Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsEasy
A residential electrician is installing a new 20-amp, 120-volt branch circuit in a dwelling unit using nonmetallic-sheathed (NM) cable. The cable passes through a bored hole in a wood joist. The nearest edge of the bored hole must be no less than what distance from the nearest edge of the joist?
- A1/2 inch
- B1 inch
- C1 1/4 inches
- D3/4 inch
Show answer & explanationAnswer & explanation
Correct answer: C. 1 1/4 inches
According to NEC Section 300.4(A)(1), where cables or raceways are installed in bored holes in wood members, the holes shall be bored so that the nearest edge of the hole is not less than 1 1/4 inches (32 mm) from the nearest edge of the wood member. This protects the cable from nails or screws.
Why the other options are wrong
- A. 1/2 inch is insufficient protection for cables in bored holes.
- B. 1 inch is insufficient protection for cables in bored holes.
- D. 3/4 inch is insufficient protection for cables in bored holes.
Bored Hole Cable Protection
NEC requirement for the minimum distance from the edge of a wood member when boring holes for cables or raceways, designed to protect the wiring from physical damage.
- Minimum 1 1/4 inches from the nearest edge.
- Applies to cables and raceways in bored holes.
- Protects against nails and screws.
Memory trick: Wood holes need a 'one-and-a-quarter buffer' for cable safety.