How to diagnose intermittent tripping of GFCI breaker

we have a GFCI breaker in our breaker box. On that circuit are the lights and outlets in two bathrooms and the garage door opener. I'm not sure if anything else is on the circuit.
Intermittently, the breaker has been tripping (usually in the middle of the night or when we are at work during the day). When I reset the breaker, it stays on. This has recently been happening on a frequency of between twice per day to once every few days. At night we have a night light on in one bathroom, but during day I can't think of anything on this circuit that would be drawing a current
One time it tripped when I was actually at home, and I found that when I tried to reset the breaker that it would immediately (within a second or two) trip again - but after about 10 minutes I was able to reset it and it stayed.
I'm not sure how to diagnose the cause of this problem if whatever is causing the short will not stay shorted.
There used to be two outdoor outlets on the circuit - but I discovered that whenever we had a hard rain, moisture would get into those boxes (which were no longer well sealed) and cause the breaker to trip - it could not be reset until the moisture was gone. Those outlets have since been removed, so are not the cause of the current problem.
Also, this has been happening recently during a period of bone-dry weather.
Any help on how to diagnose this problem and resolve it greatly appreciated.
Thanks.
-J
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Mice can be the cause.
Without a megohm meter, the best way to go is to split the circuit in two. Open a box and disconnect half of the outlets. If the problem stops, then it is farther down the line. If it persists, the problem is up the line.
With the breaker tripped it is pretty easy to figure what is on the circuit.
It could be that the breaker is going bad. If you have two GFI breakers in the box you can switch the circuits. This will tell you if it is the breaker or the wiring.
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On 8/1/2011 12:11 PM, JJ wrote:

That sounds like a strange setup. It sounds like something that was done in the late 70's early 80's. I would kill the breaker and determine what receptacle outlets are on that circuit, paying special attention to outside outlets, basement outlets, garage outlets and bathroom outlets. Once you determine what's on the circuit, I would replace the breaker with a standard breaker, and install GFCI receptacles in all the locations where they are currently required. This would include the bathroom outlets, but only the receptacles, not the lights, outside receptacles, basement, and all garage receptacles, that were on that circuit. Once that's done, it'll be clear where the problem is,or was.
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Good deduction. The house was built in '77.
Thanks for all the replies.
It occurred to me that the garage outlets are also on the circuit and the problem could be there too.
One difficulty with unplugging stuff (not much stuff actually plugged in to the affected outlets) and waiting is that that can only tell you what is not the problem - if it circuit trips with a device unplugged, you know that device it's not the culprit (unless there is more than one culprit). Waiting a day or two with a device unplugged may not be long enough to establish the device as the culprit - sometimes the circuit can trip just a few hours, but sometimes it will be fine for several days.
Perhaps I will go ahead and replace the breaker with a standard breaker and replace all the outlets with GFCI outlets. One problem is that one bathroom has a light fixture with an integrated outlet (for shavers). I guess I could just disconnect the outlet on that fixture though (it never gets used anyway).
Mice and ants were mentioned as possible culprits. I'm not sure how you mean? I could see mice chewing through wiring and leaving wires exposed - which could then short - but wouldn't that be more of a continuous problem? Can ants chew through wiring to? Or is there another way these pests could be causing a short?
Thanks.
-J
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On 8/2/2011 11:52 AM, JJ wrote:

I've had to replace GFCI outlets at swimming pools, where tiny ants literally crawl inside the device and nest. Ultimately it destroys the device
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On 8/1/2011 09:11, JJ wrote:

I had a similar problem with a GFCI breaker in an outdoor panel. As far as I know, ants were the culprit. No problem after I sprayed bug killer on the breaker panel. The house was built in 1980, when GFCIs were first required and expensive. If the problem persists, you may want to consider replacing the breaker with a standard one and replace outlet(s) on the circuit with GFCI outlets to offer continued safety. Multiple GFCIs will also also save you from having dead outlets in the bathrooms just because an exterior outlet got wet from rain.
--


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My house was wired the same way with a 15amp GFCI breaker.. If wife and daughter were both using their blow dryers it would trip the breaker every time. I replaced the 15 amp GFCI breaker with a 20 NON GFCI unit. Installed GFCI outlets in the bathrooms and put the garage on a separate circuit with a 20 A GFCI breaker. Used the old 15 A GFCI to run a circuit for the freezer in the garage about a year later as it was causing trip when I used my power saws.
Jimmie
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On 8/2/2011 12:52 PM, JIMMIE wrote:

You don't want to replace a 15 amp (gfci) breaker with a 20 amp breaker, unless the wire is 12 gauge.
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> > That sounds like a strange setup. It sounds like something that was done > in the late 70's early 80's.
Good deduction. The house was built in '77.
Thanks for all the replies.
It occurred to me that the garage outlets are also on the circuit and the problem could be there too.
One difficulty with unplugging stuff (not much stuff actually plugged in to the affected outlets) and waiting is that that can only tell you what is not the problem - if it circuit trips with a device unplugged, you know that device it's not the culprit (unless there is more than one culprit). Waiting a day or two with a device unplugged may not be long enough to establish the device as the culprit - sometimes the circuit can trip just a few hours, but sometimes it will be fine for several days.
Perhaps I will go ahead and replace the breaker with a standard breaker and replace all the outlets with GFCI outlets. One problem is that one bathroom has a light fixture with an integrated outlet (for shavers). I guess I could just disconnect the outlet on that fixture though (it never gets used anyway).
Mice and ants were mentioned as possible culprits. I'm not sure how you mean? I could see mice chewing through wiring and leaving wires exposed - which could then short - but wouldn't that be more of a continuous problem? Can ants chew through wiring to? Or is there another way these pests could be causing a short?
Thanks.
-J
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