Removing MV Cables from Ductbank and Reinstalling

[scnkapc]

Greetings All,
I cannot remember where I saw this, but is it a code violation to remove cables from a ductbank and then repull the same cables back into the the ductbank?
Many years ago I remember not being able to do this because by pulling the cables out, they would get damaged and the insulation would be compromised and make it unsuitable for reinstallation.
Some please comment and if there is a code article, please reference it in your response.

Thanks,
S

 

[electrofelon]

Greetings All,
I cannot remember where I saw this, but is it a code violation to remove cables from a ductbank and then repull the same cables back into the the ductbank?
Many years ago I remember not being able to do this because by pulling the cables out, they would get damaged and the insulation would be compromised and make it unsuitable for reinstallation.
Some please comment and if there is a code article, please reference it in your response.

Thanks,
S

Removing and reusing cables and conductors is not prohibited by code. However there are several general sections such as 110.2, 110.3, and 110.7 that an AHJ could possibly cite. I would think
a megger test should ameliorate any concerns.

 

[paulengr]

Greetings All,
I cannot remember where I saw this, but is it a code violation to remove cables from a ductbank and then repull the same cables back into the the ductbank?
Many years ago I remember not being able to do this because by pulling the cables out, they would get damaged and the insulation would be compromised and make it unsuitable for reinstallation.
Some please comment and if there is a code article, please reference it in your response.

Thanks,
S

It’s not illegal IF they can be removed and installed without damage. I’ve seen installations (first time) where it cannot be used. Doesn’t matter what or where it is.

The first issue is that shielded cables will have terminations. Depending on the duct size you might not be able to get it through the duct. This is especially true of say triplex or quadplex where you have multiple layers and terminations that spread everything out.

Old cables (MV or not) have 3 problems with disturbing them. The first is that the copper gets stiff and not as easy to work. The second is that if the insulation is thermoset and it exposed to overheating it might still be functioning but it becomes brittle and disintegrates when you try to disturb it. The third problem related to the first two is that cables have a memory and tend to hold their shape. This is why for instance it tends to coil from being wound onto a spool. So the memory can make it hard to remove.

That is all cable issues. The final issue is that duct banks frequently are not clean, open spaces. Water and dirt can infiltrate and act like concrete from the ends or sometimes in the middle from unseen damage or ground heaving. Often even ducts that look clean and dry have issues that you can’t see underground. About 1 out of every 4 or 5 ducts cannot be pulled and you better have spares or plan for potentially running new ones. This even applies to sites where the first say 4 ducts pull easy with no issues.

When you bid duct banks just be sure that you capture this in your bid. Somehow you need to make sure the customer understands up front that all kinds of things can go wrong that can lead to totally abandoning not only the cable but one or all ducts. I’ve had it happen multiple times from both sides of the table and as a general rule I avoid ducts whenever possible. You can inspect, repair, and replace tray and conduit cheaply and easily. Anything buried has its advantages but it blows up all budgets when repairs are required and you can’t inspect it.

 

[scnkapc]

Thank you.
I appreciate the information.

S