Multiple Taps from one 400 amp CB

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NewtonLaw

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Honesdale, PA USA
Is it allowable per the NEC to to run two separate circuits from one 400 amp circuit breaker to two separate 400 amp panelboards? The circuit lengths are 50 feet for circuit one and 210 feet for the second circuit.
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It depends on the wire size. If each has an ampacity of 400 amps or greater, then you don't have a tap you have a feeder. If they are less than 400 amps you need to comply with one of the tap rules in 240.21. curious how you can physically land 2 400 amp sets on a 400 amp CB? I guess 500 cu would work using next size up rule.
 
electrofelon said:
It depends on the wire size. If each has an ampacity of 400 amps or greater, then you don't have a tap you have a feeder. If they are less than 400 amps you need to comply with one of the tap rules in 240.21. curious how you can physically land 2 400 amp sets on a 400 amp CB? I guess 500 cu would work using next size up rule.
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Thank you for your response. The circuits are the same size but different lengths of 500 MCM CU.
 
electrofelon said:
It depends on the wire size. If each has an ampacity of 400 amps or greater, then you don't have a tap you have a feeder. If they are less than 400 amps you need to comply with one of the tap rules in 240.21. curious how you can physically land 2 400 amp sets on a 400 amp CB? I guess 500 cu would work using next size up rule.
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I would think he would have a splice box outside the MDP using Polaris or Ilsco type splices.
 
hillbilly1 said:
I would think he would have a splice box outside the MDP using Polaris or Ilsco type splices.
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Yeah I'm trying to remember what I have seen in the past, but lugs that take 2-500's does seem unlikely. IIRC the last 400 amp frame breaker I used was an I-line and it had single ports, but they could take two conductors, but I doubt as big as 2 500's. Siemens 400A MLO panel boards have two hole lugs, a large and a small, but the smaller one only went up to 350 I believe.
 
electrofelon said:
It depends on the wire size. If each has an ampacity of 400 amps or greater, then you don't have a tap you have a feeder. If they are less than 400 amps you need to comply with one of the tap rules in 240.21. curious how you can physically land 2 400 amp sets on a 400 amp CB? I guess 500 cu would work using next size up rule.
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Take the 600kcmil/250kcmil "snowman lug" off the breaker. Replace it with a double 600 kcmil lug. (I'm aware you aren't really supposed to do this, because of product listing)
 
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Terminals on large CB's are designed to be interchanged as long as you replace them with the proper listed terminals. We reconfigure them quite often.
 
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Would it depend on what the loads of the sub panels are? I mean if the calculated loads were 225A on one and 300A on the other then you would not be allowed to land them on one 400A breaker.

What are the loads on these subpanels?
 
infinity said:
Terminals on large CB's are designed to be interchanged as long as you replace them with the proper listed terminals. We reconfigure them quite often.
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Also when larger breakers are figured into a panelboard the lug sizes generally default.
They can be changed if caught in the submittal review prior to release.
Point being there are several listed lug sizes and configurations available for breakers if one should happen to think about asking for them.


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