I am not an electrician. I am converting a bathroom outlet to a GFI outlet. There is a lightswitch next to the outlet that shares using the load (red) wire. I have set it up exactly the same as the original one (non-GFI), and the GFI outlet will work, but when I turn on the light, the GFI trips. Can someone help?

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Originally Posted by decemberist

I am not an electrician. I am converting a bathroom outlet to a GFI outlet. There is a lightswitch next to the outlet that shares using the load (red) wire. I have set it up exactly the same as the original one (non-GFI), and the GFI outlet will work, but when I turn on the light, the GFI trips. Can someone help?

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Sounds like you connected the light switch to the "load" terminal of the GFI, but left the neutral for the light connected to neutral on the "line" side of the GFI. Now think about what happens when you turn on the light - current flows through the GFI hot lead going to the light, but does not come back through the GFI on the neutral. The GFI senses the imbalance of currrent, and trips.

To fix it you need to connect both the lead to the light switch and the neutral from the light to the GFI's load terminals - the light switch to the load hot and the return from the light to the load neutral.

OK. Sorry Im new to this. Im still a bit confused.

I have 2 black wires, 1 red, and 1 white (the neutral). I plugged the white into the LEAD neutral of the GFI, as well as the black associated with it to the LEAD on the hot side. On the LOAD, I have plugged the red on the hot, and connected this to the light switch. I also have connected the other black wire (that went into the light switch previously before the upgrade) into the light switch. If I move the white into the LOAD, then the GFI outlet doesn't work at all.

What am I doing wrong here?

The problem is that there should be a second white lead somewhere. The first white lead is the neutral for the original outlet, and you connected that correctly as you had it originally. The second white lead (which seems to be missing) would be the neutral from the light -that's the one that needs to be attached to the neutral on the load side of the GFI. Are you sure there is no 2nd white lead in the box? This would be highly unusual - are you in an area that uses conduit and individual wires? If so, it's possible that the original electrician may have routed the neutral from the light fixture a different way - you could open up the light fixture connection to see. Also, please confirm that as you originally wired the GFI you had a connection on the load hot (the red going to the switch) but nothing connected to the load neutral - is that correct?

Finally, if all else fails, you could always just put the light connection back the way it was before you started all this - that is, don't bother using the GFI to protect the light circuit.

Here's a diagram that may make it clearer.
Attachment 4065

Thanks for the input. Turns out that that there was 4 white wires, all wired together with 1 lead. I unbound them, and linked the 2 from the light together and plugged into the LOAD neutral. Plugged another into the LEAD neutral, and all works.

Thanks,

Kevin.