Paralleled Feeders

[chuck@apsinc.biz]

A particular UPS manufacturer calls for parallel runs to feed and distribuite power with-in the UPS system, then doesn't provide the necessary conduit entry space for separte conduits for each set of parallel feeders. A solution presented is to install 1 oversized raceway for each feed and put the paralleled feeders in the same raceway. Provided the derating provisions of NEC 310 are followed, I do not see any code issues with this solution. Does anyone have any information that contradicts this? Is my power quality compromised in any way?

 

[ron]

Re: Paralleled Feeders

Sounds ok.
Many UPS's that have cabinets aligned, plan to use the back portion of the cabinets as a gutter/wireway.

[ April 21, 2003, 10:35 AM: Message edited by: ron ]

 

[rick5280]

Re: Paralleled Feeders

Could you explain your statement "Provided the derating provisions of NEC 310 are followed..."?

By definition, parallel conductors are considered one conductor, so, if you are talking about the number of current carrying conductors, there should not be any derating needed.

Rick Miell

 

[chuck@apsinc.biz]

Re: Paralleled Feeders

Doesn't the adjustment factors of NEC 310.15(B)(2) apply to more than 3 current-carrying conductors in a raceway? I do not see an exception for paralleled feeders in the same conduit thus the application of the adjustment factors. What am I missing? Isn't the number of current carrying conductors doubled when you combine paralleled feeders in a common raceway? Besides NEC 310.4 says conductors installed in parallel shall comply with the provisions of 310.15(B)(2)(a).

 

[don_resqcapt19]

Re: Paralleled Feeders

Rick,
If you have parallel current carrying conductors in a raceway, all of the conductors are counted for the purpose of derating. The only reason for derating is to prevent excessive heat build up in the raceway. Each individual conductor of the parallel set contributes to this heat and must be counted.
Don

 

[dereckbc]

Re: Paralleled Feeders

Chuck you got it right.

 

[frenchelectrican]

Re: Paralleled Feeders

i do agree with don with paraell conducters.. unfoturetly i have plenty experince with parllael conducters and it have to be derated anyway . you can take one wire size and try to run paralled you can expect to be doubled. but not really in most case i have to derated anyway due few reason... one is termation point where multi wires land in common spot . and second reason is derating factor per loading on the line . and the other reason i see alot of it installed in wireway or raceway ( depend what you call it ) and it can build up heat there that why i have to be carefull about derating there


sorry to get into the pointing time
that is my 2 cents worth of my time he he

merci marc