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HVAC NEC 2023

HVAC Certification Practice Test 10

A mixed-review test combining Ohm's Law, motor and capacitor diagnosis, ladder diagram logic, three-phase safety, refrigerant-circuit electrical components, and grounding/lockout-tagout safety into realistic troubleshooting scenarios.

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HVAC Practice tests

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Frequently Asked Questions

Yes — completely free with no signup required.

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: Scenario questions test whether you can apply a rule, not just recite it — read the whole scenario carefully before picking an answer.

14

Questions

25 min

Time

70%

Pass

Timer starts immediately. Progress is auto-saved.

HVAC Certification Practice Test 10 — Question List

Question 1: A control circuit has 24V applied across a component with 40 ohms of resistance. How much current is flowing?

0.6 amps
1.6 amps
6 amps
960 amps

Question 2: A technician measures 0V across a component that should be energized. What does this tell the technician?

The component is definitely shorted
Current is not flowing through that part of the circuit
The circuit is definitely a parallel circuit
The transformer is oversized

Question 3: A 24V control circuit has a low-pressure switch, a high-pressure switch, and a contactor coil all wired in series. One safety switch opens. What happens?

Only the switch that opened loses power, the rest keeps running
The whole rung loses power and the contactor de-energizes
Current reroutes automatically around the open switch
Nothing changes because it is a parallel circuit

Question 4: A condenser fan motor uses a run capacitor but has no start capacitor or centrifugal switch. What type of motor is this?

CSCR
CSIR
PSC (Permanent Split Capacitor)
Shaded pole

Question 5: A run capacitor is rated 35 MFD ±6%. A meter reads 32.9 MFD. Is this capacitor within spec?

No, it is far too low and must be replaced
Yes — 32.9 is within the acceptable range
It cannot be determined without knowing the voltage rating
No, capacitors must always read exactly at nameplate value

Question 6: On a ladder diagram, what is the resting (de-energized) state of a normally-open (NO) contact?

Closed — it opens when energized
Open — it closes only when its coil is energized
It has no defined resting state
It is always closed regardless of the coil

Question 7: Put these steps in the correct order for a cooling call: (1) NO contactor contacts close, (2) compressor runs, (3) thermostat closes Y, (4) contactor coil energizes.

1, 2, 3, 4
3, 4, 1, 2
2, 1, 4, 3
4, 3, 2, 1

Question 8: Why does a true three-phase induction motor not need a start capacitor?

Three-phase motors do not have windings
The three phases, offset 120 degrees, naturally create a rotating magnetic field
Three-phase power is always low voltage
Three-phase motors use a permanent magnet rotor instead

Question 9: A three-phase scroll compressor was just reconnected after service and is running backward. What is the danger?

It draws current and runs hot without pumping refrigerant correctly, risking rapid damage
There is no real danger, it just runs a little quieter
It will automatically correct itself after a few minutes
Reversed rotation only affects fan motors, not compressors

Question 10: How is reversed rotation on a three-phase compressor typically corrected?

Replace the compressor entirely
Swap any two of the three phase conductors
Increase the supply voltage
Add a start capacitor

Question 11: A system shuts down and a technician finds the low-pressure switch has opened. What does this most likely indicate?

A refrigerant leak, restricted metering device, or frozen evaporator coil
An oversized compressor
A dirty air filter only
Too much refrigerant in the system

Question 12: What condition would most likely cause a high-pressure switch to trip and shut down the compressor?

A dirty condenser coil or a failed condenser fan
A weak run capacitor only
A blown control-circuit fuse
Low outdoor ambient temperature

Question 13: Why does a compressor have a crankcase heater?

To keep the oil warmer than the refrigerant, preventing refrigerant migration into the oil
To preheat refrigerant before it enters the evaporator
To prevent the compressor housing from rusting
To keep the control transformer warm in winter

Question 14: During a heat pump defrost cycle, what happens to the outdoor fan motor?

It runs at full speed to help melt the frost faster
It shuts off so the outdoor coil heats up faster
It reverses direction only
Nothing changes about the outdoor fan during defrost

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

Questions14

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