Document Gm9ok6kawdv7OZdk27yygq8mx

562 CHAPTER 30 1948 Guide the service lines will not permit more than plug-in devices. The Under writers permit approved heaters of 1320 watts or less to be plugged into approved baseboard receptacles, but such heaters cannot be served oh a circuit supplying much other load without overloading the fuses. There is an increasing trend toward supplying homes with three wire 115-230 jyolt service. Where homes have such service, larger heaters can be installed. For industrial purposes, heaters should be designed to use polyphase power, which is usually supplied at 208, 220, 440 or 550 volts. All polyphase heaters should be balanced between phases. In ordering electric heaters the proper voltage must be specified as the heat produced will vary as the square of any variation in voltage. REFERENCES '--Application of Electric Water Heaters To Domestic Service, by C. G. Hillier (A.S.H.V.E. Journal Section, Heating. Piping and Air Conditioning. November. 1936. p. 632). Fourteenth Range and Water Heater Survey (Electric Light and Power, August. 1940). *--Infra-Red Lamps Speed Up Drying Operations (.Automotive Industries 82:376-7; April 15. 1940). Invisible Rays Build Visible Profits, by H. M. Archer (Electric Light and Power. May. 1940). Radiant Energy Drying and Baking for.Organic Finishing (Metal Industry 38:294-6; May. 1940). '--Infra-Red Heating. Section IV. Power Sales Manual (Edison Electric Institute). BIBLIOGRAPHY Electric Elements Well Adapted to the Air Conditioning Heating Cycle, by L. P. Hynes (Heating, Piping and Air Conditioning, January, 1940, p. 29). Electric Heating for Los Angeles Building (Healing and Ventilating 37:50-1; June, 1940). Dracker Apartments, West Los Angeles, Calif. (Heating and Ventilating 37:32; July, 1940). Electric Heat in California Homes, by P. F. Offerman, W. J. Walsh and H. H. Skilling (Electrical West, March, 1941, pp. 37-39). Radiant Heat, by F. W. Hutchinson (Electrical West, January, 1941, pp. 29-31). Radiant Heating by Electricity, by L. N. Roberson (Heating and Ventilating, Sep tember 1946, p. 89). Electric Radiant Heat vs. Steam Convection, by Douglas Dow (Electrical World, August 10, 1940, pp. 61-62). Practical Aspects of Heating Residences by Electricity, by F-. L. Lawton and P. Tellier et al (Electrical News & Engineering (Canada) July 1, 1934, pp. 32-33 and .40; July 15, 1934, pp. 29-32; August 1, 1934, p. 17; July 1, 1933, pp. 16-20; July 15,1933, pp. 21-22; August 1, 1933, pp. 23-25). Off-Peak System of Electric Heating for Buildings, by Elliott Harrington (A.S.H.V.E. Transactions, Vol. 37, 1931, p. 323). Electric Heating of Residences, by Edgar Allan Loew (University of Washington, Engineering Experiment Station, Part I, Bulletin No. 15, December, 1921; Part II, Bulletin No. 20, November 15, 1923). Reversed-cycle Refrigeration for Air Conditioning Work, by Regis D. Heitchue (Refrigerating Engineering, May, 1941, pp. 317-321). The Sixth Ingredient--The Heat Pump--The Importance of Its Development in Making the All-Electric Home a Reality, by Philip Sporn (E.E.I. Bulletin, August, 1944). Description and Performance of Two Heat Pump Air Conditioning Systems (Using Well Water and Outside Air as the Heat Source), by Philip Sporn, and E. R. Ambrose (A.S.H.V.E. Transactions, Vol. 50, 1944). Progress Report on the Heat Pump, by E. R. Ambrose (Healing and Ventilating, December 1946, p. 68). Heating of Non-Magnetic Electric Conductors by Magnetic Induction, by R. M. Baker (Electrical Engineering, June, 1944). Operating Experience with HF Heating, by Henderson C. Gillespie (Electronics Industries, Feb. 1944). Induction and Dielectric Heating Equipment by Beverly Dudley (Electronics, August 1945, p. 110). Unusual Methods of Applying Electronic Heat, by E. D. Tillson (Electronics, April 1945). Chapter 31 PANEL HEATING AND RADIANT HEATING Influence of Heat Radiation on Human Comfort, Objectives of Radiant Heating, Practical Problems of Radiant Heating from a Physiological Standpoint, Fundamental Computations, Application Methods, Calculation Principles, Measurement and Control IT has been pointed out in Chapter 12 that the human body loses heat to its environment in three ways; by convection, radiation, and evaporation. The Effective Temperature Chart takes account of con vection and evaporation, but does not provide for such radiative effects as occur when room air and its surrounding surfaces differ widely in temperature. INFLUENCE OF HEAT RADIATION ON HUMAN COMFORT When, however, the body is exposed to radiation from a hot surface or is radiating to a cold surface, the factor of radiative heat gain or heat loss may be important. This phenomenon is most marked in the case of exposure to the sun's radiative heat. On a cold day, with no wind blowing, while standing in the sunshine, one may feel perfectly comfortable but, when a cloud passes'over the sun, one may instantly feel much cooler. The cloud acts as a shield to interrupt the radiant heat from the sun. The change in feeling of comfort is due to the instant change in rate of heat loss from the body caused by the shielding effect of the cloud. A shielded thermometer under the same condition would register no change in temperature. The rate of heat loss by convection depends upon the average tem perature difference between the surface of the body and the surrounding air, the shape and size of the body, and the rate of air motion over the body. The rate of heat loss by radiation depends upon the exposed surface area of the body, and upon the difference between the mean surface temperature of the body and the mean surface temperature of the sur rounding walls or other objects. This latter temperature is called the Mean Radiant Temperature (MRT). Because these two types of heat loss supplement each other, a required rate of total heat loss can result either from a relatively low air tempera ture and a relatively high MRT, or vice versa. At the temperature which produces comfort (and at all lower tempera tures) the production of sweat is low and the heat loss by evaporation is relatively low and relatively constant, irrespective of the relative humid ity of the atmosphere. Under such conditions the heat loss from the body is chiefly related to the combined effect of convection and radiation. For unclothed subjects in a reclining posture the heat demand of the en vironment, so far as these two factors of radiation and convection are con cerned, may be measured by Operative Temperature, which is defined by the following formula, modified from that of Gagge1 by the expression of air velocity in feet per'minute and temperature in Fahrenheit degrees, 563