"Larry W4CSC" wrote in message
...
Can you explain to me why you are using these relays on the lower
switches?
Why not just parallel the lower switches with the upper switches and
be
done with it?

I guess you weren't in on the discussions leading up to this design.

Testing an earlier version of my dual pump rig with it's long dual
hoses in a plastic tub of approximately the same surface area of my
bilge sump, I discovered that the backflow through the bilge lines
with the pumps quit would raise the sump level slightly more than the
activation range of any bilge switch I could find. I didn't want to
relocate the bilge lines to shorten them or use checkvalves.

The purpose of this is to simulate a float switch with a four inch
activation range so there is no possibility of backflow setting up an
endless pumping cycle. The system has turned out to have other
advantages. The lower switches can't turn the pumps on by themselves.
When the top switches go on just once, they trip the relay and the
system then pumps all the way down. This provides built in protection
from the pumps "chirping" in a seaway due to sloshing. If I want to
pump the bilge down after it has filled enough for the lower switches
to activate but not wait for it to reach full pump activation depth, I
can just give a top switch a flick and then forget it. It will pump
full down without holding the switch up.

It turns out to be maybe unnecessary because the backflow is less than
in my test or calculations. Still, it was fun working the system out
and putting it together.

--

Roger Long