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HVAC NEC 2023

HVAC Certification Practice Test 15

This test covers reading and interpreting motor nameplate data — locked rotor amps (LRA), rated load amps (RLA), and service factor (SF) — and how each is used in real diagnostics.

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HVAC Practice tests

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Frequently Asked Questions

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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: LRA is a brief starting spike, not a sustained running value. Do not confuse it with RLA when checking a running motor's amp draw.

25

Questions

25 min

Time

70%

Pass

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HVAC Certification Practice Test 15 — Question List

Question 1: What does LRA stand for on a motor nameplate, and what does it represent?

Locked Rotor Amps — the current the motor draws at the instant of starting, before the rotor is turning
Line Rated Amps — the sustained current during normal operation
Low Range Amps — the minimum current the motor can draw
Load Reduction Amps — the current after load-shedding kicks in

Question 2: What does RLA stand for on a motor nameplate, and what does it represent?

Rated Load Amps — the expected current draw during normal running operation at rated load
Reverse Load Amps — the current when a motor runs backward
Recommended Line Amps — the maximum breaker size only
Relay Load Amps — the current through the start relay only

Question 3: Roughly how does LRA compare to RLA on a typical motor?

LRA is often about 4-6 times higher than RLA, briefly, at start-up
LRA is always exactly equal to RLA
LRA is normally lower than RLA
LRA and RLA are two names for the same measurement

Question 4: What does a motor's service factor (SF) tell a technician?

How much above its rated horsepower the motor can safely handle on a continuous basis
The exact refrigerant charge the system needs
The number of starts the motor can survive per hour
The voltage tolerance of the control transformer

Question 5: A motor nameplate lists a service factor of 1.15. What does this mean in practical terms?

The motor can continuously handle up to 115% of its rated horsepower
The motor will fail if run above 15% of rated load
The motor requires 115V to start
The motor's efficiency rating is 15%

Question 6: Is service factor the same concept as NEC branch-circuit sizing (like MCA/MOP)?

Yes, they are exactly the same value under different names
No — service factor is a motor nameplate concept about load-handling capability, separate from branch-circuit conductor/overcurrent sizing
Service factor replaces the need for MCA entirely
Service factor only applies to three-phase motors

Question 7: A technician sees a brief 85A spike when a compressor with an LRA of 90A starts, then it settles to 15A running (RLA 14A). Is this normal behavior?

Yes — the brief spike close to LRA at start-up, settling near RLA once running, is expected
No, this indicates the motor is failing
No, the running current should always equal LRA
No, this pattern is impossible on any motor

Question 8: A compressor with LRA 90A and RLA 14A hums but never starts, and the ammeter holds steady near 90A for several seconds instead of settling. What does this suggest?

This is completely normal running behavior
The compressor is stalled at locked rotor current instead of starting, and needs to be shut down before it overheats
The nameplate values must be printed incorrectly
This means the compressor is oversized for the application

Question 9: Why is LRA relevant when selecting overcurrent protection (like the MOP value) for a compressor circuit?

The overcurrent device must tolerate the brief high starting current without nuisance tripping, while still protecting the circuit
LRA has no relevance to overcurrent protection sizing
LRA determines the refrigerant charge amount
LRA is only relevant to control transformer sizing

Question 10: Where does a technician find a compressor's RLA and LRA values?

On the equipment or compressor nameplate
They must be calculated fresh with a formula every time, never printed anywhere
Only in the thermostat's programming menu
They are the same for every compressor regardless of model

Question 11: What is the risk of consistently operating a motor above its service-factor-adjusted load limit?

Increased heat and wear, shortening the motor's service life
There is no downside to exceeding service factor indefinitely
It automatically improves motor efficiency
It has no effect since service factor is only a suggestion

Question 12: A motor nameplate lists a service factor of 1.0. What does this indicate?

The motor has no built-in margin above its rated horsepower for continuous operation
The motor can run at 100% above rated load indefinitely
The motor cannot start at all
The motor requires exactly 100V to operate

Question 13: What meter feature would help a technician actually capture a motor's real-world starting current spike for comparison against nameplate LRA?

A min/max or inrush-capture feature on the clamp meter
A standard voltage-only meter with no current function
A megohmmeter only
A capacitor tester only

Question 14: Why is RLA a useful baseline when troubleshooting a running compressor?

A measured running current well above or below RLA is an early clue that something may be wrong
RLA has no diagnostic use in real fieldwork
RLA only matters when the compressor is off
RLA is only relevant to the condenser fan, not the compressor

Question 15: True or False: Seeing a brief current spike near the nameplate LRA value the instant a compressor starts is, by itself, a sign of a problem.

True
False
Only true on three-phase compressors
Only true if it happens more than once a day

Question 16: A motor nameplate lists a voltage range like "208-230V." What does this tell a technician?

The motor is designed to operate properly anywhere within that voltage range
The motor requires exactly 208V and nothing else
The motor requires exactly 230V and nothing else
The range refers to the control transformer secondary only

Question 17: Between two otherwise identical motors, one with SF 1.0 and one with SF 1.15, which has more built-in continuous overload margin?

The motor with SF 1.0
The motor with SF 1.15
They have identical margin regardless of SF value
Service factor does not relate to overload margin at all

Question 18: A large compressor's high LRA at start-up can sometimes cause a brief, noticeable dip in building voltage. Why?

The brief high inrush current draws heavily on the supply, momentarily lowering voltage elsewhere on the same circuit
LRA has no relationship to voltage at all
This only happens with three-phase compressors
This indicates the compressor is undersized for the load

Question 19: When replacing a failed compressor, why should a technician compare the new compressor's nameplate LRA and RLA against the original?

To confirm the existing wiring, breaker, and start components are still appropriately sized for the replacement
Nameplate values never need to be compared during a replacement
Only the physical size of the compressor matters, not its electrical data
RLA and LRA are identical on every compressor model, so comparison is unnecessary

Question 20: If branch-circuit conductors were undersized relative to a compressor's actual starting and running current needs, what general risk does this create?

Excess heating in the conductors and increased risk of a fire or insulation failure over time
There is no risk as long as the compressor starts successfully
Undersized conductors only affect the thermostat display
Undersized conductors always trip the disconnect instantly with zero risk

Question 21: Why is it important to check whether a compressor nameplate specifies single-phase or three-phase before wiring it?

Wiring a compressor to the wrong phase configuration can prevent proper starting or cause serious damage
Phase configuration is only a labeling detail with no real effect
All compressors work identically on any phase configuration
Phase configuration only matters for the condenser fan, not the compressor

Question 22: Which nameplate value would a technician use to judge whether a brief starting current spike is within the expected range?

Service factor
LRA
Voltage range only
RLA

Question 23: Which nameplate value would a technician use to judge whether a sustained running current reading looks normal?

LRA
RLA
Service factor alone
The disconnect distance rating

Question 24: True or False: A motor's service factor can be used in place of following the nameplate MCA value when sizing branch-circuit conductors.

True
False
Only true for motors with SF 1.0
Only true on single-phase equipment

Question 25: A compressor nameplate lists RLA 18A, LRA 108A, SF 1.15. A technician measures a brief start-up spike near 105A settling to 17A running. Is this within expected behavior?

No, both readings indicate a serious fault
Yes — the spike is close to LRA and the running value is close to RLA, both within normal expectations
No, the running current should always equal the LRA value
This data is insufficient to draw any conclusion

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