I have an energy guiding drag chain that needs to be modified. My solution is to parallel two #8 conductors (for power not control.)
I am required to follow NEC in this modification and 310.4 pretty much destroys my options.
Does anybody know anyway of bypassing 310.4 based on the fact that this is a drag chain? Or are there any better ideas?

Thanx ... Richard

Pardon my ignorance, but what is a energy guiding drag chain?

http://www.wampfler.us/INDEX.asp?lang=2&page=31,1,3&zuf=0.6372517867116791
http://www.kabelschlepp.com/quantum.htm

Great links, although I still don't follow the application. The energy guiding drag chain seems to be a flexible cable tray that moves with an operator.
If you need 80 amperes of conductor (parallel #8awg), what prohibits you from using #3awg instead of paralleling #8 (which as you mentioned is not permitted)?

http://www.portofoakland.com/pdf/mari_reso_crane_02.pdf

If you look at the above link, this crane is in its operating condition. When it returns to its stowed position, the boom retracts away from the water - the energy chain moves with it.
The energy chain is already in place on the crane and these chains require to be load balanced and careful design goes into them. We have no other conductors available other than the #8 AWG. If I cannot use them, I will have to remove the chain.

Thanks for your help ... Richard

gbbrwh — Ron has given you accurate information. Is there any way the load could be divided so that part of it was left on the presently-energized set of 8AWG conductors and part on the 8AWG spares?

I think I understand, the chain comes premade with the cables already in it. There isn't any wire existing with the capacity to do what he needs to do.

If this is required to code, your stuck, unless there is room in the chain to add some welding cable, (to give you the flex you need) into the chain.

good luck, did you spec the chain? or did some engineer do it.

TW

Yes - the chain arrives premade with the cables installed. The chain was getting so heavy and wide, we had to remove numerous spare conductors before it was built.
One simple mistake has led to this problem. All we have left are the #8s and various #10s and #12s. We can't split the load. The only option I can think of is to parallel two #8s together - otherwise the chain has to come back down and sent back to the factory in Germany
Adding a cable would be difficult as these chains are designed in such a way to avoid cables contacting one another.
An engineer I know spec'd it but the responsibility falls right at my door.

I would try it and see just how currents share. Sometimes "engineering supervision” can justify practices that aren't exactly what everyone is used to in industrial facilities. It's not perfectly code compliant, but It may not kill anyone or damage anything. Careful documentation is in order to "CYA" and lessen confusion to future troubleshooters. It would be a deviation, but unquestionably in a “location accessible to qualified persons only” and “In industrial establishments… where conditions of maintenance and supervision ensure that only qualified personnel are involved” that the NEC uses to justify special cases.

Gbbrwh:
Have you called your local AHJ?????
You have a piece of industrial equipment.
Your link states it was made in 1968

The #8's that you have in the track; what kind of wire/cable and what insulation??

Talk to your local AHJ! Explain the facts of the situation to him... Certain situations can receive "special permission", but get it in writing.

IF you presented your situation to me, and had engineering documentation to "back-it-up" more than likely, I would grant special permission.

John


Your link also mentions 4160 volt as the power supply, is that correct.

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