Thread: Service equipment and sub panel(s) question

I have a service panel rated for 125A and it has in it, a 100A main breaker and a 100A breaker for 1 sub and another (30A) below that to another sub. I was under the assumption that the subs cannot exceed 80% of the panel's max. Your thoughts please. thanks.

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Originally Posted by Marc M

I have a service panel rated for 125A and it has in it, a 100A main breaker and a 100A breaker for 1 sub and another (30A) below that to another sub. I was under the assumption that the subs cannot exceed 80% of the panel's max. Your thoughts please. thanks.

Urban Myth.

Oh no, you used the 'sub' word. Jerry's going to get you.

Originally Posted by Marc M

I was under the assumption that the subs cannot exceed 80% of the

Subs should not exceed 100% of their rated depth, beyond that depth they enter into the 'dead zone'.

Fred is correct, of course.

You could have service equipment with a disconnect rated at 100 amps and a remote panel rated at 400 amps, it will not matter, no way are you going to get 400 amps through that 100 amp main to the 400 amp rated panel (unless the overcurrent disconnect is inoperative for whatever reason, such as being an FPE, in which case it is entirely likely ).

If a service panel has feed through lugs a sub panel can have the same rating as the service panel. The size of any additional panels is limited by the maximum rating of allowable branch breakers.

The above doesn't limit the size of a main breaker in the sub panels. There would be no reason that a sub panel with a 200 AMP main breaker can't be fed from a service panel with a 150 AMP rating.

you guys are funny. Yea, I caught myself on the "sub" word but it was too late. I understand now, I should have thought this one out before posting.

I think Brian should install an automatic pop-up warning whenever anyone tries to use the term sub-panel.
A loud siren might help, too.

Originally Posted by Bill Kriegh

If a service panel has feed through lugs a sub panel can have the same rating as the service panel. The size of any additional panels is limited by the maximum rating of allowable branch breakers.

Incorrect.

The size of remote panels can be as high of rating as one likes, regardless of the size of the overcurrent protection protecting it - as long as it is *at least* the rating of the overcurrent protection.

Other incorrect and insufficient information in the other part too.