# under ground heat shrink



## gpop (May 14, 2018)

On thhn when making a underground connection in a pull box how do you deal with the clear sacrificial jacket before heat shrinking?


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## MDShunk (Jan 7, 2007)

I never worried about it. 

In fact, I've heat-shrunk very little in UG pull boxes . If it was too big for wire nuts it got Polaris bugs. 

I reserved heat shrink for crimped UG butt splices in things like direct burial URD.


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## trentonmakes (Mar 21, 2017)

Im with Shunk on this 1....always wire nutted in pullboxes.

I just did a UF splice friday with a barrel lug and heat shrink. It was part of a UF splice kit.

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## splatz (May 23, 2015)

I'd say leave it on unless the instructions said to remove it, which I doubt. The adhesive lining in the heat shrink is probably made to bond to the nylon. Adhesives for plastics are funny, they bond great to the kind of plastic they are made for but not other types.


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## gpop (May 14, 2018)

Sry guys i should have said larger cables #4 or larger. 

Normally these are crimped with barrel connectors then covered with 3m glued heat shrink. The problem i see is after many years (probably 20 years plus) the clear separates from the cable so if the heat shrink is glued to the clear coat then technically there is a gap between that and the cable for moisture to penetrate. Anything underground in florida has a chance to be underwater during a hurricane so the joints need to be watertight and remain that way.


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## trentonmakes (Mar 21, 2017)

Wouldnt rubber tape work? Maybe heat shrink over that?

Im thinking overhead service drops...not under water but they are exposed to the elements.

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## 460 Delta (May 9, 2018)

Right or wrong I use 130c rubber tape nice and tight and then cover it well with clear pvc cement, just dob it on and smear it on evenly. This is how I do splices on wires to our submersible well pumps. It hasn’t failed me yet.


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## telsa (May 22, 2015)

Polaris, ILSCO, torqued, for the big stuff. A touch of Scotch Kote if there are any gaps.

However, I'll usually do hand stands before designing in a field splice for my feeders.

Such splices are driven by events outside my control.


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## matt1124 (Aug 23, 2011)

I like that you call it sacrifial. Some will argue until they are blue in the face, others “good, it did its job” when it’s skinned off. 

I think I read somewhere it *is* part of an oil rating in some cases. I was taught it was sacrificial, found tech data backing that, and passed it on that way to apprentices. 

In this case, I’d caferully remove it and heat shrink. It always cracks off, underground or in the sun.


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## matt1124 (Aug 23, 2011)

MDShunk said:


> I never worried about it.
> 
> In fact, I've heat-shrunk very little in UG pull boxes . If it was too big for wire nuts it got Polaris bugs.
> 
> I reserved heat shrink for crimped UG butt splices in things like direct burial URD.


Do you bury the splice?


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## MDShunk (Jan 7, 2007)

matt1124 said:


> Do you bury the splice?


What splice?


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## gpop (May 14, 2018)

matt1124 said:


> I like that you call it sacrifial. Some will argue until they are blue in the face, others “good, it did its job” when it’s skinned off.
> 
> I think I read somewhere it *is* part of an oil rating in some cases. I was taught it was sacrificial, found tech data backing that, and passed it on that way to apprentices.
> 
> In this case, I’d caferully remove it and heat shrink. It always cracks off, underground or in the sun.



I hope its sacrificial as i just pulled some 500mcm copper with a colored jacket not to long ago and i swear you could peel the clear with your finger nail. the clear seem to stick to better to black cable for some reason. 

One of the reason i ask is with no lubrication required cable the clear really doesn't like to come off but will bubble when its heated so i was hoping someone had a trick in how to deal with it.


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## Wiresmith (Feb 9, 2013)

i remove the nylon where the heat shrink goes, it often has some breaks in it from the install originally. doesn't take long. southwire no-lube thhn will come off with knife easy once you get it started


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