CSLB C-10 Electrical ContractorWiring Methods and MaterialsEasy
An electrician installs NM-B cable into a metal single-gang device box equipped with an internal cable clamp. Per NEC 334.30, within what maximum distance from the box must the cable be secured to a framing member?
- A18 inches
- B12 inches
- C8 inches
- D6 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 12 inches
NEC 334.30 requires NM cable to be secured within 12 inches of every box, cabinet, or fitting where a cable clamp is used, and at intervals not exceeding 4.5 feet thereafter. This prevents strain on terminations and protects the cable from mechanical damage.
Why the other options are wrong
- A. 18 inches exceeds the permitted maximum.
- C. 8 inches applies to the exception for single-gang nonmetallic boxes without clamps, not the standard rule.
- D. 6 inches is more restrictive than the code requires.
NM Cable Securing (334.30)
Type NM cable must be stapled/secured within 12 inches of boxes with clamps and at 4.5-foot intervals along the run.
- 12 inches from box with clamp
- 4.5 feet between staples in the run
- 8-inch exception applies only to single-gang nonmetallic boxes without clamps
Memory trick: A foot from the box keeps the cable in check.