New home construction –
The service entrance panel is a 200 Amp rated Cutler Hammer panel with a 200 Amp main breaker. One of the breakers it contains is a 125 Amp that feeds the garage sub-distribution panel.
The garage sub-distribution panel is also a 200 Amp rated panel with a 200 Amp main breaker. This panel has 22 - 20 Amp breakers for the various usual circuits.
Is my assumption correct that if any of the 20’s trip in the sub distribution panel, the first power to shut-down would be the 125 Amp in the service panel, not the 200 of the sub distribution ?
The 200 amp disconnect in the distribution panel is worthless, except as a means to disconnect (de-energize) the panel.
That’s what I thought.
Basically, it is a 125 amp sub due to the feeding breaker being the lowest rating out of everything. If any of those 20 amp breakers trip, nothing upstream should trip.
Weakest link in the chain ,is the one that breaks.
As jeff stated, the 200 amp breaker in the sub acts as a disconnect. There is no violation or defect here, as the sub feeders are properly protected at the main panel by the 125 A breaker.
Look at it this way, the garage sub does not even require a disconnect or a main breaker, unless it is detached from the house.
Those Cutler hammer 200 amp main breaker panels are cheaper than the main lug only panels, which is probably why they did it that way.
I agree with Brian,
As long as the sub panel contains an isolated Neutral (Grounded Conductor),
The 200A breaker is no problem, and serves as a disconnect to that panel.
According to my Uncle who is a practicing Master Electrician in Massachusetts,
If the sub panel does not have an isolated Neutral, it may cause the breakers not to trip in an actual fault/overload condition.
One thing to look for is if the panel is rated to accept a 125A breaker, some may be only rated for a 110A per bus stab.The old read manufacturers instructions thing.