I installed a GFCI receptacle yesterday, the instructions were saying that if you see more than 4 wires in the box (excluding the ground) call an electrician.

In my case everything you see to the right of the brown dotted line was connected to one box (4x4)

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  • Can you post photos of the inside of the box please? Feb 24, 2020 at 12:38
  • It is closed and the cover is on, I am not going to open it again soon.
    – MiniMe
    Feb 24, 2020 at 13:14
  • 5
    Because writing instructions for up to 4 wires is easy(ish) - with certain assumptions made about the wiring. Once you have more than 4 wires you really need to know which ones go where and do what. So the manufacturers include the instructions for up to 4 wires, but (probably to reduce their potential liability) tell you to call a pro for anything more complicated.
    – brhans
    Feb 24, 2020 at 13:21
  • ok if it is only that then it is not a problem, it is working as expected for me. That box was a little bit "crowded" but with proper wiring everything fitted in in the end. I made sure all the hot wires were also covered by tape (I run two rounds of tape around the switch and around the GFCI
    – MiniMe
    Feb 24, 2020 at 14:03
  • @minime do the lights and receptacles in the garage turn off when you turn off your indoor switch light? I ask as they probably don’t but may, and if everything is not controlled by that switch , you can see how easy it would be to make a wiring mistake.
    – Ed Beal
    Feb 24, 2020 at 15:04

2 Answers 2


I have seen those instructions, I thought it was funny at first but after thinking of the number of times DIY folks get line and load mixes up with just 4 wires and all the rat’s nests I have repaired over the years it may make sense for those that do not understand what they are doing.

The line terminals connect to the feeder from the panel normally black on brass and white on silver then a receptacle that is fed from this would be on load same color combinations.

Where things can get sketchy if there happened to be 1 additional red wire for a switched outlet as GFCI receptacles do not have a tab to break the top receptacle feed from the bottom one (if there is not a wired light in the room additional work needs to be done to maintain a switched receptacle as code has required for decades if no wired light fixture)

Other things like multi wire branch circuits can be there with an additional wire normally red again , this circuit has 240v between the red and the black and is a way to have an additional circuit while running less wires (saves $) .

Last as you have multiple feeds to other circuits, so it is not as easy as this goes there and the reason the MFG suggests a pro this way if you hook it up wrong the mfg is not liable for damages. 4 wires can be messed up but as you can see it may not work but with a multi wire branch circuit you could be shorting the 2 legs of your service together if done wrong and that is about the worst thing that can be done especially if you find yourself in the circuit some way.

  • Totally agree... a DIY nightmare .. +
    – JACK
    Feb 24, 2020 at 14:52
  • In my case I connected the wires coming from outside to the GFCI and then I took the hot wire of the load and I connected that to the switch. The other end of the switch then was tied together with the blacks of the two lights. The white of the GFCI load was tied together with the whites of the lights, The ground of outside wire was connected to the wire of the box and then all the grounds in the box (GFCI and the two lights ) were connected to the ground of the box ..so as long as, after the GFCI you do not mix the colors it's OK. Agree the MFG can't provide instructions 4 all situations
    – MiniMe
    Feb 24, 2020 at 15:06
  • above "connected to the wire of the box" wanted to be "connected to the ground of the box"
    – MiniMe
    Feb 24, 2020 at 18:06

Instructions are obtuse because of UL

This has to do with the device's UL listing. UL only approves devices for certain applications; i.e. you can't use an Alumiconn to splice 9600V wiring. Two things assure you stay within those applications: First NEC 110.3(B) which requires you obey the labeling and instructions, and second, UL also approves the labeling and instructions as part of the listing. That is because, generally, they only test for conditions described in the instructions (e.g. they don't test Alumiconn for 9600V splices). Anyway, if you wonder why some instructions are so stilted and weird, that is why.

When a manufacturer writes instructions likely to be read by amateurs, UL gives it extra scrutiny. It is UL who is imposing the "See electrician for >4 wires" issue. You have to hook up the two LINE terminals or the device won't function. With only 2 additional wires, UL feels comfortable with the instructions. >4, there become several wrong/dangerous ways to hook it up.

Just use LINE. Leave LOAD alone.

Anyway, for you, it is simplicity itself. Everything goes onto LINE. Don't even remove the warning tape from the LOAD terminals. So you would just pigtail.

Do not use the LOAD terminals at all unless you have a specific reason to do so, and only for the pairs of wires where that reason exists. The instructions will say something else; they want you to ignorantly protect parts of your circuit without realizing you are doing so, and because of the side-effects, that's something I do not agree with.

Why not use LOAD for everything? Well, you're perfectly allowed to; and you're advised to by the instructions. That will place everything downline into the GFCI protected zone. That seems oh, so clever: Free protection! And that is the purpose of having LOAD terminals! However, this has a dark side, if those downline loads don't need GFCI protection. Any trivial leakage from those things will stack i.e. cumulate, increasing your risk of nuisance trips. Nuisance trips drive people crazy. Do people do a laborious bug hunt on each leg of the downline that wasn't even part of the project in the first place, to suss out every last dirty contact or NM wire that's getting wet, or stick isolation transformers on their refrigerators? No, they don't; they rip out the GFCI.

So "GFCI everything" is a grand theory, but not something you can really live with. UL doesn't care about that. They say "you should do the bug hunt". UL can come and do the bug hunt, IMO.

What is a good idea to not protect?

  • Grounded hardwired loads, esp. lighting where dangerous power tools operate (e.g. curling irons)
  • Any downline outlet which has its own GFCI protection
  • Refrigerators that are cord-and-plug connected (post NEC 2014 you'll need to get a variance if the fridge is in a location where all receps need GFCI)
  • Safety equipment of any kind (including refrigerators). It won't do to have an emergency fire pump trip a GFCI the moment it starts; the purpose of the gadget is to protect from fire, not electrical shocks.
  • Can you please detail on this? I did use the load to go from the GFCI to the switch and from there further to the lights ... they indeed recommend that you use the load to feed anything downstream. If I have problems with the insurance I will show them the instructions :-) ..I can't point them to this post :-))
    – MiniMe
    Feb 24, 2020 at 15:17
  • 4
    @MiniMe In a nutshell: other receptacles need GFCI (and then Load means you can use a non-GFCI receptacle and still be protected) but lights/fans/other built-in items generally do not need GFCI. Using Load for lights means if your GFCI trips you are in the dark. If you use Line then the lights stay on. Which is important if the trip was due to a power tool or hair dryer around wet areas... Feb 24, 2020 at 16:03
  • 1
    Harper: I tend to agree with sentiments...in many cases GFCI protection creates more problems than it solves...you'd think we don't have ground wires anymore. But this gets worse with the NEC 2020 code: Just about EVERYTHING will require GFCI including 240 v appliances (Ranges, dryers, water heaters!!!!, furnaces, etc.) Feb 24, 2020 at 16:11
  • At the same time, a GFCI in a bathroom might NEED the load terminals to protect (eg) a light over the shower, etc - it's equally easy for Joe handyman to get lost among the wires and improperly remove protection from parts of the circuit that should have had it. The bottom line is, the warning is there because OP probably should consult an electrician if they're even remotely unsure about which wires go where.
    – J...
    Feb 25, 2020 at 15:09

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