182 Modern Commercial Wiring Copyright Goodheart-Willcox Co., Inc. General = 2 × 80′ × × × 80′ × × 3 1/2 VA/ft2 × lighting load = 44,8 4, 80 0 VA Show-window = 50′ × 200 VA lighting load = 10,000 VA Exterior or = 30 × 175 VA lighting h ti load = 5250 VA Receptacle load = 200 × 180 VA = 36,000 VA Heating/air- = 85,000 0 VA V conditioning load Motor load = 3 × 3.5 A A × 360 V = 3780 0 VA The total lighting load a d is the combination of the three separate lighting g ht loads. Total lightin i ng load = 44,800 VA + 10,000 VA + 5250 VA = 60,050 VA The motor mo load and lighting loads are continu- ous, s, so the conductors must supply 125% of th t he full-load fu current: Total lighting load = 60,050 VA × 1.25 2 5 = 75,063 VA Motor load = 3780 VA × 1.25 5 = 4725 VA All loads are added to dete er mine the total load: Total load = 75,063 3 VA + 36,000 VA + 85,00 0 00 VA + 4725 VA = 200,788 2 VA The total current en can be calculated: I = P _ E E E = 200,788 VA ______ 360 V V = 557 A Using Table 310.15(B)(16), 1250 kcmil conductors will be sufficient. ffi SAMPLE PROBLEM 12-14 Problem: A restaurant is is supplied with three- wire, 120/240-volt service, vi is 50′ × 80′, and has ′ several loads: (1) 12-kW electric ec range (120-volt) (1) 10-kW w wa ter heater (240-volt) (2) 8-kW W fryers (240-volt) (2) 1.5-kW 5- coff (120-volt) ffeemakers ff (1) 2 2. 5-kW steam table (120-volt) (2) ) 3.0-kW toasters (120-volt) (1) (1 2.5-kW disposal unit (120-volt) (1) 1.5-kW outdoor sign (120-volt) (1) 40-kW heating unit (26) duplex receptacles Copper THW conductors are use s ed as feeders. What size should the current-carrying t- feeders be? Solution: First, the loads d s must be computed. General lighting load oa = 50′ × 80′ × 2 VA/ft2 = 8000 VA Sign lighting g load = 1500 VA Receptacle ac load = 26 × 180 VA = 4680 VA Heating He load = 40,000 VA The Th cooking equipment will be combined ed as the cooking equipment load: Electric range: 12,000 VA Water heater: 10,000 VA Fryers: 16,000 VA Coff 3000 VA ffeemakers: ff Steam table: 2500 VA A Toasters: 6000 0 VA Disposal unit: 2500 50 VA Cooking equipment pm load = 52,000 VA Table 220.56 contains on load-reduction factors for commercial ki k it chen equipment. For six or more pieces of equipment, eq the feeder conductors can be designed ig for 65% of the load. Reduced Re cooking = 52,000 VA × 0.65 equipment load = 33,800 VA (Continued)