PCBelarge wrote:
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As an inspector, this document provides some interesting information, but I would be hard pressed to say that in a commercial installation I would not allow NM cable to be installed exposed where it is protected from physical damage - whatever physical damage may be.

I could have used one of the other NEC standards, but, chose to go with the physical damage issue. But, it probably would have been better to approach it from the perspective of 110.3.
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110.3 Examination, Identification, Installation, and Use of Equipment.
(A) Examination. In judging equipment, considerations such as the following shall be evaluated:
(1) Suitability for installation and use in conformity with the provisions of this Code
FPN: Suitability of equipment use may be identified by a description marked on or provided with a product to identify the suitability of the product for a specific purpose, environment, or application. Suitability of equipment may be evidenced by listing or labeling.

Or I could have used 334.10(3). Which is identical to the information in the NEMA publication.
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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.
(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.
FPN No. 1:Building constructions are defined in NFPA 220-1999, Standard on Types of Building Construction, or the applicable building code, or both.
FPN No. 2:See Annex E for determination of building types [NFPA 220, Table 3-1].

The NEC handbook provides a better description of the building types than Annex E.

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The five fundamental construction types used by the model building codes are Type I (fire resistive), Type II (noncombustible), Type III (combination of combustible and noncombustible), Type IV (heavy timber), and Type V (wood frame). Types I and II basically require all structural elements to be noncombustible, whereas Types III, IV, and V allow some or all of the structural elements to be combustible (wood).

The building in question here (wooden barn) is obviously in the Types III, IV, V category (more than likely Type V). So... Both the NEMA publication and the NEC seem to be in sync. They both allow NM cable in buildings other than dwellings. But, the difference is... in dwellings it can be installed exposed, but, in "other than dwelling units" that are not constructed of "non-combustible" material... it would seem NM has to be concealed. This is not what I see as I do inspections.

So... Glenn confused! [Linked Image]

Personally, I don't see why there is a "lower" standard for dwelling units. [Linked Image] I think it should be concealed everywhere unless the "exposed" NM is in an unoccupied attic or crawlspace. Which would essentially mean that it is "concealed" for all practical purposes.

Sometimes (like in this case) I am trying to figure out where the NEC language came from... which in this circumstance is obviously NEMA. Or maybe this is a chicken and egg scenario. [Linked Image]

Edited for spelling errors. I guess that’s what happens when you are typing fast. [Linked Image]

[This message has been edited by safetygem (edited 12-13-2004).]