Journeyman Electrician’s Exam Journeyman Electrician's Boxes and Enclosures 1 — Questions and Answers
Question 1: According to NEC Table 314.16(B), what is the volume allowance assigned to each 14 AWG conductor for box fill calculations?
- 1.75 cubic inches
- 2.00 cubic inches (Correct answer)
- 2.25 cubic inches
- 2.50 cubic inches
Correct answer: 2.00 cubic inches
NEC Table 314.16(B) assigns a volume allowance of 2.00 cubic inches for each 14 AWG conductor in box fill calculations.
Question 2: Per NEC 314.16(B)(4), how does a duplex receptacle (wiring device) count in a box fill calculation?
- One conductor based on the largest AWG in the box
- Two conductors based on the largest AWG in the box (Correct answer)
- Three conductors based on the largest AWG in the box
- Devices are exempt from box fill requirements
Correct answer: Two conductors based on the largest AWG in the box
NEC 314.16(B)(4) states each wiring device (switch or receptacle) counts as two conductors based on the largest AWG conductor present in the box.
Question 3: Per NEC 314.16(B)(5), all equipment grounding conductors (EGCs) inside a box collectively count as how many conductors in box fill?
- Zero — EGCs are exempt from fill calculations
- One conductor based on the largest EGC present (Correct answer)
- One conductor per each individual EGC
- Two conductors based on the largest EGC present
Correct answer: One conductor based on the largest EGC present
NEC 314.16(B)(5) requires all EGCs together to be counted as a single conductor based on the largest EGC in the box.
Question 4: A 4-inch square metal box 1-1/2 inches deep has a listed volume of 21 cubic inches. Using only 12 AWG conductors (no devices or clamps), how many conductors are permitted?
- 7 conductors
- 9 conductors (Correct answer)
- 11 conductors
- 14 conductors
Correct answer: 9 conductors
Each 12 AWG conductor occupies 2.25 cubic inches; 21 ÷ 2.25 = 9.33, which rounds down to 9 conductors maximum.
Question 5: Per NEC 314.16(B)(2), how do all internal cable clamps inside a box count toward box fill?
- Zero — internal clamps are not counted
- One conductor (all clamps together) based on the largest AWG in the box (Correct answer)
- One conductor per clamp based on the largest AWG
- Two conductors total for all clamps combined
Correct answer: One conductor (all clamps together) based on the largest AWG in the box
NEC 314.16(B)(2) requires all internal cable clamps as a group to count as a single conductor based on the largest wire size in the box.
Question 6: A box contains three 14 AWG conductors, one duplex receptacle, and one equipment grounding conductor. What is the minimum required box volume?
- 8.00 cubic inches
- 10.00 cubic inches
- 12.00 cubic inches (Correct answer)
- 14.00 cubic inches
Correct answer: 12.00 cubic inches
Calculation: 3 conductors × 2.00 + device × (2 × 2.00) + EGC group × 2.00 = 6.00 + 4.00 + 2.00 = 12.00 cubic inches minimum.
Question 7: Per NEC 314.16(B)(1), a conductor that passes through a box without any splice or termination counts in box fill as:
- Zero — pass-through conductors are not counted
- One conductor (Correct answer)
- Two conductors (once for entering, once for exiting)
- Only counted if the conductor is larger than 10 AWG
Correct answer: One conductor
NEC 314.16(B)(1) requires each pass-through conductor to be counted once because it still occupies space inside the box.
