Journeyman Electrician's Boxes and Enclosures Flashcards
7 cards from real Journeyman Electrician’s Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Journeyman Electrician's Boxes and Enclosures flashcards as text
Per NEC 314.20, in walls or ceilings constructed of combustible material (such as wood paneling), electrical boxes must be installed:
Answer: Flush with or projecting from the finished surface
NEC 314.20 requires that boxes in combustible walls or ceilings be flush with or project beyond the finished surface to prevent fire hazards from air gaps.
Per NEC 314.20, in noncombustible walls such as plaster or tile, what is the maximum allowable setback of an electrical box from the finished surface?
Answer: 1/4 inch
NEC 314.20 permits boxes in noncombustible surfaces to be set back a maximum of 1/4 inch from the finished surface.
According to NEC 314.23(B)(1), a box mounted without a direct structural connection must be fastened to a structural member within:
Answer: 12 inches
NEC 314.23(B)(1) requires boxes to be secured to a structural member within 12 inches of the box to ensure stable support.
A 4-11/16 inch square metal box 2-1/8 inches deep has a listed volume of 42 cubic inches. Using only 10 AWG conductors (no devices), how many conductors are permitted?
Answer: 16 conductors
Each 10 AWG conductor occupies 2.50 cubic inches per Table 314.16(B); 42 ÷ 2.50 = 16.8, which rounds down to 16 conductors.
Which of the following is a true statement regarding nonmetallic (plastic) electrical boxes used with nonmetallic-sheathed cable (NM)?
Answer: The equipment grounding path is carried by the EGC wire in the cable, not the box
Nonmetallic boxes are non-conductive, so the equipment grounding path relies entirely on the EGC within the NM cable rather than the box body itself.
Per NEC 314.15, boxes installed in wet locations must be:
Answer: Listed as weatherproof and suitable for the specific wet or damp location
NEC 314.15 requires boxes in wet or damp locations to be listed as weatherproof and appropriate for the specific condition (wet vs. damp).
A metal box whose dimensions do not appear in NEC Table 314.16(A) must be marked with its cubic-inch volume so that the installer can:
Answer: Apply the conductor fill calculations of 314.16(B) for any wire size used
Without a table entry, the installer needs the marked volume to perform the fill calculation from 314.16(B) for whatever conductor sizes are being installed.