100 Amp branch circuit breaker in 100 Amp panelboard

[designer82]

If I have a 100 Amp panelboard with a MCB, can I also put a 100 Amp branch breaker in this panel to feed a 100 amp MLO sub-panel?


Thanks

 

[augie47]

As long as it's not prohibited by the manufacturer.
(some loadcenters have a max size branch)
A :sub-feed lug kit may be available and less expensive.

 

[kwired]

Usually yes.

Most the time you are not actually adding an additional 100 amps of load.

Sometimes I use a 60 amp breaker but still use 100 amp conductor, figuring if the 60 trips frequently all that would need to be done is swap breaker for a 100. Never really have had to come back to change to 100 amp breaker though in dwelling situations anyway.

 

[kwired]

As long as it's not prohibited by the manufacturer.
(some loadcenters have a max size branch)

The one I am most familiar with on that max size being less than the panel rating is those 6 and 8 space QO loadcenters with a horizontal bus. The bus is rated 100 amps but they are only rated for 70 amp max breakers to plug onto them. Then of course most 200 amp loadcenters are limited to 100 or 125 amp branches, with exception being use of larger breakers that take more than one space per pole.