Taking 110.3(B) too far?

Considering our very litigious society, installation of listed products is becoming more and more common, even when the NEC may not require listing of a particular product, such as for a general use luminaire.  When installing listed products, section 110.3(B) is required to be complied with.  To paraphrase section 110.3(B), listed products must be installed within the parameters of the listing and labeling instructions.  While that sounds very easy to comply with, many times this can become a very difficult thing to address. 

For example, what about the wire nut type of connectors that come with some luminaires?  Since these come with the listed product, and are shown in the instructions, does this mean that we must use them?  What if they are too small?  What if they are too big?  What if you just hate the fact that they are cheaper and perhaps less reliable than the connectors you like to use? Does throwing them away and using your own (listed) wire nuts then void the listing of the luminaire? 

I should hope not, but as silly as this sounds, this is the literal interpretation of some installers and inspectors.  How far do we go with 110.3(B)?  Sometimes I think we take it too far.  Let me give you an example of a question that was brought up at the Mike Holt Code Forum:

Question: “I am presently working as a journeyman electrician on the remodeling of an exhibit/shop/promotion. On Thursday the job foreman displayed concern that some pendant light fixtures had been installed and the 1" X 8-32 machine screws provided by the manufacturer had not been used to attach the fixture plate to the 4" to round plaster ring mounted on the outlet box. Instead (in most instances), we had used 1/2" X 8-32 machine screws (industry standard, and produced by a major manufacturer) to secure the fixture plate to the plaster ring. In every instance there was direct metal to metal contact between the fixture plate and plaster ring, and at least 1/4" of the machine screw was visible inside of the box. However, the foreman claimed that since the 1" X 8-32 machine screws provided by the fixture manufacturer was not used, this was a potential violation of the UL listing of the light fixture and potentially exposes the electrical contractor (and individual electrician) to increased liability.

Now, of course, there was no question that unauthorized "field alterations" to fixtures, devices or other equipment will, in fact, violate the provisions of that items UL listing. For instance, failing to use the provided light fixture installation plate will render the UL listing invalid because such plates are necessary for heat dissipation, grounding and/or other purposes. But, the specific issue here was whether or not the act of not using the factory provided screws was a violation. Have you any specific knowledge or comments concerning this issue.”

Now I personally think that this is an example of getting much too excited about the minutia of the entire job, and as an inspector myself, I personally think there are much more important things to worry about.  However, this seems to be a legitimate question considering the literal language of 110.3(B). Here is Underwriters Laboratories (UL) response to this question:

“The length of the screws packaged with the luminaire takes into account that there are installations that involve different spacings between the luminaire and the junction box. Also, it permits the manufacturer to use one set of screws for many different luminaire models, thereby reducing their inventory. The clause in UL 1598 that addresses the length of luminaire mounting screws is 10.2.1. It specifies that the length of the screw has to be at least 1/2 in. longer than the distances between the mounting surface and the luminaire surface with the screw hole.

You have elected to replace those screws with shorter screws of the same diameter and thread pitch. The use of those shorter screws that protrude past the other side of the threaded hole by at least 1/4 inch are sufficient to secure the luminaire. This does not void the UL Listing.”

As you can see from UL’s response, a small alteration, such as using a different screw, is probably nothing to worry about.

Ryan Jackson
Electrical Code Consultant,
Mike Holt Enterprises, Inc.