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1200 CHAPTER 49 1957 Guide Fig. 14. Heat Pomp Arrangement for Hot Water Supply high water temperatures are desired. This is due to the fact that higher water outlet temperatures result in lower coefficients of performance. For coefficients of performance of 4 or higher, the heat pump water heater may be more economical to operate than a conventional water heater. Although the first cost of domestic hot water heat pumps is somewhat high, they have the advantages of eliminating products of combustion, odors and soot, and not needing a chimney. A further advantage is that they may be used for cooling purposes. With a coefficient of performance of 2| to 3, water temperatures of 140 to 150 F may be obtained.6 REFERENCES 1 Water Distributing Systems for Buildings, by R. B. Hunter (National Bureau of Standards, Report BMS79, p. 6-9). (Charts extended to flow of 0.30 gpm). ! Private communication from Howard E. Degler. ' F.nough Hot Water--Hot Enough, by J. Stanford Setchell (American Gas Asso ciation. 1950). * Plumbing Practice and Design, by Sve nd Plum (John Wiley and Sons, Inc., 1943) ` Progress Report on a Heat Pump Water Heater, by P. Sporn and E. R. Ambrose Healing and Ventilating, February, 1949, Vol. 46, p. 78). BIBLIOGRAPHY Laundry, Kitchen and Hospital Equipment, by H. C. Russell (A.S.H.V.E. Trans actions, Vol. 35, 1929, p. 45). Water Consumption, Cost and Savings, by G. C. St. Laurent (American Hotel Association, Hotel Engineering, Vol. 1, 1940). Water-Supply Piping for the Plumbing SyBtem, by F. M. Dawson and A. A. Kalinske (Technical Bulletin No. 3, National Association of Master Plumbers). Use of Solar Energy for Heating Water, by F. A. Brooks, Smithsonian Institution, Washington, D. C. Methods of Estimating Loads in Plumbing Systems, by R. B. Hunter (National Bureau of Standards, Report BMS65, 1940). Plumbing Manual, Report of the Sub committee on Plumbing, Central Housing Committee on Research, Design and Con struction (National Bureau of Standards, Report BMS66, 1940). Water-Distributing Systems for Buildings, by R. B. Hunter (National Bureau of Standards, Report BMS79, 1941). Hot Water Requirements, by M. B. Mackay (Modem Sanitation, August, 1949, Vol. 1, p. 30). Urban Domestic Water Consumption, by M. A. Pond (Journal of the American Water Works Association, Vol. 31, No. 12,1939, p. 2003). CHAPTER 50 RESIDENTIAL SUMMER AIR CONDITIONING Consumer Requirements, Equipment Capacity Selection, Types of Equipment, Types of Application, Central Systems for Summer, Central Systems for Heating and Cooling, Location of Cooling Equipment, Noise, Air Distribution Methods, Operating Costs, Effects on Future House Design IN RECENT years, summer air conditioning in residences has developed to the stage where it has become a major factor in the air conditioning field and has created a heavy interest among home-owners, builders, architects and business men. Residential cooling, particularly for the small home, received its initial impetus when equipment specifically designed for such purposes became available in the 1930's. Recently it has caught the public fancy resulting in a tremendous increase in the number of sales and installa tions. The first installations were made by using the commercial and industrial methods as the estimating basis and did not prove as satisfactory as the installer or designer desired. Actually, the difference between estimating the residential summer air conditioning and commercial summer air condi tioning loads is in the design temperature differences used, the type of internal load in the conditioned area, and the method of calculating equip-, ment size. CONSUMER REQUIREMENTS With cooling, as with heating, the requirements of the individual cus tomer are the foremost consideration. Present practice is to design residential summer air conditioning on the basis of an 80 F indoor tem perature. Design on this basis will permit the home owner to maintain somewhat lower temperatures during most of the cooling season, by main taining a thermostat setting of 75 or 76 F. During the heat of the day on a design day the temperature may rise to the design temperature. This method of design utilizes the thermal storage effect of the house and house hold furnishings to level out the short duration peaks. Analog computer studies substantiated by extensive field investigation1 have proven the adequacy of this equipment selection procedure. The preference of individual home owners, however, may dictate the occasional use of indoor design temperatures below 80 F. Oversizing leads to several objectionable operating characteristics to be discussed later. To insure comfort, it is essential that the proposed operation and per formance of the system be explained to the user in advance; Usually the greatest degree of comfort can be obtained by keeping the house closed and operating with a fixed thermostat setting throughout the cooling season. In some climates the opening of the house to utilize night air cooling creates humidity difficulties that take several hours to overcome during the following day. The use of night air cooling may lead to un satisfactory conditions when the equipment is not turned on again suffi ciently early the next day. It will also allow unfiltered air to enter the house thus reducing the cleanliness advantage of air conditioning. 1201