Bilge pump electricity

drynoc · #1 (**permalink**) 08-27-2007

I have a small 12V bilge pump which has recently quit working. Testing with a multimeter and a marina mate suggest that the pump is fine but that there is a ground or some other problem in the wiring. The pump came with 16 awg wire, and I had to add about about 20 feet more of 16 awg wire to reach the distribution panel. I have to believe that that is too long a run for that pump, and that the wire must have burned up. The only possible solution that I can think of is to enlarge the wire to 14awg. But is it safe to have 14 awg wire running from the distribution panel and connecting to the 16 awg wire on the pump? There is only about 1 foot of 16 awg wire on the pump.

Any suggestions on the problem and possible solutions would be welcome.

k1vsk · #2 (**permalink**) 08-27-2007

wire doesn't "burn up", at least not uneventfully. If your test included removing the pump for testing to ensure it is running, then the only other possible problem would be a connection. The voltage drop along 20 ft of 16 g wire is insufficient to prevent the pump from running and any improvement using 14 g wire would be marginal and would be lost in the additional splice you'd need to make.

Gary M · #3 (**permalink**) 08-27-2007

K1vsk is correct 16 awg should be big enough for a bilge pump.

14 awg wire is typically rated for 15 amps, I cannot quickly find the rating for 16 awg but you can assume it will be at least 10 amps so that should be plenty.
If your pump runs when connected up to 12 volts then you do have a connection of damaged wire problem but you should not need to upgrade to heavier wire.

Gary

drynoc · #4 (**permalink**) 08-27-2007

Thanks for the replies. That is exactly the kind of help I was looking for. The pump causes the 15 amp circuit breaker it is attached to to trip, but the tester didn't reveal any heavy resistance across the pump. That lead me to believe that the wire is the problem, but other than the splice connection to the pump it is a straight run to the distribution panel so it is hard to figure what could have happened to the wire unless too much resistance built up somewhere.

sailingdog · #5 (**permalink**) 08-27-2007

Actually, it really depends on the size of the bilge pump and the length of the wiring run. For a wiring run of 20' one-way, if the pump draws more than five or six amps, it will probably have some issues. With a 10 amp draw, you have over a 1 volt drop in voltage with 16 gauge wire.

Also, if the 15 Amp breaker is tripping, then something else is going on. If the wire were corroded or any of the connections were corroded, it would draw less electricity rather than more, since the resistance would go UP, not DOWN. It is drawing significantly more electricity, since it is tripping the breaker... so there is likely a short somewhere in the wiring.

k1vsk · #6 (**permalink**) 08-27-2007

Quote:

Originally Posted by drynoc

Thanks for the replies. That is exactly the kind of help I was looking for. The pump causes the 15 amp circuit breaker it is attached to to trip, but the tester didn't reveal any heavy resistance across the pump. That lead me to believe that the wire is the problem, but other than the splice connection to the pump it is a straight run to the distribution panel so it is hard to figure what could have happened to the wire unless too much resistance built up somewhere.

That's a different problem than what I had assumed. Doesn't sound like it has anything to do with the wiring. Tripping the breaker such as you described is more symptomatic of a pump problem which can't be determined simply by doing a resistance check across the pump leads.
A nominal sized bilge pump won't draw anywhere near 15 amps unless something is wrong with it, regardless of the wiring type, size or condition.

IT almost sounds like it's simply clogged

Gary M · #7 (**permalink**) 08-27-2007

Did you try hooking the pump up to a power source directly ? A short run of wire right from the panel would do. If it runs OK then you have a wiring problem, if it does not then you need a new pump.

What is it and how big ?

Gary

drynoc · #8 (**permalink**) 08-27-2007

I'm sorry that the bilge pump went out, but I'm learning a lot. There's probably something wrong with that.

It was 101 degrees on Saturday, and hotter than that inside the boat, so I apparently didn't do a thorough job of fault finding. I cut the lines leading to the pump and attached the multimeter to the pump with the aforementioned results. Then I attached the two wires leading to the distribution panel to the multimeter, and got a spark and a little smoke from the negative wire. I didn't think about the pump being clogged because it is not automatic, and since I am always there to run it, I know that it has not sucked up something that it cannot handle. Of course, that does not prove that something hasn't accumulated inside of it over the course of the last year. I'm not clear what might have happened to the negative wire, if it didn't burn up, since it is an uninterrupted run to the distribution panel.

I don't know the name or type of the pump. I don't have any of the documentation here with me. I bought it at Harbor Freight Tools for about $25, knowing that if it didn't work out I didn't lose much. It paid for itself the first few times I used it, so I'm not complaining.

I have a difficult time following instructions on how to use a multimeter. I'm never clear on where I should do the hookups to get the readings I need, or even which readings I should go for. I have both Don Casey's and Nigel Calder's books, but do you guys have any other recommended reading that I could do on the proper use of a meter?

sailingdog · #9 (**permalink**) 08-27-2007

drynoc-

try reading the user manual located here. while it is for a different meter it has the basics covered.