176 Modern Commercial Wiring Copyright Goodheart-Willcox Co., Inc. SAMPLE PROBLEM 12-8 Pro r ob lem: Determine (a) the re ec eptacle load for a an 80′ × 120′ hardware store a an d (b) the number of 15-amp circuits needed t to supply the load. The number of receptacles s is unknown. Solution: (a) The numb m be r of receptacles is unknown, so a receptacle ac load of 1 VA/ft2 can be calculated: Area = 80′ × 120′ 0 ′ = 9600 ft2 t 2 Receptacle load oa = 1 VA/ft2 × 9600 ft2 = 9600 VA (b) To determ mi ne the number of circuits required, qu fi rst calculate te the allowable load for a single e circuit: fi Max loa o ad = 120 V × 15 A = 1800 VA Divide e the total receptacle load by b y the maxi- mum m load per circuit to determine in the mini- mum u number of circuits: Circuits = 96_____VA00__ 1800 V = 5.33 This is the minimum numbe er , so round up to six circuits. SAMPLE PROBLEM 12-9 Problem: The hardwa ar e store introduced in Sample Problem 12-5 - will have one duplex receptacle for every 12′ 1 of wall around the stor- age area and showro oo m. A total of twelve floor r fl receptacles will be used. Determine the recep p- tacle load, including n show-window receptacles le for 20′ and 25′ show ho windows. S Sh owroom Storage area (Continued) Solution: Receptacles will be e placed along six 80′-long walls and two 40′-long 40 walls. Deter- mine the number of receptacles ec needed for each 80′-long wall: Receptacles per e r 80′ wall = _80′_ 12′ = 6.67 Seven receptacles ce are needed for each 80′ wall. Next, determine de the number of receptacles s neede d ed for each 40′ wall: Receptacles per 40′ wall = _40′_ 12′ = 3.33 Four receptacles are needed for r each 40′ wall. The total number of wall receptacles ep can now be calculated: Wall receptacles = (6 6 × × 7) + (2 × 4) = = 42 + 8 = 50 One receptacle c le is needed for every 12′ of show window o length, so the 20′ show window requires tw t wo receptacles and the 25′ show win- dow req e qu ires 3 receptacles. Therefore, the show windows d require a total of fi ve receptacles e s. fi The Th total number of receptacles can be found ou b by adding together the wall receptacles, s, floor fl receptacles, and show-window receptac a cl es: Total receptacles = 50 + 12 + 5 = 67 receptacles p ta The total receptacle load a d can then be determined: Receptacle load = 6 67 × 180 VA = 12,060 VA The total recepta ac le load is 12,060 VA. For feeder sizing, the first r st 10,000 VA must be counted at fi 100%, but o on ly 50% of the additional load needs to be con ns idered. Determine 50% of 2060 VA: 206 0 60 VA × 0.50 = 1030 VA Feeder load = 10,000 VA + 1030 VA = 11,030 VA The receptacle load on the feeder is 11,030 VA.