My new bilge pump switch for a Rule 3700

The old switch failed, got stuck which would leave the pump running.

So bought this $2 magnetic reed switch on Ebay. I had all the other parts here.
The reed switch will turn on the 40 amp relay which will turn on the pump.

I sealed up the wires to the reed switch and pulled the cube relay apart out of its case and put sealer on to keep it dry. Plan to put marine grease in the wiring plug. Used Loctite S30 polyurethane roof and flashing to seal this.

I am using that SS sheet metal to hold the switch.
I think it will work well.
This is an emergency type pump incase other pumps fail, and eventually plan to raise it up higher.

Power comes in on red wire shared to reed switch connected to green wire which grounds relay coil when water rises and lifts float.
The relay takes place of the original failed switch.

I imagine this could fail if some dirty sticky stuff gets stuck on the reed switch float. Although float has lots of side clearance
It has a plastic c-clip so can be removed and cleaned off.

 

Is it spark-proof? Otherwise it may cause an explosion if any flammable gasses accumulate in the bilge.

 

You should add a few components, like a diode to protect the reed switch from the induction voltage of the relay and a delay circuit to keep the pump running for a few seconds after the reed switch has opened. That way you can prevent the situation where the water returning through the pump and the reed switch keep each other busy.

 

Yes, it is spark proof. Everything is totally sealed.
Would the diode go across the reed switch in parallel or series? Polarity which way? Reed switch is completing the ground circuit.
Reed switch can handle 500 milliamps.

Reed switch has a small range, it is not instant on -offing. Also bilge pool of water it would pump is quite large surface area which I think helps that quick cycling issue.

I will test it by putting weights on the other pump switches and flood the bilge.

Found this about the diode. Good explanation and shows small switches.
https://reference.digilentinc.com/learn/fundamentals/electronic-components/flyback-diodes/start
http://www.douglaskrantz.com/ElecFlybackDiode.html

It looks like the diode is reverse biased on the install, so cathode goes to the positive side of the coil.

 

Got the reverse biased flywheel diode 1N5819 cathode towards positive across the coil
http://www.diodes.com/_files/datasheets/ds23001.pdf
Sealed in hot glue, it fit into the center hole of the plug, and I put a band of heat shrink to hold the two wires secure.

 

Installed the switch-relay today and it works great.
The reed switch has a range. Move float up turns on, drops down 1/4 inch it turns off. So it works to pump with no quick cycling.

 

Won't waves trigger it on and off?

 

Not the way I have it screwed on.
This switch is not sitting in bilge water. It is up a lot higher. The plan is to also raise the rule 3700 pump higher. This pump is only for emergency pumping.

I suppose something like boat hull rocking might make this switch cycle on and off if used as a normal pump switch.
I bought 2 reed switches so if another pump switch fails, I will test - try it being used as a regular pump switch. I have 5 bilge pumps in this boat. The switches always eventually fail, they either stick on or off or just quit working after maybe 5 years.

I knew I had a sticky pump switch on this pump, so when I was away for 5 days, I came back to find the pump running continuously, I figure pump did so for 2 days after the snow storm flooded the bilge when it melted, so I decided this was time to fix it.

An Ultra Switch also uses a reed switch combined with a waterproofed relay, the concept is very good for a bilge pump automatic switch.

The differential is still only ' 3/4" differential. ' in the description. My switch might be 3/8 it is at least 1/4 inch.

https://www.amazon.com/s/?ie=UTF8&k...hvtargid=kwd-5026738466&ref=pd_sl_5i98o9kjj_b

Maybe a reed switch can be found with a bigger differential... but can you ?

Here is another one looks longer range, but they do not say.
http://www.fluidswitch.com/fs52-float-bulk-head-mount-switch.php

I think the ones having a free float without a hinge are better. And if mounted in a cylinder or box, that will reduce the wave action on the float.
I think a perfect housing would be a broken boxed bilge pump float switch. Pull out the old mechanism and put in a reed switch into the old housing..
Just drill a hole and bolt it in place.

 

Just FYI, nothing to do with your switch, when your pump quits replace it with a USA made johnson pump. Rule pumps are ***** since they moved production to mex.

 

An update, the switch is not worth the effort. The on-off range is too tight, if I put a delay off timer them might be ok. Meaning when it turns on, the pump would run long enough to actually pump it down so that when the timer turns off, the float is down and the pump won't start again. the issue was short cycling of the pump. Too bad this switch does not have a large range between on and off, then would be fine. I kept the relay to use with the standard bilge pump switch.

I went with a standard bilge pump float switch.