Next NATE AC Service Practice Test 2

NATE_AC_SERVICE NEC 2023

NATE AC Service Practice Test 1

This test covers the basics of superheat and subcooling on residential AC systems. You will practice reading saturation temperatures, calculating superheat and subcooling, and reading normal ranges for fixed-orifice and TXV systems.

TOPICS COVERED

NATE AC 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: Superheat is always measured on vapor, and subcooling is always measured on liquid. Keep that one rule straight and many questions get easier.

30

Questions

30 min

Time

70%

Pass

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NATE AC Service Practice Test 1 — Question List

Question 1: What is superheat?

The pressure drop across the metering device
The difference between actual vapor temperature and saturation temperature
The difference between liquid line temperature and outdoor temperature
The total heat removed by the evaporator

Question 2: What is subcooling?

The difference between saturation temperature and actual liquid temperature
The difference between suction pressure and head pressure
The amount of heat absorbed in the evaporator
The temperature drop across the condenser fan

Question 3: True or False: Only refrigerant vapor can have superheat. Liquid refrigerant cannot be superheated.

False, liquid can also be superheated
True
False, only subcooling applies to vapor
True, but only in TXV systems

Question 4: Where does a technician normally measure superheat on a residential split system?

At the compressor discharge port
At the condenser inlet
At the thermostat sensor
On the suction line near the evaporator outlet

Question 5: Where does a technician normally measure subcooling on a residential split system?

On the liquid line near the condenser outlet
On the suction line near the compressor
At the evaporator inlet
At the indoor blower motor

Question 6: On a system using a fixed-orifice metering device, what is a typical normal superheat range?

Roughly 8 to 15 degrees F
Roughly 40 to 50 degrees F
Roughly 1 to 3 degrees F
Roughly 60 to 70 degrees F

Question 7: What is a typical normal subcooling range for most residential AC systems?

Roughly 30 to 40 degrees F
Roughly 2 to 4 degrees F
Roughly 50 to 60 degrees F
Roughly 10 to 15 degrees F

Question 8: A technician measures superheat that is much lower than normal. What does this most likely indicate?

A refrigerant leak in the liquid line
A dirty air filter only
Overcharge or evaporator flooding
A failed run capacitor

Question 9: A technician measures superheat that is much higher than normal. What does this most likely indicate?

Overcharge of refrigerant
Undercharge or a restriction in the refrigerant circuit
A dirty condenser coil only
Normal operation, no action needed

Question 10: A technician measures subcooling that is much lower than normal. What does this most likely indicate?

Undercharge
Overcharge
A dirty air filter
A miswired thermostat

Question 11: A technician measures subcooling that is much higher than normal. What does this most likely indicate?

Low outdoor ambient temperature only
A weak blower motor
Overcharge or a liquid-line restriction
Normal for all systems

Question 12: True or False: A thermostatic expansion valve (TXV) uses a sensing bulb on the suction line to actively hold superheat near a target value.

False, only fixed orifice valves use a sensing bulb
False, TXVs control subcooling, not superheat
True, but only on commercial systems
True

Question 13: The suction line saturation temperature is 40 degrees F. The technician measures the suction line temperature at 52 degrees F. What is the superheat?

92 degrees F
12 degrees F
8 degrees F
40 degrees F

Question 14: The condensing saturation temperature is 105 degrees F. The technician measures the liquid line temperature at 95 degrees F. What is the subcooling?

10 degrees F
200 degrees F
95 degrees F
15 degrees F

Question 15: True or False: A fixed-orifice metering device has no feedback control, so its superheat varies more with load and outdoor conditions than a TXV.

False, fixed orifice devices hold superheat perfectly steady
False, TXVs vary more than fixed orifice
True, but only in heating mode
True

Question 16: A technician finds superheat well below normal and subcooling above normal on the same system. What does this combination most likely point to?

A refrigerant leak
A dirty air filter
Overcharge
A failed thermostat

Question 17: A technician measures superheat of 30 degrees F on a fixed-orifice system, well above the normal range, along with low subcooling. What should the technician check first?

The condenser fan capacitor size
Refrigerant charge level, possible undercharge
The thermostat program schedule
A dirty condenser coil

Question 18: Which two readings does a technician need to calculate superheat?

Suction line temperature and suction saturation temperature
Liquid line temperature and outdoor temperature
Indoor return air temperature and supply air temperature
Compressor amp draw and voltage

Question 19: Which two readings does a technician need to calculate subcooling?

Return air temperature and supply air temperature
Suction line temperature and suction saturation temperature
Liquid line temperature and condensing saturation temperature
Outdoor ambient and indoor setpoint

Question 20: An R-410A system has been off for hours and has equalized at 75°F. The P-T chart shows about 217 psig for R-410A at 75°F, but the gauges read 245 psig. What does this suggest?

The system is undercharged
The refrigerant in the system is subcooled
Nothing; standing pressure is normally about 30 psi above the chart
Non-condensable gases (such as air or nitrogen) are in the system

Question 21: An R-410A system's liquid line pressure is 365 psig, which the P-T chart shows as 110°F saturation. The liquid line temperature is 98°F. What is the subcooling?

110°F
8°F
12°F
22°F

Question 22: Why do technicians check superheat and subcooling instead of just checking pressures alone?

Because pressures alone do not confirm correct charge; temperature must also be checked
Because gauges are not accurate enough to use
Because pressure readings are illegal to use for charging
Because only subcooling matters, superheat is not needed

Question 23: Suction saturation temperature is 45 degrees F. The suction line reads 58 degrees F. What is the superheat, and is it normal for a fixed-orifice system?

103 degrees F, abnormally high
3 degrees F, abnormally low
58 degrees F, abnormally high
13 degrees F, within normal range

Question 24: A technician confirms subcooling is well below the target and superheat is well above the target, with no visible leaks found yet. What is the most appropriate next step?

Recover all refrigerant and replace the compressor immediately
Increase the thermostat setpoint and take no other action
Carefully add refrigerant while monitoring readings, and keep checking for a leak
Remove refrigerant from the system

Question 25: How does a technician find the saturation temperature needed for superheat and subcooling calculations?

By guessing based on outdoor temperature
By reading pressure and converting with a pressure-temperature chart
By measuring compressor amp draw
By checking the thermostat display

Question 26: What does a pressure-temperature (PT) chart show a technician?

The saturation temperature matching a given pressure
The superheat target for the system
The recommended breaker size for the compressor
The airflow rating of the blower

Question 27: A technician clamps a thermometer on the liquid line near the condenser outlet. What reading is this used to calculate?

Compressor amp draw
Static pressure
Subcooling
Airflow (CFM)

Question 28: A technician clamps a thermometer on the suction line near the evaporator outlet. What reading is this used to calculate?

Line voltage
Duct static pressure
Blower RPM
Superheat

Question 29: True or False: It is possible for a system to show normal superheat while subcooling is abnormal, for example if a liquid-line restriction is present.

False, superheat and subcooling always move together
True
False, subcooling only exists on fixed-orifice systems
False, this is impossible on any system

Question 30: For the most reliable charge diagnosis on a fixed-orifice system, which pair of readings should a technician check together?

Superheat and subcooling checked together
Compressor amp draw alone
Indoor humidity alone
Thermostat setpoint alone

EXAM CARD NATE_AC_SERVICE

Questions30

Time limit30 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

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Source: NEC 2026 (NFPA 70)