I've just had a holiday lights company install some outside tree lights, and I found they had done it so that at several places the prongs of mains cable plugs had been left exposed, and carrying mains voltage. I've put a couple of pictures here: https://tinyurl.com/tk-wiring-pics (In the one with the voltmeter, that plug is just as it was left lying on the grass by the installer — I didn't have to unplug it to get to the pins.)
Is that permitted under the US NEC?
I know there is provision in the NEC for temporary (up to 90 days) installations, and the installer has told me that their setup is fine because of that. But that sounds a bit dubious if it implies you can leave 100V+ lying around in the grass for some kid to stand on.
Also, I think I found the reason it has happened, and that is that the installer has made up some of their own cables, and one of them has a plug at both ends (i.e. instead of a plug at one, and a socket at the other). As a result they have in a sense "reversed the direction" of plug-to-socket, and so instead of the usual power going into plugs and out of sockets, they have a big section of our yard lights where power is going into sockets and out of plugs (several of which are then exposed to the outside).
Seems very unsafe to me but, again, is that actually allowed by NEC under the temporary installation allowances?
Best Answer
It's incorporated by reference. The electrical code cites 110.3
Which punts the entire matter over to UL.
Let's test the theory that this is legal. They either bought this item off the shelf, or they modified it themselves.
If they bought it off the shelf -- then UL would have had to test, approve and list the cable with male NEMA 1‘s on both ends. I think we can reject that as highly improbable.
If they modified it -- then they would need to be doing so in accordance with instructions to do so, these instructions being approved by UL as part of the testing, approval and listing of that product. Now, can you imagine UL approving instructions that advise or fail to prohibit attachment of a male connector in more than one place? I am not a product manufacturer so I don't know the guts of the UL rules, but I don't see that happening.
Realistically, they modified it gypsy/illegal, which violates 110.3.
As a practical matter I would buy a bare NEMA 1 socket for about a dollar, and slip that over the bare contacts, tape it down with electrical tape (to make it obvious this should not be taken apart) and call it good. That is so stupid-easy I cannot believe the installer didn't just do that. Don't lop off an extension cord to do this, as the cut end will have hot and neutral about 1mm apart and could burn little fingers. Or big ones.