Jon wrote:
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

It's a no-go from the start. The electrical code requires you
to use a listed transfer switch. It *may* also prohibit you
from doing it yourself, even if you use listed equipment, and
require that the work be preformed by a licensed electrician.
Next, you need some large gauge wire from the generator to
the existing service if you will supply 20 amps from the
generator. You need to do a voltage drop calculation based
on how much current you will allow to be drawn and the
distance the wire must run, to verify that you are using
large enough wire. Next, the code won't allow you to use
the same wires, regardless of transfer switches, for both
branch circuit wiring and feeder wiring.

What can you do yourself? Dig the trench, plan the system,
check the codes, make sure the licensed electrician (if
you use one) agrees with all that is to be done and who
is to do it, lay the wire between the buildings. Start
by making a *complete* list of *every* electrical device,
receptacle, appliance etc that is permanantly connected to
your wiring and identify which fuse/breaker controls
which circuit. Then figure out the absolute minimum that
you intend to run from the generator, and "layers" beyond
that. The "layers" could be something like: "minimum",
"convenient", "nice to have" and "full service". The more
you want, the more it'll cost.

If money is no object, the simplest is to hire a pro and
specify complete backup, automatic transfer and let him/her
specify the equipment. Unless you have a huge wallet,
that's probably a non-starter, too.

Ed