Plug-in connections inside industrial control panels, code violation?

[cerskine]

I am doing a design review on another engineer's control panel design. He has a desktop UPS plugged into a DIN-rail 120 VAC receptacle and several "wall-wart" power supplies plugged into the UPS receptacles.

I don't think this is a good idea. I have found the following sentence in an Allen-Bradley hardwired UPS sales brochure:

"Electrical codes typically do not allow plug-in connections within a control panel."

I have been unable to find any reference to this in my copies of NEC 2008, UL-508A 2001, NFPA-79 2007.

Does anyone know what section(s) of the codes cover plug-in connections on an industrial control panel? Any help appreciated!

 

[jim dungar]

I have been unable to find any reference to this in my copies of NEC 2008, UL-508A 2001, NFPA-79 2007.

I am not surprised you can't find it. I have never seen this type of prohibition. In fact UL508A contains information on the use of receptacles in control panels. The A-B quote is probably marketing, after all they have a product to sell.

That said, though, I would be happy if fewer plug-in devices were used. For some reason wall-warts and indutrial grade just don't seem to go together. Many commercial grade products were never intended to be sealed up in an enclosure.

 

[pfalcon]

Not a prohibited application. Very commonly done for supplying laptops for servicing programmable devices.

Note that the UPS supplies conductors that remain energized when the main disconnect is in the OFF position. ORANGE marking is required.

 

[tom baker]

I use and like the UPS made by AB that is hard wired. Its actually made by APC for AB. Using a UPS in a control panel requires cords and receptacles, however if the UPS fails it can be quickly bypassed. The only NEC rule against this would be portable wiring shall not be used as a substitute for the fixed wiring of a building. Art 400 Uses not permitted.