The service is 225 amps for the house. The generator/transfer switch are rated at 100 amps. Generator controlled circuit breakers will drop enough circuits in the house to keep the generator happy.
Maybe what you should do is place all the loads you want the generator to run during a blackout in a sub-panel, and place the transfer switch in the sub-panel feed coming from the main panel. The rest of the main panel would feed loads you don't mind dead during a blackout.
