I have a client that got a used 85kW, 208/120V generator that they want to install for emergency circuits. They have an existing distribution panel (480V) with two spare 3P breakers (100A & 200A). We want to use the 100A breaker for normal power input to the transfer switch (through a transformer of course), but I'm not sure what size transfer switch is required. I calculate the FLA of the generator at about 300A (assuming an 80% pf), but the normal power at 208V would be about 230A. How do I size the switch and the feeders?