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Old 28-12-2008, 06:29   #1
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To circuit protect or not

I bet a least one or two shy and retiring types here just might have an opinion that they would be willing to share on this subject. How bout it?

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All About Bilge Pumps


Those Essential Devices for Keeping Your Boat Off the Bottom

by David Pascoe

<<Contrary to common belief, the pumps themselves rarely fail; its the electrical system from which they operate that is usually the cause of the failure. Because of this, one way to improve reliability is with redundancy, or increasing the number of pumps to decrease the odds of complete loss of pumping ability.>>

<<It would be my guess that well over 50% of all pump failures are caused by water getting at wire connections and causing corrosion and high resistance. People just don't realize that corroded connections cause a power loss that can either cause the pump to burn up, or the wire connections to overheat and terminate all power flow. >>

<<I do not agree with the ABYC standard that bilge pumps must have circuit protection. Far too often, the circuit breaker or fuse is the cause of a boat sinking. If you want to eliminate circuit protection, try to keep the wire run as short as possible. While its not good practice to wire anything direct to the battery, I'd say the lone exception would be bilge pumps. If there's no other practical way, go ahead and do it. This applies to submersible pumps only. These pumps have no history of burning up and starting fires.>>

<<No doubt someone will send me an e-mail saying "How dare you recommend violating the rules," but I am not telling you that you must go to the main panel because with many panels that is nearly impossible to do.>>

--http://www.yachtsurvey.com/bilge_pumps.htm
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Old 28-12-2008, 06:53   #2
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I'll agree with you. My first boat had the bilge pump on the panel. You could just walk up and flip off the pump and leave the boat. Guess what happened? It was and it didn't. The water rose to just below the sole when it was found. Took about 1/2 hour to drain the bilge.

We had a small runabout boat in a slip where the bilge pump had an ON/Auto/Off switch. The switch had been set to off. A bit of water lowered the transom such that the wake on any passing boat sloshed just a little bit more. Two of us walking down the dock saw the boat. We got several dock lines to hold the boat up. Contacting the owner we got some more help and got the boat pumped. When it was all over the bilge pump switch had been in the off position and was in perfect working order.

So two cases of where having the bilge pump set up so it could be turned off resulted in it being turned off. The unthinkable happens. My current boat has no off position but has an on and auto position not wired through the panel.
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Old 28-12-2008, 07:25   #3
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I think corroded connectors are a common cause of bilge pump failure, but this is usually the connectors close to the bilge pump or float switch (why do they use such short wires).
The risk of corroded connectors well above the waterline is much less and I feel the benefits of having a circuit breaker in the system outweigh the risk of electrical failure.
My own yacht has 3 separate 3500 rule bilge pumps wired directly to the 3 separate battery banks battery but with waterproof boxes next to the batteries with appropriate circuit breakers and alarms.
All electrical connections are well above the bilge. they have been soldered followed by 3 coats of plastic seal and 2 layers of glue lined heat shrink tubing.
The bilge is normally completely dry so I lift the float switches ever few months to check the function.
The bilge pumps I use draw 20A and the large cabling needed to reduce voltage drop means the would generate significant heat if they did short circuit without the protection of a circuit breaker.
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Old 28-12-2008, 08:53   #4
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To circuit protect or not - Hmmm

The procedure to install a bilge pump descriped by "Noelex 77" is excellent technique to minimize the corrosion problem and potential external shorts.
If you are wiring the pump direct to the power source, I would also make sure that the pump motor is "impedance protected". This will minimize current draw on a failed motor (mechanically jammed or internally electrically shorted rotor) and avert any danger of fire or battery damage.
This will not however prevent overloads due to pump external shorts. This needs to be addressed by the technique of the wiring installer. Much care should be taken with any unattended direct to battery load connection.
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Old 28-12-2008, 10:18   #5
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Hmmm, it seems like a tough choice, fire or flood...

But I seriously wonder about any boat bigger than a runabout that has a single bilge pump, or two bilge pumps powered off the same circuit.

A couple of comments on things said so far: Circuit protection does NOT always equal a switch on the main electrical panel. Putting bilge pump switches there has always seemed like a bad idea to me. It is way too easy to sweep off one too many switches when leaving the boat. Fortunately, for reliable circuit protection we have an option: a fuse that can't be accidentally shut off.

If the fuse blows, you know that there was an excess current draw, and risk of fire.

My boat has a separate fuse panel wired before the main shutoff switch specifically for those things that should always be on. Smoke and CO detectors, and bilge pumps. There are three bilge pumps, each with its own circuit and each with its own fuse, and each with its own pilot light in the main cabin so a blown fuse can be easily detected.

All the things that are described above are an excellent idea to keep water out of the bilge pump connections. But those things still don't assure there will never be a short circuit. If preventing electrical fires was as simple as good "technique of the wiring installer" we could all save a lot of money on circuit protection.

I have seen four boat fires, all related to electrical problems, three of which I helped put out. They are terrifying and they will kill you. A bilge pump that has been ignored and failed will "only" sink the boat.
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Old 28-12-2008, 10:36   #6
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Good thread. It seems that connections are the weak spot in marine wire. Moisture gets there and wreaks havoc. The connection many not short, but become resistant to the load that it must carry for the device it serves to work properly. This can heat up and cause a fire and not show as a short before it's too late.

So it's best to have clean connections where moisture can do its mischief and it's best to have as few as possible.

Rule has an electronic bilge pump which comes alive every few minutes and if there's no water it shuts off. I am not sure how it works or how reliable it is or why a fuse would be need to protect this "circuit" if it were simply wired to the batts. Of course this relies on the electronics to work properly. And then there is the motor itself. How long can they last? how reliable are they? Here you probably want some decent amount of redundancy.
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Old 28-12-2008, 14:23   #7
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Originally Posted by defjef View Post
Good thread. It seems that connections are the weak spot in marine wire. Moisture gets there and wreaks havoc. The connection many not short, but become resistant to the load that it must carry for the device it serves to work properly. This can heat up and cause a fire and not show as a short before it's too late.

So it's best to have clean connections where moisture can do its mischief and it's best to have as few as possible.
100% correct. If a connection is heating up because of high resistance, no amount of over-amperage protection will prevent the fire.

BUT... just because circuit protection is not perfect at preventing all problems doesn't mean you should skip it. There are many reasons a circuit can short. It might happen because of chafe on the lead wires, or be internal to the motor when it's water seal fails or a housing cracks, or a bearing wears out and the armature rubs against the case, or you drive a screw through the wires you forgot were behind the bulkhead. I know, I know, someone will argue that all of these things are preventable, but accidents happen. You should have circuit protection on your bilge pump circuit just like you should have more than one bilge pump if you have a wet bilge.

If you carry insurance on your boat you might want to check with your underwriter before you install any unfused circuit. I very much doubt they will think it is a good idea.

Quote:
Originally Posted by defjef View Post
Rule has an electronic bilge pump which comes alive every few minutes and if there's no water it shuts off. I am not sure how it works or how reliable it is or why a fuse would be need to protect this "circuit" if it were simply wired to the batts. Of course this relies on the electronics to work properly. And then there is the motor itself. How long can they last? how reliable are they? Here you probably want some decent amount of redundancy.
It makes NO difference what kind of load you have on the circuit, it should be protected. A properly sized fuse or circuit breaker is NOT protecting the motor, it is preventing the wires from starting a fire during a short circuit. Why should these types of pumps be any less likely to suffer a short in their wiring???

Someday for fun and games, take a battery up to a parking lot, and connect a 10 AWG wire from one terminal to the other, and be prepared for INSTANT fireworks as the wire literally vaporizes in a cloud of sparks and acrid smoke. You'll never underestimate the energy available in a short circuit again.

But then again this IS the internet, so you will find someone to tell you the sky is red.

And as an aside, if you live on your boat or just spend the night aboard, this type of bilge pump might just might drive you crazy as you listen to to fire up every few minutes. I had a dock neighbor with one once and I bought him a new float activated pump so I didn't have to listen to his gurgle every 3.5 minutes all night.
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Old 28-12-2008, 14:31   #8
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Has anyone on the forum ever had a problem with a butt splice made with a good (3M or Ancor) connector with the built in adhesive lined shrink tubing? I find it hard to believe they can EVER go bad under normal use. Seems like we should be talking about better wire runs and connections before leaving out the protector...
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Old 28-12-2008, 14:45   #9
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Fuses have been suggested. I think a circuit breaker is worth the extra cost. If the bilge floods and debris jams the pump, a fuse or circuit breaker may trip. This is not the ideal time to try replace a fuse.
Just make sure the breaker can interupt the high current in a short cuicit situation. Some cheap thermal breakers will fry themselves.
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Old 28-12-2008, 17:49   #10
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I go along with the redundant pumps, each on it's own protected circuit.

I also agree that it's dangerous to not protect an electrical circuit. However, fuse or breaker are really owner's choice. Sounds like GreatKetch has a good system on his boat.

As an aside I sailed on a 50+ boat once that had one bilge pump about the size of a windshield washer pump. Well, I guess it was a little bigger but it would not have kept the boat afloat very long with much of a leak. I was quite amazed.
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Old 29-12-2008, 05:56   #11
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DC Overcurrent Protection (Fuses or Breakers)
Excerpted from ABYC Section E-11
AC and DC ELECTRICAL SYSTEMS ON BOATS (Effective 2004 - Now SUPERCEDED)
Goto:
DC Overcurrent Protection (Fuses or Breakers)

Some excerpts fron older ABYC Standards:


Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection within a distance of 7 inches (175mm) of the point at which the conductor is connected to the source of power measured along the conductor (excepting cranking motor conductors).

E-9.12.1 Motors or Motor Operated Equipment - Motors and motor operated equipment, except for engine cranking motors, shall be protected internally at the equipment, or by branch circuit overcurrent protection devices suitable for motor current. The protection provided shall preclude a fire hazard if the circuit, as installed, is energized for seven hours under any conditions of overload, including locked rotor.

E-9.12.3.1 Each ungrounded conductor of a branch circuit shall be provided with overcurrent protection at the point of connection to the main switchboard unless the main circuit breaker or fuse provides such protection.

E-9.12.7 Integral Overcurrent Protection Devices - Integral overcurrent protection devices without a manual reset may be used as an integral part of an electrical device provided the rest of the circuit is protected by a trip-free circuit protection device(s) or a fuse(s).

Unfortunately, I'm not aware of any commercially available Bilge Pump. whose motor has thermal overloads, or impedance protection. I'd be very pleased to hear from anyone who knows of one.

See also:
A Guide to Understanding: Short-Circuit Protection Devices, Overload Protection Devices, and Coordinated Protection
http://literature.rockwellautomation...r001_-en-p.pdf
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Old 29-12-2008, 06:14   #12
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I agree that the protection is necessary and quality butt splices are one choice of a necessary evil. I have had very good luck on my powerboat (sorry) with soldering the connections and then filling a piece of heat shrink tubing with silicone and then heating with a heat gun. As the heat shrink shrinks(?) the silicone will actually squish out the tubing and make a watertight bond between the tubing and the wire insulation. I've been boating since about 1970 and have never had a failure in this type of repair. Of course this is just an internet opinion and subject to much ridicule.
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Old 29-12-2008, 07:42   #13
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If the boat sinks due to a blown fuse I have to go swimmin.
If the boat sinks because of fire I have to go swimmin.
Seems a protected circuit cuts my chance of swimmin by more than half if one figures in a manuel bilge pump.
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Old 29-12-2008, 08:47   #14
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Maybe I just have bad luck when it comes to bilge pumps but I've had them fail for a whole lot of reasons.

That's why I now go with a 3 pump setup. Two large pumps are set on a shelf 3" above the bottom of the sump with separate float switches, separate fused circuits, and no "on/of/auto" switch. Each of these pumps also has a loud alarm. Once a year I pump water into the bilge to make sure they still work. The 3rd pump is a $20 tiny rule pump that will pump the sump down to 1/4" set in the bottom of the sump. I even used some epoxy filler to slope the bottom of the sump to a little well where this pump sits. It has on a on/auto/off switch but no alarm.

I carefully secure any splices well above the bilge water level. To protect the wire from nicks, I also put a piece of shrink wrap over the whole piece of wire that might stay wet. Electrical leakage from a submerged bilge pump wire is one of the easiest ways to get really nasty dc stray current corrosion.

My favorite splice technique is to thread two pieces of adhesive shrink wrap on before making the crimp. First a 3" piece is put over the connector. Then a 6" piece is put over the 3" piece.

Carl
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Old 29-12-2008, 14:16   #15
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The thing that really shocks me is how many bilge pumps use non-tinned wire for their wire tails!
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