Journeyman Electrician (NEC) — All Questions

Capacitor circuit conductors must have an ampacity of at least what percentage of the rated current of the capacitor?

• a.135 percent✓
• b.150 percent
• c.125 percent
• d.115 percent

Conductors supplying a capacitor must be sized at not less than 135 percent of the rated current of the capacitor. See NEC 460.8(A).

As defined in Article 100, what does 'in sight from' mean in terms of distance?

• a.Anywhere on the same floor level
• b.Visible and not more than 50 feet away✓
• c.Within 75 feet whether visible or not
• d.Visible and not more than 25 feet away

'In sight from' means the equipment is visible and not more than 50 feet distant from the other equipment. See NEC Article 100.

A 40-horsepower, 460-volt, three-phase motor has a table full-load current of 52 amperes. What minimum ampere rating must the disconnecting means have?

• a.46 amperes
• b.65 amperes
• c.52 amperes
• d.59.8 amperes✓

The disconnecting means must be at least 115 percent of the full-load current: 52 x 1.15 = 59.8 A, so a 60-ampere or larger switch would be selected. See NEC 430.110(A).

A 5-horsepower, 460-volt, three-phase motor has a table full-load current of 7.6 amperes. Using 75 degrees C copper, what is the minimum branch-circuit conductor size?

• a.16 AWG
• b.14 AWG✓
• c.12 AWG
• d.10 AWG

The conductor must carry 7.6 x 1.25 = 9.5 A. 14 AWG copper (20 A at 75 degrees C) is adequate; motor branch-circuit conductors are sized under Article 430 and are not restricted by the small-conductor rule of 240.4(D). See NEC 430.22.

A continuous-duty motor over 1 horsepower is marked with a temperature rise of 40 degrees C. What percentage of nameplate full-load current sets the maximum overload device?

• a.140 percent
• b.115 percent
• c.125 percent✓
• d.130 percent

A motor with a marked temperature rise not over 40 degrees C, like one with a service factor of 1.15 or greater, is permitted overload protection at 125 percent of nameplate current. See NEC 430.32(A)(1).

A feeder supplies a 30-horsepower motor (40 amperes), a 20-horsepower motor (27 amperes) and a 10-horsepower motor (14 amperes), all 460 volts three-phase. What minimum conductor ampacity is required?

• a.91 amperes✓
• b.101.25 amperes
• c.81 amperes
• d.95 amperes

Feeder ampacity = 125 percent of the largest motor plus the sum of the others: (40 x 1.25) + 27 + 14 = 50 + 41 = 91 A. See NEC 430.24.