"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

"Roger Long" wrote in
:

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.



Backflow is inevitable in such cheap impeller pumps we put in boats.
Backflow is also important in CLEARING the pump of trash it has sucked into
its intake grate. A good splash of backflow blows the trash out of the
pump so the next time it comes in it will start cleared until the trash
gets sucked into it again. Therefore, I don't consider backflow to be
"bad". The bilge isn't going to be dry with these pumps, anyways.

When Geoffrey bought Lionheart, an Amel Sharki 41 (39 if you're talking to
our marina people), I was amazed that all the sink drains, shower drain and
bilge water didn't simply make an awful smelly mess in the bilge. The
original French pump Amel installed was a positive-displacement diaphram
pump, quite large, but manually operated by the breaker. The former owner
had no concept of "maintenance" on such as DC motors or pumps, so it was
just worn in two from lack of a few drops of oil. The armature was against
the stator dragging every time it came on. It was replaced by the biggest
Rule, some bogus rating of 4000 gph, which was placed way down in the keel,
about 5 feet under the galley sole with a Rule float switch. Everything in
the boat dumps into this deep space whos sides are very steep, indeed. A
pipe with a ball valve on the end so you can secure it, runs forward to the
shower/sink which dump unceremoniously into the bilge under the false deck
in the head. The shower really has no drain at all, it just falls through
the holes in the wooden deck into the forward bilge, forward of the 2nd
watertight bulkhead, the forward bulkhead of the main cabin. You secure
the hatch with a mahogany (of course) bar and turn off the drain valve to
prevent flooding.

The arrangement works quite well. Once at sea, after dishwashing, I get
out the old pump handle to the manual monster under the steps and use it to
pump out whatever solids have collected. It has a very nice foot piece at
the bilge bottom that really sucks it dry. The big Rule sucks out most of
it.



--
Larry

You know you've had a rough night when you wake up and your outlined in
chalk.