Breaker "stacking"

RD35

Senior Member
Question came up the other day and I cannot find an answer. When installing a whole-house generator one often ends up re-routing the service conductors to the new main breaker in the service rated transfer switch. Then new feeder conductors are routed from the load lugs of that new switch to the existing main breaker of the house panel (which is now....in essence....a sub panel after the bond is removed and the grounded conductors are separated from the grounding conductors, etc.)
So....is there any code violation that arises when feeding, say, a 200A MCB in a panel with a feeder that is already protected by a 200A breaker up stream? I am thinking it's fine, but would like to ask the group for some re-assurance...or correction if I'm missing something.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
You can even have a 400 amp main breaker in the panel fed by a 200 amp, as long as load calculations support it. Redundant over current protection is no problem, and totally legal.
 

RD35

Senior Member
Okay thanks! I know coordination studies are needed where adjustable breakers are involved, but those are usually cascading in amperage from high to low numbers as the feeders progress to the load. I just had not been asked about redundant protection at the same (or as you stated..higher) amperage...especially on these small non-adjustable units.
Thanks hillbilly! Appreciate the quick response! Have a great day!
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I love finding a main breaker ahead of the main panel. That means the neutrals and grounds are already separated.
 
Coordination's not an issue when there's one breaker outdoors and one main breaker indoors. The reason for coordination is to assure that a fault will take out only the circuit that's faulted, not trip a breaker further upstream and take out other, uninvolved circuits. In this circumstance, you don't have any other 200-amp circuits.
 
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