BRAIN BUSTERS

20 Brain Buster Questions

Ready? Let's see what you know.

Work through all 10 questions before checking the answers. Choose the answer you believe is correct, use the hint if you need it, and write down your answers if you're working from a printed copy.

These questions are based on the 2023 NEC.

⚡ 2023 NEC Brain Busters ⚡

20 Brainbuster Questions

Ready to test yourself?

Work through all 20 questions before checking the Explanation Key.

Choose the answer you believe is correct. Use the hint if you need it, but try to solve the problem yourself first.

Based on the 2023 NEC.

⚡ Brain buster #1 ⚡

How many small-appliance branch circuits are required for the kitchen, pantry, dining room, and breakfast room of a dwelling unit?

A. 1

B. 2

C. 3

D. 4

💡 Hint: Look at the minimum number of small-appliance branch circuits required for these dwelling-unit areas.

⚡ Brain buster #2 ⚡

A hermetic refrigerant motor-compressor has a nameplate rated-load current of 20 amperes. No branch-circuit selection current is marked.

According to the 2023 NEC, what is the minimum ampere rating permitted for the disconnecting means serving the motor-compressor?

A. 20 A

B. 23 A

C. 25 A

D. 30 A

💡 Hint: For the disconnecting means, don't confuse the 115% requirement with the 125% conductor requirement.

⚡ Brain buster #3 ⚡

A raceway contains the following copper THHN/THWN-2 conductors:

8 × #2 AWG

12 × #6 AWG

10 × #10 AWG

Assume all conductors are in one RMC raceway and no equipment grounding conductor is included.

What is the minimum RMC trade size permitted by the 2023 NEC?

A. 3"

B. 3-1/2"

C. 4"

D. 5"

💡 Hint: Calculate the total conductor area, then compare it with the 40% allowable fill area for RMC.

⚡ Brain buster #4 ⚡

A pool pump motor is supplied by a branch circuit. The motor is hardwired directly to the pump and is not connected by a cord-and-plug connection.

According to the 2023 NEC, is GFCI protection required for the branch circuit supplying the pool pump motor?

A. Yes, GFCI protection is required whether the motor is cord-and-plug connected or hardwired.

B. No, GFCI protection is required only when a receptacle is installed.

C. No, hardwired pool pump motors are exempt from GFCI requirements.

D. Yes, but only when the pump motor is rated 120 volts.

💡 Hint: Pay attention to the wording of the GFCI requirement for outlets supplying pool pump motors.

⚡ Brain buster #5 ⚡

A pool-area motor is connected to the branch-circuit equipment grounding conductor as required. The motor is also bonded to the pool's equipotential bonding grid.

Which statement is most accurate?

A. The additional bonding connection is prohibited because it creates a parallel grounding path.

B. The equipotential bonding grid is supplemental bonding; it does not replace the required equipment grounding conductor.

C. The equipment grounding conductor is not required when the motor is bonded to the equipotential bonding grid.

D. The additional bonding connection is permitted only when the motor is GFCI protected.

💡 Hint: Remember the different purposes of the EGC and the equipotential bonding grid.

⚡ Brain buster #6 ⚡

A box with a flush-type cover is installed in a noncombustible wall surface. There is a gap between the edge of the box and the surrounding finished surface.

According to the 2023 NEC, what is the maximum permitted gap at the edge of the box?

A. 1/16 in.

B. 1/8 in.

C. 1/4 in.

D. 1/2 in.

💡 Hint: Look at the NEC requirement dealing specifically with gaps around boxes.

⚡ Brain buster #7 ⚡

A raceway contains 14 total #12 AWG copper THHN conductors:

12 ungrounded conductors

1 grounded conductor

1 equipment grounding conductor

The raceway is RMC.

What is the minimum RMC trade size permitted based on conductor fill?

A. 1/2"

B. 3/4"

C. 1"

D. 1-1/4"

💡 Hint: Use the conductor area from Chapter 9, Table 5 and the 40% raceway-fill limitation.

⚡ Brain buster #8 ⚡

Using the 2023 NEC standard method, what is the calculated demand load for the following dwelling-unit general load?

Dwelling size: 2,000 ft²

General lighting load: based on the dwelling-unit unit load

Two required small-appliance branch circuits

One required laundry branch circuit

What is the calculated demand load after applying the applicable dwelling-unit demand factor?

A. 4,925 VA

B. 5,100 VA

C. 5,625 VA

D. 7,500 VA

💡 Hint: For the 2023 NEC, remember the dwelling-unit general lighting unit load and the 1,500 VA load assigned to each required small-appliance and laundry circuit.

⚡ Brain buster #9 ⚡

A 125-volt, 20-ampere receptacle is installed in the ceiling of a dwelling-unit garage to supply a garage door opener.

According to the 2023 NEC, is GFCI protection required?

A. Yes, because the receptacle is in a dwelling-unit garage.

B. No, because the receptacle is located on the ceiling.

C. No, because the receptacle serves a dedicated appliance.

D. Yes, but only if the receptacle is within 6 ft of a sink.

💡 Hint: The location of the receptacle matters more than what appliance is plugged into it.

⚡ Brain buster #10 ⚡

A single-pole wall switch controls a ceiling luminaire in a finished habitable room. The switch box is wired using NM cable.

The switch box contains the line conductor, switched conductor, and equipment grounding conductor, but no grounded (neutral) conductor.

There is no raceway or accessible wiring method that would allow a neutral conductor to be added later without opening the finished wall.

According to the 2023 NEC, is this installation compliant?

A. Yes, because a neutral is not required when controlling only one lighting outlet.

B. Yes, because switch loops are permitted in NM cable.

C. Yes, because the neutral is present at the luminaire.

D. No, a grounded conductor is required at the switch location unless an applicable exception applies.

💡 Hint: Look at 404.2(C) and determine whether one of its exceptions applies.

⚡ Brain buster #11 ⚡

A 24-ampere continuous load is supplied by copper THHN conductors installed in EMT.

The conductors terminate on equipment rated 75°C.

The installation is in a 40°C ambient temperature, and there are 6 current-carrying conductors in the same raceway.

What is the minimum conductor size required?

A. #12 AWG copper

B. #10 AWG copper

C. #8 AWG copper

D. #6 AWG copper

💡 Hint: You need to account for the continuous load, conductor adjustment, and ambient-temperature correction. Use the 90°C rating of THHN for adjustment and correction, then verify the termination limitation.

⚡ Brain buster #12 ⚡

An apprentice installs a subpanel in a detached garage supplied by a feeder from the dwelling.

The neutral and equipment grounding bars are bonded together in the detached-garage panel.

The feeder includes an equipment grounding conductor.

What is the issue with this installation?

A. No issue exists as long as the feeder is 100 amperes or less.

B. The neutral and equipment grounding conductors must be bonded together at every building disconnect.

C. Bonding the neutral and equipment grounding conductors at the detached building creates an objectionable parallel path for neutral current.

D. The installation violates conduit-fill requirements.

💡 Hint: Think about where the grounded conductor is permitted to be connected to the equipment grounding system.

⚡ Brain buster #13 ⚡

For a single electrical service, what is the maximum number of service disconnecting means permitted under the 2023 NEC when the requirements of 230.71(B) are met?

A. 1

B. 2

C. 6

D. Unlimited if grouped together

💡 Hint: Look at 230.71(B), titled “Two to Six Service Disconnecting Means.”

⚡ Brain buster #14 ⚡

A 120-volt, 20-ampere residential branch circuit is installed in Schedule 40 PVC raceway beneath a dwelling-unit driveway.

Assume the circuit is GFCI protected and has a maximum overcurrent protection of 20 amperes.

What is the minimum cover required according to Table 300.5 of the 2023 NEC?

A. 6 inches

B. 12 inches

C. 18 inches

D. 24 inches

💡 Hint: Identify the correct row for a dwelling-unit driveway and the correct column for the wiring method.

⚡ Brain buster #15 ⚡

A 120-volt branch circuit supplies a continuous load of 16 amperes.

What is the minimum branch-circuit ampere rating permitted by the 2023 NEC?

A. 15 A

B. 20 A

C. 25 A

D. 30 A

💡 Hint: A continuous load requires the branch-circuit rating to be at least 125% of the continuous load.

⚡ Brain buster #16 ⚡

A dwelling unit has the following calculated connected loads:

General lighting = 3,000 VA

Three required small-appliance branch circuits = 4,500 VA

One laundry branch circuit = 1,500 VA

Using the 2023 NEC dwelling-unit demand factors, what is the calculated load before adding other dwelling loads?

A. 4,500 VA

B. 5,100 VA

C. 6,000 VA

D. 9,000 VA

💡 Hint: First determine the total general load, then apply the dwelling-unit demand factor.

⚡ Brain buster #17 ⚡

A dwelling unit contains four household electric ranges, each rated at 14 kW.

Using NEC Table 220.55 and the applicable notes, what is the calculated demand load?

A. 17 kW

B. 18.7 kW

C. 20 kW

D. 22 kW

💡 Hint: Start with the demand value from Table 220.55 for four ranges, then apply the applicable adjustment for ranges rated over 12 kW.

⚡ Brain buster #18 ⚡

A dwelling unit has a 120-volt branch circuit supplying 10 general-use receptacle outlets.

For dwelling-unit load calculations under the 2023 NEC, how are these general-use receptacle outlets calculated?

A. 1,200 VA

B. 1,500 VA

C. 1,800 VA

D. No separate load is calculated for these receptacle outlets; they are included in the dwelling-unit general lighting load.*

💡 Hint: Do not automatically apply the 180 VA-per-receptacle rule used for many other receptacle loads.

⚡ Brain buster #19 ⚡

An electrician is laying out receptacles in a dwelling unit.

Along one wall is a stationary appliance that is 3 ft wide. The electrician is determining how the wall space is measured for the required receptacle outlets.

According to the 2023 NEC, which statement is correct?

A. The stationary appliance is included as wall space, so the entire wall must still be considered when determining receptacle spacing.

B. A stationary appliance interrupts the wall space for purposes of the receptacle-spacing requirements of 210.52(A).

C. A stationary appliance only interrupts wall space if it is permanently connected to the electrical system.

D. A stationary appliance does not affect receptacle spacing because only doorways and fireplaces interrupt wall space.

💡 Hint: Pay close attention to the 2023 NEC change involving stationary appliances and the definition of wall space.

⚡ Brain buster #20 ⚡

A 120-volt, 20-ampere branch circuit supplies receptacle outlets in a dwelling-unit bedroom. The circuit is protected by a circuit breaker, and the wiring method is NM cable.

According to the 2023 NEC, which statement is correct regarding AFCI protection?

A. AFCI protection is not required because the circuit is only 20 amperes.

B. AFCI protection is required because the branch circuit supplies outlets in a dwelling-unit bedroom.

C. AFCI protection is required only when the branch circuit supplies lighting outlets.

D. AFCI protection is required only if the bedroom contains a smoke alarm.

💡 Hint: Look at 210.12 and determine which dwelling-unit locations require arc-fault circuit-interrupter protection.

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⚠️ Educational Disclaimer

These Brainbusters are provided for educational and study purposes only and are based on the 2026 edition of the National Electrical Code (NEC).

Code requirements can vary based on the edition adopted by your jurisdiction, local amendments, and the specific installation. Always verify the applicable NEC requirements and local regulations before applying any information to an actual installation.

These Brainbusters are not a substitute for the NEC, professional judgment, or requirements enforced by the local Authority Having Jurisdiction (AHJ).

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