I am working in my basement where the wiring is from the early 70s. I am replacing a couple of fluorescent lights with new ones so I can put in LED bulbs (the others are original). I am not new to wiring and have done quite a bit. I learned from my dad (and I also know his style). I got into mess from right at the beginning.my mess

I should clarify this. The two wires heading down out of the picture is to the light fixture.

Not knowing what the heck was happening there, I started tracing wires. One set is the hot wires. The other 14-2 goes to a switch. The 14-3 I was confused about for quite a while, but finally figured out that it powers the outlets switches. The red goes to a switch the power the top outlet, the black keeps the bottom outlets hot full time. I matched the wiring back up and tested it. My GFI breaker (in a separate box flips and separate circuit). I do some more looking, and "properly wired" the switch for the light (I really didn't like how they wired it). updated wiring (The green tape is labeled switch). Tried again and it still blows the GFI breaker. All of the grounds are wired correctly, all of the commons are linked correctly. Could these new ballasts blow an older GFI breaker?

If you want I can upload a picture of how I currently have it wired, I can. I am at a loss of what is happening. I'd hate to call an electrician for something that could be a simple fix.

Here are the boxes. This first one is the box I'm working in. enter image description here This second box is where the GFCI is tripping. newer box with GFCI

On the other hand, I discovered that the outlets are all twisted and soldered wires then covered in tape. I am going to fix that crap right away and fix the open grounds that I discovered as well in this series of outlets.

Update: Added more pictures and added my second light without any issues.

  • I have a feeling that when you say "GFCI breaker", you mean something else. Is it in your main service panel and has a lever switch handle with a "15" or "20" on the handle? Or is it in living space near switches and have sockets on it where you could plug on a cord? Dec 10, 2018 at 1:13
  • 1
    If you look at the photos, I show the breaker box with the GFCI breaker. See the "Push to Test" button? That is the one.
    – Mike Wills
    Dec 10, 2018 at 1:18
  • This Cutler Hammer fuse box has me very concerned. It is a subpanel. I have a feeling it is a 240V fuse box being powered from two breakers (it should be powered by one 2-pole breaker). Given the number 13 written on it, that is the space the GFCI is in! I have a hunch it is powered by that and another plain breaker. can you confirm or deny? Dec 10, 2018 at 4:38
  • I didn't show the whole panel. The 13 is for another fuse. The main is two fuses I believe.
    – Mike Wills
    Dec 10, 2018 at 4:56
  • First, unhook any old fluorescent fixtures (disconnect their hot and netutral) and see if the GFCI trip goes away. If so, done. Otherwise........ This gets hard. So the GFCI breaker in space 13 doesn't power anything at all in that fuse box?? If it powers some things through that fuse box, that is critical data. Are you comfortable taking the covers off fuse box and breaker panel and shooting pictures of the interior of each? The internal wiring arrangement may be the key here. Dec 10, 2018 at 16:40

1 Answer 1


First, don't sweat bullets over the last guy's work. "The last guy did a bodge job and I had to fix it" are famous last words, said right before your project goes sideways into "hire an electrican" land.

Stay in focus. Keep the project scope as small as possible, don't try to fix two different things at once.

"common" isn't

You mentioned "common", and that's a typical way an electronics or automotive guy talks about mains neutral. In electronics, everything connects back to a "common" which is a big groundplane, or the chassis of the car, and in those cases, that is the normal current return. Not in mains wiring.

In mains wiring, the closest thing to "common" is actually the Equipment Safety Ground (green/bare wire), and it is not a current return at all (except during a fault condition). Other than that, mains electrical is wired like an isolated system where both supply and return are 100% separated from the groundplane. What's more, circuits are isolated from each other - or at least, they're supposed to be. The reason is EMFs and eddy current heating, but this also bears very heavy on GFCIs. They work like this:

enter image description here

The GFCI is a simple current transformer. It wants to see currents are equal (sum to zero) in all conductors.

As said, circuits mustn't share neutrals, and you can see the havoc that would follow if circuits did. Even if a circuit was not on GFCI, but it returned neutral on a circuit that was on GFCI, it would guarantee a GFCI trip on that unrelated circuit.

I think that is the root of your trouble.

  • I don't know what the education on GFCI has to do with this. I am not working on the GFCI circuit, but somehow it's being tripped when I flip the switch on the circuit I am working on. I am working on the #6 Bussman circuit. When I say "common" I mean what is typically the white wire. Hot, ground, common. Sorry, if that is not the right terms. That is how I learned it. I do know how to hook up a GFCI outlook and have done it many times, again I don't think this has anything to do with what you are saying here.
    – Mike Wills
    Dec 10, 2018 at 2:13
  • Also I went this route because Mendard's LED 2x4 lights like that do not have replacable bulbs. Instead I would have to replace and rewire the entire light if something goes bad.
    – Mike Wills
    Dec 10, 2018 at 2:15
  • "I am not working on the GFCI circuit" ... "Somehow it's being tripped" ... Apparently your circuit disagrees with you! Socketless LEDs are a great choice. Sell your old troffers on craigslist, someone will want them for LED conversions (or in my case I just stick with fluorescent). Dec 10, 2018 at 2:37
  • I hear you @Harper. I would have thought the same thing. I can turn each circuit off independently and not affect the other circuit. So I am sure they are not linked. Besides they are both in the different boxes. Could there be an issue in the ballast?
    – Mike Wills
    Dec 10, 2018 at 3:32
  • Sure, that's common enough. But the ballast is about to go away, right? Dec 10, 2018 at 3:38

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