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Old 15-10-2008, 23:33   #1
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Bilge Pump Wiring Question

I'm on my brother-in-law's catamaran again. Our bilge pump system consists of pump, float switch, panel switch, alarm and 12V source. Presently the pump and float switch are disconnected (by previous owner). When panel switch is turned ON, the alarm sounds.

My questions:

1. Is the panel switch supposed to be connected parallel to the float switch? I'm guessing Yes, as an emergency override.

2. If not, what is the purpose of the panel switch? Possibly to silence the alarm???

3. Should the alarm be wired in parallel with the pump so that the alarm sounds anytime the pump is running? I'm guessing Yes.

4. When sailing normally, should the panel switch be on or off? I have determined that turning the panel switch ON causes a relay to operate which provides 12 V to wires going to motor.

5. I'm an electrical engineer and understand how circuits work but am uncertain of HOW the bilge circuit SHOULD work.

I have looked in Nigel Calder's Boatowners Mechanical and Electrical Manual as well as Charlie Wing's Boatowner's Illustrated Electrical Handbook but haven't found a good circuit for bilge pump electrical system.

I'd appreciate any help. Thanks.

jes
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Old 16-10-2008, 00:01   #2
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Here is how ours is wired. Alarm can be placed where lamp is.

The only thing about our setup I don't like is that the bilge switch is in the cokpit next to the engine panel. Someone keeps knocking the switch frm Auto to off. I need a switch guard or something.
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Old 16-10-2008, 02:04   #3
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Wiring Diagram - Bilge Pump c/w Alarm:
http://www.cruisersforum.com/attachm...ch_cct-med.jpg

And Schematic & Cabling Diagrams:
http://www.cruisersforum.com/gallery...p?i=4850&c=500
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Old 16-10-2008, 02:39   #4
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Quote:
Originally Posted by Ex-Calif View Post
Here is how ours is wired. Alarm can be placed where lamp is.
Dan, shouldn't the postiive from the float switch run to the pump rather than back to the battery?

BWS
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Old 16-10-2008, 03:00   #5
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For my two bobs worth, the bilge pump(s) should not go through the main panel. It should be on a fused circuit of its own.
It should be wired directly to a main battery with as water tight connections as possible.

It should definately NOT have any relays. Each pump should have a Auto/manual/and off switch.

The choice of alerting devices is up to you , but rember a light that cant be seen is a trap, in the same way that an audible alert that cant be heard is a trap. The position of a light is critical. Can you see it from all positions . An audible alarm that is drowned out by engine noise or the noise of a storm is equally a problem.

Further. For every device that you add to this critical piece of equipment you are lessening its reliability. I am not saying dont have warnings, but I am saying think very carefully of their purpose and location.

The bloody thing better work in the dark with all other systems out in the worst possible scenario.....

If you need to have complications, then go for it...BUT install a "last man standing" bilge pump that has none as well.

If you think that a manual one will compensate...try yours for half an hour with a hose running into the bilge....I think that you will find that the joy of an electrical one running while you run around trying to stem the inflow is worth it. : )
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Old 16-10-2008, 03:08   #6
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ex cal...the switch should be high up and inside. There is no advantage (and obvious disadvantages to having it outside.) It is not like a manual pump. If the insides are swimming then there is a fair chance that your engine and/or battery are under. The reason for a (and I use the term again) last man standing MANUAL bilge pump from the cockpit, is a last ditch effort to steer and slow ingress. A situation I never want to be in. At this stage it is fair to assume that all electrics are compromised.
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Old 16-10-2008, 03:14   #7
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Quote:
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Dan, shouldn't the postiive from the float switch run to the pump rather than back to the battery?

BWS
Not sure what you mean. There are two separate +12V sources of power. One directly from the battery runs through the selector swtch via the "auto" postion.

A separate supply comes from the distribution panel and is fused for the momentary on "manual" position.

And correction - We do have the lamp wired that way to show anytime the bilge pump is powered but if I were to wire an alarm - we don't have one - I would run it only on the float switch circuit upstream of the switch. I wouldn't want an alarm notification that I had manually operated the bilge pump - LOL.
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Old 16-10-2008, 03:42   #8
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Further... I think its important to think about WHY water is coming in. And how that relates to the bilge pump system.

Let me expalain.
If it is a hull breach...there is a fair chance that you will know it. You will be actively moving or at the least have felt some kind of crunch.

If it is the far more common situation , it is a failure of "systems". The most common being a hose coming off.


In the first ...you would be looking for trouble. Flick to manual and look and hope.

In the second...you could be doing anything ...an audible alarm is the only thing that will work across the whole boat.

Back to the original discusion ...a very noisy pise with a single switch in parallel. as simple as you can get....NOT through the main panel anyware . A simple earth problem can take your system out with out you even knowing.
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Old 16-10-2008, 03:48   #9
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Not sure what you mean. There are two separate +12V sources of power. One directly from the battery runs through the selector swtch via the "auto" postion.
OK, I got it. Please disregard my query. Agree on the alarm wiring.

BWS
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Old 16-10-2008, 04:26   #10
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Bilge Pump Sizing:
Do you have enough bilge pumping capacity?


Approximate Flooding Rates, for smooth holes at specific depths, are calculated using the formula:

Flooding Rate in gpm [ Q] = 20 x d x h

where:

d = diameter of hole in inches
h = depth of hole underwater in feet (head)
h = square-root of h

Hence, for a 2" diameter hole at a 3 Ft depth:

Q = 20 x 2" x root 3 = 20 x 2 x 1.73 = 69.2 gpm (4,152 Gal per Hour)

The actual initial flow rate ('Q') will be less than calculated above, due to frictional & turbulence losses at the aperture.
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Old 16-10-2008, 07:30   #11
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THANKS for some great answers. My brother-in-law was just amazed that we could get 9 answers in such a short time from all over the world. I appreciate the wisdom expressed also. Now to find out what those relays really do.

jes
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Old 16-10-2008, 07:35   #12
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On my boat I have a 3800 GPH pump and the auto wire is fused to the batteries. The manual switch is momentary and goes thru a relay because the amperage is so high. I have a separate high water alarm.
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Old 16-10-2008, 11:56   #13
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in my boat i have a 400 gph on a float switch and manual over ride. then up higher in the engine bay i have a 1600 gph ( iirc ) with a float switch and a buzzer. for the second pump the water in the boat would be 6 inches deep
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Old 16-10-2008, 13:07   #14
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bilge pump sizing

The smaler the boat the bigger the pump.
(it fills faster)
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Old 16-10-2008, 13:13   #15
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The smaller the boat the bigger the pump.
(it fills faster)
Indeed ...
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