BRAIN BUSTERS

10 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 2026 NEC.

⚡ 2026 NEC Brain Busters ⚡

10 Brainbuster Questions

Ready to test yourself?

Work through all 10 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 2026 NEC.

⚡ Brain buster #1 ⚡

A 5 HP, 230-volt, single-phase motor is rated for continuous duty and has a service factor of 1.15. The motor nameplate indicates a full-load current of 22 amperes.

The branch-circuit conductors are copper THHN, and the terminals are rated 75°C.

What are the minimum branch-circuit conductor size and the maximum initial overload setting permitted under 430.32(A)(1)?

A. #12 AWG Cu THHN and 25.3 A
B. #10 AWG Cu THHN and 27.5 A
C. #10 AWG Cu THHN and 35 A
D. #8 AWG Cu THHN and 27.5 A

💡 Hint: Don't use the motor nameplate current alone to size the branch-circuit conductors.

⚡ Brain buster #2 ⚡

How many #12 AWG THHN conductors are permitted in a 4" × 4" metal box that is 1½ inches deep, with no devices, no internal clamps, and no equipment grounding conductors?

A. 8
B. 9
C. 10
D. 11

💡 Hint: Determine the box volume first, then apply the conductor volume allowance for #12 AWG conductors.

⚡ Brain buster #3 ⚡

According to the NEC, what is the maximum trade size permitted for Intermediate Metal Conduit (IMC)?

A. Trade Size 4
B. Trade Size 5
C. Trade Size 6
D. Trade Size 8

💡 Hint: Look at the NEC article and table covering IMC dimensions and permitted trade sizes.

⚡ Brain buster #4 ⚡

A feeder supplies the following two motor-operated loads:

30 A air compressor

24 A dust collector

The equipment is listed and designed so only one load can operate at a time.

According to the 2026 NEC, what is the minimum calculated load for this feeder?

A. 30 A
B. 37.5 A
C. 54 A
D. 67.5 A

💡 Hint: Consider whether both loads must be included simultaneously when the equipment is designed so they cannot operate at the same time.

⚡ Brain buster #5 ⚡

A living room wall is 14 ft long, unbroken by doorways, fireplaces, or similar openings.

According to NEC 210.52(A)(1), what is the minimum number of receptacle outlets required on this wall?

A. 2
B. 3
C. 4
D. 5

💡 Hint: Apply the receptacle spacing rule based on the wall's length.

⚡ Brain buster #6 ⚡

A 120/240V, single-phase dwelling service is installed using a 200A panelboard. The grounding electrode system consists of two 8-ft ground rods driven 6 ft apart. A grounding electrode conductor is run from the service equipment to the first rod and then to the second rod.

The measured resistance of the first rod to earth is 38 ohms.

According to NEC 250.53(A)(2) and 250.53(A)(3), what is required for this grounding electrode system?

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

B. A supplemental grounding electrode is required because resistance exceeds 25 ohms.

C. The system must be reconfigured because ground rods cannot be used in pairs.

D. The grounding electrode conductor must be increased in size to reduce resistance.

💡 Hint: Pay close attention to the exception involving a single rod's resistance to earth.

⚡ Brainbuster #7 — Commercial Kitchen Demand Factors

A restaurant feeder supplies the following kitchen equipment:

Electric range

Deep fryer

Ice machine

Dishwasher

According to NEC 2026 Article 120.56, which statement correctly describes the equipment that may be included when applying the commercial kitchen equipment demand factors?

A. Only electric cooking appliances qualify.

B. Only cooking appliances and dishwashers qualify.

C. Qualifying commercial cooking equipment, dishwasher booster heaters, water heaters, instantaneous water heaters, and other qualifying kitchen equipment may be included.

D. All equipment located anywhere in the restaurant automatically qualifies.

💡 Hint: Pay close attention to the phrase “other kitchen equipment” and the requirements in 120.56.

⚡ Brain buster #8 ⚡

A restaurant has the following kitchen equipment connected to a feeder:

Electric Range = 12 kW

Deep Fryer = 8 kW

Griddle = 10 kW

Convection Oven = 15 kW

Using the applicable NEC demand factors for commercial kitchen equipment, what is the calculated demand load?

A. 33.75 kW
B. 36.00 kW
C. 40.50 kW
D. 45.00 kW

💡 Hint: Don't simply add the nameplate ratings. Identify and apply the applicable demand factor.

⚡ Brain buster #9 ⚡

A dwelling unit contains 4 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 number of appliances and their individual ratings, then apply the applicable Table 220.55 demand factor and notes.

⚡ Brain buster #10 ⚡

A single-family dwelling has 2,400 square feet of floor area, calculated from the outside dimensions and excluding open porches, garages, and unfinished spaces.

According to the 2026 NEC, at what VA per square foot is the general lighting load calculated for:

determining the minimum number of branch circuits required, and

performing the standard feeder/service load calculation?

A. 2 VA/ft² for both

B. 3 VA/ft² for both

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

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

💡 Hint: The NEC uses different values for these two purposes. Pay close attention to which calculation you're performing and which table or section applies.

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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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