BRANCH-CIRCUIT, FEEDER,

AND SERVICE CALCULATIONS A. General 220-1. Scope. This article provides requirements for determining the number of branch circuits required and for computing branch-circuit, feeder, and service loads. Exception: Branch-circuit and feeder calculations for electrolytic cells as covered in Section 668-3(c), Exception Nos. 1 and 4. 220-2. Voltages. Unless other voltages are specified, for purposes of computing branch-circuit and feeder loads, nominal system voltages of 120, 120/240, 208Y/120, 240, 480Y/277, 480, and 600 volts shall be used. 220-3. Computation of Branch Circuits. Branch-circuit loads shall be computed as shown in (a) through (d) below. (FPN): See Section 600-6(c) for exterior signs and outline lighting. (a) Continuous and Noncontinuous Loads. The branch-circuit rating shall not be less than the noncontinuous load plus 125 percent of the continuous load. Exception: Where the assembly, including overcurrent devices, is listed for continuous operation of 100 percent of its rating. (b) Lighting Load for Listed Occupancies. A unit load of not less than that specified in Table 220-3(b) for occupancies listed therein shall constitute the minimum lighting load for each square foot (0.093 sq m) of floor area. The floor area for each floor shall be computed from the outside dimensions of the building, apartment, or other area involved. For dwelling unit(s), the computed floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. (FPN): The unit values herein are based on minimum load conditions and 100 percent power factor, and may not provide sufficient capacity for the installation contemplated.