AZ C-39 Air Conditioning Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
Section 1: HVAC Fundamentals and Refrigeration Principles
1. What is the primary function of an air conditioning system in
cooling mode?
a. To generate cold air directly through chemical reactions
b. To increase indoor air pressure
c. To remove heat and moisture from indoor air and transfer heat
outdoors
d. To convert electrical energy entirely into cold air
Rationale: An air conditioning system removes sensible heat and, when
conditions permit, latent heat from indoor air. The refrigeration cycle
,transfers this heat to the outdoor environment. The system does not
generate cold directly; it moves heat from a lower-temperature indoor
space to a higher-temperature outdoor space using mechanical work.
2. Which component of a conventional split-system air conditioner
absorbs heat from the indoor air?
a. Condenser
b. Compressor
c. Evaporator
d. Receiver
Rationale: The evaporator contains refrigerant at a low pressure and
temperature. As warm indoor air passes over its coil, the refrigerant
absorbs heat and evaporates. The condenser performs the opposite
heat-transfer function by rejecting heat to the outdoor air.
3. What is the primary purpose of the compressor in a vapor-
compression refrigeration system?
a. To reduce refrigerant pressure before evaporation
b. To remove moisture from indoor air
c. To raise refrigerant vapor pressure and temperature so heat can be
rejected outdoors
,d. To convert refrigerant vapor into liquid by direct cooling
Rationale: The compressor draws low-pressure refrigerant vapor from
the evaporator and compresses it into a high-pressure, high-
temperature vapor. This enables the refrigerant to reject heat in the
condenser at a temperature above the outdoor air temperature.
4. Which sequence correctly describes the basic refrigeration cycle?
a. Evaporator, expansion device, compressor, condenser
b. Condenser, compressor, evaporator, expansion device
c. Compressor, evaporator, expansion device, condenser
d. Compressor, condenser, expansion device, evaporator
Rationale: The compressor raises the refrigerant vapor pressure, the
condenser rejects heat and condenses the refrigerant, the expansion
device reduces its pressure, and the evaporator absorbs heat as the
refrigerant boils. The cycle then returns low-pressure vapor to the
compressor.
5. What happens to refrigerant pressure as it passes through a
properly operating thermostatic expansion valve (TXV)?
a. It increases substantially.
b. It remains constant.
, c. It decreases substantially.
d. It alternates between high and low pressure.
Rationale: A TXV meters refrigerant into the evaporator and creates a
pressure drop between the high-pressure liquid side and the low-
pressure evaporator side. This pressure reduction lowers the
refrigerant's saturation temperature, allowing it to absorb heat at the
evaporator.
6. What is superheat in a refrigeration system?
a. The temperature of liquid refrigerant below its saturation
temperature
b. The total heat contained in the condenser
c. The temperature of refrigerant vapor above its saturation
temperature at a given pressure
d. The difference between outdoor and indoor air temperatures
Rationale: Superheat is calculated by subtracting the saturation
temperature corresponding to the measured refrigerant pressure from
the actual vapor temperature. It helps technicians assess evaporator
feeding and ensure that refrigerant entering the compressor is vapor
rather than liquid.
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
Section 1: HVAC Fundamentals and Refrigeration Principles
1. What is the primary function of an air conditioning system in
cooling mode?
a. To generate cold air directly through chemical reactions
b. To increase indoor air pressure
c. To remove heat and moisture from indoor air and transfer heat
outdoors
d. To convert electrical energy entirely into cold air
Rationale: An air conditioning system removes sensible heat and, when
conditions permit, latent heat from indoor air. The refrigeration cycle
,transfers this heat to the outdoor environment. The system does not
generate cold directly; it moves heat from a lower-temperature indoor
space to a higher-temperature outdoor space using mechanical work.
2. Which component of a conventional split-system air conditioner
absorbs heat from the indoor air?
a. Condenser
b. Compressor
c. Evaporator
d. Receiver
Rationale: The evaporator contains refrigerant at a low pressure and
temperature. As warm indoor air passes over its coil, the refrigerant
absorbs heat and evaporates. The condenser performs the opposite
heat-transfer function by rejecting heat to the outdoor air.
3. What is the primary purpose of the compressor in a vapor-
compression refrigeration system?
a. To reduce refrigerant pressure before evaporation
b. To remove moisture from indoor air
c. To raise refrigerant vapor pressure and temperature so heat can be
rejected outdoors
,d. To convert refrigerant vapor into liquid by direct cooling
Rationale: The compressor draws low-pressure refrigerant vapor from
the evaporator and compresses it into a high-pressure, high-
temperature vapor. This enables the refrigerant to reject heat in the
condenser at a temperature above the outdoor air temperature.
4. Which sequence correctly describes the basic refrigeration cycle?
a. Evaporator, expansion device, compressor, condenser
b. Condenser, compressor, evaporator, expansion device
c. Compressor, evaporator, expansion device, condenser
d. Compressor, condenser, expansion device, evaporator
Rationale: The compressor raises the refrigerant vapor pressure, the
condenser rejects heat and condenses the refrigerant, the expansion
device reduces its pressure, and the evaporator absorbs heat as the
refrigerant boils. The cycle then returns low-pressure vapor to the
compressor.
5. What happens to refrigerant pressure as it passes through a
properly operating thermostatic expansion valve (TXV)?
a. It increases substantially.
b. It remains constant.
, c. It decreases substantially.
d. It alternates between high and low pressure.
Rationale: A TXV meters refrigerant into the evaporator and creates a
pressure drop between the high-pressure liquid side and the low-
pressure evaporator side. This pressure reduction lowers the
refrigerant's saturation temperature, allowing it to absorb heat at the
evaporator.
6. What is superheat in a refrigeration system?
a. The temperature of liquid refrigerant below its saturation
temperature
b. The total heat contained in the condenser
c. The temperature of refrigerant vapor above its saturation
temperature at a given pressure
d. The difference between outdoor and indoor air temperatures
Rationale: Superheat is calculated by subtracting the saturation
temperature corresponding to the measured refrigerant pressure from
the actual vapor temperature. It helps technicians assess evaporator
feeding and ensure that refrigerant entering the compressor is vapor
rather than liquid.
