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I have a GFCI outlet on top of my pergola outside that had solid 3-conductor wire ran from there to an outlet on the other side of my patio when my parents built the house. My Mom wants me to put some decorative exterior lights on top of the pergola, so we bought a strand but they have a 3-prong plug. Although the GFCI outlet has a ground connection, it is not actually hooked up where it plugs into the wall. This is because when my Dad ran the cable and he used a very heavy gauge solid core wire. Unfortunately, when I went to terminate the cable into a 3-prong outlet with screw terminals, the wires were so stiff that I could not get the ground wire connected to the screw terminal (I put one of those stickers on the GFCI outlet indicating it is not grounded). I've attached a photo for further clarification.

My question is; do I need to connect the ground for the lights to operate safely, or is it good enough that they are connected to a GFCI outlet?

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I think I'm going to end up going with Harper and RME's solution with the pigtail. I can confirm that the outlet DOES WORK without a ground connection, just an FYI. I'll install the pigtail this weekend maybe when it's not so hot outside....

migrated from electronics.stackexchange.com Jul 5 '17 at 20:06

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    Just bridge a lower gauge wire onto the ground wire and wire the outlet correctly. And yes, anything that has a ground plug should use a ground. – Jarrod Christman Jul 5 '17 at 18:24
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    Wait - there is a ground in the cable running between the two receptacles, but it's just not connected to either receptacle? Does your supply from the panel have a ground in it? Is it connected anywhere? What gauge wire is used? – mmathis Jul 5 '17 at 20:11
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    @dandavis -- wrong. the NEC explicitly allows for GFCIs to be used to provide retrofit ground fault protection for ungrounded circuits – ThreePhaseEel Jul 5 '17 at 22:00
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    @dandavis: In my opinion, GFCIs are somewhat mis-named. They measure the difference in currrent between Line and Neutral - if there is a difference (more than 5 mA, I think), the GFCI will trip. It doesn't measure ground current, or care what causes the current difference. – Peter Bennett Jul 6 '17 at 0:54
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    @dandavis -- yeah, there's no reason to omit the ground for want of a pigtail :P – ThreePhaseEel Jul 6 '17 at 3:21
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Pigtail it

Heavier wire for long runs is a good thing. If it's just a problem of fitment of the wire, solve that with a pigtail.

Get the correct size cable for your circuit (12AWG for a 20A circuit, 12 or 14 AWG for a 15A circuit). Cut off a 6" length of each wire, attach them to the receptacle (tip, do this sitting at a bench, a real back saver), then simply wire-nut those pigtails onto the wires in the box. Push it all into the back of the box. Done.

Why 2 GFCIs though?

If you don't know what you're doing, you should only use the LINE terminals of the GFCI. But then, you did come over from the Electronics forum. So here's the skinny.

The LOAD terminals are special. They are not simply another pair of screws like on a common outlet.

When you extend the circuit off the LOAD terminals, that extension is also protected by the GFCI. Feeding that into another GFCI is basically doing a "Yo, dawg" joke. it's not dangerous, just pointless.

In fact, the smart electrician will arrange his circuit so the GFCI device is indoors, with all the outdoor receptacles downline and fed off those LOAD terminals. That way he doesn't have to spring for outdoor-grade GFCIs, and the outdoor wires themselves are also protected.

GFCI breakers are expensive for my old panel, so I have 4 GFCI receptacles right at the panel. You can plug something in there if you really want to, but their real purpose is that their LOAD terminals go right back into the panel to power other circuits.

  • Why send the load cable back into the panel? What are they doing once back inside? Wouldn't it be easier to daisy chain out the other side of the receptacle box? – CactusCake Jul 6 '17 at 21:26
  • @CactusCake most of my work is in conduit, and rerouting a conduit especially crossing other conduit is a pain. Easier to go back into the panel and use it as a gutter. It also allows me to use the GFCI to proof other circuits temporarily that will not be on GFCI after that. – Harper Jul 6 '17 at 22:24
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Within most parts of the US, it is legal to install a GFCI without a ground connection provided that it is marked "NO EQUIPMENT GROUND". Although most multi-receptable assemblies do not provide any means of separating the grounding conductors, it would be safer to have all the grounding conductors detached from each other than to have them attached to each other without any sort of earth path. If there is some means of attaching them to something that's kinda-sorta grounded but would not pose a hazard if briefly tied to hot through a low-resistance path, that would likely be safer yet, but I don't know of any such means that would be recognized by electrical codes.

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This is a misinterpretation of NEC Article 406.4 (D)(2) which provides a method of installing a three wire receptacle in lieu of a two wire receptacle in dwellings built pre 1968. In new dwellings you can not have ungrounded receptacles and mark them as such. If your wire size is too large to install on a receptacle you can simply pigtail a smaller wire onto the larger wire and connect to the receptacle. Providing the smaller wire still has the current carrying capacity of the breaker protecting it. It can either be solid or stranded.

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