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?
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)?
#84372 - 03/26/0312:15 PMRe: Conductors In Parallel
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
#84373 - 03/26/0302:36 PMRe: Conductors In Parallel
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.
#84376 - 03/26/0303:54 PMRe: Conductors In Parallel
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.
#84377 - 03/26/0304:34 PMRe: Conductors In Parallel