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148 Chapter 7 1945 Guide 'where----------------------------------------------------------------- -- ---------------------^ . H -- heat to be removed from outside air entering the building; Btu per hour. Q = volume of outside air entering building, cubic feet per hour. v -- cubic feet of outside air per pound of dry air. ho = enthalpy of outside air, Btu per pound of dry air. hi = enthalpy of inside air, Btu per pound of dry air. The latent heat gain resulting from outside air introduced may be determined by Equation 4: * 2Hi = - - Afg (Wo - Wi) (4) where Hi = latent heat to be removed, Btu per hour. Afg = latent heat of evaporation at temperature at which water is condensed, Btu per pound. W0 -- humidity ratio of outside air, pounds water per pound dry air. Wi -- humidity ratio of inside air, pounds water per pound dry air. Heat Emission of Appliances Heat generating appliances which give off either sensible heat or both sensible and latent heat in an air conditioned enclosure may be divided into three general classes of equipment or devices: (1) electrical ap pliances, (2) gas appliances, and (3) steam heating appliances. In the first group may be found such devices as lights12, fans, motors, toasters, waffle irons, etc. The wattages are usually marked on the name plates and it is only necessary to multiply the aggregate wattage by 3.413 (Btu per watthour) in order to estimate the heat added to the conditioned space by such devices in Btu per hour. Electric motors are usually rated in units of horsepower output. To determine the corresponding input, which is the rate at which heat is added to the conditioned space by full-load operation of such motors, some idea of motor efficiency is necessary. The aggregate input in horsepower should then be multiplied by 2546 (Btu per horsepower hour). When motor efficiencies are not known, the data in Table'9 may be used. Table 9. Heat Generated by Motors Name-plate Rating Hobsepower H to 3 3 to 20 Heat Gain in Btu per Houb pee Horsepower . Connected Load in Same Room Connected Load Outside of Room 4250 3700 2950 1700 1150 400 In the second group belong such appliances as coffee urns, gas ranges, steam tables, broilers, hot plates, etc. For heat generating capacities of such appliances refer to Table 10. Judgment must be used in the application of data given in Table 10. Consideration must be given to the heat contributed by appliances which are in use at the time of peak load. The quantity of heat will ^Cooler Footcandles for Air Conditioning, by W. G. Darley (A.S.H.V.E. Transactions, Vo!. 46, 1940, p. 367). Lighting and Air Conditioning Design Factors, Report of I. B. S.--A.S.H.V.E. Joint Com* mittee on Lighting in Air Conditioning (A.S.H.V.E. Journal Section. Heating, Piping and Air Con ditioning, September, 1941. p. 605). Lighting and Air Conditioning, by Howard M. Sharp (Heating and Ventilating, November. 1942, p. 35). J Cooling.Load 149 Table 10. Heat Gain from Various Sources3 Source Per Cent Name- plate Rating Percentage or Btu per Hour Sensible Latent Total Electrically Heated Equipment ' . .r 70 7 Hnt Plat** 19 Sandwich Grille 13. Toaster--Intermittent or Timed Control___________________ 20 30 50 . 80 100 75 70 40 60 50 100 16. Permanent Wave Machine in Beauty Parlor--24-25 w Units.. -- 80% 90% Rf}% 100% 65% 90% 90% 90% 90% 2050 2050 20% 20% 6% 35% 25% 10% 10% -- 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 2050 Gas Burning Equipmentb 17. Gas Heated Oven--Baking--.............. ....... no vent connection gravity vent connection 18. Open Top Burner---per Hole-.________________ _____________ 19. Hot or Closed Top--per Burner . .no vent connection gravity vent connection 20. Coffee Urn--Large 18 in. Diam.--Single Drum 21. Coffee Urn--Small 12 in. Diam.--Single Drum 22. Coffee Urn--per Gallon of Rated Capacity 23. Plate Warmer ........................_.................... no vent connection gravity vent connection 24. Steam Table--Water Bath Type.. . no vent connection gravity vent connection 25. Frying Griddles.__________________________no vent connection gravity vent connection 26. Fry Kettle................................................. .no vent connection gravity vent connection 27. Egg Boiler--per Egg Compartment 28. Cigar Lighter--Continuous Flame Type.. ____ .. 29. Curiine Iron Heater .. 70 35 50 100 70 60 10 60 42 75 52 70 49 72% 100% 45% 45% 50% 5000 3000 500 90% 100% 55% 50% 81% 90% 72% 80% 2500 2250 2250 28% 100% 0% 100% 55% 100% 55% 100% 50% 100% 5000 10.000 3000 6000 500 1000 10% 100% 0% 100% 45% 100% 50% 100% 19% 100% 10% 100% 28% 100% 20%. 100% 2500 5000 250 2500 250 2500 200 Steam Heated Equipmentc 31. Steam Heated Surface Not Polished--per Square Foot of 32. Steam Heated Surface Polished--per Square Foot of Surface -- 130 . 80 400 220 110 2000 1200 2500 300 " 0. 800 " -330 130 . 80- 220 110 4000 2400 5000. 1100 Miscellaneous 41- Heat Liberated By Food per Person, as in a Restaurant______ -- 30 30 60 42. Heat Liberated from Hot Water used direct and on towels per hour--Barber Shrms 100 200 300 Heat gam from electric or gas residential ranges or cooking stoves depends on size of the family, socio economic status of the individual, time of day for principal meal, and whether the equipment is manually or automatically controlled. Total heat gain will probably not exceed 40 per cent name-plate rating. Pei cent sensible and latent heat will depend upon use of equipment; dry heat; baking or boiling.- ' / bNanie-pla,te ratings of gas burning equipment can be obtained from a Directory of Approved Gas Appliances and Listed Accessories, obtainable from American Gas Association. '' n Requirements of Process Equipment, Report of the Commercial Relations Committee, National District Heating Association (Heating, Piping.and Air Conditioning, November, 1942, p. 675). .