On Tue, 06 Sep 2005 15:21:20 GMT, Ignoramus25850
wrote:

I have been playing with using relays of various kinds, as well as
contactors. I already built 2 phase converters, and a remote switch,
for instance. I have a few 90A and 75A contactors and solid state
relays and mag starter buttons and whatnot.

Here's what I have been thinking about. I have a 7 kW Onan DJE
generator that I have for emergencies. I want it to power my entire
house in emergencies (I know that I cannot run AC and some other
devices while under generator power).

It is expensive and painful to install a transfer switch. I want to
make something easier and cheaper to power the house in case of
emergencies, while at the same time preventing backfeeding.

I can, instead of a transfer switch, build a system that includes a
contactor, a mag starter, and a relay that only closes the main
generator contactor when the main circuit breaker is in the OFF
position.

Go get yourself a UL Listed transfer switch of some sort. The
cheapest way is a Double-Throw safety switch. Looks just like the
fused disconnect for a motor, but the lever goes On-Off-On.

Or do some heavy-duty scrounging and buy a new or good used
automatic transfer switch that you can install. DO NOT TRY TO INVENT
THIS YOURSELF. It is life-safety critical, and there is absolutely no
reason for you to reinvent the wheel. Better you should pay a bit for
the right equipment - Use a proven design.

If your homebrewed transfer switch design is flawed, creates a
backfeed and kills a lineman or two working on power restoration (or
even just surprises the hell out of them when they find out the line
is energized) I can guarantee that they will find you, and that the
proceedings will not be pleasant.

If you do anything permanent, get it checked out and passed by the
local building inspector, and by the local utility. This is critical.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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