Where NM cable (Romex) is not allowed
NM cable cannot be used as service-entrance cable, embedded in concrete or masonry, in wet or damp locations, or in places like hoistways and battery rooms. Except in dwellings, it cannot run exposed above drop ceilings.
What the code requires
The NEC lists places NM and NMC cable may not go. It cannot be used in any structure that 334.10 does not permit, or as service-entrance cable. It cannot run exposed in dropped or suspended ceilings, except in one-, two- and multifamily dwellings.
It is also not allowed in commercial garages with hazardous (classified) locations under 511.3, in theaters except as 518.4 allows, in motion-picture studios, in storage battery rooms, or in hoistways, elevators and escalators. It cannot be embedded in poured cement, concrete or aggregate, or used in hazardous (classified) locations unless another article permits it.
Type NM specifically cannot be used where exposed to corrosive fumes or vapors, embedded in masonry, concrete, adobe, fill or plaster, or run in a shallow chase in masonry, concrete or adobe covered with plaster or a similar finish. It also cannot be used in wet or damp locations.
On the job
- NM cable run outdoors, even inside conduit, is a frequent correction, because Type NM may not be used in wet or damp locations.
- In commercial spaces, NM cable run exposed above a drop ceiling is a violation.
Related sections
- NEC 334.10: Where NM cable (Romex) is allowed
- NEC 300.9
- NEC 511.3
- NEC 518.4
Where this comes from
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Kyle Robert Anderson KBC Electric · CSLB #1073066 · C-10 Electrical · Licensed since 2021