On Mon, 13 Oct 2003 12:54:54 +0100, Chris Wilson wrote:

I am looking for advice on the easiest way to wire up a modified
electrical distribution panel here at home, to allow a generator to be
fired up and take over power supply to the house during one of our fairly
frequent mains failures.

What you are wanting to do is not going to be a cheap option. If you
want a generator that can take over the whole house installation then
realistically you've got to be looking at something like 10kva capacity,
and that's exercising some caution on loading when it's running. As a
ball-park figure, cost is likely to run to perhaps £15-20k for a fully
automatic installation.

If you want to pursue a more or less automatic arrangement, but a little
less costly, I'd suggest splitting off some of the installation onto a
separate 'essential supplies' (ES) consumer unit. Typically this would
supply some lighting circuits, the central heating boiler and pump, and
possibly one or two sockets dotted around the place. You might then be
able to get away with a 2 or 3kw generator. You'd need to make sure that
SWMBO realises she can't run the washing machine or similar when running
from the generator!

You'd need to insert a two pole break-before-make changeover contactor,
in the feed to the ES consumer unit, with one side going to typically an
industrial style weatherproof male socket. The generator supply would be
connected to this using a female plug. You've also got to arrange for
battery starting for the generator, with mains-fail sensing. You need to
consider a small time-delay to allow for auto-reclosing on the mains
supply, say five minutes.

You've also got to think of generator earthing. Most leccy companies
will allow you to bond to their earth terminal *providing* the incoming
supply is PME. You should also allow for an RCD as well.

All things considered, I'd be surprised if you got away with a limited
capacity more-or-less automatic system for less than £4-5K. Your biggest
problem I would think would be sourcing a battery start generator at a
realistic price, and getting a suitable control system to operate the
generator. It's certainly possible to do what you want, but you should
have some idea about designing control circuits. It ain't really the
sort of thing that you should be hoping to do by asking questions here!

If you want a much simpler system, then use a break-before-make
changeover isolator instead of a contactor and automated control system.
If you have an ES consumer unit, then when mains power comes back to the
non ES consumer unit, your wife should be able to see that mains is back
and switch over the isolator to mains supply. You'll still need to make
sure that the genny is earthed properly.