Chapter 12 Branch Circuits and Feeders 171 Copyright Goodheart-Willcox Co., Inc. load is continuous, the calculated load is multi- plied by 1.25 (the inverse of 80%) to determine the circuit requirements. The general lighting load is not required if the load for each lamp is determined separately. If the individual load is continuous, it must be multiplied by 1.25. When determining the cur- rent draw of fl uorescent fixtures, fl use the current fi rating of the ballast, not the tube wattage. SAMPLE PROBLEM 12-1 Problem: A 25,000 ft2 t 2 offi ce building is being ffi designed. What is the e general lighting load and what load does the circuit c need to supply? Solution: From Tab a bl e 220.12, the unit load for o an office building g is 3 1/2 VA/ft2. ffi The gener e ra l lighting load is de et ermined by multiplying this t value by the squa u ar e footage of the building: g: 3 1/2 VA/ft2 × × 25,000 ft2 = 87,500 VA The general lig gh ting load is 87,500 volt-am mp eres. However, the e load is continuous and can ca only be 80% of the h load supplied by the circ cu it. This value must t be multiplied by 1.25 to d de termine the circuit requirements: 87,500 0 VA × 1.25 = 109,375 VA The c ci rcuit is designed to supply 109.375 5 kilovolt-amperes. Show-Window Lighting The show-window lighting load is not consid- ered as part of the general lighting load. Section 220.43(A) of the Code requires that show- window lighting be computed as 200 volt-amperes per linear foot or as the maximum volt-ampere rating of the equipment and lights, whichever is greater. The Code includes several sections applicable to show-window lighting: • Section 220.43(A)—Show-window lighting • Section 220.14(G)—Load computation. The Code also requires at least one receptacle outlet for every 12′ of show-window space mea- sured horizontally with the load computed at SAMPLE PROBLEM 12-2 Problem: A 4′ long, tw t wo -lamp fluorescent fix- fl fi ture ballast draws 0.7 7 amps at 120 volts. How many of these fixtures re can be connected on a a fi 20-amp circuit? Solution: This is a a continuous load, so the cu ur - rent used by the lights l can only be 80% of the t circuit current rat ti ng: Allowable current u = 20 A × 0.80 = 16 A By dividing the allowable load by the h load of each lam mp , the total number of l la mps is determined: d 16 A _____ 0.7 A = 22.8 fixtures _ e fi The max a xi mum number of fi xtures o on the circuit fi is 22. CODE ALERT Show Window According to Article 100 of the 0 NEC, a C C show window is any window used or designed to be used for the display of goods or advertising material, whether it is fully or partly enclosed or entirely open at the rear and whether or not it has a plat- form raised higher than the street floor level. fl Goodheart-Willcox Publisher Figure 12-3. Minimum general lighting loads are dependent on the type of area being lit. General Lighting Loads Type Building Unit Load Lo (VA/ft2) Auditoriums Banks Barber shops ps Churches ur ch Dwelling Dw units Hospitals Hotels Offi ce buildings ffi Restaurants Schools Stores Warehouses 1 3 1/2 3 1 3 2 2 3 1/2 2 3 3 3 1/4