In article ,
"Roger Long" wrote:

I've now done what I should have first thing, made some calculations
of my sump size and hose volume. I want generous pumping capacity
which means 1 1/8" hose to avoid head losses in the long runs. The
volume of hose divided by the area of my sump is greater than the ON /
OFF range of any switch I have been able to locate.

I don't want to use check valves because a little bit of fluff sucked
into one could set up the endless pumping cycle. Also, if the water
drained back from the check valve, the line would essentially be
airbound.

Our check valve worked just fine for about a decade. The primary reason
I put it in was because our stern wave sometimes comes halfway up our
transom and I don't like the idea that the bilge pump hose could lead
that water into the boat.

One trick that could change the mix: Add a vacuum break elbow close to
the pump, but above the moving waterline

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

On Sun, 15 May 2005 23:57:08 GMT, "Roger Long"
wrote:

Oh of course. Like this, right?

http://home.maine.rr.com/rlma/Switch.jpg

(I loaded the new sketch into the same URL)

I remember now the big fog lights I had on a car years ago. There was
a relay under the hood so all the juice for the big lights wouldn't be
running through the tiny switch in the panel. The relay was pretty
well sealed and intended to survive under the hood of a car so should
do pretty well if kept above the bilge water. I'll look for a couple
of those tomorrow.


Now, you're talking.
1) Make that a 12 volt relay with two normally open
20A DC rated switches
2) Dedicate one switch to the pump supply.
3) Add a snubber of 10 ohms in series with 0.01 microfarad (200 volt +
working)
across each of the two inductive pieces, which are
3.1) the relay coil
3.2) The motor inputs

4) Remember that sparking contacts in the vicinity of a gas
tank/engine make loud noises, so a metal clad relay would be better,
in a decent blade socket.

Brian Whatcott Altus, OK

Brian Whatcott Altus OK

That's it. Headlight relay might do, just make sure it is meant to be on all
the time; not short term like a horn relay might be.
"Roger Long" wrote in message
news
Oh of course. Like this, right?

http://home.maine.rr.com/rlma/Switch.jpg

(I loaded the new sketch into the same URL)

I remember now the big fog lights I had on a car years ago. There was
a relay under the hood so all the juice for the big lights wouldn't be
running through the tiny switch in the panel. The relay was pretty
well sealed and intended to survive under the hood of a car so should
do pretty well if kept above the bilge water. I'll look for a couple
of those tomorrow.

--

Roger Long

It's a diesel boat.

Would you please explain the snubber business? I'm sure a lot of us
besides myself would like to know what it's for.

--

Roger Long



"Brian Whatcott" wrote in message
...
On Sun, 15 May 2005 23:57:08 GMT, "Roger Long"
wrote:

Oh of course. Like this, right?

http://home.maine.rr.com/rlma/Switch.jpg

(I loaded the new sketch into the same URL)

I remember now the big fog lights I had on a car years ago. There
was
a relay under the hood so all the juice for the big lights wouldn't
be
running through the tiny switch in the panel. The relay was pretty
well sealed and intended to survive under the hood of a car so
should
do pretty well if kept above the bilge water. I'll look for a
couple
of those tomorrow.


Now, you're talking.
1) Make that a 12 volt relay with two normally open
20A DC rated switches
2) Dedicate one switch to the pump supply.
3) Add a snubber of 10 ohms in series with 0.01 microfarad (200 volt
+
working)
across each of the two inductive pieces, which are
3.1) the relay coil
3.2) The motor inputs

4) Remember that sparking contacts in the vicinity of a gas
tank/engine make loud noises, so a metal clad relay would be better,
in a decent blade socket.

Brian Whatcott Altus, OK

Brian Whatcott Altus OK

On Mon, 16 May 2005 01:18:55 GMT, "Roger Long"
wrote:

It's a diesel boat.

Would you please explain the snubber business? I'm sure a lot of us
besides myself would like to know what it's for.


An inductive element like a relay coil or a motor stator or rotor
has a predictable reaction to suddenly cutting off the current through
it: a back voltage which can rise to a fast peak of hundreds of volts,
making a spark that jumps the opening contacts for a little while.

This wears the contacts out. And ignites gasoline vapor too.

If something is arranged to let the current through a coil fall more
slowly, the voltage rise is much lower. If some resistance is in
circuit, the energy stored in the coil is used by the resistance -
which heats up a little.
This combination of a capacitor and series resistor is called a
snubber, because it snubs (or damps out) the spark.
The cap and resistor is placed across the coil.

Make sense?

Brian Whatcott Altus, OK

Like this, right?

http://home.maine.rr.com/rlma/Switch.jpg

I can appreciate the effect. I made a box in high school with a coil
in it and a switch made from a nail dangling in a ring. It had
textured aluminum foil sides wired to the coil and said "Mystery Box"
on top. It was a hoot when I left it in the faculty room.

Do you think I can get away with a single contact relay? The sealed
fog light relays that are readily available seem like they should be
sized and just right for this application.

--

Roger Long

"Roger Long" wrote in
:

Like this, right?


Oh, goody-goody! Let's all keep making the damned bilge pump more and more
complex, with lots more failure points so it can flood the damned boat and
put it on the bottom.....

Parallel two Rule float switches in series with EACH of two bilge pumps
hooked straight up to the batteries through a 3A fuse....

The boat will never sink.....until the flooding exceeds the combined
capacity of the pumps, of course.

SIMPLE IS ALWAYS BETTER!

On Mon, 16 May 2005 09:15:37 -0400, Larry W4CSC
wrote:

Oh, goody-goody! Let's all keep making the damned bilge pump more and more
complex, with lots more failure points so it can flood the damned boat and
put it on the bottom.....

Parallel two Rule float switches in series with EACH of two bilge pumps
hooked straight up to the batteries through a 3A fuse....

The boat will never sink.....until the flooding exceeds the combined
capacity of the pumps, of course.

SIMPLE IS ALWAYS BETTER!

Yeah, what he said.

__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at world wide wiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

Larry W4CSC wrote:

"Roger Long" wrote in
:


Like this, right?



Oh, goody-goody! Let's all keep making the damned bilge pump more and more
complex, with lots more failure points so it can flood the damned boat and
put it on the bottom.....

Parallel two Rule float switches in series with EACH of two bilge pumps
hooked straight up to the batteries through a 3A fuse....

The boat will never sink.....until the flooding exceeds the combined
capacity of the pumps, of course.

Or, of course, the capacity of the batteries.



--
Stephen

-------

For any proposition there is always some sufficiently narrow
interpretation of its terms, such that it turns out true, and
some sufficiently wide interpretation such that it turns out
false...concept stretching will refute *any* statement, and will
leave no true statement whatsoever.
-- Imre Lakatos

"Stephen Trapani wrote:

Or, of course, the capacity of the batteries.

And, in this case, it would have had to be pretty impressive capacity.
After the fiasco with the oil sensing switches, I'm all for the
simplicity promoted above. What's driving this now is the fact that
the pumping capacity I want (enought to have a fighting chance of
surviving a burst stuffing box hose), combined with the hose lengths
forced by the design of the boat, means that any float switch on the
market will go into an endless cycle of pumping out the hose.

--

Roger Long