See related question here:
Using portable generator with transfer switch
I live on a property with 600 AMP service (2x200AMP service to home, 1x200AMP service to workshop / barn). The home and barn are new construction, and due to the rural location, standby generator transfer switch for the property was provisioned (Without the generator being purchased).
The home has 2 200amp panels, and the barn has a single 200amp panel.
Due to the property being serviced with 600amps, but my transfer switch equipment is only rated for 200amps, I assume that transfer switch is only setup to service partial loads within my home.
How can I determine which loads will be serviced by the generator (Once I have one setup). With my existing setup, is there any possibility to service the full property (Home and barn)?
Best Answer
Easy. The bog-standard way of provisioning 400A service to a residence is to fit dual 200A panels. Because 200A gear is readily available at sane cost (e.g. $120/panel) in the consumer space, whereas true 400A gear requires you go into industrial-tier arcana, with industrial-tier pricing (i.e. nobody blinks at $3000/panel).
In your case, from the equipment and wiring used, and the breakers, it's obvious that they ran two feeders to your house. One of the feeders comes straight off utility and feeds one 200A panel. The other feeder comes via the transfer switch and feeds the other 200A panel.
If the installers knew what they are doing, they were careful to put loads you'd likely to want on generator on the generator-enabled panel.
400A service to houses is usually for things like 140A of heat pump emergency heat or 180A of on-demand water heater. Those few huge loads would be in the non-generator panel, since powering them is hopeless with a generator that isn't Cat yellow.
So you should be "all set"; just tie the generator in at the ATS and all the right circuits will have power available.