Electrical Voltage Labels

My non-code-expert opinion:

If the 120V is derived from the 480V by a transformer inside the panel, you only need the 480V sticker.

If the 120V comes from a different source, you need both stickers. If the 120V isn't cut off when you open the door or disconnect, you need a warning sticker specifically describing that fact and the source of the 120V !
 
Ask yourself what is the "120V" label for. Is it to warn, as Ken suggested, that a second source of voltage is present? If so, a clearer warning such as "Multiple sources of power are present" label would be better.

If it is just to indicate that more than one voltage level is present, I would say mark only the highest voltage in cabinet. The main reason is to avoid warning sign clutter.

NFPA 70E requires labeling of the "nominal system voltage." :confused:
 
Ken is right and there are specific labels for that too. But technically, if it is a control panel, Article 409 of the NEC would apply and 409.110 delineates the marking requirements that basically say you need BOTH things, the voltage of each service entering the box, an a label identifying that the source is from outside. However if the source is a control power transformer INSIDE of the same box, disconnected when the main 480V is disconnected, then you do not need to identify that at all on the outside.
 
The question was for multiple panels on lime we are putting in so I have situations where the main disconnect kills everything and there is a 480x120 transformer in the panel as well as 120x24 Volt DC supplies so on those just mark using the 480 label right?

I have 2 panels that have a 480 main disconnect bit there is a 120 circuit that feeds in from a MCC panel board that is still live when the 480 disconnect is off and on those we are using this label http://www.emedco.com/device-powered-by-several-sources-electrical-label-sqs110g.html

But on the voltage label for the panels with 2 feed sources should I apply the 480 and 120 label or just the 480 label in that case also? Meaning is the 480 label and the dual source warning label enough or should I also label the 120 on that one?
 
My vote is 120V not needed. The only danger I could think of is the 480V label getting damaged or removed, leaving only 120V and dual source labels. Baring that, I don't see an issue with putting both.
 
spot on Keith

I might add - I always tell apprentices that unless you can confirm the actual voltage by the correct test measuring systems,
to treat the Panel as containing the maximum / highest voltage.
Also never to enter a panel past the door hinge (assuming no components are mounted to the door)
 
I would just put a yellow trangle with the lightning bolt on it. There is some dangerous voltage in that panel and as far as personnel safety goes, it does not really matter be it 120, 240 or 480V.

Anything above 1 kV is a different game, of course.
 

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