My system has a breaker for the pump and another one for everything else - the breaker that's tripping is the "everything else" one. This just started happening yesterday, curiously during the time that a company was staining my fence, and they had to move some things around (e.g. pool chemical storage box) near the power center. I know what time it started happening within a 15 minute window, because I have a homemade logging/control component in my system (I've had it for years, it's definitely not the problem, before someone asks ).
I'm trying to think of what could cause this, and the only thing that even makes any sense to me is the transformer going bad, but it seems really coincidental that it would happen at that time. I know that breakers themselves can go bad, but that's rare. The outside wiring is all up to code and uses heavy conduits, and there are no visible breaches, so I don't think it's that. It will run for anywhere between a minute and 10-15 minutes when I reset the breaker, but then it trips again. All panels and lights look normal while it's running, and there are no abnormal sights, smells or sounds near the power center (even with the inside panel cover off) while it's running.