Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsHard
A residential electrician is installing a new 20-amp, 120-volt branch circuit in a dwelling. The cable will pass through bored holes in wood studs. According to NEC 300.4(A)(1), what is the minimum distance the edge of the bored hole must be from the nearest edge of the wood member to avoid the need for protection by a steel plate or bushing?
- A1 1/4 inches
- B2 inches
- C1 1/2 inches
- D1 inch
Show answer & explanationAnswer & explanation
Correct answer: A. 1 1/4 inches
NEC Section 300.4(A)(1) states that where a cable or raceway-type wiring method is installed through bored holes in wood members, the holes shall be bored so that the edge of the hole is not less than 1¼ inches from the nearest edge of the wood member. If this distance cannot be maintained, a steel plate or bushing must be installed.
Why the other options are wrong
- B. This distance significantly exceeds the minimum, which is permissible but not the minimum required to avoid protection.
- C. This distance exceeds the minimum, which is permissible but not the minimum required to avoid protection.
- D. This distance requires protection by a steel plate or bushing.
Bored Hole Cable Protection (Wood)
The NEC requirement for minimum clearance between a bored hole and the edge of a wood member to protect cables from nails or screws.
- Prevents accidental damage to conductors.
- Applies to cables and raceways in bored holes.
- Requires steel plate protection if clearance is insufficient.
Memory trick: One and a quarter for the wood's border, keeping wires in order.