Document 8RZQJw6J894X4m9gdGOb8xMeB

American Society of Heating and Ventilating Engineers Guide, 1931 2. Indirect Heaters a. Hot Water or Steam Radiators. Electric immersion unit to heat water in radiators, or (2) to generate steam.. . I_____ A.______-____ * _____ 1` A._____ _______ n^ A._____________ A._____ A. ' EachU^tS ' ^ tor is a separate unit connected to the electric wiring system b. Central Heating Plant Using Instantaneous Heating, (n . heated by passing directly over electric heating elements art then circulated by a duct system to the spaces to be heated (2) Steam generated in electric boiler at times and in quantiti ' required by the heating demand. (3) Water heated to the tei^ peratures and in quantities required for the heating demand. ^ c. Central Heating Plant Using Thermal Storage. This is described^ in the following paragraph and is applicable to warm air, hot ' water and steam heating. STORAGE OR OFF-PEAK SYSTEM OF HEATING The off-peak storage system of electric heating is intended to take advantage of the low off-peak electrical energy rates which some power companies are now making available if the energy is taken at hours when the generating stations are not working at full capacity. Insulated tanks of water are heated during hours designated by the power company and the stored heat is used as required by the building under thermostatic control. Power companies in various parts of the country are investigating anu sponsoring development of off-peak electrical house heating and are pre- paring to support its widespread use. The nature of the load and its ; bettering effect on the power factor and load curve is favorable both to the public utility and the consumer. The characteristics of the electric heating load, when used with the thermal storage system are ideal from the electrical operating standpoint. The units are non-inductively wound so that the load is unity power factor, and the load is timed so as to be Used exactly at the time specified by those responsible for the operation of the systems. It is, therefore, corrective in its effect and tends to fill up the valleys in the load curve. It corrects the inherent peak characteristics of the domestic load in that it places a load at hours when otherwise a resident would use no electricity. The electricity is taken at the hours when the electric light and power company most desires load and the stored heat is used during the day when it is needed to heat the house. The public service companies charge usually a rate of about I cent, per kilowatt-hour or less if the energy is taken during the period specified. This rate does not make electricity a price-competitor of oil and natural gas for heating, but in some localities it compares favorably with manu factured gas. The high cost of the equipment necessary for this type of heating system is sometimes a prohibiting factor. Hot Water System The tank used with these storage systems is heavily insulated and is equipped with built-in electrical heating elements. The size of the tank \ 290 Bang -- JgffIgjipffetjTinrrbte-he-kAsicinfhdSeymoseftedtmaenvek.lopAedhfoourswinagrmis-abiruhilet aatirnogunsdysttehmestamnakk,esfrousme of the which Sfadiate the supply ducts to the registers in the rooms. The return air Igfucts from the house are connected back to the tank housing. An Attended surface type of unit heater is mounted within the housing with 'Sits flow and return connections joined to the top and bottom of the hot water storage tank. The fan on the unit heater is controlled by the house -thermostat, which causes the desired day and night temperatures iStat, wmv.i ------'tfoumBbeeaccmaeuassieynsta-ateiifnnnma>eenddisi;iisonnbutttshhaeeeidnerrtoodooo, mmcaissnrc..du'ilatties tphoesswibalermtoauirs,ethsme aelflfed`cutcotsf --aanfdiano-f such shapes as will accommodate themselves architecturally to the struc ture of the house, which of course cannot usually be done with warm air where the circulation is solely by natural convection. DoTmheestisctoHroatgeW.parteinrcHipeleateforsr using electricity at off-peak periods is also applied to domestic hot water heaters. Installations of this type of electrical heating have been made in many houses in the middle west : during the past five years. COMPARATIVE HEATING COSTS WITH ELECTRICITY Cost comparisons between various fuels and electricity for house heating should be made on a heat unit basis, giving due consideration in each case to efficiency. A rate of I cent per kilowatt-hour is equivalent . to a cost of about $3.00 per 1,000,000 Btu, assuming a transmission . loss through the wiring system of 2 per cent. A comparison between , * the cost of heating with electricity and the cost of heating with coal, oil or gas may be made by referring to Chapters 15, 16 and 17. The importance of insulation and weatherstripping for electrically heated houses cannot be over-emphasized. The remarks in Chapter 17 on this subject apply equally to electric heating. The more costly the fuel, the greater the need for insulation, weatherstripping and storm sash. HEAT EQUIVALENTS OF ELECTRICITY The relation between electrical energy and heat and power is given . by the following equations: 1 horsepower = 746 watts. = 33,000 ft ib per min 1 Btu = 777.64 ft lb 291 5E3S