CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationEasy
An electrician bores a hole through the center of a 2x4 stud for NM cable, and the hole edge ends up located 3/4 inch from the face edge of the stud. According to NEC requirements as applied in residential wiring, what must be installed to protect the cable?
- AA double stud must be installed at that location
- BThe cable must be rerouted through the top plate instead
- CNo protection is required since the hole is within the stud
- DA 1/16-inch thick steel plate covering the area of the cable
Show answer & explanationAnswer & explanation
Correct answer: D. A 1/16-inch thick steel plate covering the area of the cable
NEC 300.4(A)(1) requires a steel plate or bushing at least 1/16 inch thick when a bored hole is located less than 1-1/4 inches from the nearest edge of the framing member, to protect the cable from screws or nails.
Why the other options are wrong
- A. Doubling the stud is not a code remedy for insufficient cable clearance.
- B. Rerouting through the top plate does not address the exposed cable hazard at this stud location.
- C. Protection is required because the hole is closer than 1-1/4 inches to the stud edge.
Bored Hole Cable Protection
NEC 300.4(A)(1) requires steel protective plates when wiring passes through framing holes closer than 1-1/4 inches to the framing edge, to prevent nail/screw punctures.
- Minimum 1-1/4 inch clearance avoids need for a plate.
- Steel plates must be at least 1/16 inch thick.
- Applies to both bored holes and notches in framing.
Memory trick: 'Too close to the edge? Steel plate saves the wedge (cable).'