§ 152.46 STANDARDS FOR RESIDENTIAL SERVICE LOAD CALCULATIONS.

   The National Electric Code is applicable as follows.

   (A)   NEC Table 220-2(b) shows three watts per square foot.

   (B)   NEC Section 220-16(a) rates the two small appliance circuits at 3,000 watts (1500 watts each circuit).

   (C)   NEC Table 220-19, Column C, shows the load for two cooking units to be 65% of the sum of the nameplate rating of the two units.

   (D)   NEC Section 220-16(b) rates the laundry circuit at 1500 watts.

   (E)   NEC Article 220-2(b) states: “Unit lighting load for dwelling units shall not be less than three watts per square feet (Table 220-2(b))”. To determine the load on a watts per square foot basis, use the outside dimensions of the dwelling.  The computed floor area shall not include open porches, garages, or unused or unfinished spaces unless adaptable for future use.  Watts per square foot load shall be apportioned evenly among branch circuits, according to their capacities.  By using the example in NEC Chapter 9 for general illumination, one 15 ampere, 115-volt branch circuit would be required for every 575 square feet of occupied floor area. Example:

3 watts per sq. ft. X 575 = 1725 watts ÷ 115 volts = 15 amps.
A calculated load for a total occupied area of 30 ft. X 55 ft. = 1650 sq. ft. X 3 watts per sq. ft. = 4950 watts

      (1)   Calculating the minimum number of lighting circuits.

         (a)   The total required amperes is equal to:

Amperes = - watts
                   volts

Amperes = 4950 watts
                                              115 volts  =  43.04 Amperes

         (b)   The minimum number of circuits required for a general lighting load is obtained by dividing the total required amperes by the maximum amperage rating of each circuit. Example:

          43.04                                  maximum required
        15 amp rating                     =      2.86 or three circuits
                                                      minimum required

      (2)   Convenience outlets. NEC Table 220-2(b) states “receptacles other than those of the two small appliance circuits are considered part of general illumination and require no allowance for additional load...”.  An electric clock outlet may be installed on the general lighting circuit.

(Prior Code, § 152.31)