334.10 Nonmetallic-Sheathed Cable. Uses Permitted.
Code Change Summary: A clarification was made to restrict the use of nonmetallic sheathed cables “where prohibited by 334.12”.
Nonmetallic sheathed cables (NM, NMC, NMS) can be used in many locations except where section 334.12 prohibits it. The previous code language didn’t say that exactly.
In section 334.10, the location of the phrase “except as prohibited in 334.12” is important. Where it was in the 2011 NEC® created a completely different interpretation of how type NM cable could be used. A literal interpretation of the old code language would allow a type NM cable to be used in any residential storage building, with no restrictions on what’s being stored in the building or what the building was being used for.
Section 334.12(B) does not allow type NM cable to be installed in wet locations or where exposed to corrosives such as chlorine but without the revised code language, sections 334.10 and 334.12(B) were in conflict with one another.
In the 2014 NEC®, the phrase “except as prohibited in 334.12” has been moved to the parent text of the section to make it apply generally to items 1 through 5.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2011 Code language:
334.10 Uses Permitted. Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following:
(1) One- and two-family dwellings and their attached or detached garages, and their storage buildings.
(2) Multifamily dwellings permitted to be of Types III, IV, and V construction except as prohibited in 334.12.
(3) Other structures permitted to be of Types III, IV, and V construction except as prohibited in 334.12. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
(4) Cable trays in structures permitted to be Types III, IV, or V where the cables are identified for the use.
(5) Types I and II construction where installed within raceways permitted to be installed in Types I and II construction.
2014 Code Language:
334.10 Uses Permitted. Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following, except as prohibited in 334.12:
(1) One- and two-family dwellings and their attached or detached garages, and their storage buildings.
(2) Multi-family dwellings permitted to be of Types III, IV, and V construction.
(3) Other structures permitted to be of Types III, IV, and V construction. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
(4) Cable trays in structures permitted to be Types III, IV, or V where the cables are identified for the use.
(5) Types I and II construction where installed within raceways permitted to be installed in Types I and II construction.
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334.10 Nonmetallic-Sheathed Cable. Uses Permitted.
Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:Type NM cable can be used in which of the following locations?
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