OCPD Size Limits

[Alecto]

I think article 240 puts limits on the maximum OCPD size, I'm wondering if I can have 20A branch breakers protected by a 60A main or if the main cannot be over a certain size?

Thank You

 

[roger]

You could have a 6000A OCPD ahead of a 20 amp branch breaker. Your question really doesn't make much sense.

Roger

 

[Alecto]

You could have a 6000A OCPD ahead of a 20 amp branch breaker. Your question really doesn't make much sense.

Roger

That was the question, thank you. So it is acceptable then, I wasn't sure if the NEC prohibits IE, 20A branch breakers protected by a 6,000A OCPD or if there is a limit. The answer is there is no limit.

 

[broadgage]

In practice you might not be able to have a 20amp branch circuit breaker immediately downstream of a 6000 amp main.
A 6000 amp main implies a vast available fault current, likely 100KA or more and almost certainly beyond the breaking capacity of any common branch circuit breaker.

With an HRC fuse protecting the branch circuit it should be doable.

 

[Jraef]

So the answer is, the NEC doesn't have anything restricting how a panel is configured, but from a practicality standpoint there are real-world limitations. The conductors down stream of that 6,000A MCB would need to handle 6,000A, so bus bar is in order. But as mentioned, for a 6,000A bus switchboard a 20A breaker that will bolt to the bus is unlikely to have enough IC for the available fault current.

Your original question however was a 60A main, and that's totally acceptable.

 

[drktmplr12]

they make (non-custom) switchgear rated above 4000 amps?

that might be a good time to consider distribution at 4160