200A ATS with 125Amp Main Breaker


New Jersey
Residential Electrical Installer
Ran into a problem installing a 22kw Generac whole house generator (100 amp breaker) w/ 200amp service rated ATS and a planned 200A service upgrade.
Its a typical 1 phase single family dwelling with 87amp load. Everything is underground with the meter on one side of the house and the panel on the opposite side in the garage. the utility confirmed the existing service conductors would handle 200amps and when i looked at the job the panel had 2/0 copper so I ASSUMED we were good to go.
So today we pull everything out and find there's #2cu spliced to 2/0 in the conduit on the outside of the home and unfortunately when my guy pulled the meter he didn't notice the #2's in there (they're USE 2 so they are pretty thick but...)
We were able to get the feeds into the ATS and splice in the gutter space so we could safely get the old panel back in (100amps for now, looking to settle for 125). the ATS is now an expensive J-Box.
Question is the 200Amp breaker in the ATS with #2 feeds going to be a problem? thinking I may propose Monday cutting in a 125Amp service disconnect before the ATS or will a 125amp main breaker immediately after the ATS ( they are back to back) on the load side be sufficient protection?
Its been a long loosing day and I probably wont sleep thinking I'm waiting 2 months (and another $600) for a 100amp transfer switch and scraping the whole upgrade.
I'll reread 230.208 in the morning when my heads clearer but any direction would be greatly appreciated.
thanks in advance
PS Changing the feeds would be a disaster, under paver driveway, front walk, stone walls, etc.


Master Electrician Electric Contractor Richmond VA
Henrico County, VA
Electrical Contractor
Welcome to the forum.

With a back-to-back service, the tap rules make your proposed installation okay.

curt swartz

Electrical Contractor - San Jose, CA
San Jose, CA
Electrical Contractor
I think I just answered my own question. Looks like the Generac transfer switches use Siemens QN breakers which are only available in 150, 175 & 200.