Ratio of main to branch circuit ratings

Originally Posted By: Eric Mies
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Is there a limit to the total amperage of branch circuit breakers based on the size of the main?


Example; A 100 amp main with total branch circuits totaling 450 amps, is this acceptable?


Originally Posted By: bking
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yes, it is ok. An exception would be if you see an unusual number of permanantly connected high wattage items. This would indicate that someone may be resetting the main often.



www.BAKingHomeInspections.com

Originally Posted By: bbadger
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You can have any number of branch circuits regardless of the service size.


Adding up the breaker ratings means nothing.

Lets say you had a 100 amp service with a 50 amp breaker for air conditioning and a 60 amp breaker for electric heating along with the other branch circuits.

At the outset this looks bad however the AC will not run at the same time as the heat and the NEC allows for this.

All that matters is the "Calculated Load" or the "demand load" if that is available.


--
Bob Badger
Electrical Construction & Maintenance
Moderator at ECN

Originally Posted By: jmyers
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Eric,


I agree with Bob. While having all those breakers is not a problem, using them all at the same time can result in overloading the panel. Generally, I add up the continuous loads in the panel and I call for a load calculation when the exceed 90 to 95% of the panel rating, depending on the panel rating.


--
Joe Myers
A & N Inspections, Inc.
http://anii.biz