HVAC Systems
HVAC
Systems
The objectives
of HVAC systems are to provide an acceptable level of occupancy comfort and
process function, to maintain good indoor air quality (IAQ), and to keep system
costs and energy requirements to a minimum.
The components
in a typical roof-mounted package HVAC system (Figure 1-1) are:
1. An indoor fan (blower) to circulate the
supply and return air.
2. Supply air duct work in which the air
flows from the fan to the room.
3. Air devices such as supply air outlets and
return air inlets.
4. Return
air duct work in which the air flows back from the room to the mixed air chamber
(plenum).
5. A mixed air chamber to receive the
return air and mix it with outside air.
6. An
outside air device such as a louver, opening or duct to allow for the entrance of
outside air into the mixed air plenum.
7. A filter section to remove dirt and
dust particles from the air.
8. Heat
exchangers such as a refrigerant evaporator and condenser coil for cooling, and
a furnace for heating.
9. A
compressor to compress the refrigerant vapor and pump the refrigerant around
the refrigeration system.
10. An outdoor fan (blower) to circulate
outside air across the condenser coil.
11. Controls to start, stop or regulate the
flow of air, refrigerant, and electricity.
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| HVAC Systems, pharmavoicebd24, |
Figure 1-1.
Roof-mounted Package Air Conditioning Unit
HVAC
COMPONENTS
H is for
Heating
Boilers (Figure
1-2)
• Types of
Boilers
— Steam
— Water
• Boiler
Pressures
— Low
— High
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| HVAC Systems, pharmavoicebd24, |
Figure 1-2.
Fire Tube Boiler
• Boiler Fuels
— Natural Gas
— Oil
— Coal
— Electricity
• Boiler
Configurations
— Fire Tube
— Water Tube
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| HVAC Systems, pharmavoicebd24, |
Figure 1-3.
Natural Gas Furnace
• Furnace Fuels
— Natural Gas
— Oil
— Coal
— LPG (Liquid
Petroleum Gas)
— Electricity
Heating Coils
(Figure 1-4)
• Types of
Heating Coils
— Steam
— Water
— Electrical
V is for
Ventilation for each of the following:
1)
Approximately 20 cfm (cubic feet per minute) of air volume per person of
outside air (OA) for ventilation for non-smoking areas.
2) Make-up air
(MUA) for exhaust systems such as:
— Kitchen hoods
— Fume hoods
— Toilets
3) Room
(conditioned space) pressurization
— +0.03 to +0.05 inches of water gage for
commercial buildings.
AC is for Air
Conditioning
(air conditioner, air conditioning unit)
(air conditioner, air conditioning unit)
For most of us,
air conditioning means comfort cooling with either chilled water systems or
refrigerant systems. Both of these
systems include
cooling coils to remove heat from the air.
• Chilled Water
Systems
—
Vapor-compression system
— Absorption
system
• Refrigeration
(DX) Systems
—
Vapor-compression system
• Cooling Coils
— Water coil
— Refrigerant
(DX) coil
Cooling and
heating coils (Figure 1-4) are heat transfer devices or heat exchangers. They
come in a variety of types and sizes and are designed for various fluid
combinations: water, refrigerant or steam. Water coils are used for heating,
cooling or dehumidifying air and are most often
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| HVAC Systems, pharmavoicebd24, |
Figure 1-4. Hot
Water Heating Coil
made of copper
headers and tubes with aluminum or copper fins and galvanized steel frames.
AC (Air
Conditioning) also means conditioning the air in the following ways:
• Temperature
(tempering the air)
Cooling
(removing heat)
Heating (adding
heat)
• Humidity
control
— Dehumidifying
(removing moisture)
— Humidifying
(adding moisture)
• Volume of
airflow
— cfm (cubic
feet per minute)
• Velocity
(speed) of airflow
— fpm (feet per
minute)
• Cleaning
— Filtering
• Pattern of
airflow
— Direction
• horizontal
• vertical
CENTRAL
HVAC SYSTEM COMPONENTS
(heating and cooling systems, furnace repair)
(heating and cooling systems, furnace repair)
Components
Cooling Tower,
CT
Condenser Water
Pump, CWP
Condenser Water
Supply, CWS
Condenser Water
Return, CWR
Condenser, Cond
Evaporator
(Water Chiller, Water Cooler), Evap
Compressor,
Comp
The condenser,
evaporator and compressor together are typically called the Chiller, CH
Chilled Water
Pump, CHWP
Chilled Water
Supply, CHWS
Chilled Water
Return, CHWR
Chilled Water
Coil (Cooling Coil), CC
Heating Water
Coil (Hot Water Coil, Heating Coil), HC
Heating Water
Supply, HWS or HHWS
Heating Water
Return, HWR or HHWR
Heating Water
Pump, HWP
Boiler, B
Supply Air Fan,
SAF, SF
Supply Air
Duct, SA
Manual Volume
Damper, MVD
Flex Duct, Flex
Ceiling
Diffuser, CD
Return Air
Inlet, RA
Return Air
Duct, RA
Return Air Fan,
RAF
Return Air
Dampers, RA, ATC Damper (Automatic Temperature
Control Damper)
Exhaust Air
(Dampers), EA, ATCD
Outside Air
(Dampers) OA, ATCD
Filters, F
Water Valves,
3-way or 2-way ATC Valve (Automatic Temperature Control Valve). MBV (Manual
Balancing Valve) or Self-regulating Balancing Valve
This AHU is
located on the roof and is therefore designated as a “roof top unit” (RTU).
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