Using the standard calculation method, what is the general lighting and receptacle minimum unit load (line and neutral) for a 3,200 sq-ft one-family dwelling with two small-appliance branch circuits and one laundry branch circuit?

Using the standard calculation method, what is the general lighting and receptacle minimum unit load (line and neutral) for a 3,200 sq-ft one-family dwelling with two small-appliance branch circuits and one laundry branch circuit?

• A. 5,310 VA - L5,310 VA - N
• B. 6,885 VA - L6,885 VA - N
• C. 7,700 VA - L7,700 VA - N
• D. 9,600 VA - L6,720 VA - N

Answer: (B)

The calculation tests how to size a dwelling’s general lighting and receptacle load using the standard NEC method, which combines lighting/receptacle load with appliance and laundry loads and then applies demand factors to arrive at a practical unit load for the service. Start with the general lighting and receptacle load: 3 VA for each square foot, times 3,200 ft² gives 9,600 VA. Add the appliance loads: two small-appliance circuits at 1,500 VA each equals 3,000 VA, plus the laundry circuit at 1,500 VA. The total before demand factors is 14,100 VA. Then apply the NEC demand factors for a dwelling of this size (the table used for homes). After applying those factors, the resulting minimum unit load for line and for neutral works out to 6,885 VA. In this method, the line and neutral loads are shown as equal, which is typical for a single-phase dwelling calculation. Therefore, the general lighting and receptacle minimum unit load is 6,885 VA on both the line and the neutral.

The calculation tests how to size a dwelling’s general lighting and receptacle load using the standard NEC method, which combines lighting/receptacle load with appliance and laundry loads and then applies demand factors to arrive at a practical unit load for the service.

Start with the general lighting and receptacle load: 3 VA for each square foot, times 3,200 ft² gives 9,600 VA. Add the appliance loads: two small-appliance circuits at 1,500 VA each equals 3,000 VA, plus the laundry circuit at 1,500 VA. The total before demand factors is 14,100 VA.

Then apply the NEC demand factors for a dwelling of this size (the table used for homes). After applying those factors, the resulting minimum unit load for line and for neutral works out to 6,885 VA. In this method, the line and neutral loads are shown as equal, which is typical for a single-phase dwelling calculation. Therefore, the general lighting and receptacle minimum unit load is 6,885 VA on both the line and the neutral.