Potting epoxy for bilge pump connections

[capn_billl]

I have a box of the solder connectors, but rarely use them.

Regular crimp on connectors with a spot of NoAlox, works fine.

The connections outlast the pump.

[JAFO]

Originally Posted by Bycrick

I can never find the "satire" font when I need it.

At another forum where I'm an admin, we solved a similar problem by adopting the convention that anything written in purple text was sarcasm. That solved a whole lot of misunderstandings and arguments literally overnight.

[ssMakai]

In the mining industry we used a simple 2 pot epoxy joint for instrumentation. I used this to 1200m water head. Stagger strip the wires and intertwine each pair so no short can occur. Run a short length of plastic pipe or metal tube for 30-40mm each side of the staggers. Place upright and seal the bottom. Fill with epoxy. The wires will wick the glue up and down by capillary. The disadvantage is you will have a stiff joint about 100mm (4") long. Cheap and easy to do and effective.

[MBWhite]

I can recommend 3 different products depending on the application. the first is the ubiquitous heat shrink with hot glue on the inside. When I worked as a marine technician on Lake Michigan we had a 3M product, don't remember the name just that it was sold by the inch at that time! Used with just an uninsulated butt splice but was quick and trouble free. Now if a person is concerned about absolute waterproofing the bees knees is this stuff called Scotchkote, now they have a Scotchkote FD (fast drying), either product is awesome for stuff either underwater or buried underground. Works great for sealing Antenna connections also. The trick is that whatever you use it for, if you think you might ever have to take it apart wrap it with electrical tape first then coat it. If you need to disassemble then just carefully cut the tape and peel it off. Back then for junction blocks we sprayed them with "Boeshield" but nowadays for my own stuff I want to stay clean and corrosion free I use an automotive product called "Tite Seal" that's actually made for sealing ignition systems. Sprays on and penetrates a little then hardens up into a firm plastic coating but easily removes screws and nuts. You get that at automotive stores like NAPA. To me the main thing is to just use quality materials, for electric tape I like Scotch "Super 33" electrical tape, you can buy a tube or 2 of the chinese tapes for what one roll costs but it is well worth the price to make a durable connection.

[RaymondR]

Originally Posted by ssMakai

In the mining industry we used a simple 2 pot epoxy joint for instrumentation. I used this to 1200m water head. Stagger strip the wires and intertwine each pair so no short can occur. Run a short length of plastic pipe or metal tube for 30-40mm each side of the staggers. Place upright and seal the bottom. Fill with epoxy. The wires will wick the glue up and down by capillary. The disadvantage is you will have a stiff joint about 100mm (4") long. Cheap and easy to do and effective.

Some decades ago I was responsible for the management of a drill rig which had a number of submersible pumps set about 40' deep in the ocean and used to pump seawater cooling water">engine cooling water.

The pumps came from the manufacturer complete with cable however out maintenance crew used to cut the cables to allow less expensive air freight back to the manufacturer for overhaul.

One of the things I noticed was that the overhauled pumps never lasted anywhere near the new pumps and that they were usually removed from service because of low resistance readings between the conductors.

When the manufacturer was contacted they informrd us that the returned pumps appeared to have salt water contamination of the mineral free water the electric motors were filled with.

We found that because the epoxy in the splicing kits set rigid, the pressure on the cable caused it to shrink away from the rigid epoxy allowing the sea water to enter the cable and gradually work it's way down into the motors.

We changed away from the rigid epoxy filled splicing kits to heat shrink and an elastomer type sealant which never set rigid and never had the problem again.

[NBs]

Hi,

This is easy and work fine. Starbrite liquid electrical tape

https://starbrite.fi/tuote/nestemainen-sahkoteippi-30g/

Nbs

[SailingVeracity]

If you want to go really over-the-top use:
https://www.divecommercial.com/produ...1-up-to-2-awg/
We use these to seal connectors on deep ocean science gear to 6,000 meters with no leakage!

[team karst]

I think the original concern is folly. If one breaks open a failed pump and looks at the winding wire gauge, one will see magnet wire suspiciously small.

[sailingharry]

Originally Posted by Bycrick

My point was that the short (3’) pigtail of #14-16 wire didn’t have much overall effect on the total voltage drop.

The problem here is that OP is 100% correct. That short pigtail is much more important than you are giving it credit for. A typical 3 ft pigtail, or 6 ft of #16 wire, at 15 amps results in a 6% voltage drop right there. Add to that the voltage drop for the run to the batteries and it becomes almost impossible to stay within the recommended 10%. 3% is gone before you start. Even if the mfgr used #14, the pigtail alone is 3.5% drop.

[Bycrick]

We’re both right. The 3’ pigtail is too small if you want to make the longer supply run with smaller wire. You’ve used up a fair percentage of the overall "desirable" voltage drop in the pigtail. But, IMHO, it’s a "better" overall design to make the supply wiring bigger, thus allowing more voltage drop at the load end of the circuit, than trying to design for the end-to-end voltage drop.

Using my somewhat more convenient wire sizing program, a 3-foot pigtail of #18 wire drops 5% at 15 amps. A #14 pigtail is 2%. So I think that making the longer run bigger is far more important than worrying about the drop in the pigtail itself.

[Spot]

Short of convincing pump manufacturers to use thicker wires...
Would a good compromise be:
1. pig-tailing the pump about a foot (30cm)
2. using the proper step down crimps so that the (for example) 16 AWG (1.3mm^2 cross section) pump leads are ran up to something like 12 AWG (3.3mm^2 cross section).
3. after making the crimps cover with heat shrink tubing. If you are clever you add this before you crimp then slide in place then 'shrink'...
4. Run the new 12 AWG wires up to a terminal block above the waterline
5. Have a back-up pump wired the same way laying in wait

I have ordered the step-down butt crimps from Waytek, sized for hooking 20 AWG tailed LED's into 14 AWG existing wiring in my RV. Also handy for any other undersized leads like compass illumination, etc.

[team karst]

Rule 2k gph @12v = 8.3 A

[sailingharry]

Originally Posted by Bycrick

Using my somewhat more convenient wire sizing program, a 3-foot pigtail of #18 wire drops 5% at 15 amps. A #14 pigtail is 2%. So I think that making the longer run bigger is far more important than worrying about the drop in the pigtail itself.

The whole voltage drop calculations is always confusing. The calculators don't make their assumptions crystal clear. I *think* that most require you to double the length -- so a 3 foot pigtail is 6 feet of wire. The calculator I use (genuinedealz.com) has about double the drop you have.



Team Karst -- indeed, the 15A is a big pump. The decently sized (and fairly common) 2K is half the current of 4K pump, so half the drop -- getting the standard #16 pigtail down to 3% voltage drop, which gets you to the ABYC maximum before you start toward the batteries.

[Bycrick]

Yes, when using a wire size program, one needs to know what data to input. The one I used has a separate input field for the length the two wires. I won’t make any claims for its' accuracy otherwise. For me, when sizing a wire, the rules are "bigger is better" rather than "how small can I make it." Thus, I’ve never taken the time to actually verify the computations. In those rare cases that the number is really important, I usually go back to the reference books and figure it from scratch. After 40 years in computers, I’m not likely to feel comfortable trusting my life to somebody else's unverified algorithm. And yes, that attitude leaves me feeling skeptical in today's world.

[Cyrus Safdari]

Originally Posted by Bycrick

"Trying to use a standard butt connector to join #14-16 on one side to #10-12 on the other is going to result in some poor compromises.

This is another reason why waterproof junction boxes are textbook standard for bilge pump connections.