Electrical Wiring in the Home/Tripping GFCI


My issue is with a tripping GFCI.  After building an addition on the back of the house, I had to run new wiring to the back outside of the addition and the garage (same wiring, dedicated circuit). The circuitry to the garage all works well with the exception that when I turn on (from the house) the garage exterior lights, the GFI trips. Other garage electrical functions also running from the GFI are fine.  The GFI is the outlet on the outside of the house, with hot, ground, neutral, and garage light switch return wires running underground through appropriate underground conduit to the garage.  The wires are all #12 (running 20 amp service throughout the addition with a new service panel, GFCI also 20 amp).  I have replaced several wires in the affected circuit as well as the inside switch with no success. I have the ability (VOM) to test  the circuits to some degree if that would be helpful.  I understand that GFCI's can be finicky but I haven't any other ideas about a solution to the problem and would greatly appreciate any suggestions you might have. Thanks in advance for any help you can provide.

It may be that the garage exterior lights are using one circuit for the hot wire, and another wire for the neutral.  If that is the case, there is nothing you can do, other than run another wire and make sure both wires are on the same circuit. Probably the hot wire starts at the switch on an inside circuit, and the neutral is using the garage neutral.

Lights do not need to be on a GFCI, so you could replace each outlet, outside and garage with its own GFCI. This would also prevent you from losing all your power if there is a problem, and makes it easier to find any problems.
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Electrical Wiring in the Home

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Bob Sponaugle


Just about any home wiring question. (not appliance repair) I have done all kinds of home wiring for myself, including adding a new breaker box, etc. Please, questions from North America only. Please be specific with details.

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