Branch CB Smaller than Main CB of Subpanel

[Electriman]

Good morning,

I just have a quick question. Can I feed a subpanel with a main CB of 60A with a 30A branch circuit breaker in the main panel in order to run #10 cable to subpanel? The load of the subpanel is not more than 10 A so a 30A breaker should be able to support the load.

Thanks in advance.

 

[Jraef]

Sure, so long as the conductors are properly protected. But why bother having a 60A main in the sub panel then? Waste of money unless it’s something you already have and want to use.

 

[sgayam]

Yes. If there are no other Taps off of the 30A branch circuit breaker OR you do not care about selective-coordination.

Basically, in this scenario, it is always the branch circuit breaker in your Main panel that is going to operate for any faults/overloads downstream of your subpanel.

 

[Jraef]

Yes. If there are no other Taps off of the 30A branch circuit breaker OR you do not care about selective-coordination.

Basically, in this scenario, it is always the branch circuit breaker in your Main panel that is going to operate for any faults/overloads downstream of your subpanel.

Which may end up being a significant nuisance if the main panel is far away...

 

[Electriman]

Sure, so long as the conductors are properly protected. But why bother having a 60A main in the sub panel then? Waste of money unless it’s something you already have and want to use.

It is a legacy panel. We are not supposed to touch it.

 

[winnie]

Totally fine. The other situation where this is common is when a cheap panel with a main breaker is less expensive than a main lug panel

 

[Lioneye]

The 60A becomes a disconnect at that point