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Author Topic:   Three-position Switch with Rule 35A Float Switch
Frank from Philly posted 05-18-2008 09:43 AM ET (US)   Profile for Frank from Philly   Send Email to Frank from Philly  
Do I really haffta use a three-position toggle switch when I'm using a float switch on the bilge pump? Here's what I wanna hook up:
- Rule 25D Bilge Pump
- Rule 35A Float switch
- Existing two-position toggle switch (SPST) in console

Can't I just wire the toggle switch and the float switch in parallel? That way, the pump will only come on if the toggle is set to on, or if the float switch is made. And there will be no short circuit if they both are turned on for some reason. Will there?

I also realize that the power pole of each switch must have a direct connection to 12-volt positive. And also in-line fuses. I understand the convienence and value of a three-position switch, and the positive isolation between the float switch and the toggle ON switch. But is it really that big a deal? I can't see where there would be a short unless I'm too dumb to see sumthin' else here. I have a 3 position switch in my other boat. The problem with the boat in question here is that there may be no room in the console. Lemme know what'cha think.

Thanks for this message board!


jimh posted 05-18-2008 09:55 AM ET (US)     Profile for jimh  Send Email to jimh     
An electrical load can be controlled by more than one switch. As you observed, if you wire an ON-OFF switch in parallel with the float switch, the pump will actuate when either switch is closed.

The disadvantage to this wiring arrangement is that there is no way to shut off the pump system. The float switch will always be able to actuate the pump. If the float switch sticks in the closed position (due to debris or other cause) the pump will run until the battery dies.

seabob4 posted 05-18-2008 11:04 AM ET (US)     Profile for seabob4  Send Email to seabob4     
You are correct in the fact that if the float gets jammed, it will turn on the pump until the battery konks out. However, ALL builders wire the float to where one gray wire goes to constant hot, and the other is wired in parallel with the brown from the pump to the switched side of a on/off rocker/toggle switch. The reason for this set-up is the fact that if bilge water is left to accumulate in an unattended boat left in the water, it could sink the boat. A very heavy prolonged rainstorm could do it if the deck hatch gutter drains can't keep up with the water flow.

I would not disable the ability of the float to turn on the pump by itself. What I would do is to make sure my bilge is clear of debris and to make sure that there is the ability to inspect the bilge on a periodic basis. If you live far away from where your boat is moored, have the marina or a friend check on her once in a while.

jimh posted 05-18-2008 12:51 PM ET (US)     Profile for jimh  Send Email to jimh     
It is impossible to describe electrical circuits using narratives. That is why the schematic diagram was invented. For more information on how to wire a bilge pump, see my article

seabob4 posted 05-18-2008 01:30 PM ET (US)     Profile for seabob4  Send Email to seabob4     
I believe my description was straightforward, to the point, and easily able to be followed, given some 12V elctrical knowledge on the part of the user.

The real point of the reply was to emphasize why a bilge pump float switch is wired the way it is. The ability for the float to activate the pump when there is bilge water accumulation on an unattended boat is of the utmost importance. No, Whalers won't sink, but they can be swamped.

Frank from Philly posted 05-18-2008 01:55 PM ET (US)     Profile for Frank from Philly  Send Email to Frank from Philly     
Thanks Jim & Bob!

The way it appears to me, is that it's a handy feature provided by the 3 way switch to be able to disconnect the pump from the battery by setting the switch to "off", thus totally disabling the pump power circuits. But I think this is more for a service and/or storage convienence than for battery protection. It's also convienent for someone who trailers the vessel to be able to be sure the pump is off when the boat is out of the water. And of course when the boat is out of the water the drain plug is out, and any rainwater can drain out of the boat thru the open drainhole.

But when the boat is in the slip at the marina, obviously the plug is in, and the only way the boat can drain any accumulated rain water is with the bilge pump. The pump needs to operate automatically, responding to the float switch, if water builds up. This will happen if a 3 way switch is left in the "Auto" position, OR if the float switch is wired direct to the battery. If I wire an "on-off" switch in parallel with the float switch, (as I asked about in my original post)I can operate the pump any time I want.
Another good feature about the 3 Position switch is the spring-loaded "momentary on" feature that makes sure that someone can't leave the pump running dry.

I looked at the wiring diagrams Jim, and I gotta say yi'v done a fine job!

Thanks for the inputs Jim and Bob.


seabob4 posted 05-18-2008 04:29 PM ET (US)     Profile for seabob4  Send Email to seabob4     
BTW, bilge pumps can be run dry. At least the ones made in the last decade or so. Won't hurt it a bit and will quit when the battery dies.
Frank from Philly posted 05-18-2008 04:56 PM ET (US)     Profile for Frank from Philly  Send Email to Frank from Philly     
Yeah, I hear ya. What I really meant was that someone would run it unnecessarily (man, that's a long word ain't it?). The pump bearings ain't water lubricated as are some circulator pumps that we use in plumbing and HVAC work. Bilge pumps are like little sump pumps, right? And they have oil in them, right? Or could it be that I'm fulla' poop, right?


seabob4 posted 05-18-2008 06:29 PM ET (US)     Profile for seabob4  Send Email to seabob4     
God, you are full of questions, aren't you!! That's a good thing. Bilge pump impellers are not "hard" against their housings, therefore there is no heat buildup due to friction. Put some water in your bilge, turn the pump on until it doesn't suck anymore, then turn it off. All the water in your discharge hose will come back THROUGH the pump into the bilge. That's why they don't burn up when run dry.
Frank from Philly posted 05-18-2008 09:04 PM ET (US)     Profile for Frank from Philly  Send Email to Frank from Philly     
Well, then that means that they're little centrifugal pumps. Okay. But they still gotta have shaft bearings that gotta be lubricated, unless they're made outta some special material that doesn't require lubrication...
So, some manufacturers use sealed bearings, with the lube sealed in them.
But also, as I said, some HVAC pumps are lubricated with the water that flows thru them such as "Wet Rotor" pumps,and never need to be lubed, and can take runnin' dry for awhile but evenchully they'll sieze up. Other pumps I deal with require periodic lubrication and some even have ceramic seals. "Oy vey, Sol, such a lotta kinds'a pumps we haffta know about these days"
I guess I'm straying from the common small boat bilge pump here aren't I?...
I can't help it. It's the cawfee...


seabob4 posted 05-18-2008 09:38 PM ET (US)     Profile for seabob4  Send Email to seabob4     
You ever hear or "permanantly lubricated"? Yeah, seems like an oxymoron, or at least a moron. The key idea is to keep water from accumulating in your bilge. The bilge pumps of today have a lubrication system that is more-or-less non-servicable. So pay attention to the water in your bilge! And send me a cheese steak while your at it!

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