It is rare that a house would have 3 phase which would have 4 wires to the
main service panel. But there are some very large homes, so sometimes.

Anyway outside of air-conditioning and elevators (things with very large
electric motors), everything in an office would be single phase.

So just a matter of installing a transfer switch. It would be easy if there
was one separate main line going to the offices and the offices had one
subpanel for power to both offices. Then just install a transfer switch
ahead of that subpanel.

BUT!!! How much wattage do both offices draw? Don't want to overload the
generator. If too much total wattage, then might need to do a bit of
re-wiring for things which will have backup power. May need to move these
things to a new separate subpanel. Then only circuits on that subpanel would
get backup power.

Also generators provide "dirty" "rough" electricity. This can damage
electronic stuff like computers, phones, etc. So best to also have a power
line conditioner between anything electronic and the generator.


wrote in message
I have a 6.5kw 220v single phase generator that I want to wire up to
supply backup supply to a couple of offices in my house. The mains
supply in the house is three phase 220v...
Is there a way to wire this up? Something like an isolator/generator
switch on one of the phases (as long as the offices are on the same
phase)? I don't want to go to the additional expense of purchasing a 3
phase generator or a single to three phase converter but would like
backup power into the office circuits. I'm not too concerned about
have the entire house on the generator but do need the offices....
Thanks