Document 8Nm7b8mvD03BOD6byoEj0J3k

y JPanel Healing and Cooling Analysis, by B. F. Raber andF. W. Hutchinson (John wiley and Sons, New York, 1945). .1 , Radiant Heating, by T. Napier Adlam (Industrial Press, 148 Lafayette St.,'New York.1947). Radiant Healing, by R. W. Shoemaker, 1948 (McGraw-Hill Book Co., New York). Chapter V (pages 103-115) of Heating and Air Conditioning, by J. R. Allen, J. H. Walker, and J. W. James (McGraw-Hill Book Co., New York--Sixth Edition, 1946): Chapter 12 (pages 363-392) of Heating, Ventilating and Air Conditioning Funda mentals; by W: H. Severns and J. R. Fellows (John Wiley and Sons, New York, Second Edition, 1949). . " 'ii . ;l 'I j! :|j CHAPTER 25 UNIT HEATERS AND UNIT VENTILATORS Definitions; Unit Heaters: Classification, Application, Ratings, Location, Space Temperatures, Control, Piping, Maintenance Boiler Capacity; Unit Ventilators: Ratings, Capacity Requirements, Application, Selection, Control, Location, Exhaust Flues; Window Ventilators DESCRIPTIONS of heating, cooling, ventilating, humidifying, and dehumidifying systems are given in other chapters. This chapter deals with unit heaters and unit ventilators. Unit air conditioners and unit coolers are discussed in Chapter 26. Definitions The generally accepted meaning of the word unit in the terms unit heat ers, unit ventilators, and unit humidifiers, is that of a factory-made en cased assembly of the functional elements indicated by its name. Such units can be shipped complete or in sections, so that the only field work necessary is the assembling of the sections, providing proper supports, and connecting the unit to sources of heat (or fuel), power and water supply and, if necessary, to vent pipes for combustion gases. The term unit heater denotes an assembly of elements, the principal function of which is heating. The essential elements of a unit heater are a fan and motor, a heating element, a housing, and outlet vanes or diffusers. Some types are shown in Figs. 1 to 4. The term unit ventilator denotes an assembly, the principal function of which is to ventilate and cool the space by the introduction of outdoor air. It may serve to heat and circulate the air within the space, or introduce air from outdoors, or may accomplish both in varying proportions. The essential elements of a unit ventilator are fans and motor, heating element, dampers, and outlet grilles or diffusers, all encased in a housing. UNIT HEATERS Classification The various types of unit heaters which are at present available can usu ally be classified according to one of the three following methods: 1 - By type of healer. Under this classification there are three types of heating elements to be considered: (o) the steam or hot water type, (b) the electric type, and (c) the direct fired type which may be gas, oil, or coal fired. 2. By type of fan. Under this classification there are two types of fans to be considered: (a) the propeller type1 and (6) the centrifugal type. Either type may be arranged for horizontal or vertical delivery of air. 3. By arrangement of elements. Under this classification there are two ^Pes of heaters to be considered: (o) the draw-through type, in which the Ian draws air through, and (b) the blow-through type, in which the fan blows air through the heater. Unit heaters are available in any combination of the three preceding gen- 573