Main Breaker Tripping after 4+ hours Troubleshooting - Line goes out to GFCI sub panel

I have an electrical issue I can't diagnose but trying to see if I can troubleshoot a bit more before calling electrician back. I have a main breaker that goes out to UF cable (in steel conduit) that goes underground to a GFCI pool panel. At the end of the season we turn off the subpanel outside but the main breaker stays on. Over the winter I noticed the main breaker tripped but didn't think much of it. Now we just went to open the pool. Turned on the main and the Sub Panel. The pool pump ran for a while then the main tripped eventually (not the pool pump GFCI). I called an electrician and he suggested to replace all the breakers (which I did) and everything ran for about 5 hours until it tripped again. If I turn off the subpanel completely, the new main breaker will trip after about 5-8 hours. If the subpanel is on it will trip after 3 hours or so. I would think a damaged wire and new breakers would trip almost immediately. Any idea what I can be missing? Is the only thing left that underground wire is damaged. Its probably about 30 years old but its UF cable in conduit. I can't imagine how it possibly got damaged. But I can't think of anything else. A new wire run will be complex and costly. Thanks submitted by /u/vassilliosman [link] [comments]

May 3, 2025 - 18:49

I have an electrical issue I can't diagnose but trying to see if I can troubleshoot a bit more before calling electrician back.

I have a main breaker that goes out to UF cable (in steel conduit) that goes underground to a GFCI pool panel. At the end of the season we turn off the subpanel outside but the main breaker stays on. Over the winter I noticed the main breaker tripped but didn't think much of it.

Now we just went to open the pool. Turned on the main and the Sub Panel. The pool pump ran for a while then the main tripped eventually (not the pool pump GFCI). I called an electrician and he suggested to replace all the breakers (which I did) and everything ran for about 5 hours until it tripped again.

If I turn off the subpanel completely, the new main breaker will trip after about 5-8 hours. If the subpanel is on it will trip after 3 hours or so. I would think a damaged wire and new breakers would trip almost immediately.

Any idea what I can be missing? Is the only thing left that underground wire is damaged. Its probably about 30 years old but its UF cable in conduit. I can't imagine how it possibly got damaged. But I can't think of anything else. A new wire run will be complex and costly.

Thanks

submitted by /u/vassilliosman
[link] [comments]