Bad GFI Outlet ?

When it rains, that household circuit that covers my bathroom pops the breaker in my main service panel. The bathroom has a GFI outlet, and I suspect that it is part of the problem. What I mean is that I probably have a small moisture-related short somewhere, and the GFI is sensing it. What I don't understand is why the service panel circuit breaker is blowing. The house is in Southern California, so things stay relatively dry. The house is about 30 years old. The bathroom wiring is original, and although I don't know if the GFI outlet is, I know it hasn't been replaced in a long time, so it's got some years on it. Any idea what's going on here?
- Bronco Leonard
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On 21 Feb 2004, Magnusfarce wrote:

The GFI outlet only interrupts power at that outlet and any that are wired "downstream" of it. If your "small moisture-related short"* is somewher in the wiring between the service panel and the GFI, it would likely still blow the breaker after the GFI trips.
* - there really is no such thing as a "small" short. It's either a short circuit or it isn't.
You have a leak somewhere when it rains, and the water is running into some electrical connection on that particular circuit. You know which breaker it is, so next time it trips on rain, I would shut it all the way off (don't leave it in tripped limbo) then start tracing the wiring until you get to your GFI location. Somewhere in there you'll find the box that is collecting water.
Oh yeah, now for the *really* bad news, maybe...House is 30 yrs old = original roof??? Yike$..
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Actually there are breakers in the main panel that also act as GFI so his description MAY be correct - but as they say in the other NG -- it's kind of hard to see it from here (especially without more details).

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On 21 Feb 2004, Henry77 wrote:

Yep, I thought about that, but that would mean somebody along the line did something wasteful or stupid or however you want to say it: they installed a duplex GFI on a circuit that already had a GFI breaker. I guess that could happen at times :-)
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However on the flip side some places call this a fail-safe system so if the outlet GFI fails the main panel GFI will trip - I guess it's called a redundant failsafe system.

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While someone is unlikely to install a GFI outlet on a circuit already GFI breakered, I could easily see the converse.
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Magnusfarce wrote:

Hit the test button on that GFI. Then check all your outdoor outlets and the ones in the garage and see which one(s) are not working. The problem will be with one of the ones not working.
That GFI likely protects not just the bathroom, but also one or more outside or garage outlets. One of them is likely setting it off.
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Magnusfarce wrote:

It sounds to me like the circuit serves outdoor outlets as well as the bathroom. The problem is almost certain to be with dirt or insect nests, or other "stuff" in one or more of the outdoor outlets. Cleaning them will usually fix the problem.
It also sounds like the circuit breaker is a GFI type, and the GFI outlet in the bathroom is redundant. Check the circuit breaker for a reset button. If it has one, it is a GFI. Where two GFIs are used in series, as may be the case in your bathroom it is anybody's guess which one will trip. Frequently, both will trip. It may be worthwhile to invest in an outlet tester that has a GFI test button on it. These are in the $3 or $4 neighborhood at most hardware stores.
See also: http://dotznize.com/electric/?a=gf
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