Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsMedium
A commercial electrician is installing a new 20-amp, 120-volt branch circuit in a suspended ceiling using Type MC cable. The cable is supported by straps and is not passing through any fire-rated assemblies. What is the maximum distance between points of support for this Type MC cable?
- A4 1/2 feet
- B6 feet
- C3 feet
- D10 feet
Show answer & explanationAnswer & explanation
Correct answer: B. 6 feet
According to NEC Section 330.30(B), Type MC cable must be secured and supported at intervals not exceeding 6 feet (1.8 m). This ensures the cable is properly maintained and prevents undue strain or sagging.
Why the other options are wrong
- A. 4 1/2 feet is incorrect for MC cable support intervals.
- C. 3 feet is a common support interval for some wiring methods but not the maximum for MC cable.
- D. 10 feet is too far for supporting Type MC cable.
MC Cable Support Requirements
The NEC specifies maximum distances between points of support for Type MC cable to prevent sagging, damage, and maintain proper installation integrity.
- Maximum support interval is 6 feet.
- Must be secured within 12 inches of boxes or fittings.
- Specific rules apply for unsupported lengths in suspended ceilings (330.30(D)).
Memory trick: MC cable needs a hug every 'six-foot stretch', don't let it sag.