NEC Wiring and Protection 4

Question 1

Unless specifically permitted elsewhere, NEC 240.4(D) limits overcurrent protection for 12 AWG copper conductors to what maximum?

Accepted Answer

20 A

Answer

Under the small-conductor rule in 240.4(D), 12 AWG copper is limited to 20-ampere overcurrent protection.

Question 2

What is the maximum overcurrent protection permitted for 10 AWG copper conductors under the small-conductor rule of NEC 240.4(D)?

Accepted Answer

30 A

Answer

NEC 240.4(D) limits 10 AWG copper to 30 A, even though its table ampacity can be higher.

Question 3

NEC 240.4(B) allows using the next higher standard overcurrent device rating when a conductor's ampacity doesn't match a standard rating, as long as the device rating does not exceed what value?

Accepted Answer

800 A

Answer

The next-size-up rule applies only when the overcurrent device is rated 800 A or less.

Question 4

A branch circuit supplies a 16-ampere continuous load with no noncontinuous load. Per NEC 210.20(A), what is the minimum overcurrent device rating?

Accepted Answer

20 A

Answer

16 A × 125% = 20 A, so a 20-ampere device is the minimum.

Question 5

The informational note to NEC 210.19 recommends sizing branch-circuit conductors to keep voltage drop no greater than what percentage at the farthest outlet?

Accepted Answer

3%

Answer

The note recommends no more than 3% on the branch circuit and 5% total for feeder plus branch circuit.

NEC Practice Test

NEC Practice Test

NEC Wiring and Protection 4