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HVAC NEC 2023

HVAC Certification Practice Test 11

This test covers superheat and subcooling fundamentals — what they measure, normal ranges, and how to calculate them from pressure and temperature readings.

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HVAC electrical exams cover electrical theory (Ohm's Law, circuits), transformers, single-phase and three-phase motors, control wiring, safety, and troubleshooting.

Requirements vary by state. HVAC technicians typically need EPA 608 certification and may need a separate electrical license for line voltage work.

Exam Tip: Only vapor can be superheated, and only liquid can be subcooled. Keep straight which measurement point (evaporator outlet vs. condenser outlet) goes with which calculation.

25

Questions

25 min

Time

70%

Pass

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HVAC Certification Practice Test 11 — Question List

Question 1: What does "superheat" measure in a refrigeration system?

How many degrees the refrigerant vapor is above its saturation (boiling) temperature
How many degrees the liquid refrigerant is below its saturation temperature
The total heat content of the refrigerant at the compressor discharge
The temperature difference between indoor and outdoor air

Question 2: What does "subcooling" measure in a refrigeration system?

How many degrees the liquid refrigerant is below its saturation (condensing) temperature
How many degrees the vapor is above its boiling point
The pressure drop across the metering device
The amperage drawn by the condenser fan

Question 3: Where is superheat typically measured on a residential split system?

At the condenser outlet / liquid line
At the evaporator outlet / suction line near the compressor
At the thermostat sensor
At the control transformer secondary

Question 4: Where is subcooling typically measured on a residential split system?

At the evaporator inlet
At the compressor discharge only
At the condenser outlet / liquid line
At the indoor thermostat

Question 5: Suction pressure gives a saturation temperature of 40°F. The suction line temperature reads 52°F. What is the superheat?

92°F
12°F
40°F
8°F

Question 6: Discharge pressure gives a saturation temperature of 110°F. The liquid line temperature reads 98°F. What is the subcooling?

208°F
98°F
12°F
22°F

Question 7: On a typical fixed-orifice residential system, what is a commonly accepted normal superheat range?

Roughly 8-15°F
Roughly 50-60°F
Exactly 0°F
Roughly 100-110°F

Question 8: What is a commonly accepted normal subcooling range for a residential system?

Roughly 10-15°F
Roughly 45-50°F
Exactly 1°F
Roughly 90-100°F

Question 9: True or False: Liquid refrigerant can be superheated.

True
False
Only on very cold days
Only in a TXV system

Question 10: True or False: Refrigerant vapor can be subcooled.

True
False
Only during defrost
Only on very hot days

Question 11: How does a technician find the saturation temperature needed to calculate superheat or subcooling?

Read the system pressure with a gauge, then look up the matching temperature on a pressure-temperature (P/T) chart for that refrigerant
Measure the outdoor air temperature only
Use the thermostat's indoor temperature reading
Saturation temperature is always exactly 32°F

Question 12: Suction saturation temperature is 45°F. The suction line reads 53°F. What is the superheat, and is it inside the normal 8-15°F range?

98°F, and it is far above normal
8°F, and it is at the low edge of normal
8°F, and it is far below normal
45°F, and it is far above normal

Question 13: Discharge saturation temperature is 105°F. The liquid line reads 88°F. What is the subcooling, and is it inside the normal 10-15°F range?

193°F, and it is far above normal
17°F, and it is slightly above the normal range
17°F, and it is far below normal
88°F, and it is normal

Question 14: Why does a properly set superheat matter for compressor protection?

It confirms refrigerant is fully vaporized before reaching the compressor, preventing liquid from entering it
It has no relationship to compressor protection
It only matters for the condenser fan motor
It prevents the thermostat from short-cycling

Question 15: Why does adequate subcooling matter for the metering device?

It has no effect on the metering device
It ensures solid liquid, not vapor bubbles, reaches the metering device
It only matters for three-phase compressors
It controls the reversing valve position

Question 16: Why can't a technician use an R-410A pressure-temperature chart to find the saturation temperature of an R-22 system?

Each refrigerant has its own unique pressure-temperature relationship
P/T charts are universal and work for any refrigerant
R-22 has no measurable saturation temperature
Only synthetic oils require refrigerant-specific charts

Question 17: Suction saturation temperature is 38°F. The suction line temperature reads 60°F. What is the superheat?

98°F
22°F
38°F
18°F

Question 18: Discharge saturation temperature is 118°F. The liquid line reads 112°F. What is the subcooling?

230°F
112°F
6°F
16°F

Question 19: What would a suction line temperature reading equal to the saturation temperature (0°F superheat) suggest?

Refrigerant may still be partially liquid at that point, which is a compressor damage risk
This is the ideal, target reading for every system
It means the system has too little refrigerant
It has no relevance to compressor safety

Question 20: What two measurements does a technician need, at minimum, to calculate superheat at the evaporator outlet?

Suction pressure (converted to saturation temperature) and actual suction line temperature
Only the outdoor ambient temperature
Only the compressor amperage draw
Only the indoor thermostat setpoint

Question 21: Which metering device is designed to actively hold superheat close to a fixed target as conditions change?

Fixed orifice
TXV (thermostatic expansion valve)
Capillary tube only
None — all metering devices behave identically

Question 22: Which formula correctly calculates subcooling?

Actual liquid temperature minus saturation temperature
Saturation temperature minus actual liquid line temperature
Suction pressure minus discharge pressure
Actual vapor temperature minus saturation temperature

Question 23: Which formula correctly calculates superheat?

Saturation temperature minus actual vapor temperature
Actual vapor temperature minus saturation temperature
Discharge pressure minus suction pressure
Actual liquid temperature minus saturation temperature

Question 24: A technician calculates a negative superheat value (suction line temperature reads lower than the calculated saturation temperature). What does this most likely indicate?

The system is running perfectly and this is the ideal target
A measurement or gauge error, since true superheat cannot physically be negative
The refrigerant charge is exactly correct
This is normal for R-410A systems only

Question 25: Suction saturation is 42°F, suction line reads 50°F. Discharge saturation is 115°F, liquid line reads 103°F. What are the superheat and subcooling?

Superheat 92°F, subcooling 218°F
Superheat 8°F, subcooling 12°F
Superheat 12°F, subcooling 8°F
Superheat 42°F, subcooling 115°F

Key NEC References for This Test

Article	What It Covers
Art. 440	Air Conditioning Equipment — use nameplate MCA and MOCP, not FLA alone
Art. 430	Motors — general motor rules that Art. 440 modifies

Study Tip: Practice reading ladder diagrams. Trace each rung from L1 to the load: contacts open → circuit dead. Contacts closed → current flows. This is how HVAC electrical troubleshooting works.

EXAM CARD HVAC

Questions25

Time limit25 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 Art. 440 & electrical theory