Journeyman Electrician’s Exam Journeyman Electrician's Service and Feeder Calculations 3

Question 1

A feeder supplies a motor with a 40A full-load current and a 30A continuous non-motor load. What is the minimum feeder ampacity required?

Accepted Answer

87.5 A

Answer

Motor feeder = 40A × 125% = 50A; continuous non-motor = 30A × 125% = 37.5A; total = 87.5A minimum.

Question 2

What NEC section requires that the neutral conductor of a 3-wire, single-phase service be sized to carry the maximum unbalanced load?

Accepted Answer

NEC 220.61

Answer

NEC 220.61 addresses feeder and service neutral load calculations including the maximum unbalanced load.

Question 3

A 240V, single-phase dryer rated at 5,000W is installed in a dwelling. What demand load does NEC 220.54 assign to a single dryer?

Accepted Answer

5,000 W

Answer

NEC 220.54 requires the nameplate rating or 5,000W, whichever is larger, so 5,000W applies.

Question 4

When multiple feeder conductors are installed in parallel, each conductor in the parallel set must be what minimum size?

Accepted Answer

1/0 AWG

Answer

NEC 310.10(H) requires each parallel conductor to be a minimum of 1/0 AWG.

Question 5

A commercial occupancy has 10,000 sq ft of office space. Using NEC Table 220.12, what is the general lighting load at 3.5 VA per square foot?

Accepted Answer

35,000 VA

Answer

10,000 sq ft × 3.5 VA/sq ft = 35,000 VA for office general lighting.

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