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Control Panel Requirements: UL508A & NFPA 79

Control Panel Requirements: UL508A & NFPA 79

Control Panel Requirements: UL508A & NFPA 79

NEC articles 90.7 and 110.3 make it clear that electrical equipment must be "suitable," and the best way to indicate suitability of a control panel is via third-party listing. In the US, that typically means UL508A listing. As I read Article 409, UL508A listing isn't explicitly required. It's just one option.

But what if the control panel will be installed as part of a piece of industrial machinery as defined in Article 670.2? Does this then mean that the control panel construction must follow the requirements in NFPA 79 as well? Or does NFPA 79 just govern the installation of these control panels? It's not clear to me if NFPA 79 is mandatory, and if so, when. Any thoughts?


RE: Control Panel Requirements: UL508A & NFPA 79

UL508A - Here is UL in a nutshell. If you order all parts in your panel as UL listed. UL also specifies any heat producing components have proper spacing. I would also have the panel built by a UL listed shop, then you can have the added sticker on the panel as UL listed by panel shop. If you UL list your panel and sell into USA then its a lot easier for a local electrical inspector to sign off on the local installation. You also have UL listed sub assemblies which is another discussion where UL sticker was given to a manufacturer on a product line when multiply components are used together.

NFPA 79 is also a standard for machinery with control panels. I think when i was doing unit operation machines that this was a kind a of bible. I would review this document if this is the case for requirements.

I think if you comply with both docs then your job at the far end during project sign off will be a lot easier.

RE: Control Panel Requirements: UL508A & NFPA 79

Hmmm... a little late, but I'll put it this way.

1) Not all states REQUIRE listing of assemblies by "NRTLs" (Nationally Recognized Testing Labs), it's something that individual states adopt by ammending the NEC for their state. So for example here in California, we have the California Electric Code, which is basically a document adopting a VERSION of the NEC (we just adopted the 2014 NEC this year) and ammending it with other specific requirements. one of those other requirements is that all electrical assemblies of more than 5 components (including the box) must bear the approval of an acceptable NRTL, using the list maintained by OSHA (click for link). UL is ONE of the NRTLs on that list and ostensibly the most well known, but not the only one.

2) In addition to that state-by-state NRTL requirement, Article 110 and 409 of the NEC also now mandate SCCR values be listed / shown on electrical equipment that has line power components. So starters, panelboards, load centers, MCCs, control panels etc. etc. One of the listed ways that you can ATTAIN a valid SCCR label is by following UL508A Supplement SB2, which is available to UL 508A shops.

3) Nobody enforces NFPA79 standards, but they are considered a "reference standard" by OSHA when developing and maintaining an employers' REQUIRED program of electrical safety, just as NFPA 70E is a "reference standard". OSHA will not force you to follow the standards, but if you DON'T and there is an accident that they think would have been preventable had you followed it, you could be CRIMINALLY prosecuted for negligence. It rarely happens, but I've seen them "make an example" of people a couple of times, usually grossly negligent. Generally though, large companies will have insurance underwriters who will insist on it, so it becomes a "company standard". If you are making and selling machinery and not following NFPA79, you could be called to the carpet by a buyer who likely had it in a purchasing spec, or who has an internal inspection that turns it up as an issue. So it's far far better to just follow the rules rather than buck them to save a buck.

" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

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