200 amp feeder landed on 400 amp main

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mm12866

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I have a situation where we are relocating a customers UPS and maintenance bypass switch to their new location. We will be feeding the bypass switch with a 200 amp feeder fed from a 200 amp breaker. The existing input for the bypass switch is a 400 amp breaker. Is there any reason I can't do this? The 400 amp breaker isn't really protecting anything, more of just a disconnecting means in this situation. I can't see why this would be a violation of any code, but it just doesn't seem right to land the 3/0 feeder on a 400 amp breaker. Any thoughts?

Thanks
 
If your conductors are not rated for the 400A protection, at least 351A with a calculated load not more than the conductor ampacity or protection device rating, then you have to comply with one of the tap rules of 240.21(B).
 
mm12866 said:
We will be feeding the bypass switch with a 200 amp feeder fed from a 200 amp breaker.
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Smart $ said:
If your conductors are not rated for the 400A protection, at least 351A with a calculated load not more than the conductor ampacity or protection device rating, then you have to comply with one of the tap rules of 240.21(B).
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OP says the feeder has overcurrent protection.
 
I reccomend adjusting or replacing the main breaker or pulling it out and replacing with a lug kit. Also check the aic ratings on both panels, I've seen when the small panel added on the supply has too low of an AIC. I also reccomend marking this panel with its upstream breaker and size so that someone is able to figure this out in the future and also not connect too much load. Not really a code problem but certainly a series coordination problem and facility standard practice problem

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mm12866 said:
I have a situation where we are relocating a customers UPS and maintenance bypass switch to their new location. We will be feeding the bypass switch with a 200 amp feeder fed from a 200 amp breaker. The existing input for the bypass switch is a 400 amp breaker. Is there any reason I can't do this? The 400 amp breaker isn't really protecting anything, more of just a disconnecting means in this situation. I can't see why this would be a violation of any code, but it just doesn't seem right to land the 3/0 feeder on a 400 amp breaker. Any thoughts?

Thanks
Click to expand...

As long as the lugs are rated for 3/0, you're fine.

I've installed several 200 amp main breaker subpanels in detached buildings fed with only a 100 amp feeder, just for the extra spaces.

It's no different than than say, running a 225 amp feeder through a 400 amp disconnect.
 
mm12866 said:
I have a situation where we are relocating a customers UPS and maintenance bypass switch to their new location. We will be feeding the bypass switch with a 200 amp feeder fed from a 200 amp breaker. The existing input for the bypass switch is a 400 amp breaker. Is there any reason I can't do this? The 400 amp breaker isn't really protecting anything, more of just a disconnecting means in this situation. I can't see why this would be a violation of any code, but it just doesn't seem right to land the 3/0 feeder on a 400 amp breaker. Any thoughts?

Thanks
Click to expand...

As long as the lugs go small enough for the 3/0 feeder, I feel you've answered your own question.

JAP>
 
dkidd said:
OP says the feeder has overcurrent protection.
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OP is confusing. He says the input for the bypass switch is 400A breaker with 3/0 feeder. Now if the 400A breaker is fed by the mentioned 200A breaker, all is fine. OP'er needs to clarify.
 
Smart $ said:
Whether bypass switch and 3/0 feeder have 200A or 400A protection. Said one thing, then said another. Which is which?
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The way I read it is that the feeder is protected by a 200A OCPD and is rated for 200A but will be terminated into a bypass switch with a 400A rated OCPD device. So he is asking can he terminate a conductor rated at 200A, being protected by an OCPD rated at 200A....into a bypass with a 400A rated OCPD device that he intends to use a simply a switch.

Thats kinda how I read it but hey..I could be wrong I guess.
 
MasterTheNEC said:
The way I read it is that the feeder is protected by a 200A OCPD and is rated for 200A but will be terminated into a bypass switch with a 400A rated OCPD device. So he is asking can he terminate a conductor rated at 200A, being protected by an OCPD rated at 200A....into a bypass with a 400A rated OCPD device that he intends to use a simply a switch.

Thats kinda how I read it but hey..I could be wrong I guess.
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If your wrong, I don't see how. :)


JAP>
 
MasterTheNEC said:
The way I read it is that the feeder is protected by a 200A OCPD and is rated for 200A but will be terminated into a bypass switch with a 400A rated OCPD device. So he is asking can he terminate a conductor rated at 200A, being protected by an OCPD rated at 200A....into a bypass with a 400A rated OCPD device that he intends to use a simply a switch.

Thats kinda how I read it but hey..I could be wrong I guess.
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That's kinda how I read it... but I didn't want to let the possibility I read wrong to slip by.
 
MasterTheNEC said:
The way I read it is that the feeder is protected by a 200A OCPD and is rated for 200A but will be terminated into a bypass switch with a 400A rated OCPD device. So he is asking can he terminate a conductor rated at 200A, being protected by an OCPD rated at 200A....into a bypass with a 400A rated OCPD device that he intends to use a simply a switch.

Thats kinda how I read it but hey..I could be wrong I guess.
Click to expand...

That's the way I read it too.
 
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