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Conference unifix::sailing

Title:	SAILING
Notice:	Please read Note 2.* before participating in this conference
Moderator:	UNIFIX::BERENS

Created:	Wed Jul 01 1992
Last Modified:	Mon Jun 02 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2299
Total number of notes:	20724

1050.0. "bilge pump switch failures" by VLNVAX::FRENIERE () Mon Nov 28 1988 10:37

bps.txt

	3 years ago the original Rule-a-matic bilge pump switch
	failed on board Hope. I replaced it with another $15.
	Rule-a-matic. It failed this summer. I replaced it with a
	Rule "Super Switch" for $24.00. Guess what happened.

	I had left Hope on a mooring in Bristol for several weeks.
	The pump was working off a marginal battery. I had not
	expected to be away for so long a period. Hope takes on
	very little water thru the hull. What comes thru the
	cockpit sole and seats is another matter. We had had 
	several storms during the period with heavy continuous
	rain. As a precaution against freezing, my cockpit drain
	seacocks are shut off. All that fresh water dumps into the
	bilge.

	When I got down to check her, water was just up under the
	cabin sole. I switched batteries and she pumped in no time.
	On the 19th we sailed from Bristol to Mattapoisett. On the
	20th, you folks in New England will remember, another day of
	continuous torrential downpours. I went down on the 22nd to
	check. Water in the bilge again, but the battery was good.

	Proved to be the Super Switch had failed this time. After
	hand pumping, I found the top of the switch float in two
	pieces. The mercury switch was exposed. You could see the mercury
	make contact yet no workee.

	I cut the line to the switch and shorted them and the pump ran.
	The wires exposed were shiny... no evidence of salt erosion.
	I went back this weeked and installed a run of the mill sump
	switch. It will be hauled this Wednesday so I'm not concerned
	about the safety of the boat.

	I called Rule in Gloucester. Well I explained how it was wired,
	how I had used crimp connectors covered and sealed with Scotch
	Electrical Moisture Sealant. The problem I was told was in that
	I had not used Rule Sealant. It is likely that in sloshing
	around in Bristol harbor with a full bilge, some water would
	have found its way about the splices which are stapeled to
        a floor just under the sole. Rule told me that the capilary
	action would have carried moisture down to the switch. It
	would have caused a high resistance which would have heated up
	enough to cause the sealed float to litterly explode. I
	responded that I had to really stretch the imagination to
	have that unit, submerged in 50 degree water, generate enough
	heat to blow apart.  Tha twas all they could answer. Must be
	from capillary action due to my using the incorrect sealant!

	Well, that is stretching it, to have that occur over just 3 days.
	There was some lightning about in the storms that weekend. I
	could believe that somehow lightening was the culprit. However
	ther were no other signs of any lightning strike. All electronics
	and electrical systems were fine.

	Anyone have similar experience?

	What do you use for a bilge pump switch?

	Remember, Ive a woodie so my switch sees a lot more action!

Don

T.R	Title	User	Personal Name	Date	Lines
1050.1	Fault Tolerant	CECV03::WARDROP		`Mon Nov 28 1988 12:37`	13
	Don't you just love the way manufacturers get sooo immaginative and creative in rationalizing how it was that their product wasn't at fault. Especially in situations where the real cause is unlikely to be discovered. It sounds like whatever kind of switch you settle on, you should have two. Wire two switches in parallel so your whole boat isn't risked on a single $15 part with a proven high failure rate. You may even want to install a second pump as backup and have two redundant systems. Don't forget to check them indepentantly now and then. Rick,
1050.2	redundant systems	BRUTWO::BAHLIN		`Mon Nov 28 1988 16:45`	23
	I second the backup system. Mind you I don't have one myself but that is the beauty of this file you get to spend other people's money on speculative fixes :^). Seriously, I've really considered this strongly. My thinking was something like this...... a small (<1500GPH) pump with float mounted at lowest possible point in bilge. The backup system has a pickup and float at a higher level. This means the small [cheap] system is getting the bulk of the wear and tear doing the day to day drip maintenance and the big [expensive] system is in reserve, mothballed until the prime system fails. Also, this system provides you with reserve capacity when needed at sea. Each pump should be provided with a manual override switch (out of the bilge) and I would think it is safer to make all splices as high as possible, ideally in the same panel as your override switches (at least not in the bilge). I also would like some good ideas for a cheap monitoring system that would allow one to detect run time on these pumps. I was thinking about an engine hour meter as a cheap method but maybe counting on/off cycles is easier or better.
1050.3	check the pump before spring	BRUTWO::BAHLIN		`Mon Nov 28 1988 16:54`	19
	Sorry 'bout this but I forgot your original comments while spending your money......... You might have something wrong with your pump that is causing the switches to be eaten. A few shorted turns in the windings might cause excess current conditions (enough to quickly eat a switch). I too think that 'Rule explanation' is a fantasy. If there was enough resistance to heat the switch to oblivion I would think this would be enough current to allow the pump to run (slowly maybe but nevertheless...). Also that much current in an unplanned current path would have caused some powerful (and quite noticeable) corrosion in the path. Do these pumps have diode protection? I don't know if the typical 'Rule' is protected but would think that the lack of protection could also take out a poorly designed/manufactured switch from arcing. Just a thought.
1050.4	well, maybe	MSCSSE::BERENS	Alan Berens	`Mon Nov 28 1988 17:17`	35
	re .0: Hmmmm, at first I thought that Rule's explanation of the switch failure was implausible at best. After further thought, the explanation makes some sense. As the resistance of the switch contacts increases, the voltage drop across the contacts also increases, which results in power dissipation (heating) in the switch. If you assume that the bilge pump motor is a pure resistive load, then the power dissipated in the switch will be at a maximum when the resistance of the switch contacts equals the resistance of the pump motor. For example, if the pump motor draws 12 amperes normally, then under the right (wrong) conditions, some 36 watts would be dissipated in the switch. This could well be enough to cause dramatic switch failure. Of course, the pump isn't going to run very fast with a large voltage drop across the switch, but if you're not there listening to it you might not notice. How long it would take for enough water to cause failure to reach the switch internals is another question. I can't quite accept capillary action would cause a failure quickly, but a manufacturing defect that allowed water into the switch might. re .3: The Rule pumps are not reverse polarity protected -- they simply run backwards (and don't pump much water) if improperly connected. It would be nice if the pump manufacturers would put long wires (say 25') on the pumps instead of 18" or so. The short wires almost force you to have connections in the bilge. An engine hour meter to measure pump running time isn't a bad idea -- it will give those of you with leaky boats an idea of how much leaking is occurring.
1050.5	A no-float solution?	NAC::P_RICKARD		`Mon Nov 28 1988 18:06`	15
	I installed a Waterwitch Switch to my rule bilge pump. It has the advantage of no moving parts to get jamed with debris. It is solid state and has a sensor which if senses water for 12 continuous seconds completes the connection to the bilge pump. I've been told that it can fail if it gets greasy but in my clean bilge it worked fine. During one period of long absence with torrential downpours along with leaky ports and mast boot it cycled on and off some 150 times! Another advantage is that it takes up practically no room. (I'm not entirely sure I've got the correct name, I purchased it through Coast Navigation in Annapolis). Pam Rickard
1050.6	On the proposed diode...	BTO::JPETERS	John Peters, DTN 266-4391	`Wed Nov 30 1988 10:47`	6
	The diode's not to protect the pump from reverse polarity, it's to protect the switch from an inductive voltage spike from the motor's windings when the switch opens. J
1050.7	how waterproof is it?	MLCSSE::BERENS	Alan Berens	`Wed Nov 30 1988 17:37`	10
	re .5: The Waterwitch sounds good ..... but solid state (electronics) in the bilge? Ye gods, the waterproofing had better be absolutely perfect if it is going be reliable for long. It is easy to wire bilge pumps so that they can be turned on by either a float switch or manually -- perhaps a good idea if float switch failure is common.