Over Current Protection for Sub Panel with higher rating than Main Switch

[BMacky]

Would someone please direct me to a specific NEC article(s) that would cover that it's OK to put a 200A subpanel downstream from a 100A Main switch? I have to prove to a customer that this is OK, and can't seem to find the specifics in Article 230, or wherever it may be.

I realize it does not actually state that it's an approved practice, but that protection must not exceed the stated ampacity of ungrounded conductors, the panel rating, etc.

If that's all there is to it, then OK. But is there something more to consider?

Thanks!

 

[kwired]

408.36 Overcurrent Protection.
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.

If the calculated load is larger than 100 amps that is a problem. But it is not a problem with the 200 amp panel. It is a problem with the 100 amp switch and supply conductors if they are also sized for 100 amps. The panel needs protected to its 200 amp rating as a maximum.

This is kind of like asking if it is ok to run 6AWG when 12 would work.

 

[Little Bill]

Would someone please direct me to a specific NEC article(s) that would cover that it's OK to put a 200A subpanel downstream from a 100A Main switch? I have to prove to a customer that this is OK, and can't seem to find the specifics in Article 230, or wherever it may be.

I realize it does not actually state that it's an approved practice, but that protection must not exceed the stated ampacity of ungrounded conductors, the panel rating, etc.

If that's all there is to it, then OK. But is there something more to consider?

Thanks!

Try 408.36(A) exception no. 1. That's not exactly the article you need but it shows you could use a 200A MLO panel being fed/protected by a 100A feeder. It's late and I don't have time to find exactly what you need. But you can feed a sub panel (200A in your case) as long as the rating is the same or less than the panel being fed. You would still need to know the load on the sub panel.

 

[Smart $]

...a 200A subpanel downstream from a 100A Main switch? ...

The above needs clarafication.

Having a 100A-rated switch or a 100A-rated ocpd at the source end of a feeder makes a major difference in the proper response...

 

[infinity]

If you feeder is protected at 100 amps and your load calculation is for 100 amps or less then the 200 amp panelboard is fine with a 100 amp feeder.

III. Panelboards
408.30 General.
All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated in accordance with Parts II, III, IV, or V of Article 220 as applicable.
FPN: See 110.22 for additional requirements.

408.36 Overcurrent Protection.
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.