Electrical System Design & Installation Flashcards

A 480V, 3-phase transformer has a 75 kVA rating. What is the full-load secondary current for a 208Y/120V secondary?

Answer: 208A

FLA = kVA × 1000 ÷ (√3 × V) = 75,000 ÷ (1.732 × 208) = 75,000 ÷ 360.3 ≈ 208A.

Per NEC 210.52(C), receptacle outlets in a kitchen must be installed so that no point along the countertop wall space is more than how far from a receptacle?

Answer: 24 inches

NEC 210.52(C)(1) requires that no point along a kitchen countertop wall space be more than 24 inches from a receptacle outlet.

What protection is required for all 125V through 250V receptacles installed in a crawl space at or below grade level?

Answer: GFCI protection

NEC 210.8(A)(4) requires GFCI protection for receptacles in crawl spaces at or below grade level due to moisture hazards.

When installing EMT in a concrete slab, what NEC requirement applies to the minimum concrete cover?

Answer: 2 inch minimum cover

Per NEC 358.10(B) and 300.6(D), EMT embedded in concrete must have at least 2 inches of concrete cover unless listed for less.

A load center in a residential garage must have its panelboard mounted at what maximum height per the NEC?

Answer: 6 feet 7 inches to the center of the highest breaker

NEC 240.24(A) requires that the center of the grip of the operating handle of a breaker, when in its highest position, not exceed 6 feet 7 inches above the floor.

What is the minimum size equipment grounding conductor (EGC) required for a circuit protected by a 100A overcurrent device per NEC Table 250.122?

Answer: #8 AWG copper

Per NEC Table 250.122, a 100A overcurrent device requires a minimum #8 AWG copper equipment grounding conductor.

Which wiring method is specifically listed by the NEC as suitable for direct burial without conduit protection?

Answer: USE-2 cable

USE-2 (Underground Service Entrance) cable is rated and listed for direct burial applications without requiring conduit.