I'm about to wire for a 7500 KW Generac generator which is something my nephew has already done. In his case the system was wired by an electrician using a double pole 50amp breaker at the panel and 100amp wire. The system worked flawlessly. Then years later, in an attempt to upgrade the system, he called upon a second electrician that rewired using double pole 30amp breakers and 30amp wire sighting that the Generac was only providing 30amps and that the way the system was wired was overkill. Made sense at the time but when the first emergency took place, and the generator put to use, it surged and blew its breaker, while the fridge and fish tank pump made unnerving sounds, while lights would flicker and wall switches failed to work? He has since rewired to original and things are back to working fine.
My electrician is on the same page as my nephews second electrician, and who am I to argue with a professional, but I fear the same results if I wire using the 30amp logic.
Can anyone tell me why the 50amp breaker/100amp wire works while the 30amp solution fails??? Are the watts unavailable to the house due to circuit size?
Kind Regards, Bewildered
Best Answer
There's nothing wrong with overdesign. Tearing out 100A-rated cable simply because it's "too big" is just wrong. I'm not saying you should oversize every wire, but if you are in an situation where the existing wire is larger than needed, it works in your favor.
However there is something wrong with overfusing. Fuses and breakers protect wiring and equipment. A breaker which is too large will not protect the equipment. That's not a worry if the generator has its own breaker onboard.
If the generator has its own fuse or breaker protection that is correct to protect the generator, then the input breaker in the panel is allowed to be larger than the generator. The original setup was fine.