UNDERGROUND splicing of wires
we have a project that involved repairing underground wire splices for HOA area lighting and I need to get current on Best Practices (aside from replacing all the feeders with CU).
A lot of this is aluminum feeder to copper up to the fixture. (Yes, I know. I have NO-OX.)
Some splices are the classic layers of tape. Some use the new “waterproof” wire nuts.
??? What is the current Best Practice on this? I have not done this since the mid 90s.
??? Any hints on opening an above ground transformer enclosure to check a bad feeder? (Like: don’t or Use this tool)
The ToolBear
“Never met a man who couldn’t teach me something.” Anon.
Replies
3M makes a splicing kit just for this...
spendy but about bullet proof...
GB has one too...
the 3M you can get at the supply house abd IIRC the GB at the big box...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
This is from 4LORN more than a year ago. I used his method to a T, and so far so good:
First the obvious: These splice kits are for buried cables only. There is a similar kit that does individual conductors for direct burial or use in wells. Neither of these is suitable for wiring in a structure. When properly used and protected by a well casing or two feet of dirt there is little danger of causing a fire if these units fail. I have seen them used in place of a junction box by people who don't know any better. Misused and forgotten in a wall these units could represent a significant fire risk. They are not an alternative to installing an accessible box and proper connections.
I use these units quite a bit, a couple of times a year, and keep two or three kits on my truck. Given a choice I like the ones with an inner heat-shrink sleeve that doubles the amount of plastic between the bulky splice adapter and the dirt. If I get one without a inner sleeve I wrap the core tightly with several layers of tape before shrinking on the outer sleeve.
The reason being that the plastic core that hold the brass splice tubes commonly has projections and points that can eat their way through the sleeve from the inside. Particularly if the splice is surrounded by rocks or roots. I have seen them fail due to this.
Tips:
A silly but common mistake is to forget to slip the sleeve/s over the cable before making the connections. Makes you undo everything to get the sleeves in place.
Don't strip the cable jacket too far back. You only need enough separate wire to get lined up with and into the brass sleeves. The longer the jacketed run under the heat shrink sleeve the better the seal is likely to be.
Don't strip the wires too far back. Just enough to have bare conductor in the brass sleeves is right. Insulation up to but not in the sleeves is perfect.
Check the set screws in the core before messing with the cable. Sometimes one or more will bind up. Easy enough to fix while standing at the truck it can be a pain when you are standing on your head in the rain. Often a drop of WD40 will get it working properly. This is also important because you tighten these tiny set screws by feel. A bound up set screw feels like a properly tightened one but leaves a loose connection likely to overheat and fail.
Do not get carried away tightening up the set screws. They are tiny, usually 8-32 I think, and threaded into a thin brass tube. If you horse them down they will strip. So tight enough but no more. Judgment and experience is the key. The set screw should dimple the copper conductor but no more. If you plan on doing a few of these experiment at the truck in good weather. Many times you will only need three connections on a four connection kit so go ahead and strip one out so you know how far to go. Once you mess up one sleeve remove the brass tube and save it and the set screws for spares. I do this with helpers.
Double check the phasing, order of wires, before messing with the sleeves. You can often correct this problem without reopening the splice by moving connections at either end but why get into it.
Bring a piece of cardboard, an old doormat or other material to keep the splice up out of the dirt while you work your magic. Dirt in the splice can cause the sleeves to leak and the connection to fail. This also helps keep your hands, boots and tools out of the mud. It also helps if a set screw falls out as they are tiny and easily lost in the dirt.
If the wind is blowing, I always seem to get these repairs when it is raining, a piece of plywood or similar can keep the wind off and make using a torch much easier. In heavy rain I have been known to throw the 8' by 12' tarp I carry on my truck over the hole and work underneath it. It also helps with nosey HOs.
Use a marker, keel or even a piece of tape to mark the planned location of the end of the heat shrink. Without a reference mark it is easy to get the sleeve too far to one end and barely making a seal on the other.
Dry the cables off before applying the heat shrink. A clean cloth and a bit of torch work gets it there. Clean dry surfaces make a better seal with the hot melt compound.
I have used an electric heat gun and even once, when caught without any other heat source, set a small fire in the bottom of the trench to provide heat for the splice. Both worked. The gun a bit better than the fire but given a choice a propane torch, preferably one with push button ignition, is what I use to form the heat-shrink.
When heating the sleeve work around the plastic core first to keep the sleeve from sliding. Once it looks like a bow tie work out toward the ends alternating between ends and flipping the joint over to get the back. Properly done there should be a nice bead of hot glue all the way around the cable at the ends.
Resist the urge to touch the glue. It is hot, sticky, holds heat for a very long time and causes painful burns. Napalm has nothing on this stuff.
Expect to use two kits. Typically the cable run is to a well or out building and was run too shallow. Roto-tilling, post hole digging or trenching in pipes or cables cuts the cable. Sometimes it will fail months or years later but usually, unless the break is near the end there is not enough slack to make a splice so you need to add a length of cable and two splice kits.
Don't forget to check the cables before trying to splice them. Just because you find a place where the cable is broken don't assume it is the only spot. I once got a call where a man had aerated his lawn and found his garage lights didn't work. We spliced the line only to find out that the garage still had no power. The cable was cut in four places and damaged in at least six. It had been buried only two or tree inches deep. We pulled the shredded cable up, it came up quite easily through the sod, and dug in a new one at a more appropriate depth. With multiple breaks it is often better to replace the run.
All this makes it sound complicated. There are lots of details but most are common sense once you get into it. Maybe these tips will save someone having to learn them the hard way like I did. Not that I didn't have fun screwing up just about every way possible. So it goes.
Folks,Thanks for the input. Heat shrink might be the ticket. I see that West Mariner offers adhesive heat shrink tubing for the same thing. I will make a printout of the data for the boss.The blacktop people buried one of my repairs today - a gate sensor loop - using big box weatherproof wire nuts with ?silicone? inside. Stuck the nuts inside 1" PVC couplings in craters chiseled in the asphalt. At least there is some mechanical protection to the poor things.The ToolBear
"Never met a man who couldn't teach me something." Anon.