Journeyman Electrician (NEC)

A 208-volt, single-phase branch circuit supplies a continuous load of 24 amperes. What is the minimum standard overcurrent device rating permitted?

1. A30 amperesCorrect
2. B25 amperes
3. C24 amperes
4. D40 amperes

Why: An overcurrent device supplying a continuous load must be rated at not less than 125 percent of that load: 24 A x 1.25 = 30 A, which is a standard rating in 240.6(A). The 24 A and 25 A choices ignore or under-apply the 125 percent factor, and 40 A jumps past the next standard size above the calculated value.2023 NEC §210.20(A)

A service uses 3/0 AWG copper ungrounded service-entrance conductors. What is the minimum size copper grounding electrode conductor?

1. A4 AWGCorrect
2. B6 AWG
3. C2 AWG
4. D1/0 AWG

Why: Table 250.66 groups 2/0 and 3/0 copper service conductors together and calls for a 4 AWG copper grounding electrode conductor. The 6 AWG row applies to service conductors of 1 or 1/0 AWG, 2 AWG copper is required only above 3/0 through 350 kcmil, and 1/0 applies to service conductors above 350 through 600 kcmil.2023 NEC Table 250.66