HVAC

HEATING VENTILATION
AND AIR CONDINTIONING
(HVAC)
BY
SAJJAD AHMAD
OFFICER PRODUCTION

2
HEATING VENTILATION & AIR-CONDITIONING
CONTENTS
 INTRODUCTION
 FUNCTIONS
 TYPES
 COMPONENTS OF HVAC
A. AIR HANDLING UNIT (AHU)
 HOUSING
 MIXING BOX
 FILTERS
 HEATING COILS
 COOLING COILS
 DE-HUMIDIFIERS
 HUMIDIFIERS
 BLOWER
B. DUCTS
C. GRILLS/REGISTERS/DIFFUSERS

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INTRODUCTION
HVAC stands for Heating Ventilating and Air-conditioning system.
HEATING:
 Heating is provided by heaters. Heaters are appliances whose purpose
is to generate heat for the building. This can be done via central
heating or by direct heating system.
VENTILATION:
 Ventilating or ventilation (the V in HVAC) is the process of
exchanging or replacing air in any space to provide high indoor air
quality which involves temperature control, oxygen replenishment,
and removal of moisture, odors, smoke, heat, dust, airborne
bacteria, carbon dioxide, and other gases. Ventilation removes
unpleasant smells and excessive moisture, introduces outside air,
keeps interior building air circulating, and prevents stagnation of the
interior air.
 Ventilation includes both the exchange of air to the outside as well
as circulation of air within the building. It is one of the most
important factors for maintaining acceptable indoor air quality in
buildings.

4
INTRODUCTION
Air-Conditioning:
An air conditioning system provides cooling and humidity
control for all or part of a building. Air conditioned
buildings often have sealed windows, because open
windows would work against the system intended to
maintain constant indoor air conditions.
Dehumidification (air drying) in an air conditioning
system is provided by the evaporator. Since the
evaporator operates at a temperature below the dew
point, moisture in the air condenses on the evaporator
coil tubes. This moisture is collected at the bottom of the
evaporator in a pan and removed by piping to a central
drain or onto the ground outside.

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FUNCTIONS OF HVAC
 To Control Temperature.
 To Control Humidity.
 To Develop Differential Pressure.
 To Prevent Cross Contamination.
 To Maintain proper Air Movement.

6
TYPES OF HVAC
There are two types of Air-Conditioning system.
1. Ducted
2. Non Ducted
 Ducted
It includes,
 Chilled Water System
 Dx System (Direct Expansion)
 Non Ducted
It includes
1. Window System
2. Split system

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TYPES OF HVAC
Ducted System:
Chilled water system.
In chilled water system the refrigeration system in chiller is used to
first chill the water, which is then used to chill the air used for cooling
the rooms or spaces.
Technically speaking, water can be classified as a refrigerant
Chilled water system is indirect method of cooling the air.
A typical chiller uses the process of refrigeration to chill water in a
chiller barrel. This water is pumped through chilled water piping to the
building AHU where it will pass through a coil.
 Air is passed over this coil and the heat exchange process takes place.
The heat in the air is absorbed into the coils and then into the water.
The water is pumped back to the chiller to have the heat removed. It
then makes the trip back to the building AHU and the coils.

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TYPES OF HVAC
Chilled water system:
Chiller.
Many chillers have cooling towers where the heat removed in the chiller
barrel is transferred to another barrel.
 It is the condenser barrel where the refrigerant is condensed and sent back
to the evaporator barrel to remove the heat. The process is in reverse in the
condenser barrel. The water absorbs heat from the refrigerant and allows it
to condense.
The water is then transferred to a cooling tower where the heat in this
water is removed to the atmosphere.
 Once the heat is removed from the water it is pumped back to the chiller
barrel to absorb more heat from the refrigerant.

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TYPES OF HVAC
Ducted System:
Direct Expansion (DX Type).
In the DX system the air used for cooling the room or space is
directly passed over the cooling coil of the refrigeration plant.
DX is direct type of cooling air.
In the direct expansion or DX types of air conditioning plants the air
used for cooling space is directly chilled by the refrigerant in the
cooling coil of the air handling unit (AHU).
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.

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TYPES OF HVAC
Non Ducted System:
Window system.
 Window system 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.
Split System.
The split air conditioner comprises of two parts,
i. Outdoor unit
ii. Indoor unit
 The outdoor unit, fitted outside the room contain components
like the compressor, condenser and expansion valve.
 The indoor unit comprises the evaporator or cooling coil and the
cooling fan.

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COMPONENTS OF HVAC
A. Air Handling Unit (AHU)
 The definition of air handling unit from ANSI/AHRI Standard 430-2009
states that it is "A factory-made encased assembly consisting of a fan or
fans and other necessary equipment to perform one or more of the
functions of circulating, cleaning, heating, cooling, humidifying,
dehumidifying and mixing of air.
 An air handler is usually a large metal box containing a blower, heating or
cooling elements, filter racks or chambers, sound attenuators, and
dampers. Air handlers usually connect to a ductwork ventilation system
that distributes the conditioned air through the building and returns it to
the AHU.
 (AHU) are the lungs of any HVAC system.
 An air handling unit is a device used to regulate and circulate air as part
of the heating, ventilation and air conditioning system.
 The AHU takes in outside air, reconditions (filtered and either heated or
cooled) it and supplies it as fresh air to the air conditioned room.
 Air handler that conditions 100% outside air, and no recirculated air, is
known as a makeup air unit (MAU).

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COMPONENTS OF AIR HANDLING UNIT
1.Housing.
The housing that contains all the other components of an AHU is usually make
of metal, some are painted to prevent corrosion.
In sections where the fans and the coil are located,1-2 inches of polyurethane
foam or PU is used to insulate them to prevent the condensation on the panel.
2.Mixing Box.
Mixing box has air inlets that are attached to the dampers.
This is the place where the outside fresh 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.
3.FILTERS:
Filters are typically placed first in the AHU in order to keep all the
downstream components clean.
Coarse-grade Panel filters or Pre filters are placed in front of a fine-grade Bag
filters and then come "final" filtration medium (HEPA).
The panel filter is cheaper to replace and maintain, and thus protects the
more expensive bag filters.

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COMPONENTS OF AHU
Filter Classification
Following types of filters are used.
1. Standard Filters
2. Aerosol Filters
1. Standard Filters
It include following
i. Coarse Filters
ii. Medium Filters
iii. Fine filters
i. Coarse Filters G1,G2,G3,G4
It includes
a. Mesh Filters (Aluminum Washable)
b. Pre Filters/Panel Filters/Primary Filters
ii. Medium Filters M5,M6
iii. Fine Filters F7,F8,F9
it includes
Bag Filters/Secondary Filters

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COMPONENTS OF AHU
Filter Classification
2. Aerosol Filters:
It includes,
i. Efficient Particulate Air Filters (EPA) E10,E11,E12
ii. High Efficient Particulate Air Filters (HEPA) H13,H14
iii. Ultra Low Particulate Air Filters (ULPA) U15,U16,U17

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COMPONENTS OF AIR HANDLING UNIT
4.COOLING COILS
 Cooling coils are used to cool and dehumidify the air.
 There are two methods to cool air in cooling coils.
i. Chilled water system
in this air in coil is cooled by circulating chilled water.Use of Chiller.
ii. Direct Expansion (Dx Type)
 In this air is cooled directly by refrigerants which circulate in the coil.
 Both DX & chilled water cooling coils are available for use depending on the system
design. These coils are arranged in rows with different fin spacing.
 Aluminum 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.
5.HEATING COILS
Heating Coils are used to heat the air.
 Are of 2 types
i. In Direct heat exchangers.
Air is heated by the hot water which circulate in coils. Use of Boiler.
ii. Direct heat exchanger
Air is heated directly by electric heaters or gas heaters.

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COMPONENT OF AHU
6.Dehumidifier
 If dehumidification is required, then the cooling coil is employed to over-cool so that the dew
point is reached and condensation occurs.
 A heater coil placed after the cooling coil re-heats the air (therefore known as a re-heat coil)
to the desired supply temperature. This process has the effect of reducing the relative
humidity level of the supply air.
7.Humidifiers
 During winter, the humidity level of the air can be low hence causing discomfort to the
occupants/working.
 The humidity of the air is increased by using the humidifiers. Here are the commonly used
humidifiers:
i. Spray Type
 Has a header and spray nozzles that spray water with a pressure of 15 psi or more.
ii. Steam Pan Type
It 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.
iii. Steam Grid Type
It 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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COMPONENTS OF AHU
8:Air Blower/Fan
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
Air handlers typically have a large squirrel cage blower or fan driven by
eleectric motor to move the air. The blower may operate at a single
speed, offer a variety of set speeds, or be driven by a variable-frequency
drive to allow a wide range of air flow rates.
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 blowers in an air handler can create substantial vibration and the
large area of the duct system would transmit this noise and vibration to
the occupants of the building. To avoid this, vibration isolators (flexible
sections) are normally inserted into the duct immediately before and
after the air handler and often also between the fan compartment and
the rest of the AHU.

29
COMPONENTS OF HVAC
B. DUCTING SYSTEM
Ducts are passages 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.
TYPES OF DUCTS:
Following are types of ducts
SAD = (Supply Air Duct)
It supplies air from AHU to the required area to be conditioned. This air is treated
air & contains all the desired qualities as provided by the air conditioning system.
RAD =(Return Air Duct)
It supplies air from conditioned area back to the AHU for retreatment and
recirculation or fully exhaust in the air.
FAD = (Fresh Air Duct)
It supplies ambient/fresh air to the AHU from the outside atmosphere. This air is
supplied to the AHU inlet from the outside atmosphere after being initially
treated/filtered.

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COMPONENTS OF HVAC
DUCT SHAPES
i. Rectangular Duct
ii. Circular Duct
iii. Square Duct
iv. Spiral Duct
DUCTING MATERIALS
Following type of materials are used
i. Galvanized iron
 Low Cost & Easy Fabrication.
ii. Aluminum Sheet Metal
 It is used for light weight & resistance to moisture application.

32
COMPONENTS OF HVAC
iii. Fiber Glass Duct
 Low velocity application only otherwise heavy vibration will generate.
iv. Thick Black Mid Steel
This sheet are used for exhaust duct.
v. High Corrosion Resistance Application
 Marine galvanized steel sheets with heavy deposition of zinc (not less than
270gms/sq.m) for internal ducting & stainless steel grade 316L for external ducting.
vi. PUF (polyurethane foam)
 These Ducts are flexible & do not require insulation as PUF is an insulation material.
But it is costly & may generate toxic gases in case of fire.

33
COMPONENTS OF HVAC
CLAIFICATION OF DUCTS
i. Low Pressure Duct Work
Velocity <600mpm & static pressure 5cm of H20 gauge.
No specified requirements of class of cleanliness.
Space do not require specific +ve pressure.
ii. Medium Pressure Duct Work
Velocity <600mpm & static pressure 5-15cm of H20 gauge.
 Specified class of cleanliness often incorporates deburring (exclude) of coil, absolute
filters, supply, Return, Exhaust & Fresh air ducts.
Clean room application require Medium pressure duct work because heavy pressure lose
take place through high efficiency filters.
Care to be taken to seal all duct joints to prevent leakage. Joint should be soldered or
sealed with good quality sealant.
Sheet used should be free from flaking or any such defects as this likely to add eroded
metal particles to the conditioned air.
iii. High Pressure Duct Work
Velocity >600mpm & static pressure 15cm of H20 gauge.
For specified class or marine applications.
Pressure drop in supply Air Ducting: 10-15cm of H20 gauge.
Pressure drop in Return Air Ducting: 5-10cm of H20 gauge. circular (or) spiral ducting
(machine fabricated) is recommended as the helically wound longitudinal joints provide
adequate mechanical strength.

34
COMPONENTS OF HVAC
C. Grille/Register/Diffuser
GRILLE:
 A fixed opening through which air passes. Typically used for return air applications.
 A grill is used on the return side to protect the system from objects entering the intake. As a grill is
often used on the return side, it must be free of a damper to ensure the unrestricted flow of air back
to the central system
REGISTER:
 A grille equipped with a damper which supplies conditioned air. Typically used for supply air
applications.
DIFFUSER:
 An air flow device designed to discharge conditioned air in a specific direction, path, or pattern.
 Used for supply air applications.
 The main role a diffuser plays is spreading the air around a given space to increase the impact area of the air.
 A diffuser also allows air to be comfortably spread, as opposed to pouring directly out of a duct onto the space
below it. The diffuser is beneficial for noise reduction.
 Diffuser can come in many shapes (square, rectangle, linear or round), the most popular and recognizable
style is the large round diffuser.
MATERIAL OF CONSTRUCTION:
i. Aluminum
ii. Mild steel
iii. Stainless steel
iv. Plastic

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COMPONENTS OF HVAC
Types of Grille:
There are following types of grilles,
i. Egg grate grille
ii. Bar grille
iii. Transfer grille
Types of Diffusers:
i. Louvre bladed diffuser
ii. Straight bladed diffuser
iii. Linear slot diffuser
iv. Swirl diffuser
v. Floor outlet diffuser
vi. Jet diffuser
vii. Punkah diffuser
viii. Barrel diffuser
ix. Perforated diffuser
x. Plain face diffuser

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For Correction & feed back
email@
sajjad_formanite@yahoo.com

HVAC

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