Branch Circuit Load Calculation

[steve66]

Can I use the following procedure to calculate the load permitted on a 20A branch circuit with lights and receptacle?

1. Add 180VA per receptacle.
2. Add the VA of each light fixture multiplied by 1.25 (for a continuous load).
3. Make sure the result is less than 2400VA. The 2400VA comes from (120V x 20A).

The reason I ask is this isn't how I have done these calculations in the past. I have always just added the VA for each fixture and for each receptacle together and made sure the result was less than 1920VA. The 1920VA comes from (120V x 20A x 0.8).

However, the first method lets me place more load on the branch.

Steve

 

[tim robben]

Re: Branch Circuit Load Calculation

The first method is correct per Article 210 of the code. Although the second method would also be allowed, it is more conservative. UNLESS you know that the receptacles are serving loads that are continuous, then the second method is correct. But for general purpose convenience outlets use the first method.