Branch Circuit Load Calcs.

[big john]

I recently encountered a 12 pole subpanel on 30A breaker: Eleven 15A circuits, one 20A circuit. Supplied almost all the lighting and convenience receptacle loads for two floors of a large house, including some heavy-duty intermittents: disposal, compactor, etc. They'd never had a problem with overloading.

Had I been the installer, a lot of ampacity in that sub would've probably gone to waste: Lighting circuits all calculated to 80%. Seven or eight receptacles on one 20A breaker.

The problem is I take a lot of pride in my work, and because of that, I never want the homeowner to be inconvenienced by my design: They go to plug the vacuum cleaner into a branch circuit that already has the entertainment center on it and it ends up tripping the breaker. To avoid that, I end up trying to plan for any eventuality and probably wasting a lot of available circuit space because of it.

The ultimate question being: How do you guys generally figure residential branch circuit loads? Any rules-of-thumb or general load values for receptacles/lighting or anything I can use in the future that might help me learn to better distribute available power?

Thanks a million.
-John

 

[templdl]

Re: Branch Circuit Load Calcs.

To be competitive one would meet the minimum requirements for lighting, outlets, etc. However, with all practicality, one must also consider the user as you would like to do. If the user wants low price then he must understand that your installation will meet the minimum requirements as others electricians would. If the user expresses a desire for a distribution system that meets his specific needs then he must understand that there are extra costs involved like additional circuits to reduce the posibility of a circuit overload, extra outlets and quadraplex outlets to reduce the necessity of power strips, etc.
But all this stuff comes at a price. How much extra stuff do you have to give away to be a nice guy and still stay in business to make a living?