How do you determine the number of branch circuit for lighting load?

Answer 1

An engineered set of blueprints will have all of the pertinent information about circuit loading and circuit numbers and panel balancing already calculated. If there is no wiring schedule on the print then you refer to the electrical code book and abide by the regulations that are set out for circuit loading and the amount of devices that can be connected to that circuit.

Single family dwelling: multiply the number of square feet by 3. So a 2500 sq ft home times 3 = 7500 watts. Divide that number by 1500 for #14 wire circuits or 2000 for #12 wire circuits. 7500 divided by 1500 = 5 #14 wire circuits or if divided by 2000 + 3.75 or 4 #12 wire circuits. This would be for the lighting load and general use receptacles through out the home. I always lay my circuits out where a circuit only covers 500 sq ft of the dwelling.