ECN Forum Forums Code Related Discussion NEC & other Code issues Conductors In Parallel

John - I contacted the AHJ and they said it had to comply with NEC.
Reason being that all electrical items are being replaced including cables, j-boxes, lights etc.
The cable is unscreened, flexible bending PUR power drag chain cable. The core insulation is KS-TPM (halogen free.) The cable has no paired or total screening.
The picture I showed was just a typical shuttle crane to show what was going on. I did not have a handy picture of the one we are working on.

I would confirm the ability to not parallel flexible conductors with the crane manufacturer and/or the energy chain manufacturer. I believe they are the only ones that can give an opinion on their listed equipment.

On a side note, many people expect to find every answer in the NEC but it is not the "bible" for everything electrical.

For example:
If this energy chain is part of the machinery, it is not subject to the NEC. The NEC is only applicable to premises (Art 90.2(A)) and therefore only the supply conductors feeding the industrial machinery (Art 670.1).

But, if this energy chain is part of the wiring system that supplies the crane then it is subject to the NEC, including Article 610.

Would using {auto}transformers to double and then halve voltage on the other end of the cable be possible?

I'd try this first....
90.4 Enforcement.
....By special permission, the authority having jurisdiction may waive specific requirements in this Code....
If that doesn't work, I would try to reason with them out of the ampacity tables in 610.14 Rating and Size of Conductors.
You may find some information there, that might help your cause.

Best of Luck,
Doc

Thanks for all your help everyone. I got some really good ideas from this.
I am still thinking if the transformers would work. The NEC help was great.

Thanks Again .... Richard

I can't visualize what you are up against, but as I interpret the situation, you might be able to supply redundant wiring (simply two supplies to the same device or equipment) where each circuit is fully sized. This is not the same as "parallel" wiring. Although it is wiring that is paralleled, it doesn't serve "to form a single conductor"! Without a reduction in circuit wire size, there is no 310.4 infraction (via paralled conductors smaller than #1/0). I expect that this distinction might be a hard sell to the AHJ though.

Caught a virus of sorts and was dumped off before I could edit my reply. I hadn't noticed the clarification that the conductors couldn't be larger than #8, so I guess my suggestion is besides the point. Sorry.

[This message has been edited by Elzappr (edited 03-29-2003).]

Is these cables in the chain German? If so, are they really to US specifications, or are they simply German cables "relabled" to US specifications? The thing is that #8 is 8mm2, bu t the closest size on German cables is 10mm2, i.e. 20% larger.

Have you checked the actual ampacity of the cables with the chain manufacturer or is it your responsibility? If the other cables are lightly loaded, the need to derate for bundling is reduced.

Check out Chainflex from Igus at http://www.igus.com. They manufacture 2/0AWG x 4C, 2AWG x 4C, 350MCM x 1C, and a bunch of other stuff specifically for energy chains. Even though they are a German company they have a distributor here in Providence, RI. You can run the crane to one limit and pull the cable in the chain without opening it up, just as you might pull in a closed cable tray... Except for the last bit where the bend is at. We have had Chainflex in operation for about 6 years now and have had no problems. Don't use standard SO or welding cable... it isn't engineered for the continual flexing. All of your conductors will break and the insulation will get rubbed off requiring you to replace it quite soon. Hope this helps!!!

As an inspector I would accept the wiring as is. It's part of the crane and designed by the manufacturer. If the crane is interment duty, there is no over heating in the cables