate arrestance (HEPA),[1][2] also sometimes

called high-efficiency particulate arresting or high-efficiency particulate air, is a type of air
filter. Filters meeting the HEPA standard have many applications, including use in medical
facilities, automobiles, aircraft and homes. The filter must satisfy certain standards of efficiency
such as those set by the United States Department of Energy (DOE). To qualify as HEPA by US
government standards, an air filter must remove (from the air that passes through) 99.97% of
particles that have a size of 0.3 µm. HEPA filters are composed of a mat of randomly arranged
fibres. [4]The fibres are typically composed of fiberglass and possess diameters between 0.5 and
2.0 micrometers. Key factors affecting its functions are fibre diameter, filter thickness, and face
velocity. The air space between HEPA filter fibres is typically much greater than 0.3 μm. The
common assumption that a HEPA filter acts like a sieve where particles smaller than the largest
opening can pass through is incorrect and impractical. Unlike membrane filters at this pore size,
where particles as wide as the largest opening or distance between fibres can not pass in
between them at all.

 Term chiller off means- energy off term chiller shut down means all water is removed from
it.

 Mechanical gauge:- use to find static pressure.


 21

42. Duct terminologies

SAD SUPPLY AIR DUCT/DIFFUSER

RAD RETURN AIR DUCT

BOD BOTTOM OF DUCT

BOFC BOTTOM OF FALSE CEILING

BOS BOTTOM OF SLAB

BOG BOTTOM OF GRILL

SAG SUPPLY AIR GRILL

RAG RETURN AIR GRILL

BOR BOTTOM OF ROOF

43. STANDARDS AND CODES

II ISHRAE INDIAN SOCIETY OF HEATING REFRIGERATION AIR CONDITIONING& ENGINEERING

ASHRAE AMERICAN SOCIETY OF HEATING REF. AND AIR CONDITIONING

ISO INDIAN STANDARD OFD ORGANISATION

I.S:655 HVAC SYSTEM DUCT

I.S:659 SAFETY CODE FOR A.C SYSTEM

I.S:1239 M.S TUBES AND PIPES

I.S:4894 CENTRIFUGAL FANS

I.S:5312 CHECK VALVE

I.S:8183 THERMAL INSULATION MATERIALS

I.S:325 III PHASE INDUCTION MOTOR

ECBC ENERGY CONSERVING BUILDING CODES

ANSI AMERICAN NATIONAL STANDARD INSTITUTE

NEMA NATIONAL ELECTRICAL MANUFACTURING ASSOCIATION

ETL ELECTRICAL TESTING LABORATARIES

CSA CANADIAN STANDARDS ASSOCIATION

 22

NEA NATIONAL ELECTRICAL CODES

IEC INTERNATIONAL ELECRO CHEMICAL COMISSION

44. methods for finding the duct dimention

 Equal friction method:- in this we consider the friction as constant 0.085 as per standard
for all cfm
Eg;- 100 cfm 0.085
200 cfm 0.085
300 cfm 0.085 …….. cont….
We put the value of cfm and friction in the duct sizer as constant and other value come
automatically
 Velocity reduction method :- we are considering preferred standard we take cfm and
velocity value from standard value and put in the duct sizer we get the friction value
according to that.
Note:- SMACNA standard
 High velocity duct:- main duct--> 2500 to 4500 cfm
Branch duct

45. HEAT LOAD CALCULATION:- according to the heat load calculation the designer will suggest the
client to go with the a.c method { split , window, package ……. Etc.)

HEAT TRANSFER MODES

A. CONDUCTION:- Heat transfer through walls and roofs

B. CONVECTION:- through the flow of atmosphere
C. RADIATION:- through the window glass.

SURVEYING:-
 23

A) EXTERNAL SURVEYING:- SURVEY OUT SIDE OF THE BUILDING

1. ORIENTATION- standard direction of the building
2. Latitude- the direction of building where the rays are falling
3. Altitude- surface of sea level to ground.
B) BUILDING SURVEYING:- it consist of the calculation of the building material consist of civil work
wall, glass, roof, ceiling, door and floors.
C) INTERNAL SURVEYING:- the materials which are present inside the room like light, equipment,
people.

To calculate the heat load in a required area we have to go in the three steps.
a) Internal h.l.c:- to calculate the heat load of the internal object which produces heat the
equipments which are not exposed to the sun.( person, lights, equipments, partition, ceiling,
floors, doors)
b) External h.l.c:- it is the hlc for the external objects which are exposed to the sun{ wall, roof,
glass windows)
c) External to internal h.l.c:-hlc of air which transfer the heat from outside to inside.
 Outside air (atmospheric air, ventilation air)
 Infiltration (small holes)

SURVEY OF THE BUILDING ( INDOOR AND OUT DOOR UNIT)

 Where there is no obstacle to the air flow and where the cooled air can be evenly distributed.
 A solid place where the unit or the wall will not vibrate.
 A place where wiring and piping work will be easy to conduct
 A place where receiving part is not exposed to the direct rays of the sun.or the strong rays of the
street lighting.
 Outdoor unit must be installed where the good air circulation can be obtained
 A place where the unit will not be effected by other heat sources.
 Do not install th outdoor near sea side or where there is possibility of chlorine gas.
BUILDING SURVEYING:-
 The accurate survey of the load components of the space to be air conditioned is the
basic requirement for a realistic estimate of the cooling load.
 The completeness and accuracy of all drawing is very impotant.
 Some time survey by photograph is very important.

ORIENTATION OF BUILDING:-

LOCATION OF THE AIR CONDITIONED W.R.T .

 Compass point (sun , wind effect )

 Near by permanent structure shading effect.
 Reflective surfaces ( water sands , parking lots)
USE OF SPACES:-
 Offices
 Hospitals
 Department stores
 m/c shops
 factory
 restaurants etc.

PHYSICAL DIMENTION OF SPACE:-

 24

 LENGTH
 WIDTH
 HEIGHT
 CLEARANCE B/W CEILING FALSE CEILING AND THE BEAM.

COLUMB AND BEAMS:-

 SIZE
 DEPTH
 LOCATION ETC.

CONSTRUCTION MATERIALS:-

 WALL
 ROOF
 CEILING
 FLOOR
 PARTITION
 INSULATION

SURROUNDING CONDITION:-

 Exterior colour of the wall and roofs shaded by adjacent building or sunlight, surrounding space
conditioned or un condition.

DOORS:-

 Location
 Type
 Size
 Frequency of use

PEOPLE:-

 No of people
 Duration of occupancy
 Nature of activity
 Room dry bulb temp.

LIGHTNING:-

 Wattage at peak
 Type of light ( incandescent, fluroresent, exposed)
 If there is lack of information it is required to estimate on the basis of watt per squ. Ft)

WINDOW:-

 Size
 Location
 Wood or metal
 Type of glass single or multi layered.
 25

Stairways elevator & escalators:-

 location
 temperature of space (if open or unconditioned).

MOTORS:-

 LOCATION
 NAME PLATE
 HORSE POWER

Appliances:-

 Business machines
 Electronic equipments
 Location
 Rated
 Wattage
 Steam or gas or power comsumption
 Loaded or unloaded
 VENTILATION
 CFM PER PERSON
 CFM PER SQURE FT
 CFM AS PER NO OF AIR CYCLE.

Heat load calculation procedure :-

i. STUDY THE CO-ORDINATE DRAWING

Civil drawing
Architectural drawing
Fire fighting drawing
Electrical drawing
PHE drawing
Roof drawing
Plan view top view
Elevating drawing front view
Sectional drawing
ii. Location
New delhi
Latitude: 28.35 ºN 65’-4”
Altitude 216 mtr
iii. Type of application :- residential
iv. orientation
29’-8”

v. Thermal condition
 26

DBT Fº WBT Fº RH % HR gr/lb Daily range

Outdoor 110 75 20 76 25
condition
Indoor 75 63 50 68
condition
difference 35 12 30 8

For daily range selection page no. 83 table 12

Correction valve 17.5 ( among daily range and correction value take maxm of the daily range and
correction value

vi. Find the transmittion co- efficient ‘ u-factor”

Conductivity (k)= 1/resistivity
Transmittion co-efficient U= 1/resitivity=1/R1+R2+R3…….
U=btu per hr/sqft*ΔT

ELEMENT SPECIFICATION U-FACTOR

WALL (PAGE NO 92) Solid brick – fade and 0.33 btu per hr/sqft*ΔT
common3/8” plaster on the wall
sand aggregareates 3/8”
GLASS (PAGE NO 90) Double plane ordinate glass no 0.90( no unit)
shade
ROOF (PAGE NO 94) Concrete (sand and gravel) 0.20 btu per hr/sqft*ΔT
6” , suspended plaster , ½ inches
insulation,
FLOOR(PAGE NO. 99) Floor tile , sand aggr. , 59 lbs sq. 0.57 btu per hr/sqft*ΔT
ft.), ½ “ (sand plane )
PARTITION (PAGE NO. 96 ) 0.37 btu per hr/sqft*ΔT
vii. Differential temperature ΔT (page 82)

element direction ΔT Fº
wall N 2+25=27
E 18+25=45
W 10+25=35
S 10+25=35
At 140lbsqft/4 p.m

glass N 23
E 12
W 163
S 12

ROOF EXPOSED TO SUN 32+25=57

@80LBS PER Sq.ft
Partition or ceiling or Diff 5ºF =ODT-IDT-5
floor 110-75-5
=30ºF

viii. Summary
 27

ix. Internal sensible heat load

 28

x. External sensible heat.

 29

xi. External to internal sensible heat.

 30

xii. Room latent heat loads.

 31

xiii. Total room sensible heat load.

xiv. Effective room sensible heat loads

 32

xv. Effective room sensible heat factor

 33

xvi. Outside air load at cooling coil

xvii. Grand total heat load

 34

xviii. Apparatus dew point

xix. Dehumidification rise

xx. Dehumidified rise

 35

46. equal friction method. (model)

s.no section CFM FPM FRICTIO EQUIVALENT W H L A.R

N ROUND
DUCT DIA
1 A-B 3980 1250 0.085 24.20 45 12 40 4:1
2 B-B’ 450 “ 0.085 10.6 10 10 15 1:1
3 B-B” 150 “ 0.085 7.5 8 8 9 1:1
4 0.085 8.0
5 0.085
6 0.085
7

THIS IS ALWAYS CONSTANT

VELOCITY REDUCTION METHOD ( FOR LOW VELOCITY 1250 FOR MAIN/ 750 FOR BRANCH )

s.no section CFM FPM FRICTIO EQUIVALENT W H L A.R

N ROUND
DUCT DIA
1 A-B 3980 1250 0.085 24.20 45 12 40 4:1
2 B-B’ 450 750 0.091 10.2 10 10 15 1:1
3 B-B” 150 750 0.181 6.1 6 6 9 1:1
4 7.0
5
6
7
36