Wiring Methods and Materials Flashcards

What box fill volume allowance does Table 314.16(B) assign to each 12 AWG conductor?

Answer: 2.25 cubic inches

Table 314.16(B) assigns 2.25 cubic inches per 12 AWG conductor.

In a box fill calculation, how is a single-gang receptacle on a yoke counted?

Answer: As two volume allowances based on the largest conductor connected to it

NEC 314.16(B)(4) counts each yoke or strap as a double volume allowance based on the largest conductor connected to the device.

A box contains four equipment grounding conductors. How many volume allowances do they add to the box fill calculation?

Answer: One, based on the largest EGC

NEC 314.16(B)(5) counts all equipment grounding conductors together as a single volume allowance based on the largest one.

Listed flexible metal conduit (FMC) with listed fittings can serve as the equipment grounding conductor only if the total length in the ground return path does not exceed what?

Answer: 6 feet

NEC 250.118 allows FMC as an EGC only when the circuit is protected at 20 A or less and the combined length is no more than 6 ft.

Flexible metal conduit must generally be supported at intervals not exceeding what distance?

Answer: 4.5 feet

NEC 348.30 requires FMC to be supported every 4.5 ft and within 12 in of each box or termination.

Expansion fittings for PVC conduit are required when the expected length change due to thermal expansion and contraction reaches at least what amount?

Answer: 1/4 inch

NEC 352.44 requires expansion fittings where the expected length change is 1/4 in or more between securely mounted items.

What is the maximum percentage of conduit cross-sectional area that can be filled by three or more conductors in a conduit longer than 24 inches?

Answer: 40%

Chapter 9, Table 1 limits fill to 40% for more than two conductors.