Panel calc

[Alwayslearningelec]

If a panel has a mcb say 200a .....

1. If the calculated load of that panel is less than 200a can the breaker feeding that panel be smaller that. 200a? So can you have a 150a breaker feeding a 200a breaker in a panel and thus run wire rated at least 150a?

 

[Dennis Alwon]

Yes, as long as the wire is rated 150 amps or more and fed with a 150 amp breaker 200 amp breaker is insignificant

 

[ActionDave]

Don't tell the 200A breaker or anyone in his family that he is being fed with 150A and he will never know.

 

[Alwayslearningelec]

Don't tell the 200A breaker or anyone in his family that he is being fed with 150A and he will never know.

Lol..so it's fine?

 

[ptonsparky]

Lol..so it's fine?

Yes.

 

[marcosgue]

Question: in this scenario, the feeder of panel shoudn't be according to the capacity of the 200A busbar of the panel?

 

[infinity]

Question: in this scenario, the feeder of panel shoudn't be according to the capacity of the 200A busbar of the panel?

The feeder can be but it is not required to be sized according to the size of the bus. A load calculation would tell you what the minimum size feeder that is required for the panel. The bus can be larger than the required feeder size. It's plausible that the person who's paying for a panel with 200 amp bus thinks that they're getting a 200 amp feeder.

 

[winnie]

Sometimes you _want_ a larger panel bus than the feeder to the panel, eg. for solar installations.

Separate issue: if there is a requirement for selective coordination then having a 200A breaker downstream of a 150A breaker might be a problem. Usually there isn't such a requirement.