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HVAC EXAM QUESTIONS AND ANSWERS
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HVAC EXAM QUESTIONS AND ANSWERS
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HVAC EXAM QUESTIONS AND ANSWERSAir-Conditioning
the simultaneous control of the temperature, humidity, motion and purity of the air in a
confined space.
1. Cooling and de-humidifying of air
2. Heating or humidifying of air
3. Cleaning of air or filtration
4. Circulation of air
Functions or Elements of Air-Conditioning
for summer cooling, temperatures of 68 deg to 74 deg F and 50% relative humidity are
a frequent design average.
Air-Conditioning Standards for Cooling and De-humidifying
for winter cooling, temperatures of 70 deg to 75 deg F and relative humidity of 30% to
35% are found most satisfactory.
Air-Conditioning Standards for Heating and Humidifying
air velocity should average 4.57 to 7.6 meters per min measured 36" above the floor.
Air-Conditioning Standards for Air Motion
a. 5 cuft to 7-1/2 cuft of air per minute per person (5-71/2 cuft/min/pers). In rooms where
smoking is not allowed
b.25 cuft to 40 cuft of air per minute per person allowed in rooms where smoking is
permitted.
Air-Conditioning Standards for Air Supply
1. Passing the air through a spray of cold water
2. Passing the air through coils containing cold water
3. Passing the air through coils containing the refrigerant itself; in this case the coils are
called "direct expansion" coils
4. Passing the air through a combination of sprays and coils
Methods of Cooling and De-humidifying
1. Freon* is a gas at normal temperature and pressure. It is first subjected to high
pressure in a compressor which raises its boiling point and temperature.
2. At the same high pressure, the vapor is piped into condenser coils where it is cooled
,by water to a degree below its liquefaction point. It condenses into a liquid state and still
under high pressure, passes to the evaporator.
3. In the evaporator, the pressure is relieved by the suction stroke of the compressor.
The boiling point of the liquid refrigerant drops and evaporation into a vapor takes place.
The water which surrounds the evaporator coils gives up its heat in causing the
vaporization at low pressure, thus reducing its temperature to the temperature of the
refrigerant. The cold water can then be piped at this low temperature to any desired
point and sprayed to cool the passing air. The refrigerant is sucked back into the
compressor and the cycle recommences
Refrigeration Cycle
refrigerant used for cooling.
Freon
Dichlorodiflouromethane
Freon 12
Trichloromonoflouromethane
Freon 11
1. Central Systems
2. Split Type Air Conditioning System
3. Window Type Air Conditioning System
Types of Air-Conditioning Systems
Central Systems
Types of Air-Conditioning Systems
Split Type Air Conditioning System
Types of Air-Conditioning Systems
,Window Type Air Conditioning System
Types of Air-Conditioning Systems
All-Season Centralized Air Conditioning System
Air Conditioning System which consists of the following:
a. A method of cooling, a refrigeration plant
b. A source of heating such as a boiler or furnace
c. An Air Handling Unit (AHU) equipped with filters, pre-heater, spray, cooling coils and
re-heater
d. The air distributing equipment composed of ducts, fans and air outlets
e. The necessary manual or automatic controls
1. Refrigeration
2. Cooling and De-humidifying Equipment
3. Heating and Humidifying Equipment
4. Air Cleaning Equipment
5. Air Distribution Equipment
6. Control Equipment
Air-Conditioning Equipment classficatoins
1. Compressors
2. Condensers
3. Evaporators
Air-Conditioning refrigeration equipment
Compressors
, (Air-Conditioning refrigeration equipment)
an electric pump, or heart of the system, that circulates the refrigerant in a closed loop
between the condenser and evaporator coils.
1. Piston Type or Reciprocating Compressors
2. Centrifugal Compressors
(Air-Conditioning refrigeration equipment)
Types of compressors
Piston Type or Reciprocating Compressors
(Air-Conditioning refrigeration equipment)
Types of compressor for tonnages up to 100 tons
Centrifugal Compressors
(Air-Conditioning refrigeration equipment)
Types of compressor which are quieter, have fewer vibration problems, require less
maintenance and with better operating control
Condensers
(Air-Conditioning refrigeration equipment)
used in central air conditioning systems typically has a heat exchanger section to cool
down and condense incoming refrigerant vapor into liquid, a compressor to raise the
pressure of the refrigerant and move it along, and a fan for blowing outside air through
the heat exchanger section to cool the refrigerant inside
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