National Electrical Installation Standards

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Tuesday, July 24, 2018

Question:

Re: CQD answer published Thursday, July 12, 2018 -NM Cable in Fire Rated Construction

1) Steve should also be aware that the Massachusetts Electrical Code has amendments for the use of type NM cable

2) What code section prohibits the use of NM cable in fire rated construction? 334.10 does not limit the use to only nonrated construction. See NEC 334.10 #3. All that is required is a 15 minute finish rating which is not even 1/2 inch drywall.  Fire stopping/caulking manufacturers actually have details showing electrical cables of all types in their fire rated penetration detailing.  Please clarify where this is in the code. Thanks, Matt Varvel

3) BAD ANSWER, Joseph Hertel

A

Answer:

Hey all y'all thanks for your comments.

1) Information on the Massachusetts NEC amendments can be found here:

https://www.mass.gov/regulations/527-CMR-12-massachusetts-electrical-code-amendments

2) The question described a structure that was "fire rated on the parking level with conventional lumber" used for higher floors. Our vision was masonry construction (noncombustible for the parking level such as poured concrete with no provisions for wiring embedded in the masonry or no additional finish material. If that floor was required to be of Type I or II then NM cable is not allowed to be installed. If that floor was permitted to be Types III, IV, or V construction, but Type I or II was used by choice, then NM cable is allowed if within a 15-minute finish rating as stated in 334.10(3).

3) Shouting BAD ANSWER is not helpful.

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