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Author Topic:   Three-wire Butt Splice
Frank O posted 06-05-2012 12:59 AM ET (US)   Profile for Frank O   Send Email to Frank O  
I'm currently fixing the wiring for my bilge pump. While most of the wire connectors in the bilge area involve connecting one wire to another with a butt connector, at one point I need to connect three wires together.

The local West Marine carries some three-wire connectors, but these are of the type where three butt-type connectors all join at a central hub consisting of uninsulated metal. These are of the type I've seen where the connector's hub is attached to a metallic surface such as a fuel tank, and multiple wires are connected to it as vessel ground. This wouldn't work for my bilge pump application, since the circuit involved will be hot when the pump is running.

Is there some other connector that would be a good choice for joining three 14- to 16-gauge wires together in an area that can sometimes be wet? For example do step-down butt connectors exist that are 14-16 gauge on one side and 10-12 gauge on the other, thus allowing two wires to be inserted into one side?

L H G posted 06-05-2012 01:05 AM ET (US)     Profile for L H G    
Cole Hersey makes a three wire flat conductor like a trailer connector. I use several of these and they are excellent. I connect all of my bilge pumps this way, so if one goes bad, I can easily un-plug it and install a new one, without all kinds of wiring contortions in the boat. If you can't find a 3 wire connector, buy a flat 4 wire, and clip off the white negative leads on both sides.

There are also heavy duty 3 wire connectors for the electric trolling motor market, but they are heavier than needed for a bilge pump.

Frank O posted 06-05-2012 01:20 AM ET (US)     Profile for Frank O  Send Email to Frank O     
Thanks. When you say it's a three-wire conductor like a trailer connector, are these three separate lines? In other words, a multi-conductor plug? My situation is that I have three wires that I need to join all together to each other.
jimh posted 06-05-2012 07:57 AM ET (US)     Profile for jimh  Send Email to jimh     
I don't think you need a connector, at least not in the sense of a three-pole connector that has a mating connector. To join three wires together as you describe into a single circuit, just remove about 1-inch of insulation from each, twist them together, and solder the wires. Cover with heat-shrink insulating tubing. Then wrap with tape.

I strongly discourage the use of these pre-assembled trailer connectors. If you use a four-pole trailer connector, you will make eight splices in the conductors that attach to them. L H G keeps recommending these, and I keep offering my recommendation against them. On a small boat, where the longest electrical conductor might be 20-feet, there is really no need to make splices in a conductor. There is especially no need to make eight splices in order to use a pre-molded connector that comes with short pig-tail leads.

Most submersible sump pumps come with attached power conductors that are long enough to permit any connection to them to be made well above the sump water level, so there is not a particular need to make an electrical connection that will survive being immersed in sea water.

number9 posted 06-05-2012 09:04 PM ET (US)     Profile for number9  Send Email to number9     
These are some good splices if wire sizing allows. docId=927

Frank O posted 06-05-2012 09:22 PM ET (US)     Profile for Frank O  Send Email to Frank O     
Thanks. There's probably an issue here about terminology because manufacturers use "connector" to describe both plug-type devices and splice-type devices. It sounds like L H G was suggesting something loosely like this:

whereas what I was looking for was something that would splice three wires together like this:

As noted, the problem with the item immediately above is that its hub is uninsulated metal -- it's really designed as a connection point for ground wires. Not so good for a circuit that will be hot.

I gather that jimh is talking about twisting wires together something like this:

then soldering them, covering with heatshrink and wrapping with tape. That would certainly work, though I wondered if there was anything else out there that would seal these connections even more completely.

Then I came across this connector:

I gather this is called a "step-down" butt connector. The left side is sized for a single 14- to 16-gauge wire, and the right side is sized for two such wires. Each side is covered with heatshrink insulation. I bought a pack of 10 on eBay, and will give them a try when they arrive. On the principle of belt and suspenders, after finishing it up I will probably dab on some neoprene cement, then cover with another, larger length of heatshrink tubing to see if this helps keep it from corrosion longer.

Frank O posted 06-05-2012 09:25 PM ET (US)     Profile for Frank O  Send Email to Frank O     
I posted before seeing number9's message. Those look similar to what I just bought, though at first glance they look like they're designed for finer wire sizes.

Jerry Townsend posted 06-05-2012 11:48 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
In my mind - if you can solder it - solder it - and protect it as Jimh suggests. I don't use crimp type connectors - except when I don't have a soldering gun available. And yes - there are crimp connectors in the toolbox.

Another way to look at it - a good soldered connection eliminates something else to fail or cause problems. ---- Jerry/Idaho

Chuck Tribolet posted 06-06-2012 01:03 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The problem with bringing two wires into the same side
of a connector or solder joint is making sure there's enough
glue to fill in the waist of the figure eight. I'd be
thinking maybe using a glue gun to put a little extra in

But I'm wondering why you need to connect three wires in
the bilge area. Most bilge pumps run three wires from the
helm to the pump:

1. Ground
2. If hot, the pump runs, period.
3. If hot, the pump is controlled by the float switch or the
pump electronics (pump shuts off if there's nothing to pump).

The bilge pumps I've seen have three wires (see above).


L H G posted 06-06-2012 02:47 AM ET (US)     Profile for L H G    
I was thinking the way Chuck is describing, since bilge pumps have 3 wires.

But if you need to simply connect three wires together, put a plastic wire nut on the three wire twist, then fill the "cup" with Life Seal caulking, making sure no bare wire is exposed, let cure. I GUARANTEE you it will be TOTALLY waterproof and last the life of the boat and not corrode.
I also put a small snap tie around the three wires about 1" from the wire nut so a wire cannot be pulled out.

I know, I know, it's not "marine kosher", but if the connection will not be seen, it works well. I use these on my trailers and on an UNDERWATER bilge pump switch connection I had to make while on a trip 10 years ago, and I've NEVER had a failure.

I recently used wire nuts to connect the power leads to a Montauk bilge pump installation, which is under the floor sump cover. The white power cable (which wraps around the pump) from the console on-off switch is connected to the pump wires with caulked orange wire nuts, in a totally wet environment. No problems. This makes pump replacement easy and quick. jpg

Now you guys can start telling me it's bad idea, even though you have no experience with this type connection. If you try it, you'll see what I mean.

Phil T posted 06-06-2012 10:50 AM ET (US)     Profile for Phil T  Send Email to Phil T     
I have been through the same search for my bilge pump and float switch wiring. After alot of research (including that Ancor brand 3 wire connector posted above) I did the same as Larry did, a wire nut with sealant. No problems.
Frank O posted 06-06-2012 10:45 PM ET (US)     Profile for Frank O  Send Email to Frank O     
Thanks for the comments, interesting ideas.

To answer Chuck's question, my bilge pump doesn't have an integrated float switch or sensor. It is installed with a separate float switch, and the wiring follows this circuit that jimh includes in his discussion of bilge pumps in the reference section:

The three-way splice is at the point where the pump and float switch are connected to each other and to the brown-black wire running from the helm switch.

In his reference article, incidentally, jimh suggests an alternate wiring to make sure that the float switch receives power even when power to the helm switches is turned off: gif

The only problem with this is that it would involve adding a fourth wire to to run between the console and bilge area (since my batteries are in the console). Starting with the prior diagram, I found I could just take the brown wire off the helm switch and connect it directly to 12v+ on the house battery via an inline fuse. This means, however, that there will still be the three-way splice. I think either jimh's suggestion of twisted wires or the three-way splice I found on eBay would work.

I might note parenthetically that, having owned a soldering iron since age 9 when I put Heathkits together in the 1960s, I'm partial to solder. But I see that Ancor recommends crimp over solder with its connectors. It'd be tough to get solder in there anyway given the insulation jackets. My gut still says soldered connections will hold up better than crimped in a wet bilge, but I suppose I could learn new tricks.

Tom Hemphill posted 06-07-2012 04:58 PM ET (US)     Profile for Tom Hemphill  Send Email to Tom Hemphill     
...having owned a soldering iron since age 9 when I put Heathkits together in the 1960s...

Ha! That pretty much describes me and I suspect many of us on this forum.
jimh posted 06-09-2012 09:47 AM ET (US)     Profile for jimh  Send Email to jimh     
As an adjunct to L H G's recommendation to use household electrical wiring devices like wire nuts to make electrical connections on a boat, it should be mentioned that you can also make effective use of the plastic caps from tubes of tooth paste for this same purpose.
gusgus posted 06-09-2012 10:00 AM ET (US)     Profile for gusgus  Send Email to gusgus     
I looked and looked at those heath kits, but didn't want to even get involved. I still have (somewhere in my stored stuff) an original Heathkit catalog.
The wire nut idea does sound "out there" but I have no issue with their use. I am far [too] [unclear] to be able to do so. I know it might be perfectly water tight, but it just isn't something I could do and feel good about. I am the guy with every single crimped connection sealed with adhesive shrink tubing.
swist posted 06-10-2012 04:09 PM ET (US)     Profile for swist  Send Email to swist     
Don't know if it was this Forum but sometime back there was a discussion about this subject where some knowledgable people claimed that a properly done crimped connection was to be preferred to soldered connections in a marine environment. Something about the soldered connection being more predisposed to corrosion.

Witness the lack of soldered connections in the original wiring of most boats.

I'm not taking a position here. I solder regularly as part of my job and it's hard for me to believe there is a better method for non-stressed connections, but I am certainly no expert on the impact of a marine environment.

Frank O posted 06-10-2012 06:12 PM ET (US)     Profile for Frank O  Send Email to Frank O     
Well, I'm striking out on the crimping front. Possibly I just don't have the gene. I obtained a high-quality Ancor crimper and butt connectors, took them down to the boat this morning and had a go. The crimps were laughably poor. This was after being careful to insert the connectors in the crimper exactly as instructed.

So, I'm going with jimh's soldering suggestion, and will probably throw in Larry's idea on the wire nuts.

I'd like to spend some time working on my crimping skills, but I'd just as soon not pursue this at the marina with my head contorted around the outboard poking down into the sternwell hatch using butt connectors that cost a dollar fifty each.

swist posted 06-10-2012 07:15 PM ET (US)     Profile for swist  Send Email to swist     
Yeah, I hear you. I too have an expensive crimper and the first few times I used it, all seemed to go as instructed. Then in tie-wrapping the resultant bundles, some of the crimp conductors pulled out of their terminals like they weren't there!

I've had more success with practice, same as soldering I suppose.

I note with interest that my #2 AWG battery cables come crimped to their connectors, and it looks like only the upcoming apocalypse could pull them apart.

Chuck Tribolet posted 06-10-2012 08:37 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
NASA uses crimps because it's easier to teach crimping than
soldering. But they also use soldering. I went to collage
with a guy who had spend a summer at some aerospace company
doing soldering. He built a Heathkit. DAMN, those solder
joints looked good.

I'll use solder and Ancor hot-melt-glue heat shrink unless
there's no other choice.


gusgus posted 06-12-2012 01:16 PM ET (US)     Profile for gusgus  Send Email to gusgus     
All the connectors on Boeing are crimped.
As taught many years ago, after all crimps are completed, the connection demands a good hard pull test, then heat shrink is applied.

Will solder be a better connection? I am not so sure. Both make excellent connections, but crimps can't melt (as easily) when heated.

swist posted 06-12-2012 03:51 PM ET (US)     Profile for swist  Send Email to swist     
I think my solder connections look good too, but as I said, I do it professionally. I've seen some pretty unbelievably bad soldering in many places.

And I'm sure there are experienced crimpers who would laugh at mine.

I'm not of the mind that one is easier than the other, anything done well requires skills.

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