NATE Heat Pump Specialty Certification
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
1. What is the primary function of a reversing valve in an air-source heat pump?
A. Regulate indoor airflow
B. Control compressor speed
C. Change the direction of refrigerant flow
D. Increase refrigerant pressure
Answer: Change the direction of refrigerant flow
Rationale: The reversing valve changes refrigerant-flow direction so the system
can operate in either heating or cooling mode.
2. In heating mode, the outdoor coil of a typical air-source heat pump functions
as the:
A. Condenser
B. Receiver
C. Evaporator
D. Accumulator
Answer: Evaporator
Rationale: During heating operation, the outdoor coil absorbs heat from
outdoor air and therefore operates as the evaporator.
,3. In heating mode, the indoor coil normally functions as the:
A. Evaporator
B. Accumulator
C. Receiver
D. Condenser
Answer: Condenser
Rationale: Refrigerant releases heat and condenses in the indoor coil,
transferring heat into the conditioned space.
4. What component protects many heat pumps from liquid refrigerant returning
to the compressor?
A. Filter-drier
B. Receiver
C. Accumulator
D. Sight glass
Answer: Accumulator
Rationale: A suction accumulator can temporarily store liquid refrigerant and
help prevent liquid from entering the compressor.
5. What is the purpose of a defrost cycle?
A. Increase indoor humidity
B. Lower compressor discharge pressure
C. Remove ice from the outdoor coil
D. Increase indoor airflow
Answer: Remove ice from the outdoor coil
Rationale: Ice buildup restricts airflow and reduces heat transfer, so the heat
pump periodically enters defrost to melt accumulated frost.
,6. During a conventional timed-temperature defrost cycle, the system
temporarily operates in:
A. Normal heating mode
B. Cooling mode
C. Ventilation mode
D. Fan-only mode
Answer: Cooling mode
Rationale: The reversing valve shifts refrigerant flow so hot discharge gas can be
directed through the outdoor coil to melt frost.
7. What component commonly initiates defrost based on outdoor coil
temperature?
A. Indoor thermostat
B. Crankcase heater
C. Defrost sensor
D. Liquid-line solenoid
Answer: Defrost sensor
Rationale: A temperature sensor can detect outdoor-coil conditions indicating
frost accumulation and signal the control board to initiate defrost.
8. What happens to compressor discharge gas during a typical defrost cycle?
A. It bypasses the compressor
B. It goes directly outdoors without entering the coil
C. It is routed through the outdoor coil
D. It is vented to atmosphere
Answer: It is routed through the outdoor coil
Rationale: Hot refrigerant gas heats the outdoor coil during defrost, melting
frost and ice.
, 9. Why is supplemental electric heat commonly installed with an air-source heat
pump?
A. To cool the compressor
B. To replace the reversing valve
C. To provide additional heat when the heat pump cannot meet the load
D. To increase refrigerant pressure
Answer: To provide additional heat when the heat pump cannot meet the load
Rationale: Auxiliary or supplemental heat helps maintain indoor temperature
during low outdoor temperatures or high heating demand.
10. What condition can cause excessive frost formation on an outdoor heat-
pump coil?
A. Excessive indoor airflow
B. Restricted outdoor airflow
C. High indoor temperature
D. Open thermostat contacts
Answer: Restricted outdoor airflow
Rationale: Restricted airflow reduces heat transfer and can cause the outdoor
coil temperature to fall enough for excessive frost to accumulate.
11. What is the main purpose of a crankcase heater?
A. Heat the indoor coil
B. Heat the thermostat
C. Reduce refrigerant migration and oil dilution in the compressor crankcase
D. Increase evaporator airflow
Answer: Reduce refrigerant migration and oil dilution in the compressor
crankcase
Rationale: A crankcase heater helps keep refrigerant from condensing and
migrating into the compressor oil during off cycles.
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
1. What is the primary function of a reversing valve in an air-source heat pump?
A. Regulate indoor airflow
B. Control compressor speed
C. Change the direction of refrigerant flow
D. Increase refrigerant pressure
Answer: Change the direction of refrigerant flow
Rationale: The reversing valve changes refrigerant-flow direction so the system
can operate in either heating or cooling mode.
2. In heating mode, the outdoor coil of a typical air-source heat pump functions
as the:
A. Condenser
B. Receiver
C. Evaporator
D. Accumulator
Answer: Evaporator
Rationale: During heating operation, the outdoor coil absorbs heat from
outdoor air and therefore operates as the evaporator.
,3. In heating mode, the indoor coil normally functions as the:
A. Evaporator
B. Accumulator
C. Receiver
D. Condenser
Answer: Condenser
Rationale: Refrigerant releases heat and condenses in the indoor coil,
transferring heat into the conditioned space.
4. What component protects many heat pumps from liquid refrigerant returning
to the compressor?
A. Filter-drier
B. Receiver
C. Accumulator
D. Sight glass
Answer: Accumulator
Rationale: A suction accumulator can temporarily store liquid refrigerant and
help prevent liquid from entering the compressor.
5. What is the purpose of a defrost cycle?
A. Increase indoor humidity
B. Lower compressor discharge pressure
C. Remove ice from the outdoor coil
D. Increase indoor airflow
Answer: Remove ice from the outdoor coil
Rationale: Ice buildup restricts airflow and reduces heat transfer, so the heat
pump periodically enters defrost to melt accumulated frost.
,6. During a conventional timed-temperature defrost cycle, the system
temporarily operates in:
A. Normal heating mode
B. Cooling mode
C. Ventilation mode
D. Fan-only mode
Answer: Cooling mode
Rationale: The reversing valve shifts refrigerant flow so hot discharge gas can be
directed through the outdoor coil to melt frost.
7. What component commonly initiates defrost based on outdoor coil
temperature?
A. Indoor thermostat
B. Crankcase heater
C. Defrost sensor
D. Liquid-line solenoid
Answer: Defrost sensor
Rationale: A temperature sensor can detect outdoor-coil conditions indicating
frost accumulation and signal the control board to initiate defrost.
8. What happens to compressor discharge gas during a typical defrost cycle?
A. It bypasses the compressor
B. It goes directly outdoors without entering the coil
C. It is routed through the outdoor coil
D. It is vented to atmosphere
Answer: It is routed through the outdoor coil
Rationale: Hot refrigerant gas heats the outdoor coil during defrost, melting
frost and ice.
, 9. Why is supplemental electric heat commonly installed with an air-source heat
pump?
A. To cool the compressor
B. To replace the reversing valve
C. To provide additional heat when the heat pump cannot meet the load
D. To increase refrigerant pressure
Answer: To provide additional heat when the heat pump cannot meet the load
Rationale: Auxiliary or supplemental heat helps maintain indoor temperature
during low outdoor temperatures or high heating demand.
10. What condition can cause excessive frost formation on an outdoor heat-
pump coil?
A. Excessive indoor airflow
B. Restricted outdoor airflow
C. High indoor temperature
D. Open thermostat contacts
Answer: Restricted outdoor airflow
Rationale: Restricted airflow reduces heat transfer and can cause the outdoor
coil temperature to fall enough for excessive frost to accumulate.
11. What is the main purpose of a crankcase heater?
A. Heat the indoor coil
B. Heat the thermostat
C. Reduce refrigerant migration and oil dilution in the compressor crankcase
D. Increase evaporator airflow
Answer: Reduce refrigerant migration and oil dilution in the compressor
crankcase
Rationale: A crankcase heater helps keep refrigerant from condensing and
migrating into the compressor oil during off cycles.
