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NATE_HEATPUMP_SERVICE NEC 2023

NATE Heat Pump Service Practice Test 9

This test covers refrigerant circuit diagnostics specific to heat pumps — how superheat and subcooling measurement points swap roles between heating and cooling mode, and low-ambient cooling controls.

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NATE Heat Pump Service

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Frequently Asked Questions

Yes — completely free with no signup required. Every question includes a full explanation of the correct answer.

Two: the NATE Core exam plus at least one specialty exam (for example AC Service, Heat Pump Service, or Air Distribution Service). You can take them on the same day or separately.

The Core exam has 50 questions and each installation or service specialty exam has 100 questions. You need 70% on each to pass — 35 of 50 on Core and 70 of 100 on a specialty. Check natex.org for the current format before you book.

NATE certification lasts two years. To renew, you submit 16 hours of continuing education or retake the specialty exam before your certification expires.

No. These are independent practice tests written to match the published NATE exam topics. They are not official NATE exam questions.

Exam Tip: In heating mode, the indoor coil is the condenser and the outdoor coil is the evaporator — the opposite of cooling mode. Superheat and subcooling measurement points swap accordingly.

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30 min

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70%

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NATE Heat Pump Service Practice Test 9 — Question List

Question 1: In cooling mode, which coil acts as the evaporator?

The indoor coil
The outdoor coil
Both coils act as evaporators at once
Neither coil acts as an evaporator in cooling mode

Question 2: In heating mode, which coil acts as the evaporator?

The indoor coil
The outdoor coil
Both coils act as evaporators at once
Neither coil acts as an evaporator in heating mode

Question 3: In heating mode, where would a technician measure superheat?

At the outdoor coil outlet / suction line, since the outdoor coil is now the evaporator
At the indoor coil outlet, same as cooling mode
Superheat cannot be measured in heating mode
At the reversing valve body directly

Question 4: In heating mode, where would a technician measure subcooling?

At the indoor coil outlet / liquid line, since the indoor coil is now the condenser
At the outdoor coil outlet, same as cooling mode
Subcooling cannot be measured in heating mode
At the crankcase heater location

Question 5: Does the actual formula for calculating superheat change between heating and cooling mode on a heat pump?

No — superheat is always actual vapor temperature minus saturation temperature; only the measurement location changes with the mode
Yes, the formula reverses completely in heating mode
Yes, superheat becomes subcooling in heating mode
The formula only applies in cooling mode, not heating

Question 6: What is the purpose of a low-ambient cooling control (fan-cycling pressure switch) on a heat pump?

To allow cooling operation in cooler outdoor weather by maintaining adequate head pressure
To control the indoor blower speed only
To prevent the reversing valve from ever energizing
To heat the compressor crankcase

Question 7: Without a low-ambient cooling control, what could happen if a heat pump tries to run in cooling mode on a cool day?

Head pressure could drop too low, causing poor system performance or nuisance faults
The system would run more efficiently than normal
Nothing — cool weather has no effect on cooling mode performance
The reversing valve would permanently fail

Question 8: Many heat pumps use two metering devices, one for each direction of refrigerant flow. Why?

Refrigerant flows in opposite directions between heating and cooling mode, and check valves route flow through the correct metering device for each mode
One metering device is just a spare part with no function
Heat pumps never use more than one metering device
The second metering device only operates during defrost

Question 9: If a heat pump is overcharged, does this affect only cooling mode or both modes?

Only cooling mode is affected
Only heating mode is affected
Both modes — the total refrigerant charge is the same regardless of which mode the system is operating in
Overcharge has no effect on heat pumps

Question 10: Many manufacturers recommend checking and adjusting heat pump refrigerant charge in which mode?

Heating mode only, never cooling mode
Cooling mode, since pressure-temperature relationships are typically more stable and predictable for charging in that mode
During defrost only
It makes no difference which mode is used

Question 11: What typically controls whether the reversing valve is energized or de-energized?

A solenoid coil that shifts the valve's internal slide based on an electrical signal (often the O or B terminal circuit)
Refrigerant pressure alone, with no electrical signal involved
The condenser fan motor directly
The crankcase heater

Question 12: Why is a crankcase heater especially relevant for heat pumps sitting idle in cold weather?

Cold outdoor conditions increase the risk of refrigerant migrating into and condensing in the compressor oil while it is off
Crankcase heaters are only used in cooling-only systems
Cold weather has no relationship to refrigerant migration
The crankcase heater only operates during defrost

Question 13: Before measuring superheat on a heat pump, what must a technician first confirm?

Which mode the system is operating in, so they know which coil is currently acting as the evaporator
The color of the refrigerant lines
The thermostat brand
The indoor humidity level only

Question 14: A heat pump in heating mode shows high superheat measured at the outdoor coil outlet. What does this suggest, following the same overcharge/undercharge logic used in cooling mode?

Possible undercharge or a restriction, since the same high-superheat pattern applies regardless of which coil is acting as the evaporator
This always means the system is overcharged in heating mode
High superheat has no meaning in heating mode
This always means the reversing valve is stuck

Question 15: A heat pump in heating mode shows high subcooling measured at the indoor coil outlet. What does this suggest?

Possible overcharge or a liquid-line restriction, following the same logic used for subcooling in cooling mode
This always means the system is undercharged
High subcooling is impossible to measure in heating mode
This always means the defrost control has failed

Question 16: True or False: In heating mode, subcooling is measured using the superheat formula because the coils have swapped roles.

True
False
Only true during defrost
Only true on TXV systems

Question 17: What is the general function of a check valve paired with a metering device on a heat pump?

It allows refrigerant to bypass that metering device when flow is reversed, routing flow to the correct device for the current mode
It has no function related to metering devices
It only operates during the defrost cycle
It permanently blocks refrigerant flow in both directions

Question 18: A fan-cycling pressure switch used for low-ambient cooling control typically senses pressure where?

On the high side / discharge side of the system
On the low side / suction side of the system
Inside the indoor thermostat
On the crankcase heater circuit

Question 19: A customer reports the indoor air feels warm and cool at different times without any thermostat mode change, and airflow seems inconsistent. What refrigerant-circuit component is a reasonable first suspect?

A leaking or malfunctioning reversing valve allowing refrigerant to partially bypass internally
The thermostat batteries are always the cause
The crankcase heater is always the cause
The condensate drain line is always the cause

Question 20: Which statement correctly summarizes superheat and subcooling on a heat pump across both modes?

The formulas stay the same in both modes; only the measurement location moves to whichever coil is currently acting as evaporator or condenser
Superheat and subcooling only exist in cooling mode
The formulas fully reverse in heating mode
Superheat and subcooling cannot be measured on any heat pump

Question 21: A heat pump lacking a functioning low-ambient cooling control is run in cooling mode on a 55°F day. What symptom might the technician observe?

Unusually low head pressure and possible erratic or poor cooling performance
Unusually high head pressure with no other symptoms
No effect at all under any circumstances
The reversing valve immediately fails

Question 22: Why should a technician always follow the specific manufacturer's charging chart or instructions for a given heat pump, rather than assuming general rules apply exactly?

Metering device design, check valve arrangement, and target superheat/subcooling values can vary between manufacturers and models
All heat pumps from every manufacturer are identical in every respect
Manufacturer charts are never accurate and should be ignored
Charging charts only apply to gas furnaces, not heat pumps

Question 23: Why should a technician avoid taking superheat/subcooling readings for charge diagnosis while the system is actively in a defrost cycle?

Defrost temporarily runs the system in cooling mode with the outdoor fan off, which does not reflect normal steady-state operation
Readings during defrost are always identical to normal operation
It is actually the best time to take charge readings
Defrost has no effect on refrigerant pressures or temperatures

Question 24: Which coil acts as the condenser in cooling mode?

The indoor coil
The outdoor coil
Both coils act as condensers at once
Neither coil acts as a condenser in cooling mode

Question 25: Which coil acts as the condenser in heating mode?

The indoor coil
The outdoor coil
Both coils act as condensers at once
Neither coil acts as a condenser in heating mode

Question 26: A technician measures what they believe is subcooling at the outdoor coil while the system is actually in heating mode. What mistake has likely been made?

They measured at the wrong coil — in heating mode, subcooling should be measured at the indoor coil (the condenser), not the outdoor coil
No mistake was made — this is the correct location in every mode
Subcooling should never be measured on any heat pump
The outdoor coil is always the condenser regardless of mode

Question 27: Does the type of refrigerant in a heat pump change between heating and cooling mode?

No — the same refrigerant is used in both modes; only the direction of flow and which coil does what changes
Yes, heating mode uses a completely different refrigerant
Yes, the refrigerant converts to a different chemical in heating mode
Heat pumps do not use refrigerant in heating mode

Question 28: A heat pump in cooling mode shows high superheat at the indoor coil outlet. What does this suggest?

Possible undercharge or a restriction, same as on any standard cooling system
This always means the reversing valve has failed
High superheat is impossible to measure in cooling mode
This always means the system is overcharged

Question 29: What practical habit helps a technician avoid confusion when diagnosing a heat pump's refrigerant circuit?

Always confirm and note the current operating mode before taking or interpreting any pressure/temperature reading
Mode never needs to be considered when taking readings
Only the outdoor temperature matters, never the operating mode
Readings are identical regardless of mode, so no habit is needed

Question 30: Summarize the single most important concept for diagnosing a heat pump's refrigerant circuit across both modes.

Identify which coil is currently the evaporator and which is the condenser before applying any refrigeration diagnostic logic
Always assume the indoor coil is the evaporator no matter what
Refrigerant diagnostics do not apply to heat pumps at all
Mode never matters for any refrigerant-side diagnosis

EXAM CARD NATE_HEATPUMP_SERVICE

Questions30

Time limit30 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)