On Wed, 12 Jan 2005 09:08:43 -0800, DaveC wrote:

On Tue, 11 Jan 2005 22:19:53 -0800, Rich Grise wrote
(in article ):

It was also not specified that the switch was double-throw. The only
information given was one contact closure.

But then again, I've asked the OP about the switch itself, and what's
actually accessible, and haven't seen a response yet - maybe he's solved
it and hasn't bothered to come back and say so.

1 pair of wires coming up the well from the n.o. float switch. This is the
only sensor for level in the well (no other switches).

I've pretty much settled on the solution suggested by Fred Bloggs, earlier in
this thread which uses 2 relays:

One relay (d.p.) is set or released by mains voltage. When enabled, the float
switch (using mains voltage) controls a second relay (s.p.) which closes the
alarm contacts if/when the level rises in the well. When power has failed,
the primary relay, now de-energized, connects the float switch directly to
the alarm contacts (using battery voltage).

It seems the simplest solution.

Thanks for the update. I'm glad to hear you've got it solved. :-)

Cheers!
Rich