NEC Equipment for General Use 5

Question 1

When sizing branch-circuit conductors for a general-purpose motor, NEC 430.6(A)(1) requires the full-load current to be taken from:

Accepted Answer

NEC Tables 430.247 through 430.250

Answer

NEC 430.6(A)(1) requires using the table full-load currents, not nameplate values, to size conductors and short-circuit/ground-fault protection.

Question 2

A continuous-duty motor rated over 1 hp has a marked service factor of 1.15. What is the maximum overload protection rating per NEC 430.32(A)(1)?

Accepted Answer

125% of nameplate FLA

Answer

NEC 430.32(A)(1) allows overloads up to 125% of nameplate full-load current for motors with a service factor of 1.15 or greater.

Question 3

Per Table 430.52, what is the maximum rating of an inverse time circuit breaker for branch-circuit short-circuit and ground-fault protection of a single-phase squirrel-cage motor (design other than E)?

Accepted Answer

250% of FLC

Answer

Table 430.52 allows inverse time breakers at up to 250% of the table full-load current for these motors.

Question 4

Feeder conductors supplying three motors must have an ampacity of at least which value per NEC 430.24?

Accepted Answer

125% of the largest motor FLC plus the sum of the other motor FLCs

Answer

NEC 430.24 requires 125% of the highest-rated motor's FLC plus the sum of the remaining motors' FLCs, plus other loads.

Question 5

Branch-circuit conductors supplying a single hermetic refrigerant motor-compressor must have an ampacity of at least what percentage of the rated-load current or branch-circuit selection current, whichever is greater (NEC 440.32)?

Accepted Answer

125%

Answer

NEC 440.32 requires conductor ampacity of at least 125% of the larger of rated-load current or branch-circuit selection current.

NEC Practice Test

NEC Practice Test

NEC Equipment for General Use 5