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HVAC NEC 2023

HVAC Certification Practice Test 2

This test focuses on HVAC motor types, including PSC, CSIR, CSCR, ECM, and shaded-pole motors. You will also practice diagnosing run and start capacitor failures using symptoms and microfarad tolerance math.

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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: When a capacitor question gives you a rated value and a tolerance, calculate the acceptable range first (rated value plus or minus the percentage), then compare the measured reading to that range.

25

Questions

25 min

Time

70%

Pass

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HVAC Certification Practice Test 2 — Question List

Question 1: What does PSC stand for in HVAC motors?

Parallel Start Circuit
Permanent Split Capacitor
Power Supply Controller
Primary Speed Control

Question 2: Which of these statements is true about a PSC motor?

It always needs both a start and run capacitor
It has no capacitor at all
It uses a run capacitor only, with no start capacitor
It uses a centrifugal switch to disconnect its start winding

Question 3: What does CSIR stand for?

Capacitor Start Inverter Run
Continuous Speed Induction Relay
Capacitor Switch Ignition Relay
Capacitor Start Induction Run

Question 4: In a CSIR motor, what disconnects the start capacitor once the motor is running?

A centrifugal switch
A run capacitor
A contactor
A defrost board

Question 5: A compressor needs high starting torque, more than a CSIR motor can give. Which motor type is often used instead?

PSC
CSCR (Capacitor Start Capacitor Run)
ECM
Shaded pole

Question 6: What is an ECM motor?

A single-speed motor that always uses a run capacitor
A motor found only in window units
An Electronically Commutated Motor with a built-in inverter and no capacitor
A three-phase compressor motor

Question 7: Where are shaded-pole motors most commonly used in HVAC equipment?

Large three-phase compressors
Condenser fans on rooftop units
Variable-speed blowers
Small evaporator fans

Question 8: A PSC condenser fan motor runs but struggles and draws higher-than-normal amps. What is the most likely cause?

A weak or failing run capacitor
A shorted centrifugal switch
An oversized crankcase heater
A tripped high-pressure switch

Question 9: A motor hums but will not start turning. What does this symptom usually point to?

A tripped GFCI
A failed capacitor
Low refrigerant charge
A miswired thermostat

Question 10: A blower motor runs, but noticeably slower than normal. Which component should be checked first?

The thermostat batteries
The evaporator coil
The run capacitor
The disconnect switch

Question 11: When testing a run capacitor with a capacitor meter, the reading should be within about how much of the rated microfarad (MFD) value?

About ±25%
Exactly the rated value with zero tolerance
About ±50%
About ±6%

Question 12: A run capacitor is rated 35 MFD ±6%. A technician measures 32.5 MFD. Is this capacitor within spec?

No, because the acceptable range is about 32.9-37.1 MFD and 32.5 is below it
Yes, because 32.5 is close to 35
Yes, because any reading below the rated value is acceptable
No, because the capacitor should read exactly 35 MFD

Question 13: In a CSIR motor, the centrifugal switch fails and stays closed even after the motor reaches full speed. What is the likely result?

The motor runs cooler than normal
The start winding stays energized and overheats
The run capacitor is bypassed
The motor automatically switches to three-phase power

Question 14: What is the main wiring difference between a CSIR motor and a CSCR motor?

A CSIR motor never uses a capacitor
A CSCR motor has no centrifugal switch or start components at all
A CSCR motor keeps a run capacitor in the circuit after starting, in addition to the start capacitor used briefly at startup
A CSIR motor runs on three-phase power only

Question 15: Which statement about PSC motors is correct?

A PSC motor always needs a start capacitor and a centrifugal switch
A PSC motor cannot use any capacitor
A PSC motor only works on three-phase power
A PSC motor starts and runs using only a run capacitor, no start capacitor needed

Question 16: Which motor type is most common in modern variable-speed blowers?

ECM (Electronically Commutated Motor)
Shaded pole
CSIR
Wound rotor

Question 17: Why doesn't an ECM motor need a run or start capacitor?

It runs on 24V control voltage only
It has a built-in inverter that electronically controls the motor
It has no moving rotor
It only operates on three-phase power

Question 18: A PSC condenser fan motor hums but does not spin. Its capacitor is rated 5 MFD ±6% and tests at 4.2 MFD. What should the technician do?

Leave the capacitor alone, since 4.2 MFD is close enough
Replace the entire motor without checking the capacitor further
Replace the capacitor, since 4.2 MFD is well below the acceptable range
Add a second run capacitor in series

Question 19: Why does a true three-phase induction motor not need a start or run capacitor?

It uses a centrifugal switch instead
It runs at a fixed low voltage
It has no start winding at all
The three offset phases naturally create a rotating magnetic field

Question 20: Which motor design uses both a start capacitor and a run capacitor to provide high starting torque for a demanding compressor?

CSCR (Capacitor Start Capacitor Run)
PSC
Shaded pole
ECM

Question 21: How does a shaded-pole motor compare to a PSC motor in torque and efficiency?

Shaded-pole motors have higher torque and higher efficiency
Shaded-pole motors have lower torque and lower efficiency
They are identical in torque and efficiency
Shaded-pole motors run only on three-phase power

Question 22: What is the purpose of a run capacitor in a single-phase motor?

It only helps the motor start, then disconnects
It protects the motor from high pressure
It improves running efficiency and torque while the motor operates
It converts AC power to DC power

Question 23: What happens if a start capacitor is left connected in the circuit continuously, instead of disconnecting after startup?

It saves energy over time
It improves motor torque with no downside
It has no effect on the motor
It overheats the start winding

Question 24: A run capacitor is rated 45 MFD ±6%. A technician measures 46 MFD. Is this capacitor within spec?

Yes, because the acceptable range is about 42.3-47.7 MFD and 46 falls within it
No, because any reading above the rated value fails
Yes, because capacitors have no real tolerance
No, because it must read exactly 45 MFD

Question 25: A technician opens a compressor's electrical compartment and finds both a start capacitor with a start relay, and a separate run capacitor wired in. What motor type is this compressor most likely using?

PSC
CSCR (Capacitor Start Capacitor Run)
Shaded pole
ECM

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