I'm not an electrical contractor, but I'm a pretty experienced DIYer having done a lot of residential wiring on my own homes - under permit. I'm stumped on a current problem, so I'd appreciate any troubleshooting tips.


My home has 200 amp service. From the main service panel, I have run a 50 amp sub-panel to the other end of my basement.

The bathrooms and exterior outlets run from a GFCI breaker in the main service panel.

From the sub-panel, I have a 15 amp dedicated circuit supplying the microwave in the kitchen.

The subpanel was installed about 5 years ago - and inspected. All has been well until a few days ago.

Now, when one turns on the microwave (a dedicated circuit from the sub-panel), the GFCI breaker (in the main panel) supplying the bathrooms and exterior outlets flips off.

Any explanations or ideas?

Thanks for indulging me.
gary comfort
reston, va 20191

How old is your microwave?

Can you think of anything else that has changed? Perhaps something being left plugged in outside or in the bathroom?

Just because your subpanel was inspected does not mean that it is correct. Who wired it? Did you personally verify that it is correct?

Somebody did something somewhere and crossed a neutral.

Since all was operating correctly untill recently, try replacing the GFI breaker. After all, they are electronic devices & cannot handle surges & electrical storms any better that your computer can. Maybe you had a recent thunderstorm, maybe not. Entropy gaurantees that everything will crap out sooner or later.

Tom

He surely had many recent thunderstorms. GFCIs tend to fail on rather than false trip. It's hard to imagine lightning making a GFCI turn hypersensitive.

I was thinking it more likely that something else on the circuit, perhaps outside, was damaged by lightning and sensitive to the voltage surge when the mo starts.

Thanks for the responses.
Yes, the problem began right after a close major thunderstorm. In fact, one bolt hit close enough that it fried my pc's cable modem. Everything started then.

gary

Is everything unplugged from the GFCI circuit?

I'd hate to tell you to replace the GFCI breaker without being sure. But once you've eliminated everything else, that has to be it.
If you replace it and that wasn't the problem, you can install the old GFCI breaker on another circuit to protect that circuit too - so don't think of it as money wasted.