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NATE EXAM- AIR CONDITIONING AND
HEAT PUMPS|QUESTIONS AND
ANSWERS
The maximum temperature at which refrigerant may be stored is ____°F when the
container is no more than ____% full of liquid by volume.
a. 120°F, 60%
b. 125°F, 60%
c. 125°F, 80%
d. 135°F, 80% - correct-answer -c (125°F, 80%)
Boiling of the refrigerant occurs in which system component?
a. Compressor
b. Condenser
c. Evaporator
d. Metering device - correct-answer -c (Evaporator)
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Why is superheat necessary in a system that utilizes hermetic compressors?
a. It ensures that dry vapor reaches the compressor so that mechanical damage
does not occur
b. It increases system capacity
c. It prevents liquid refrigerant from gassing the metering device
d. Superheat is necessary only when open compressors are being used - correct-
answer -a (It ensures that dry vapor reaches the compressor so that mechanical
damage does not occur)
When the heat load on an evaporator increases, what is the effect on the system?
a. Suction pressure decreases and discharge pressure increases
b. Suction pressure increases and discharge pressure decreases
c. Suction pressure and discharge pressure both decrease
d. Suction pressure and discharge pressure both increase - correct-answer -d
(Suction pressure and discharge pressure both increase)
What type of energy is transferred when work is done in the condenser?
a. Latent heat energy
b. Sensible heat energy
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c. Both latent and sensible heat energy
d. Neither latent nor sensible heat energy - correct-answer -c (Both latent and
sensible heat energy)
What is the primary function performed by a thermal expansion valve?
a. It maintains the correct superheat in the hot vapor leaving the compressor
b. It maintains the correct superheat in the suction vapor leaving the evaporator
c. It maintains the proper subcooling level in the liquid refrigerant
d. It prevents flash vapor bubbles from developing in refrigerant entering the
evaporator - correct-answer -b (It maintains the correct superheat in the suction
vapor leaving the evaporator)
Which component pumps refrigerant through the system and raises the vapor
temperature?
a. Accumulator
b. Compressor
c. Condenser
d. Evaporator - correct-answer -b (Compressor)
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How are hermetic compressor motors cooled?
a. With air drawn around the compressor shell by the condenser fan
b. With water circulated through tubing wrapped around the compressor shell
c. With suction vapor drawn from the evaporator
d. With a combination of air and water - correct-answer -c (With suction vapor
drawn from the evaporator)
Heat pump compressors sometimes run hotter than compressors used in cooling-
only units because heat pump compressors ____.
a. exhibit low refrigerant density at low suction pressures during the heating cycle
b. pump liquid refrigerant during the cooling cycle
c. must prevent ice formation during the defrost cycle
d. must heat indoor spaces in the winter - correct-answer -a (exhibit low
refrigerant density at low suction)
When is a crankcase heater most needed?
a. Early in the morning during the cooling cycle
b. When the compressor is operating in very cold winter weather
c. When the compressor is operating in very humid conditions
NATE EXAM- AIR CONDITIONING AND
HEAT PUMPS|QUESTIONS AND
ANSWERS
The maximum temperature at which refrigerant may be stored is ____°F when the
container is no more than ____% full of liquid by volume.
a. 120°F, 60%
b. 125°F, 60%
c. 125°F, 80%
d. 135°F, 80% - correct-answer -c (125°F, 80%)
Boiling of the refrigerant occurs in which system component?
a. Compressor
b. Condenser
c. Evaporator
d. Metering device - correct-answer -c (Evaporator)
,2|Page
Why is superheat necessary in a system that utilizes hermetic compressors?
a. It ensures that dry vapor reaches the compressor so that mechanical damage
does not occur
b. It increases system capacity
c. It prevents liquid refrigerant from gassing the metering device
d. Superheat is necessary only when open compressors are being used - correct-
answer -a (It ensures that dry vapor reaches the compressor so that mechanical
damage does not occur)
When the heat load on an evaporator increases, what is the effect on the system?
a. Suction pressure decreases and discharge pressure increases
b. Suction pressure increases and discharge pressure decreases
c. Suction pressure and discharge pressure both decrease
d. Suction pressure and discharge pressure both increase - correct-answer -d
(Suction pressure and discharge pressure both increase)
What type of energy is transferred when work is done in the condenser?
a. Latent heat energy
b. Sensible heat energy
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c. Both latent and sensible heat energy
d. Neither latent nor sensible heat energy - correct-answer -c (Both latent and
sensible heat energy)
What is the primary function performed by a thermal expansion valve?
a. It maintains the correct superheat in the hot vapor leaving the compressor
b. It maintains the correct superheat in the suction vapor leaving the evaporator
c. It maintains the proper subcooling level in the liquid refrigerant
d. It prevents flash vapor bubbles from developing in refrigerant entering the
evaporator - correct-answer -b (It maintains the correct superheat in the suction
vapor leaving the evaporator)
Which component pumps refrigerant through the system and raises the vapor
temperature?
a. Accumulator
b. Compressor
c. Condenser
d. Evaporator - correct-answer -b (Compressor)
, 4|Page
How are hermetic compressor motors cooled?
a. With air drawn around the compressor shell by the condenser fan
b. With water circulated through tubing wrapped around the compressor shell
c. With suction vapor drawn from the evaporator
d. With a combination of air and water - correct-answer -c (With suction vapor
drawn from the evaporator)
Heat pump compressors sometimes run hotter than compressors used in cooling-
only units because heat pump compressors ____.
a. exhibit low refrigerant density at low suction pressures during the heating cycle
b. pump liquid refrigerant during the cooling cycle
c. must prevent ice formation during the defrost cycle
d. must heat indoor spaces in the winter - correct-answer -a (exhibit low
refrigerant density at low suction)
When is a crankcase heater most needed?
a. Early in the morning during the cooling cycle
b. When the compressor is operating in very cold winter weather
c. When the compressor is operating in very humid conditions
