NJATC Load Calculations 3

Question 1

Per NEC 430.22, at what percentage of the motor's full-load current rating must branch circuit conductors for a single motor be sized?

Accepted Answer

125%

Answer

NEC 430.22 requires branch circuit conductors supplying a single motor to be sized at not less than 125% of the motor's full-load current rating.

Question 2

When sizing feeder conductors for multiple motors per NEC 430.24, how is the largest motor's current contribution calculated?

Accepted Answer

At 125% of FLC

Answer

NEC 430.24 requires the largest motor's full-load current to be multiplied by 125% when sizing feeder conductors for multiple motors.

Question 3

What is the power factor of a purely resistive circuit, such as one supplying only electric heating elements?

Accepted Answer

1.0

Answer

A purely resistive circuit has a power factor of 1.0 (unity) because voltage and current are perfectly in phase.

Question 4

What is the maximum calculated load capacity in kilowatts of a 100-ampere, 240-volt, single-phase service entrance?

Accepted Answer

24 kW

Answer

Maximum load = 240V × 100A = 24,000W = 24 kW for a 100-ampere, 240-volt single-phase service.

Question 5

Per NEC 220.53, what demand factor may be applied when four or more fastened-in-place appliances (other than ranges, dryers, or HVAC) are served by the same feeder?

Accepted Answer

75%

Answer

NEC 220.53 permits a 75% demand factor when four or more fastened-in-place appliances (excluding ranges, dryers, and HVAC) are on the same feeder.

NJATC - National Joint Apprenticeship and Training Committee Practice Test

NJATC - National Joint Apprenticeship and Training Committee Practice Test

NJATC Load Calculations 3