meter vs. sum of circuit amperage

amakarevic · 07-13-2011, 01:25 PM

i was curious if the sum of all circuits' amperage has to be less or equal to what the meter brings in OR, as i would consider it to be realistic, each circuit can be assigned reasonable concurrent usage percentage, with which its amperage can be weighed to arrive to the sum.

e.g. if my subpanel has 50A, can i have 2 20s and a 15 circuit (total 55) considering that it is highly unlikely that at any given time every circuit would be maxed out?

thanks

McSteve · 07-13-2011, 01:28 PM

Yes. The total of the circuit breaker ratings is basically meaningless. I have a 100A service here with over 300A worth of breakers installed. The important thing is the actual calculated load. Consider that most of the time the load on a 20A receptacle circuit might only be 0-5A, with nothing, or just a few small things, plugged in.

amakarevic · 07-13-2011, 01:32 PM

exactly what i thought. thanks for the clarification.

joed · 07-13-2011, 03:11 PM

The sum af all the circuits amperage(the actual amps being used) has to be less than the main.
The sum of all the breakers means nothing since many have no actual amps going through them at any one time. And none of them will have full load marked on the breaker going through them.

amakarevic · 07-13-2011, 04:25 PM

thanks but my question was referring to the breaker amperage.

a7ecorsair · 07-13-2011, 05:56 PM

Quote:

Originally Posted by amakarevic

thanks but my question was referring to the breaker amperage.

The branch circuit breakers do not have to add up to be equal or less than the disconnect breaker. The breaker in the panel that feeds this panel has a breaker that is sized to the wire gauge that feeds this sub panel. The breaker in the sub is typically the same size but doesn't have to be.