3 sets parallel in 2 conduits

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Mountainbikeak

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I wasn’t able to come to my own conclusion, so I’m hoping some of you could help clear this up. I have two 4” RMC conduits feeding a 800 AMP MDP. I plan to run 2 sets of 600 KCMIL conductors, which would be fine. Does 310.10(H)3 prohibit running 3 sets in two conduits? EX: ABCN+ABCN in one conduit and the remaining ABCN in the second conduit, of course keeping in mind, de-rating?
Thanks
 
Not permitted.

310.10(3) Separate Cables or Raceways. Where run in separate
cables or raceways, the cables or raceways with conductors
shall have the same number of conductors and shall have
the same electrical characteristics. Conductors of one
phase, polarity, neutral, grounded circuit conductor, or
equipment grounding conductor shall not be required to
have the same physical characteristics as those of another
phase, polarity, neutral, grounded circuit conductor, or
equipment grounding conductor.
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Mountainbikeak said:
I wasn’t able to come to my own conclusion, so I’m hoping some of you could help clear this up. I have two 4” RMC conduits feeding a 800 AMP MDP. I plan to run 2 sets of 600 KCMIL conductors, which would be fine. Does 310.10(H)3 prohibit running 3 sets in two conduits? EX: ABCN+ABCN in one conduit and the remaining ABCN in the second conduit, of course keeping in mind, de-rating?
Thanks
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Why not run 4 sets (2 sets per conduit) of say 3/0 or 4/0?

Roger
 
One set of copper 600 MCM in each conduit is sufficient for 800 amp gear, unless the neutral counts as a current-carrying conductor, or you have a really long run where voltage drop comes into play.

Also, 4 inch rigid only holds 6 600 MCM cables, so your idea is a non-starter there too
 
The gear was ordered with provisions for 3 sets max (why I didn’t mention 2 sets in each conduit) with a max 500 kcmil. I think I can get away with using 600’s with offset studs or something similar to drop it from 600’s to 500’s at termination. 4” conduit is ran underground and adding another conduit would be next to impossible at this point. If I ran 3 sets in two conduits of course I wouldn’t use 600’s, I would use 3 sets of 350’s. This would have eliminated the use of a bunch of compression fittings and the larger more difficult to manage 600’s. The way I read 310.10(H)3 3 sets in 2 conduits wouldn’t work but, was hoping I was misunderstanding it.
thanksi
 
Mountainbikeak said:
The gear was ordered with provisions for 3 sets max (why I didn’t mention 2 sets in each conduit) with a max 500 kcmil. I think I can get away with using 600’s with offset studs or something similar to drop it from 600’s to 500’s at termination. 4” conduit is ran underground and adding another conduit would be next to impossible at this point. If I ran 3 sets in two conduits of course I wouldn’t use 600’s, I would use 3 sets of 350’s. This would have eliminated the use of a bunch of compression fittings and the larger more difficult to manage 600’s. The way I read 310.10(H)3 3 sets in 2 conduits wouldn’t work but, was hoping I was misunderstanding it.
thanksi
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I still don't understand why you don't reduce the conductors and use 4 sets, you can change the terminations to accommodate this.

Roger
 
roger said:
I still don't understand why you don't reduce the conductors and use 4 sets, you can change the terminations to accommodate this.

Roger
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I realize I have some options and that was the first that came up, just not sure I’ll be able to source material for this. I’m inquiring about what I think (hope) would work given my timeframe and what’s available locally. Once I elimate options that potentially could have been solved with what’s available then I’ll start looking for other options.
Thanks for the input.
 
Dennis Alwon said:
I wonder why that is. It would seem that as long as there is a full boat there wouldn't be a problem.
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you would have different inductive/capacitive characteristics therefore not equal impedance in all sets of the parallel conductor. More current will flow in the lower impedance set.
 
I may be wrong, however I do not think you're going to be able to reduce down to 500 MCM at the terminations unless they are rated for 90 degrees, which is highly unlikely.
 
4 sets of 250's in the conduit (2 sets per conduit, possibly even as small as 4 sets of 4/0's) and 3 sets of 300's going to the equipment, with 7 hole Polaris type connectors (eg. IPLD350-7) for the transition.

This would give you an even number of sets for your underground run, let you use the 90C ampacity for the underground run, and give you 3 sets to go to your equipment.

-Jon
 
If I'm understanding this you need an 800 amp feeder and your terminals only allow 500 kcmil. If you run 2 sets of 600's and your calculated load is 760 amps or less you can splice on short pieces of 500's to enter the terminals. If VD is and issue run 750's and splice the 500' to them.
 
infinity said:
If I'm understanding this you need an 800 amp feeder and your terminals only allow 500 kcmil. If you run 2 sets of 600's and your calculated load is 760 amps or less you can splice on short pieces of 500's to enter the terminals. If VD is and issue run 750's and splice the 500' to them.
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Why am I thinking that 800 amp or larger gear requires full size feeders, i.e. you cannot run two sets of 500 for 760 amps if you have an eight hundred amp breaker, regardless of load? Is that over 800 amps?

And I understood the original posters post the same way you did
 
JFletcher said:
Why am I thinking that 800 amp or larger gear requires full size feeders, i.e. you cannot run two sets of 500 for 760 amps if you have an eight hundred amp breaker, regardless of load? Is that over 800 amps?

And I understood the original posters post the same way you did
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Up to 800 amps you can go to the next standard size OCPD, over 800 amp you cannot. 760 amps is not a standard size so you can go up to the next standard size which is 800 amps. The calculated load cannot exceed the ampacity of the conductors which as mentioned is 760 amps.
 
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