BRAIN BUSTERS

⚡ 2026 NEC Brain Busters — Explanation Key ⚡

🔎 Answers & Explanations

Based on the 2026 NEC.

⚡ Brain Buster #1 — Answer: D. 1/0 AWG Cu

The three 600 kcmil service conductors in parallel are treated as one equivalent conductor for sizing the main bonding jumper.

Three conductors × 600 kcmil = 1,800 kcmil equivalent area.

The applicable table does not directly list an equivalent conductor this large, so the rule for installations using parallel conductors must be applied. Based on the applicable 2026 NEC requirements, the minimum main bonding jumper is 1/0 AWG copper.

Correct Answer: D. 1/0 AWG Cu

Code Reference: NEC 250.28, 250.102

⚡ Brain Buster #2 — Answer: A. 35%

For multifamily dwelling units, the applicable demand-factor table permits the general lighting, small-appliance, and laundry loads to be reduced after the first 3,000 VA.

For the portion of the load above 3,000 VA, the applicable demand factor for the four-unit calculation is 35%.

Correct Answer: A. 35%

Code Reference: NEC 220.42 and applicable 2026 dwelling demand-factor requirements

⚡ Brain Buster #3 — Answer: A. 3 in.

This is a mixed-conductor raceway-fill problem.

The conductors have different sizes, so you cannot simply multiply one conductor's area by the total number of conductors.

The appropriate conductor areas must be determined from the applicable Chapter 9 tables, totaled, and compared with the permitted raceway-fill area.

The resulting minimum raceway is 3-inch RMC.

Correct Answer: A. 3 in.

Code Reference: NEC Chapter 9, Tables 1, 4, 5, and 8

⚡ Brain Buster #4 — Answer: B. 1/8 in.

NEC 314.20 addresses boxes installed behind finished surfaces.

For a box with a flush-type cover installed in a noncombustible surface, the permitted gap at the edge is not more than 1/8 inch.

This question is designed to test the difference between the permitted box position and the maximum edge gap.

Correct Answer: B. 1/8 in.

Code Reference: NEC 314.20

⚡ Brain Buster #5 — Answer: A. Yes, GFCI protection is required.

The GFCI requirement is based on the location and application of the equipment—not simply whether the equipment is connected by a cord and plug.

A pool pump motor can require GFCI protection even when it is hardwired.

Correct Answer: A.

Code Reference: NEC 210.8 and applicable swimming-pool requirements

⚡ Brain Buster #6 — Answer: B.

The NEC permits certain 600-volt-rated MC cable installations in the same cable tray with medium-voltage cable when the applicable conditions are satisfied.

The fact that one cable is over 1,000 volts does not automatically mean a physical barrier is required in every such installation.

Correct Answer: B.

Code Reference: NEC 392 and applicable MC/cable-tray requirements

⚡ Brain Buster #7 — Answer: C. Type TC-ER

The ER designation identifies a cable suitable for certain exposed runs outside the cable tray.

Type TC-ER is recognized for these applications when the cable is properly listed and installed according to the applicable requirements.

UL 1277 is associated with the construction/listing requirements for this cable type.

Correct Answer: C. Type TC-ER

Code Reference: NEC 336.10 and UL 1277

⚡ Brain Buster #8 — Answer: B.

The equipment grounding conductor provides the required low-impedance fault-current path for the motor.

Supplemental bonding to an equipotential bonding grid can provide additional bonding, but it does not replace the required equipment grounding conductor.

The two functions should not be confused.

Correct Answer: B.

Code Reference: NEC 250.4, 250.110, and applicable motor/bonding requirements

⚡ Brain Buster #9 — Answer: A. 4,925 VA

The dwelling general lighting load is calculated using the applicable 2026 dwelling value.

For 2,000 ft²:

2,000 ft² × 2 VA/ft² = 4,000 VA

Then add the two required small-appliance branch circuits:

2 × 1,500 VA = 3,000 VA

Add the laundry circuit:

1 × 1,500 VA = 1,500 VA

The resulting general load is:

4,000 + 3,000 + 1,500 = 8,500 VA

Applying the applicable dwelling demand factor produces:

4,925 VA

Correct Answer: A. 4,925 VA

Code Reference: NEC Article 120 and applicable dwelling-unit load-calculation requirements

⚡ Brain Buster #10 — Answer: C. 60 A

Start with the motor full-load current:

28 A

For an inverse-time circuit breaker, the applicable percentage from Table 430.52 is 250%.

28 A × 250% = 70 A

However, the NEC uses the standard-size rule when the calculated value does not correspond to a standard rating and the conditions for using the next standard size are met.

The resulting permitted standard breaker size is:

60 A

Correct Answer: C. 60 A

Code Reference: NEC 430.52 and 240.6

⚡ Brain Buster #11 — Answer: C.

A countertop microwave does not automatically require an individual branch circuit simply because its rating is 1,200 watts.

A cord-and-plug-connected appliance can be supplied from a required 20-ampere small-appliance branch circuit when the applicable NEC requirements are satisfied and the manufacturer's instructions do not require an individual circuit.

Correct Answer: C.

Code Reference: NEC 210.52(B), 210.23, and applicable appliance requirements

⚡ Brain Buster #12 — Answer: A.

Garage receptacles are specifically included within the GFCI requirements.

The fact that the receptacle is installed in the ceiling does not remove it from the requirement.

The fact that it supplies a garage-door opener also does not create a general exemption.

Correct Answer: A.

Code Reference: NEC 210.8(A)

⚡ Brain Buster #13 — Answer: B. ¾ in.

The raceway contains:

12 ungrounded #12 conductors
1 grounded #12 conductor
1 equipment grounding conductor

The equipment grounding conductor is included in the raceway-fill calculation, and the current-carrying conductors must also be evaluated for ampacity adjustment.

The resulting minimum RMC size is ¾ inch.

Correct Answer: B. ¾ in.

Code Reference: NEC Chapter 9, Table 1; Table 4; Table 5; Table 8; 310.15

⚡ Brain Buster #14 — Answer: B. 18,500 VA

Start with the general dwelling load:

Lighting:
3,000 VA

Small-appliance circuits:
3 × 1,500 = 4,500 VA

Laundry:
1,500 VA

Total general load:

3,000 + 4,500 + 1,500 = 9,000 VA

Apply the applicable dwelling demand factor to the general load.

Then add the applicable calculated dryer and range loads according to their respective demand-factor rules.

The resulting calculated service load is:

18,500 VA

Correct Answer: B. 18,500 VA

Code Reference: NEC Article 120 and applicable dwelling load-calculation tables

⚡ Brain Buster #15 — Answer: B. 37.5 A

The two loads are specifically designed so they cannot operate simultaneously.

Therefore, they are noncoincident loads and are not simply added together.

The largest load is:

30 A

Because it is a motor load, the applicable motor load calculation must then be applied.

30 A × 125% = 37.5 A

Therefore, the minimum calculated feeder load is:

37.5 A

Correct Answer: B. 37.5 A

Code Reference: NEC 120.6, 120.11(A), and 430.22

⚡ Brain Buster #16 — Answer: A.

The familiar 25-ohm rule is frequently misunderstood.

When a single grounding rod does not demonstrate a resistance of 25 ohms or less, the NEC permits the requirement to be satisfied by installing an additional grounding electrode.

In this installation, two qualifying electrodes are already installed.

Therefore, the 38-ohm measurement does not require a third rod.

Correct Answer: A. No additional action is required because two rods are already installed.

Code Reference: NEC 250.53(A)(2) and 250.53(A)(3)

⚡ Brain Buster #17 — Answer: D.

The important point is not simply whether an item is called a range, fryer, ice machine, or dishwasher.

The commercial-kitchen demand-factor provisions address qualifying commercial kitchen equipment and establish the conditions under which equipment can be included.

Therefore, you cannot automatically declare one of the listed items excluded solely from its name.

Correct Answer: D.

Code Reference: NEC 120.56

⚡ Brain Buster #18 — Answer: B. 36.00 kW

First total the connected kitchen equipment:

12 + 8 + 10 + 15 = 45 kW

The commercial-kitchen demand provisions allow the connected equipment load to be reduced using the applicable demand factor.

Applying the applicable demand calculation results in:

36.00 kW

Correct Answer: B. 36.00 kW

Code Reference: NEC 120.56

⚡ Brain Buster #19 — Answer: C. 110%

Hermetic refrigerant motor-compressors have their own specific requirements.

The ampere rating of the hermetic refrigerant motor-compressor is determined using the applicable percentage of the nameplate-rated load current or branch-circuit selection current.

That percentage is:

110%

Do not automatically substitute the 125% motor-conductor rule when the question is specifically asking for the compressor's ampere rating.

Correct Answer: C. 110%

Code Reference: NEC 440.4(B) and 440.32

⚡ Brain Buster #20 — Answer: B. #10 AWG Cu THHN and 27.5 A

For motor branch-circuit conductors, don't simply use the motor's 22-ampere nameplate current.

The applicable motor full-load current from the NEC tables is used for conductor sizing.

For the 5 HP, 230-volt, single-phase motor, the applicable table value is 28 A.

For conductor sizing:

28 A × 125% = 35 A

#10 AWG copper THHN is sufficient under the stated 75°C conditions.

For the overload protection, the motor has a 1.15 service factor, so the applicable maximum initial overload setting is:

22 A × 125% = 27.5 A

Therefore:

#10 AWG Cu THHN and 27.5 A

Correct Answer: B.

Code Reference: NEC 430.22 and 430.32(A)(1)

⚡ Brain Buster #21 — Answer: C.

One of the 2026 NEC changes recognizes 10-ampere branch circuits for specific applications.

This does not mean 10-ampere circuits can generally replace the 15- and 20-ampere branch circuits normally used throughout buildings.

The specific application includes lighting outlets and certain dwelling-unit exhaust fans on bathroom or laundry-room lighting circuits.

Correct Answer: C.

Code Reference: NEC 210.23(A), 2026 edition

⚡ Brain Buster #22 — Answer: C.

The 2026 NEC addresses damaged wiring methods and conductors.

There is an important difference between a superficial mark and actual damage.

If inspection determines that the conductor insulation has actually been damaged, simply wrapping the damaged location with electrical tape does not make the conductor suitable for continued use.

The damaged conductor must be replaced.

Correct Answer: C.

Code Reference: NEC 300.4(C), 2026 edition

⚡ Brain Buster #23 — Answer: D.

This is one of the important 2026 dwelling-load distinctions.

The NEC uses:

3 VA/ft²

when determining the minimum number of branch circuits required for dwelling general lighting.

For the standard dwelling feeder/service load calculation, the value is:

2 VA/ft²

Therefore:

3 VA/ft² for branch circuits / 2 VA/ft² for feeder/service

Correct Answer: D.

Code Reference: NEC 210.11 and Article 120, 2026 edition

⚡ Brain Buster #24 — Answer: C.

A suspended-ceiling grid and its support wires are not intended to serve as the supporting means for electrical wiring.

Wiring cannot simply be attached to the wires supporting the ceiling grid.

The NEC does permit properly installed independent support wires for certain wiring methods and installations.

The key is that the support must be independent of the ceiling-grid support system and installed according to the applicable requirements.

Correct Answer: C.

Code Reference: NEC 300.11, 2026 edition

⚡ Brain Buster #25 — Answer: C.

This question is about one of the biggest skills required for NEC examination questions:

Read the question carefully.

A question may contain information that looks important but has no bearing on the answer.

The correct approach is to:

Identify exactly what the question is asking.
Determine which Code section applies.
Identify the minimum or maximum requirement being tested.
Separate relevant information from irrelevant information.
Verify the answer in the NEC.
Eliminate distractors that may be technically related but do not answer the question being asked.

Don't assume every number in the question must be used.

Correct Answer: C.

Exam Strategy: Read. Dissect. Verify.

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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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⚠️ 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).

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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