I'm trying to wire a transfer circuit for a generator.

The generator will be located in the barn. The electrical service is at the
house. Two 120vac wires and a ground go to the barn. There is *one* unused
wire from the house to the barn I can use for a signal circuit.

When the power goes off at the house, I need to disconnect the service to
prevent backfeed and activate for generator power to both the house and the
barn. When the service power goes on I need to disconnect the generator to
avoid damaging it and restore normal service to the house and the barn.

I have,

*one 240vac 60 amp dpdt mercury relay
*two 120vac 60 amp 3pdt relays.

Any ideas?

Jon Giffen