400 Amp MOCPD Feeding a 200 Amp MOCPD

[Vankirk Electric SR. PM]

All –

We are completing the retail power distribution for a mixed use, multi-family project in San Diego, CA.


Here's the scenario:

We have a 1200 amp switchboard with an 800 and a 400 amp retail meter and breaker. The 400 amp meter/breaker is supplying power to a 200 amp MOCPD downstream.

Is there any code violation with feeding the smaller breaker with the larger?

See below for a screenshot from the plans. I highlighted the setup in question.

Thanks for the help!

 

[smoothops10]

No, there is no issue with a smaller breaker downstream of a larger breaker. Panelboards are required to be protected with upstream overcurrent protection having a rating not greater than that of the panelboard. This is provided by the 200A main.

There is however an issue with the 400AT breaker protecting a set of 400kCMIL conductors assuming the likely case that you are using 75C conductors and terminations for an ampacity of 335A. Look at 240.4(B) and 204.6.

 

[Vankirk Electric SR. PM]

Thank you for the reply.

As for the feeders, that "4WG400" on the 1-line is a feeder identifier on the feeder schedule for a 400 amp MOCP. On the feeder schedule on the plans, "4WG400" identifier calls for (2) 4# 250 KCMIL AL + Ground for the feeders. That should give us 410 amps of wire. Sound right?

 

[smoothops10]

I see, didn't realize it was a feeder tag. I agree with your comment on the ampacity.

 

[petersonra]

will (2) 250 kcm wires fit on the lugs of the downstream breaker?

 

[Cow]

Thank you for the reply.

As for the feeders, that "4WG400" on the 1-line is a feeder identifier on the feeder schedule for a 400 amp MOCP. On the feeder schedule on the plans, "4WG400" identifier calls for (2) 4# 250 KCMIL AL + Ground for the feeders. That should give us 410 amps of wire. Sound right?

Assuming they are ran in separate conduits where derating will not apply.

 

[infinity]

Not a problem but IMO an odd design.