Conductor insulation repair?

[fastline]

During an inspection, it was discovered that an area of insulation approx 3" long of a 4/0 Copper conductor is damaged inside a pull box, likely from the original pull years ago. How it was ever missed is beyond me, but it carries 480V and needs repaired pronto! I can probably disconnect the leg to slide a shrink sleeve on, but wanted to see what you guys prefer?

 

[hbiss]

Right down to the bare copper?

-Hal

 

[fastline]

Right down to the bare copper?

-Hal

Yes, there is a small flick of Copper that can be seen. The actual conductor is not damaged.

 

[LarryFine]

I would de-energize it and put in some "liquid electrical tape" then a layer of tape.

 

[paulengr]

During an inspection, it was discovered that an area of insulation approx 3" long of a 4/0 Copper conductor is damaged inside a pull box, likely from the original pull years ago. How it was ever missed is beyond me, but it carries 480V and needs repaired pronto! I can probably disconnect the leg to slide a shrink sleeve on, but wanted to see what you guys prefer?

You are supposed to meet or exceed the OEM insulation. A shrink sleeve is one way and great if you have access.

If you don’t then 3M recommends 2 layers varnished cambric as a separator, two layers rubber 130C splicing tape, and two layers 88 or 33+ vinyl to protect it. Same as any motor splice. Should take all of 5 minutes to apply and you don’t need an open end.

Vinyl by itself isn’t all that insulating. 4/0 THHN has to be insulated to 600 V continuous, up to 2200 V in a surge, and regular THHN surges up over 3 kV at 4/0 so the tape might sound overkill but it’s not,

 

[winnie]

I rather like the stretchy rubber coated fiberglass sleeves. If you get the correct size then you can slide them on, they snugly conform to the wire, and you don't need to worry about 'shrinking' them.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

-Jon

 

[fastline]

Because I have not done one of these in over a decade, I might ask what shrink would be preferred? I seem to recall doing double shrink on one many years ago. Because the damage is so near the entrance to the structure, wrapping tape around it would be very difficult so I think shrink is the right answer here.

Winnie, thanks for the reference. I just missed ya.

 

[winnie]

Because I have not done one of these in over a decade, I might ask what shrink would be preferred? I seem to recall doing double shrink on one many years ago. Because the damage is so near the entrance to the structure, wrapping tape around it would be very difficult so I think shrink is the right answer here.

Winnie, thanks for the reference. I just missed ya.

I should revise my answer. The fiberglass sleeve is something that _I_ like when building equipment for the lab I work in, including covering high amperage cables. But I am _not_ a production electrician. You will probably get better answers from them.

-Jon

 

[paulengr]

Because I have not done one of these in over a decade, I might ask what shrink would be preferred? I seem to recall doing double shrink on one many years ago. Because the damage is so near the entrance to the structure, wrapping tape around it would be very difficult so I think shrink is the right answer here.

Winnie, thanks for the reference. I just missed ya.

At least exceed the thickness of the original insulation. I don’t try to minimize it. I just go for heavy wall adhesive lined and keep spare tubes on the van. Fit as tight as you can then warm it evenly. Much easier with a heat gun but a butane torch works OK too. Oxy-acetylene is just way too much heat. I’ve done hundreds of them in a marine environment (sand mining). They outlast the cable around them and carry UL Listings just like the tape method so nobody can point fingers later.

 

[Jraef]

There are in-line heat shrink “repair sleeves” available that wrap around and have a zipper system that holds it together as the adhesive cures, then you cut the zipper off. There was a wrap around version too, but I’m not sure that one is still available. But these are a lot more expensive so if you can disconnect an end and slide a heat shrink tube around the wire, that’s simpler and less expensive.

So long as you get heat shrink rated at 600V, it’s considered a valid repair.

 

[ggunn]

During an inspection, it was discovered that an area of insulation approx 3" long of a 4/0 Copper conductor is damaged inside a pull box, likely from the original pull years ago. How it was ever missed is beyond me, but it carries 480V and needs repaired pronto! I can probably disconnect the leg to slide a shrink sleeve on, but wanted to see what you guys prefer?

Are you sure that there isn't more damage to the insulation inside the conduit where you cannot see it?