PARALLEL NEUTRAL DERATING

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Geoff23x

Member
Location
Lake City, FL
RUNNING PARALLEL 1/0 TO 120/208 200 AMP PANELBOARD RUNNING TWO VFD'S IN COMPRESSOR ROOM. NEEDS 5 LIGHTS TOTALING 7AMPS AND TWO 20AMP GENERAL PURPOSE RECEPTS. IM WANTING TO DERATE NEUTRAL TO #2. IM NOT SEEING WHERE I CANT DO IT. PLEASE PROVE ME WRONG.
THANKS
 
All caps is wild.

1/0 is the smallest you can run in parallel. 310.10(G).

If it is all in one conduit then you can run just one neutral conductor rather than two. Derating would apply.
 
Geoff23x said:
RUNNING PARALLEL 1/0 TO 120/208 200 AMP PANELBOARD RUNNING TWO VFD'S IN COMPRESSOR ROOM. NEEDS 5 LIGHTS TOTALING 7AMPS AND TWO 20AMP GENERAL PURPOSE RECEPTS. IM WANTING TO DERATE NEUTRAL TO #2. IM NOT SEEING WHERE I CANT DO IT. PLEASE PROVE ME WRONG.
THANKS
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Just curious, why the parallel conductors? Same or separate raceways? You can reduce the neutral in a feeder down as small as the 250.122 size, 215.2(A)(2). However you still have to comply with the 1/0 minimum for parallel installations (if these are parallel). If there is a single raceway, then yes you could run a #2 for the grounded conductor.
 
While it is true that the smaller the conductor, the higher the ampacity per circular mil, I am skeptical that there would be any cost savings for a 200 amp feeder. Have you done the math both ways? How far is this? Copper or aluminum? Maybe try it with a single raceway. Even with aluminum and the derating for 6 CCC, you'll still have over 200 amps, plus you can use that small neutral.
 
Geoff23x said:
to save $$. separate. is all lower better?
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So parallel #1/0 aluminum instead of a single set of 250's? As ef questioned is there really any cost savings running two raceways instead of one? If you put the #1/0's all in one raceway (7 conductors) you can use a single neutral.
 
infinity said:
So parallel #1/0 aluminum instead of a single set of 250's? As ef questioned is there really any cost savings running two raceways instead of one? If you put the #1/0's all in one raceway (7 conductors) you can use a single neutral.
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I have done the smaller paralleled conductors in a single pipe a few times when I have needed to squeeze as much ampacity as possible, and you can get quite a bit more than a single set even after the derating - But that was when there is an existing raceway or restriction on size for some reason, not done to "save money".
 
electrofelon said:
I have done the smaller paralleled conductors in a single pipe a few times when I have needed to squeeze as much ampacity as possible, and you can get quite a bit more than a single set even after the derating - But that was when there is an existing raceway or restriction on size for some reason, not done to "save money".
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There are probably ten ways to do this so someone would have to breakdown the cost of each method if cost was the sole decider. His initial
thought of #1/0 would work even with derating in a single raceway which may save one conductor. He did say separate raceways which means he'll need a neutral in each raceway. A lot of variables, length of run, voltage drop, number of terminals available at each end, terminal sizes, etc.

electrofelon said:
Nassau national cable is showing 1/0 AL XHHW at .62/ft, and 250 at 1.34/ft.
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No cost savings there using #1/0.
 
200 amp breakers and panels are only listed to accept a single conductor. You would also need to add for the cost of installing 3 port Polaris or = connectors with a single 200 amp pigtails. Unless you are using a 400 amp bussed panel and a 400 amp frame breaker with a 200 amp trip.
 
curt swartz said:
200 amp breakers and panels are only listed to accept a single conductor. You would also need to add for the cost of installing 3 port Polaris or = connectors with a single 200 amp pigtails. Unless you are using a 400 amp bussed panel and a 400 amp frame breaker with a 200 amp trip.
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Definitely - unless we are talking about true panelboards, then those lugs would be easily changeable to two port (for a MLO, but if you want a 225/250A frame MB for some reason yes you will be stuck with splicing).
 
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