how to splice underground power cable

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Old 09-07-16, 09:01 AM
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how to splice underground power cable

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Size:  29.7 KBI have 220 volt 4 wire AWG10 underground cable supplying power to my detached garage. It was buried in a 1 inch pvc pipe about 25 years ago. It was buried under an asphalt driveway and below the concrete floor in the garage. The driveway has been dug up and the power cable and pvc to the garage has been cut in two places. If you can visualize the middle 2/3 of the total run has been removed. The pvc and cable under the garage floor is still intact but it is cut just after coming out from under the concrete pad. Then the pvc and cable were removed for about 40 feet. The cable and pvc from the power panel is intact for about ten feet.

I need to replace the middle section of the cable and pvc because we cannot easily pull a new cable through the two end pieces of pvc. The cable inside the pvc is a wide flat underground rather than the normal four separate wires. This is why it cannot be pulled out of the pvc and new separate cables run. Can this cable be spliced? The splices will have to be then buried underground.

I visualize using butt connectors and waterproof heat shrink or whatever. Hopefully these can be put into some sort of pvc box that butts or connects to the pvc pipe so the entire run is again encased in pvc.

Is this doable???? I realize that if the butt connections later fail they will be buried under a paved driveway making an expensive proposition to repair.

Any advice or suggestions would be much appreciated.

I can add photos if necessary.
 

Last edited by jeweler; 09-07-16 at 09:53 AM.
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Old 09-07-16, 09:54 AM
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The first one is the cable where it enters the ground from the electric panel. The last is the cable coming out from under the garage floor.

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Last edited by PJmax; 09-07-16 at 10:44 AM. Reason: reoriented picture
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Old 09-07-16, 10:43 AM
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You can buy direct burial UF cable splice kits:

https://www.amazon.com/Gardner-HST-1...f+cable+splice

And there are similar waterproof splice kits for individual wires. There would be nothing wrong with then sleeving them with PVC conduit; however they are large diameter and would require at least 1" conduit. But that's the smallest size I would run under a driveway anyway.

I would certainly try to avoid burying a splice of any type under a driveway, even if it means some more digging so you can place the splice somewhere else.
 
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Old 09-07-16, 11:36 AM
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splices anywhere are iffy

I already have two of the exact splice kits you linked. I can put one splice before the wall or drive way where it can be accessed with a minimum of digging. But one will need to be right where the garage apron ends and the driveway asphalt begins. That is the point shown in the up side down photo. I will just mark it in photos and measurements, then hope if never fails.

My concern is when they pulled up the pvc and cable there was water inside the pvc. The cable outer sheathing was intact so the cable was good. But what about the splice? I understand the splice kit is for underground use. However, if it is encased in pvc and gets wet it will stay wet. That is an invitation for problems.

Can't pull the cable out of the pvc under the garage without busting out the concrete floor. I would rather do the splice under the driveway. It will be easier and cheaper to access if it fails than to bust up the garage floor and do it correctly now. Plus, it may never fail. Then I saved a whole lot of work and money.
 
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Old 09-07-16, 11:57 AM
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There is always water in underground PVC pipe. When you make your splices.... they will be outside of any protection. Putting the splices inside a box attached to the existing conduit is just asking for water trouble.

You said you can't pull the UF out of the conduit because it's flat. That doesn't make much sense. Is the end of the PVC exposed in the garage or do you have UF coming out of cement and you can't see the end of the pipe ?

I'd consider splices a last resort.
 

Last edited by PJmax; 09-07-16 at 12:42 PM. Reason: typo
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Old 09-07-16, 12:16 PM
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I was told that the flat cable is iffy as to whether it can be pulled because It is wide and not very flexible. If I. Try to pull it and the pvc pulls apart or bends or breaks under the slab then I am in trouble.

I would have to pull it about 25 feet and then a 90 bend and another couple feet. You think it will pull?
 
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Old 09-07-16, 12:24 PM
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The cable terminates in the garage just a few inches above the floor. It comes out of the floor in conduit but I can't say how the conduit connects to the plastic PVC underneath the floor. I did that project 25 years ago and just do not recall the specifics. I assume the conduit connects to the PV properly because that was done by an electrician. But I don't know for sure.

What do you suggest?
 
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Old 09-07-16, 12:38 PM
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I'd try to inject a quart of slurry of water and dish soap through the pipe with an air compressor or shop vac in blow mode. Then apply some significant pressure to see if you can get the cable moving. Assuming you're able to pull it out, flush the pipe with water, then fish a nylon rope back through with a steel tape and pull a rag through a couple times to swab the pipe clean. After that you can patch in new PVC and pull fresh individual conductors into the clean conduit.
 
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Old 09-07-16, 12:45 PM
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Since you have approx 25' to the sweep and then several feet above it...... you should pull the wire out from the long end. Better to pull a few feet of wire thru the sweep than 25'.

You could also pour a bottle of soap down the pipe in the garage. Add water slowly until it comes out the underground end.

The sweep is where all the friction will be.
 
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Old 09-07-16, 01:07 PM
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Good ideas. I may try pulling it out after all.

I just had an idea. The old cable went under the asphalt paved driveway and then under the retaining wall, then underground to the wall of the house and up the side of the house to the panel. Instead of using the same route under the driveway I can instead turn the cable 90 degrees after it comes out from under the garage slab and then go through the vertical retaining wall then turn 90 degrees again and go down the outside of the wall and along the base or foundation of the new retaining wall. This way the longest part of the run (about 40 feet) will not be buried under the drive. If I do this the cable will not be able to be buried more than 6 inches. Easy to access if ever necessary. Can this be safely done? It will still be in the pvc, just not very deep. Can't bury it deeper because of solid rock beneath. I am in the Rockies at 8500 feet and it is mostly solid granite everywhere.

Which is the better place to run the line?
 
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Old 09-07-16, 01:10 PM
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Under the driveway in PVC is the better route due to cover requirements. No additional depth is required when the pipe is covered with 4" of concrete. If covered only with soil, burial depth is 18". You can only go less than 18" if you use threaded rigid steel conduit.
 
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Old 09-07-16, 01:27 PM
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I use the 3M Scotchcast kits to splice UF .

3M Scotchcast Resin/Splice Kits - Ocean Innovations
 
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Old 09-07-16, 01:39 PM
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Humbug

I was hoping to make it easier by putting it outside the wall. No way I can go the required depth.
 
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Old 09-07-16, 04:54 PM
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Success

I took your advice and squirted soapy water in the pvc and the wire pulled pretty easily. Both pieces at each end are out. Now I can run separate 10 AWG wires the full length. All I have to do is run new 1 inch pvc where it was removed and put a rope inside to pull the wires. Much better.

Is that the best way to do it?

Thanks for your help.
 
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Old 09-07-16, 06:37 PM
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Individual conductors will be much easier to pull than a cable.
 
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Old 09-08-16, 07:24 AM
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pulling wires

Do I pull all four wires at one time? I assume you just tie the four together at the end then tie and tape them to the pull rope? Any more to it than that? My total run is 78 feet with 3 or 4 elbows 90 degree.
 
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Old 09-08-16, 07:57 AM
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Just to be safe, I pull one wire and use that to pull the four wires. Takes extra wire but I don't have to worry about breaking. Overlap the pull wire with the others about two feet. Wrap with tape for about a foot, then fold the extra pull wire back over the tape and tape again. Wrap the leading edge of the bundle with another wrap of tape to create as smooth a leading edge as possible so you don't get hung up on seams and corners while pulling. And just to be safe, you may want to use a little cable pulling lube. It's messy but does help things slide along.

Good luck!
 
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Old 09-08-16, 08:50 AM
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Four #10 conductors will pull very easy in a 1" conduit. You shouldn't have too much trouble with this. Fold the wires over about 6" to make a "hook" around your pulling leader. Tape it up pretty good and use some cable lube. Have a helper available to make sure the wires don't kink and feed in to the pipe smoothly.
 
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