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812 CHAPTER 44 1948 Guide Table 7. Approximate. Maintenance Cost for Large Air Conditioning ' Installations, Using High Quality Equipment Dollars per Ton ' per Year 0.60 0.25 0.07 0.25 0.85 0.15 1.15 of operating cost is more complex, since the power, required for summer cooling is affected by many factors which are of a variable nature. Among these are solar radiation, temperature difference between outside and inside, sensible and latent heat brought in with outside air, sensible and latent heat from people, heat released by electric lights, and, in some cases motor-driven equipment, cooking devices, and other equip ment used in the conditioned spaces- Some of these factors vary with the weather while others are substantially independent of it. The relative proportion of each factor varies widely even among installations of the same application, depending on building layout and location, the size and quality of the establishment, the personal idiosyncrades of the owner, and other items. In a strict sense, it is necessary to evaluate the effect of all such factors in order to predict the operating cost of a refrigeration plant. In niost cases this procedure will prove to be too tedious, or it may not be possible because the exact breakdown of load data is unknown. The use of a simplified semi-rational formula, Equation 2, which takes into account for each application the number of hours open for business and the geographical location, will provide a value of H which may be used in Equation 3 to determine the Season Power Cost. He = m(b +cf) (2) where He = Equivalent .full load operating hours of refrigeration equipment used for summer cooling during period May 15 to October 15. m = Total hours during period May 15 to October 15 that the establishment is open for business. b = Fraction of maximum load from internal heat under average operating con ditions. c ~ Fraction of maximum load which is due to external sources at maximum design conditions. / = Ratio of the number of hours for a particular city, when the outside wet-bulb exceeds 65 F, during the period June 1 to October 1 to the total number of hours during that same period. Total hours are assumed as 8 hr per day period for barber shops, department stores, funeral, parlors, offices, short hour restaurants, and specialty shops and 12 hr per day period for drug stores, ' long hour restaurants, and theaters. Table 8 was calculated from Equation 2. It should be pointed out that certain southern cities may have seasons longer than the 5-month period indicated in Table 8. If it is desired to consider a longer season of operation, the ratio of full load operating hours to hours open for business is smaller; in other words, the refrigeration load factor is lower. This is true because the extra increment of days added will be at relatively light load, since the table already includes the more severe part of the season. T able 8. Equivalent F ull L oad Operating H ours of Refrigeration Equipment Used for Summer Cooling M ay 15 to Oct. 15a Application Hr Open FOR Atlanta Business Boston Chicago Detroit Los Angeles Barber shops............ ;.....;....................... Department Stores. D rug Stores.... ........................................ Funeral Parlors.-......... ......................... Offices!......... ............!.....;......................... Restaurant fShort Hour) ... Restaurant (Long H o u r)............................ Specialty Shops (5 & 10)... Theaters-- C ontinunun......... Theaters-- Neighborhood 1280 940 2100 600 940 1290 2100 1090 1500 900 1010 840 1630 440 870 970 1510 800 1010 640 650 720 720 560 , 610 610 .950 1060 1060 300 330 330 Owning-and Operating Costs 81& 550 580 910 950 750 , 1300. 1400 830 : 880, 770 810 400 410 1420 1530" 780 890 940 Wash ington D.C. 720 750 St. Louis 1020 840 1650 440 880 98 0 1530 810 1020 650 Okla homa City 860 720 1330 380 740.' 800 1210 690 870 520 Phila delphia 830 700 1280 370 710 ,760 1170 670 850 500 1080 890 1790 470 900 1060 1690 860 1080 650 New Orleans o > CoCDO o0lO0 o0a0' --CoO4 -- .I.oD00 obto- otCoO.oCIDD oCNSC-XOfi 560 620 620 535 620 620 820 930 930 530 590 590 700 750 750 420 450 450 Modern A ir Conditioning, Heating and Ventilating, by W. H..Carrier, R. E. Cheme and W. A. Grant (Pitman Publishing C orf. 1940, p. 73).