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HVAC NEC 2023

HVAC Certification Practice Test 1

This test covers Ohm's Law and basic circuit math for HVAC technicians. You will practice calculating voltage, current, and resistance, and see how series and parallel circuits behave differently when a component fails.

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HVAC Practice tests

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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: Write down the Ohm's Law triangle (V, I, R) before you start. Covering the value you need to find shows you which two values to multiply or divide.

25

Questions

25 min

Time

70%

Pass

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HVAC Certification Practice Test 1 — Question List

Question 1: What does Ohm's Law describe?

The relationship between voltage, current, and resistance in a circuit
The relationship between refrigerant pressure and temperature
The amount of heat a motor can safely dissipate
The speed at which electricity travels through a wire

Question 2: A heater draws 10 amps of current through a resistance of 12 ohms. What is the voltage across the heater?

12V
120V
1.2V
22V

Question 3: A control circuit has 24V applied across a 48-ohm resistance. How much current flows?

2A
48A
0.5A
1152A

Question 4: A technician measures 240V across a heating element and 20A of current flowing through it. What is the element's resistance?

4800Ω
0.08Ω
20Ω
12Ω

Question 5: In a series circuit, how does current behave through each component?

Current is the same at every point in the circuit
Current is highest at the source
Current splits evenly among the components
Current is highest at the last component

Question 6: A string of three series-wired indicator lights has one bulb burn out. What happens to the other two bulbs?

They stay on but glow dimmer
They also go out, because the open bulb breaks the only current path
They get brighter
Only the closest bulb goes out

Question 7: In a parallel circuit, what is true about the voltage across each branch?

Voltage is highest in the shortest branch
Voltage splits between the branches
Voltage is the same across every branch
Voltage is zero in all but one branch

Question 8: A house has three parallel-wired branch circuits. One breaker trips and opens that branch. What happens to the other two branches?

They also lose power
They receive double voltage
They run at half current
They keep operating normally

Question 9: A 240V compressor motor draws 15A while running. How much power (in watts) is it using?

3600W
255W
16W
3.6W

Question 10: Which statement about HVAC control circuits is correct?

Most control circuits are wired in parallel, so no single switch can stop them
Most control circuits are wired in series, so one open switch stops the whole circuit
Control circuits never use switches
Control circuits always carry full line voltage

Question 11: Which statement about HVAC power (line-voltage) loads is correct?

Power loads are always wired in series for safety
Power loads share the same current no matter how they are wired
Most power loads, like branch circuits, are wired in parallel so one failed load doesn't shut down the others
Power loads cannot be protected by individual breakers

Question 12: An electric heat strip is connected to 240V and has a measured resistance of 20 ohms. How much current does it draw?

4800A
0.08A
220A
12A

Question 13: A 24V control transformer secondary supplies a circuit drawing 0.8A. How many volt-amps (VA) is the circuit using?

19.2VA
30VA
1.92VA
24.8VA

Question 14: A series circuit has a 24V source feeding three loads. The technician measures 8V across the first load and 10V across the second load. What should the voltage across the third load be?

42V
6V
24V
18V

Question 15: What is "voltage drop" across a component in a circuit?

The total voltage supplied by the source
The resistance of the wire
The amount of voltage used up (consumed) by that component
The current flowing through the component

Question 16: A control relay coil is rated for 24V and draws 0.1A when energized. What is the coil's resistance?

2.4Ω
0.004Ω
24Ω
240Ω

Question 17: Two resistors, 5 ohms and 7 ohms, are wired in series. What is the total resistance of the circuit?

12Ω
2Ω
35Ω
0.7Ω

Question 18: A parallel circuit has one branch fail open (break). What happens to the remaining branches?

They also fail because the whole circuit is broken
They continue to operate normally because each branch has its own current path
They receive no voltage
Their current drops to zero

Question 19: A branch circuit breaker trips repeatedly when a blower motor starts. What does this most likely indicate?

The circuit voltage is too low
The circuit resistance is too high
The circuit is drawing more current than the breaker is rated for
The motor is wired in parallel with itself

Question 20: A 120V circuit draws 0.5A. What is the resistance of the load?

60Ω
0.004Ω
120.5Ω
240Ω

Question 21: A 24V transformer is rated for 40VA. The control circuit it feeds draws 1.2A. Is the transformer overloaded?

No, because 28.8VA is less than the 40VA rating
Yes, because 28.8VA exceeds 40VA
No, because current alone determines overload
Yes, because 1.2A exceeds the transformer's rated amps

Question 22: What unit is electrical current measured in?

Volts (V)
Amps (A)
Ohms (Ω)
Watts (W)

Question 23: What unit is electrical resistance measured in?

Amps (A)
Volts (V)
Ohms (Ω)
Watts (W)

Question 24: A control circuit is protected by a 3A fuse. It normally draws 2.5A. A technician adds an accessory that raises the total draw to 3.4A. What will most likely happen?

Nothing changes, because fuses only respond to voltage
The fuse rating will automatically increase
The circuit resistance will decrease to compensate
The fuse will blow because the current now exceeds its rating

Question 25: A 208V circuit has a total resistance of 26 ohms. Using Ohm's Law, what current flows in the circuit?

8A
5408A
0.125A
182A

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