ECN Forum Forums Photo Discussion Forums Photos for General Discussion Exposed NM Cable

Here's some background. This panel is located in an open sided county fairgrounds building where 4H kids show sheep. Six feet to the left of the panel and you are out from underneath the roof. The white flecks to the left of the panel are staples with little "bits" of paper attached from kids (and probably adults) staple gunning posters, show schedules, etc. to the mounting board. This "rewire" was in response to my request that they repair 40+ year old NM that had significant damage to the sheathing.

To the electrician's credit, he also responded to a concern of the fair board of circuit breakers constantly tripping during the fair, because of overloaded circuits. So... his response was to put each receptacle on its own dedicated circuit. Hence... the massive number of wires coming out of the top of the panel.

I have continuing concerns about the adequacy of this installation. Here in lies the rub. I am an "OSHA" inspector (OK let's not get off topic here with OSHA bashing!) and this installation passed the electrical inspection. I'm not bashing the electrical inspector, because he works for the same agency I work for... but, I'm at a loss to explain how this would comply with the NEC as I understand the applicable sections. And to make it perfectly clear... I am aware that Article 334 allows NM to be installed in "exposed" work.

I don't want to taint anybody's opinion about what I think the violations are, I'd just like to know what the group thinks about this type of installation practice. Am I being too picky? This has ramifications beyond this particular building. I find similar installations frequently in the buildings I inspect. All of the buildings that I inspect are owned by the government (State, County, Local).

One of the other issues that comes up in the long run is... once an installation passes final, then the only (and I do mean only) person that might look at the equipment in the future is going to be someone in my position. The only other electrical inspection that ever happens in any building after a final is when there are significant alterations that require the pulling of a permit. Until that point, the installation can rot in place until a safety inspector happens to come by and finds an serious hazard that may have existed for an extended period of time.

OK. Enough of my soapbox background discussion. Comments? Ideas? Concerns?

- Glenn (safetygem)

ARTICLE 547 Agricultural Buildings

547.5 Wiring Methods.

(A) Wiring Systems. Types UF, NMC, copper SE cables, jacketed Type MC cable, rigid nonmetallic conduit, liquidtight flexible nonmetallic conduit, or other cables or raceways suitable for the location, with approved termination fittings, shall be the wiring methods employed. Article 398 and Article 502 wiring methods shall be permitted for areas described in 547.1(A).

ARTICLE 334 Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS

334.15 Exposed Work.

In exposed work, except as provided in 300.11(A), the cable shall be installed as specified in 334.15(A) through (C).

(A) To Follow Surface. The cable shall closely follow the surface of the building finish or of running boards.

(B) Protection from Physical Damage. The cable shall be protected from physical damage where necessary by conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetallic conduit, pipe, guard strips, listed surface metal or nonmetallic raceway, or other means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetallic conduit, listed surface metal or nonmetallic raceway, or other metal pipe extending at least 150 mm (6 in.) above the floor.

Someone might hit it with a pitchfork

547.5(C)(2) Damp or Wet Locations. In damp or wet locations, equipment enclosures, boxes, conduit bodies, and fittings shall be placed or equipped so as to prevent moisture from entering or accumulating within the enclosure, box, conduit body, or fitting. In wet locations, including normally dry or damp locations where surfaces are periodically wased or sprayed with water, boxes, conduit bodies, and fittings shall be listed for use in wet locations and equipment enclosures shall be weatherproof.

Recommended Action: Have a qualified electrician repair, replace, or install the electrical equipment according to the instructions provided and in accordance with NFPA 70-2002, the National Electrical Code (NEC). Nonmetalic-Sheathed Cable (e.g., "Romex") must be installed in accordance with provisions of NEC Article 334. Paragraph 15(B) specifies requirements for its protection in "exposed work."


National Electrical Code, NFPA 70-2002 (Emphasis added)
Article 334 Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS
334.15 Exposed Work.
(B) Protection from Physical Damage. The cable shall be protected from physical damage where necessary by conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetalic conduit, pipe, guard strips, listed surface metal or nonmetalic raceway, or other means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetalic conduit, listed surface metal or nonmetalic raceway, or other metal pipe extending at least 150 mm (6 in.) above the floor.


While "physical damage" to insulation is not defined in the NEC, the NEC handbook has wording describing causes of insulation failure, "the principal causes of insulation failures are heat, moisture, dirt, and physical damage (abrasion or nicks) occurring during and after installation. Insulation can also fail due to chemical attack, sunlight, and excessive voltage stresses." It was noted during this visit that NM cable is located in various locations where the insulation could fail based on these exposures.

NOTE: The fundamental requirement to protect NM cable from physical damage has been in the NEC for more than 45 years. For example, NFPA 70-1959, Section 336-6. Exposed Work, "In exposed work, (b) It shall be protected from physical damage where necessary. " The NEC handbook from 1959 further describes the potential of damage to NM cable, "In northern climates where temperatures of 0 F or below are frequently experienced during the winter, the ordinary types of nonmetallic-sheathed cable, where installed in dairy barns and similar farm buildings, have in some cases deteriorated rapidly, due to the growth of fungus or mold inside the cable." While in several buildings, neoprene covered NM cable was found, several other buildings were still wired with older "Cresflex" type NM cable described in the handbook advisory. It is highly probable that this older wiring has significantly deteriorated and should be replaced as soon as possible and when rewired, the building conductors must be protected by conduit, preferably PVC.

You should have a person evaluate all older wiring according to the provisions of "The NETA Maintenance Testing Specifications." These specifications are written by the International Electrical Testing Association and the latest edition was published in 2001. It is available from NETA in 3 different formats. You can contact NETA on the World Wide web at: http://www.netaworld.org/ or by phone: 888-300-NETA (6382).