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.)

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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?

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    I don't know enough to cite the NEC, but I'm pretty sure exposed, live, high voltage wires are never allowed for any amount of time. They're just being lazy, and they need to fix this ASAP. All the splices in that home-made cable need to be covered too so start looking for loose wire twisted together.
    – JPhi1618
    Commented Dec 15, 2017 at 17:34
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    I agree, and since writing the above I've established that NEC section 590 is the relevant one. It seems quite clear that while many misunderstand this, it is not a shortcuts list. It provides for a couple of small relaxations in the use of NM and NMC cable, but other than that it's mostly saying that just because the installation is temporary doesn't mean you can ignore code. I'd still like to hear something definitive from someone who's up to speed on NEC 2017 though.
    – tkp
    Commented Dec 15, 2017 at 17:38
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    Seeing the second pic, I get it now... They are out of clamp on female plugs, so they are using male plugs to feed piggy back plugs. No this is NOT acceptable and is unsafe.
    – Tyson
    Commented Dec 15, 2017 at 18:23
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    I don't think the NEC or UL or any regulation is at all relevant for this one. It's a live, exposed hazard that could kill pets, children, or careless adults... even if the company could justify it under some loophole in the NEC, you would still be liable when it kills someone. Commented Dec 15, 2017 at 19:33
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    (basing on info provided in OP) KEEPS THOSE LIGHTS OFF!!! I have no words to describe what a f**** reckless job this is and have no idea how can someone sleep at night knowing he made it. Really. It can EASILY be cause of DEATH. And if you (and this is perfectly legitimate) have not enough DIY experience to realize this yourself my invitation is to call a certified electrician ASAP and even evaluate if to report whoever did this job to relevant authority. A kid picks that thing up and is dead. Commented Dec 15, 2017 at 23:58

3 Answers 3


It's incorporated by reference. The electrical code cites 110.3

listed and labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

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.

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    Whoever did this should be reported to the local building department and Better Business Bureau if they don’t immediately fix it.
    – Mark
    Commented Dec 15, 2017 at 19:47
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    I once bought a rope light (for personal use) that had a male connector at both ends; I'm pretty sure it was just a manufacturing defect. Since I bought it during an "all sales final" January closeout, I popped the fuse from one end and confirmed that disconnected the hot prong, and then wrapped the whole thing in electrical tape. The fact that there's a male at both ends wouldn't imply the installer modified it themselves, but I don't think ignoring an obvious manufacturing defect is really any better.
    – supercat
    Commented Dec 15, 2017 at 20:15
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    In this case the company actually told me they had built the cable themselves. They said they were "home made" but I misheard them, thinking maybe they'd used a technical term meaning "cable with multiple plugs". So I asked them to repeat it and the guy said more clearly "H-o-m-e M-a-d-e; you know, we made it ourselves." And in fact there were two such home-made cables: one had a male at both ends; another, while having a male at only one end and a female safely at the other, also had 5 or 6 males along its length, as "tapping" points. So I had roughly one live exposed plug per tree. Ahem.
    – tkp
    Commented Jan 3, 2018 at 22:25

You are correct in assuming there should not be any live connections exposed in any situation. I suppose it should be said that this is a dangerous situation and could be fixed fairly easy with a set of wire cutters and some appropriate wire nuts. So call the installer and see if they want to make the repair. If they give you any static I would report it to the AHJ in you area and let them deal with it.

Regardless I would not recommend you turn these lights on until a repair was made. As I said before this is a potential fire and shock hazard.

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    Chances for recourse are probably slim with a fly by night "holiday lights company". Worth a shot I guess though, but I wouldn't have these people back on my property even if they paid me to be there.
    – Mazura
    Commented Dec 16, 2017 at 1:42

Combined my comment and answer since the OP asked about NEC rules and holiday lighting .

Not legal at all!!! 406.7.A , in short says NO exposed current carrying conductors totally illegal this could never be listed! 590.5 states the holiday lighting shall be listed and labeled, there is no way this is a listed product.

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    "Jumping to 406.7, we find there is a central theme to each of the specific paragraphs in this rule. The message here is that at no time will the exposed prongs of an attachment plug or flanged inlet be energized, unless properly connected to a receptacle or connector body." (and thus, no longer "exposed") –iaeimagazine.org
    – Mazura
    Commented Dec 16, 2017 at 1:58
  • IMO, this Q isn't in the purview of the NEC, but the company opened up that box themselves. I think they meant that because it's not permanently installed, they don't (have to adhere), which is true, but that doesn't make it permissible in the real world. “contractor will perform its work in a good and workmanlike manner.” that's the part they violated, if it's applicable in the first place - but you don't need a permit to hang Xmas lights, so...
    – Mazura
    Commented Dec 16, 2017 at 2:02

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