Bad practice is actually something you shouldn't repeat. 


A Guide to the Contents

Bilge Pump Switches.  An unscientific survey of what breaks and what does not (yet).  Unscientific because the sample size is small.  But when a product fails more than twice it goes on my "don't use this one again" list.

Many boaters install check valves in the bilge pump discharge line to keep water in the line from running back into the bilge once the pump shuts off.  This is generally a bad idea and can lead to real trouble.

Coax connectors in the bilge dissolve. The wages of wetness and no waterproofing.  Also a general discussion of waterproofing electrical connections.
Improperly terminated power cables will come undone.   Details really matter.  Particularly on shore cables.  A step-by-step method for properly terminating a heavy portable cord is outlined.  If there is too much detail for you here, you should leave replacing power connectors to someone more patient and experienced.
The Sintered SSB Grounding Plate Scam Making a good RF electrical connection to the water does not require a porous plate.  In fact, the porosity of the plate can be a bad thing.  

Also, the four skinny little mounting screws provided with a sintered plate certainly don't make sense from an RF point of view.  

Three fundamental electrical lessons from one case study.  

1) Connectors are not reliable friends. What manufacturers find convenient is not always good for you. 

2) "Shotgunning" is a terrible method of fixing something.  Save your money and hire someone competent.  The problem will be fixed quickly and you will save the money and effort of mindlessly buying and replacing parts.

3) How NOT to install heat-shrink butt splices.  Hint: do not try to use a match to shrink down the jacket.

Be careful where you terminate battery cables on the engine.  Duty created by discovering a problem created by others.
No wirenuts on boats.  And no insulation-displacement power connections either.  "Why" in great detail from an actual case study.  

Also, land electricians and boat electricians are completely different breeds, if you have not figured that out yet.  

Beware cheap cable ties.  I learn a lesson about how NOT to save money.

Unreliable Bilge Pump Switches, and Some Good Ones - So Far

Are there reliable bilge pump switches?  It would seem that bilge pump switches should not be a big deal.  Even operating every 15 minutes, that's only 35,000 cycles a year.  If I have more than one failure with a particular kind of bilge pump switch I quit using it.  You would think I should have discovered the perfect switch.  I feel betrayed when a promising switch fails repeatedly, not to mention the free service call I make to replace it with something else.  Here's what does and does not work for me:


                                             BAD X 2     The Johnson ULTIMA electronic bilge pump switch.  This seemed like a good idea.  The switch features (presumably) sealed electronic sensors.  The two "Mirus" patented field sensors (behind the circles on the photo at left) switch on when covered by water.  It is like magic when it works.  When the inventor of the technology, Material Sciences Corp manufactured these under the "SensaSwitch" brand, they were completely encapsulated in plastic.  I used a half-dozen and had zero problems.  Johnson started manufacturing them and selling under the West Marine house label.  The only apparent difference is that the housing is now hollow and the seal for the wires seems, to me, a little marginal.  In their new configuration, these switches do the only thing worse than fail.  They fail intermittently.  Sometimes they work, sometimes not.  Customer complains, I go out, the system seems to work.  I get out the garden hose and play in the bilge.  Suddenly the sensor stops working.  I think water has gotten into the housing, but what do I know?  I know it's no longer a hermetic seal around the wires as it was when MSC built the product.  I know I do not use these switches any longer, at least not without greasing the rubber seal around the wires.  


Note to switch manufacturers:  This really matters.  Hopefully my customer will tell me when one of your switches I have installed fails before any reasonable person thinks it should.  Unfortunately, some of them (very reasonably) find someone else who will, they think, install something that actually works for a few years.    

6/13/08


Excellent.  The Groco pneumatic bilge pump switch is very cool.  This switch uses exactly the same technology your automatic washer uses to determine when the tub is full, a pneumatic switch.  By the way, when was the last time you automatic washer overflowed? I'll bet "never" compared to the last time your bilge pump switch failed.  Caution: keep the pressure switch itself out of the hostile bilge environment.

This is the switch I use on my own boat, and that is a big endorsement.

I have not used a lot of these, mostly in places where nothing else would fit.  I intend to start using more of them  The bottom end of the tube is the only thing that needs to be in the bilge.  It comes with a fairly short piece of plastic tubing so I went and bought a whole roll.  Now I mount the switch (the top part in the photo) somewhere environmentally benign, like behind the electrical panelboard.  It does not seem to matter, within reason, how much tubing you use.  The trip point is adjustable on the pressure sensing switch, but not the hysterisis.  That means the distance between turn-on and turn-off is fixed.  I have experimented with replacing the spring in the switch and have increased the hysteresis, but I would not recommend this surgery under any but the most desperate cases.  For one thing, you don't know whether your new spring is corrosion resistant.  Physics note: the more volume in the tube the higher the water must rise to trip the switch, but it's not a big effect as long as things are kept within reason. The device is specified to trip at 2-3/4 inches of water and switch off at 1 inch of water.

One caution: if the 3/16" ID plastic tube becomes clogged the switch will stop working.  If you have oil in the bilge it will want to coat the tube and sludge can build up.  The purpose of the little bell-shaped thing on the bottom is to trap enough air so that water and floating crud never actually enters the tube.  The bell is designed to be screwed to the bottom of the bilge.  It has little slots around the bottom edge which are intended to keep floating crud out of the bell.  The obvious weak spot for clogging is the tube barb on top of the  bell which is only 1/8 inch diameter.  You may need to improve on this "bell" device like using a short length of 1/2" PVC pipe that will reduce down to a 1/4 inch tube barb.  You want the pipe at least as long as the bilge water might rise, within reason, so that clogging deposits can never get into the tube barb.   At least your washing machine keeps the end of the tube clean.

West Marine dropped this switch from it's 2008 catalog.  The switch works, but it looks odd, is a little more expensive and takes some thinking to install properly.  Sales volumes probably were not high, so I guess that figures.  But a number of other online merchants carry it.  There is not a lot of hysteresis in the unmodified switch, so if you have lots of backflow into the bilge you will have constructed a little water oscillator.  This will make you think about check valves.



Good x 2  The trusty old rolling ball bilge pump switch.  Our good old friend from West Marine. I have heard reports that some people have had water get into the float and the ball got rusty.  That has not happened to me.  Maybe the manufacturing process has developed a better plug and maybe I am just waiting for the heavens to open up and rain failed switches.  I use a lot of these switches and have never had a failure.  You have to be careful to place them so nothing is going to get trapped under or on top of the switch.  I think that is a given with anything designed to move freely in the bilge.  Every ENCLOSED hinged float switch like the SureBail and its predecessors has eventually developed too much friction in the plastic bearings or too much stiffness in the wires for the buoyancy of the float to overcome.  So the float sticks either up or down.  Remember, oil and sludge in the bilge coat those plastic lipophillic bearings and gum them up.  This switch has a massive float, loose bearings and avoids that problem.

This West Marine switch has the largest hysteresis (differential) of any switch I've used, so it is a good solution when you are tempted to use a check valve.  This switch is so good and so simple and so cheap to manufacture that West Marine now molds it out of black plastic and puts on a gold colored label and has increased the price.  It is still inexpensive.  I take some care to make old-fashioned curly leads on the wires by winding the excess length around a Phillips screwdriver blade to forestall the development of any future problems.  I know the wire is going to get stiffer with age and with oil exposure.

I have customers who would prefer a drier bilge than this switch will give you.  For them I recommend a separate 500 gph pump and discharge hose that can keep the bilge a lot drier.  Which brings us to the automatic bilge pump which uses no float switch.     6/13/08


Bad, but I wish it were better.  This seems like such a good idea I fervently wish it worked for more than a year or two before crapping out.  It's a simple principle made possible by my old associates in the semiconductor industry.  The pump is "smart," which means it has a microprocessor inside.  Every three minutes or thereabouts the pump starts up.  The electronics package monitors the motor current.  If no water is present, the motor current is low and the pump shuts off.  If higher current is sensed it means water is being pumped and the pump stays on until the pump current drops again indicating all water gone.  I have calculated that the cycling of the pump with no water present consumes less power than the self-discharge rate of lead-acid batteries.  So it has no power penalty.  The Rule 25S, a great idea.

No troublesome float switches, small pump to get the bilge dry as possible, what is not to like?  For one thing, the fact that the pump runs every three minutes drives some customers batty, especially at night when they are trying to sleep.  Others like the reassuring murmur of the pump letting them know that their boat is snug and dry.  You never know what kind of customer you have until it is too late.

Most troubling is the fact that I have replaced at least five of these pumps after a year or two.  If the solid state parts are adequately designed they should last forever or at least until the boat takes it's next lightning strike.  With a pump that is advertised to be able to run dry, it should last a long time, like at least five or ten years.  I bough a quantity of these pumps two years ago because I thought they were so neat.  Now I use them when nothing else will do, like sticking them in a narrow, deep bilge when I have a backup pump located higher up.

If Rule ever gets the reliability thing worked out I have a modest suggestion:  Ramp up the motor speed to something less than "whine" and then coast down when trying to detect water.  This should work and it would make the pump less annoying to light sleepers.

Now, as to Rule pumps in general.  I like them, I stock them and I use them, although I find the West Marine rebranded house line of pumps to be just as good and less expensive.  Except for the Rule square 800 GPH model, which has more places to leak water than you would think possible.  It snaps apart, which would seem like a good thing to clean the pump or put a new pump on an existing base.  Good luck getting it to pump after reassembly without using a small tube of 5200.

I COMPLETELY do not get the cartridge pump concept in the WM pumps.  You mean to tell me that when this pump fails you will still be making the same thing and I can just swap in another set of guts?  Come on!  You are straining my credulity again.  Or are you telling me this pump fails so quickly I will need a quick way to slap in a replacement?  Or should I just put in a new cartridge every two years just in case?  I still have to wire the damn thing and waterproof the connections.  Loser concept, logic wise.  Probably good marketing because it is a differentiator.  6/13/08


BAD x 3:  As to Rule pump switches, I have had many, many unexplained failures.  Don't work, don't work sometimes, work if actuated slowly, do not work if actuated slowly.  So you are crouching down in the bilge testing this switch, trying to decide if, under normal conditions it will work well enough.  After all, having a boat sink in the slip because of equipment you worked on (so now are partially responsible for) is really big exposure.  NB:  The new, mercury free click-action switch seems to work just fine.

The switch that does not work when you manually pick it up and then push it below water drives me nuts.  You tease the switch up slowly and lower it slowly and it does work.  So you think, how will the water act?  And then you install a reserve pump because you cannot trust anything.   

The list of failures on previous generations of Rule switches is endless, bad, bad, bad.  And the Super Switches seemed even worse.  Ugly, ugly.  Was the mercury in the mercury switches developing an oxide coating or did water migrate in and that is what made the switch selectively unreliable?  

The bilge pump switches (not by Rule, necessarily) with enclosed free floats that rise in a cylinder or around an axle tend to get jammed from contamination.  Most of these now have electronic augmentation so they run after the float is down and so forth.  When the switches seem to take forever to shut off you wonder if the circuit is failing or the float is sticking.  I had this problem with a Rule-Mate 1500 the other day.  This pump has one of the new enclosed circular floats and a Hall effect switch.  Or maybe its a reed switch, I don't know.  As installed by someone else, it would not sit level because of keel bolts.  I bolted a piece of polyethylene on the bottom and then at least it sat level on top of the bolts.  But was the float sticking or not?  Because of the electronic delay I could not tell.  It sure stuck when the pump was at an angle.  The pump would not come on and the bilge was overfilled.  Note that the pump probably worked fine when the plumbers put it in because it was new and everything was slippery.  So what if it didn't sit straight.  Now that the pump is sludged-up it is a problem.  That's what you get for letting a plumber put in your bilge pump.

I decided the float stuck, but not badly.  The boat didn't take on water very quickly so I decided it was ok.  It air locked occasionally because of the check valve the plumbers put in.  I drilled a 3/16 hole in the hose below the check valve and now everything works.

One more gamble with my liability insurance.  By the way, I hope you are getting the underlying message here.  Unless you test the setup for at least ten minutes with water coming into the boat from a fresh water hose or an open seacock you have no idea whether an existing system works or not.  If you see taped splices you know that has to be redone.  But the hydraulics and components can be tricky.  

The second message is that if you pay to have someone like me put in a bilge pump it will be done properly, also that small costs in using the best material are usually swamped out by the labor.  People perfectly capable of installing a bilge pump will still call me to do it because they know I will fully waterproof the splices and use an all-316 hose clamp at the pump so the screw will not preferentially corrode and I will spend at least 10 minutes testing the system to make absolutely certain it works.  I will also use the right size fuse for the pump, which is important but another story.

6/13/08


Bad x 3  (maybe only bad X1 with the improved modelThe SeeWater switch.  I lost at least one customers over this switch.  West marine stopped carrying it a few years ago.  It is recently improved and I will discuss the improvements, but first the original.  This switch originally had a short metal electrode protruding from the bottom of the case in place of that long black thing in the new photo.  You mount the switch vertically and when the water rises high enough to touch the electrode the switch turns on for enough time to allow the pump to empty the bilge.  First, you must mount the switch on something vertical, like a suspended stick.  It looks like you could just screw it to the bottom of the bilge but that is a mistaken assumption.  OK, I like the stick method for retrieving switches from deep bilges.  

The problem arises because the switch depends on comparing the electrical environment at the tip of the sensor to the electrical environment around the lower part of the insulated plastic case.  Surrounded by air, the two environments are identical and the switch stays off.  When the electrode touches water, things are different and the switch comes on.  So far, so good.  If, however, the plastic case is covered by a wet film the switch will stay on even if there is no water at the tip.  Wonderful, a bilge pump switch that has a tendency to stick "on."  Couple that with an external noisy bilge pump and you do not have a happy customer.  How does the bottom of the case get wet?  It's a boat.  Water sloshes around.

If you have a clean, well-behaved bilge, fine.  Or if it's only an oily, watery bilge, fine.  If you have a dirty bilge, or, horrors, a bilge with some soap residue in it or red bacterial crud and the switch should get partially submerged and coated with a conductive film the switch will no longer see any difference between bilge water and it's case or it will see a reverse condition and think it should be on.  It can be really insidious too.  Sometimes works, sometimes not.  The key diagnostic is to reach down in the bilge and wipe off the case with a dry cloth. If the switch starts working you now know that this is not the bilge for that switch.

In their advertisement for the new, improved switch, the manufacturer makes this statement:  "New improved! for use in all areas including soapy water sumps and bilges. Extended sensor allows the switch to be mounted high above the contaminated water. By keeping the switch case clear and clean of soapy salty water insures a trouble free installation."  Notice the almost explicit acknowledgement that coating the case with soapy salty water is a problem.  Well, if your bilge is not soapy and, if so, does not slosh around enough to get the switch case wet you are in luck.

As for me, I've been bitten.  The Mirus devices worked flawlessly before they mysteriously started failing.  I may give the SeeWater another try in very selected circumstances.    Or maybe I can fish one out of my junk pile.  I guess I should try coating the case with silicone grease to make it hydrophobic.  Show me the soap solution that will wet that or wash it off.

Once a bilge switch misbehaves for any reason I tend to throw it in the junk pile.  How do I know it will not misbehave again?

 6/13/08


more to come on pumps and switches.


Ties that Shatter

 "Natural" white nylon cable ties become brittle and fall apart in a matter of months when exposed to the sun.  Black cable ties contain UV inhibitors and stand up quite well under the same circumstances.  Most of the cable ties I use are not exposed to the weather, so ultraviolet resistance really shouldn't be an issue.   But it doesn't make sense to me to stock both black and white ties,  So I just use black ones everywhere.

I buy cable ties by the thousand.  Until recently I bought them over the Web from suppliers who specialize in generic cable ties at pretty good prices.  No longer.  I finally got a really bad batch.  They're black all right, but they certainly aren't ultraviolet resistant as you can see above.

The two intact cable ties at the bottom of the picture are made by Panduit and are advertised specifically as "weather resistant."  They also have a little stainless steel tang that let you get the tie really tight.  I've always had some around to use in demanding applications, like making sure the two halves of a ferrite choke stay tightly together.  As they can be more than twice as expensive as garden-variety ties, I didn't feel that the cost was justified for everyday use.  Now it's clear I can't afford to use anything else.  Not necessarily always Panduit, but name-brand high-quality weather-resistant cable ties.      1/16/07


 

 

 No Wire Nuts on Boats!  

"Wire nuts" are ubiquitous in land-based structure electrical wiring.  They provide a means to quickly and securely splice wires.  These connectors do not perform well in the marine environment.  ABYC Standard E11.16.3.6. states "Twist on connectors, i.e., wire nuts, shall not be used."  This is one of many ways appropriate electrical practices on boats differ from those used on dry land.

A twist-on connector operates by threading a tapered spiral spring over stripped conductors.  The steel threads are harder than the copper conductors and quite sharp.  As it is twisted on to the ends of the wires, this threaded insert digs into the conductors and expands slightly to grip tightly.  Being tapered, a properly sized connector can always be properly finger-tightened on the wires.  Wire-Nut is a trademark of Ideal Industries, although in common usage it's about as specific to twist connectors by Ideal as Kleenex is to facial tissue sheets by Kimberly-Clark.

The photo shows what can happen using wire nuts in a marine application.  The spiral metal insert is usually made from plated steel.  While it's conductive, most of the current is carried by the wires themselves because they are tightly pressed together inside the spiral.  In a moist environment with salt particles in the air, the steel insert can corrode and loosen up slightly.  

Loosening the contact between the wires even slightly can lead to increased resistance in the connection as more of the current is carried by the steel spiral.  If the wires are carrying any appreciable current, the wire nut will heat up.  The splice above not only melted its own insulation, it melted the insulation on adjacent wires.  I would say, looking at the burned connector, that it would take somewhere around 2-5 watts to melt like that.  Maybe as much as 10 watts.  At 10 amps, typical in an AC feeder, the contact resistance would calculate as 20 to 100 milliohms.  Almost a perfect connection.  Not enough to measure without special equipment.

Of course, the splice was also made between different colored wires in the middle of a cable run, which meant it was unexpected and hard to find.  A wire that is bundled with other wires should look the same as it does going into the bundle as when it exits the bundle again.  Making splices in the middle of a cable bundle, and particularly changing colors in the process, only hides a potential failure.  Well supported wires do not fail.  Splices sometimes do.  Tight, neat looking cable bundles mutually reinforce the wires, but they make troubleshooting more challenging.  Often, a cable-tied bundle must be cut open if it's not clear where a wire goes.

So beware, "marine electrician" and "licensed electrician" are not the same trade.  There are plenty of similarities, but the practices and standards that apply to each trade are different for good reason.  Land electricians are usually licensed by the state, which ensures familiarity with standards and practices.  Anyone can call themselves a marine electrician, which makes finding a competent one all the more difficult.                       

   written 7/25/06