bilge pump switch woes

[serini]

I am refitting by boat and on inspecting the nuts on the keel bolt close to a submerged type bilge pump I have found some evidence of electrolysis. I suspect stray leakage from the pump and I want to eliminate all chance of this. Obviously I can change to a non-submerged type of pump but what about the switch? Does anybody know of a level switch where the electrics are remote and there is no possibility of stray current?

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[Mirelle]

God Bless you, Sir!

Grist to my mill! (see thread below on automatic bilge pumps!) Lethal devices, for just the reason that you give - stray current electrolysis.

Abolish the gadget, and sleep more easily!

Now, to try answer your question properly, I think it is perhaps not so easy to use a non-submerged type of pump, because of the problem of priming it - a submerged pump is primed by virtue of being submerged, of course. Electric pumps that will start dry and self prime, like diaphragm pumps, use a lot more juice.

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[serini]

priming

I have installed a non-submerged pump before at the bottom of a 'U' and that seemed to sort out the priming issue. Could you send me a link to the thread you mentioned? Thanks, Mark

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[andyball]

non-submerged pumps tend to cost many times more &/or pump much less.

totally sealed switches are available- cheapest uses a polypropylene float with a small magnet that operates a reed switch, this would likely need a relay for a proper size pump, since pump current too great for a tiddly reed switch.

There are also pressure operated ones (buy marine,industrial, or make your own out of a s/h washing machine one),again,no electrical contact with the water; & fluid level sensors that have no moving parts at all, but some sensitive to oily waste covering them I would think. All from RS,farnell etc (or used to be).

Then no 12/24V in the water, except for the time the pump's working. ( & not even then with a decent pump?).With a not very insulated pump, you'd still have the possibility of earth wire making contact, but a double pole relay would prevent that except when the pump was running.

Think most pump/switch combo's wd probably be electrically isolated from water anyway....but test yours with a meter when submerged if concerned. I'll check mine (both attwoods) next time I'm at the boat & let you know- it wouldn't do my aluminium hull much good, so it's something I've thought about.



auto bilge pump thread <A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=pbo&Number=446443&page=0&view=collapsed&sb=5&o=2&part=>here</A>

 

[serini]

I'm sure any reputable submerged pump or switch will have both live and neutral properly insulated but even a tiny stray current can work havok. This time I got away with just a bit of electrolytic action on a nut rather than the bolt but damage to the bolt would be so expensive (and maybe catastrophic!) that I am determined to be as sure as I can. I'll trawl through RS and see what I can come up with. I think Farnell has closed. Thanks for your post. Mark

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[ongolo]

Hi all,

Some time ago there was under practical projects a conversion of a non-submersible float switch which would be easy to make.

I think I could find a link in a electronics circuit site which has a cct diagram for a capacitive level indicator and/or ?? pump switch. Capacitive monitoring would be the neatest way until some sort of corrsion nibbles in the electronics.

However, I dont know why you guys have all these holes in your hulls.

Air cooled diesels, stand-off pipes of 200m with a flange to seal the mounted depth and speed sensor and hopefully a sterntube seal that does not leak.

Only if something penetrates my 6mm steel skin will I have a problem.

Happy easter egg to every body.

ongolo


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[pvb]

Air-operated switch...

Jabsco make an air-pressure operated switch. If you want to ensure that there's no chance of electrolytic corrosion from the pump, you need to run the pump through a double-pole relay so that it's completely isolated (remember it's the ground connection which causes the problem).

For what it's worth, I've owned boats of various types for 30 years and I've never had (or wanted) an electric bilge pump.

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