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212 CHAPTER 14 1959 Guide adding moisture to the air in the room. Tests1* show that an average evaporative rate of about 0-235 lb per (hr) (sn ' ft of water surface) may be obtained from such pans, when a radiator is steam heated and the relative humidity in the room is between 25 and 40 percent. This source of supply of moisture alone is not adequate to maintain a relative humidity above 25 percent on a zero day. REFERENCES ll -- B -- R Baseboard Heating Systems Installation Guide No. 5 (Institute'of Boiler and Radiator Manufacturers, 1953, 2nd ed.). `A. P. Krsts and W. S. Harris: A Study of Radiant Base board Heating in the I = B = R Research Home (University of Illinois, Engineering Experiment Station Bulletin No. 358, 1945). *1 = B = R Testing and Rating Code for Finned-Tube Type Radiation (Institute of Boiler and Radiator Manufac turers, 1951, 1st ed., with addenda, 1954). ` ASHVE code for testing radiators (ASHVE Transactions, Vol. 33,1927, p. 18). (This code was withdrawn in 1956.) 'Commercial Standard .for Testing and Rating Convectors (U: 8. Department of Commerce, CST40-47,' 1947). 'C. Brabbee: The heating effect * of radiators (ASHVE Transactions, Vol. 33, 1927, p. 33). *A. C. Willard, A. P. Krats, M. K. Fahnestock, and S. Konzo: Investigation of heating rooms with direct steam ra diators equipped with enclosures and shields (ASHVE Trans actions, Vol. 35, 1929, p. 77 or University of Illinois, En gineering Experiment Station Bulletin No. 192). A. C. Willard, A. P. Krats, M. K. Fahnestock, and S. Konso: Investigation of Various Factors Affecting the Heating of Rooms with Direct Steam Radiators (University of Illinois, Engineering Experi ment Station Bulletin No. 223). */ ~ B = R Testing and Rating Code for Baseboard Type of Radiation (Institute of Boiler and Radiator Manufacturers, August 1952, 2nd ed.). 'E. A. Allcut: Heat Output of Concealed Radiators (Uni versity of Toronto, School of Engineering Research Bulletin No. 140, 1933). **K. F. Hubert: Heat Emission from Radiators (Cornell University, 1C7I Engineering Experiment Station Bulletin No. 24^. " v*. oc*eiua. tCSU Ol luuuLWir (ASHVE Transactions, Vol. 33, 1927, p. 41). **J. R. Allen: Heat loss from direct radiation (ASHVE Transactions, Vol. 26, 1920, p. 11). " A. P. Krats: Humidification for-Residences (University of Illinois, Engineering Experiment Station Bulletin No. 230. p. 20). BIBLIOGRAPHY A. C. Willard, A. P. Krats^and M. K. Fahnestock: ASHVE Research Report No. 926--The application of the eupatheoscope for measuring the performance of direct radiators and convectors in terms of equivalent temperature (ASHVE .Transactions, Vol. 39, 1933, p. 303).. W. J. McConnell and C. P. Yagloglou: The Kata ther mometer--its value and defects (U. S. Public Health Service Report, Reprint No. 953, September 5, 1924, p. 2293). C.-E. A. Winslow and Leonard Greenburg: The thermointegrator--a new instrument for the observation of thermal interchanges (ASHVE Transactions, VoL 41, 1935, p. 149). C.-E. A. Winslow, A. P. Gragge, Leonard Greenburg, I. M. Moriyama, and E. J. Rodee: The calibration of the thermomtegrator (The American Journal of Hygiene, July 1935, p. T. Bedford and C. G. Warner: The globe thermometer in studies of.heating and ventilation (The Journal of Hygiene, Vol. 34, No. 4). ' Residential baseboard radiation (Reference Section, Air Conditioning, Heating and Ventilating, November 1957, p. 81). Commercial and industrial finned-tube radiation (Reference Section, Air Conditioning, Heating and Ventilating, December 1957, p. 71). CHAPTER 15 UNIT VENTILATORS AND UNIT HEATERS Unit Ventilators.- Classification, Ratings, Capacity, Requirements, Application, Control, location, fxhaust Vents, Window Downdraft Prevention, Mechanical Cooling; Unit Heaters: Classification, Application, Heating Medium, Type, location, Sound level. Ratings, Control, Piping, Maintenance. NIT ventilators and uuit heaters are discussed in this Ventilators.1 .This code requires OF entering air temper U chapter. The types, characteristics, method of rating, ature, unit fan operating at rated speed with standard louver and procedures for selection and application of these prodo r grille on the outlet, and dry saturated steam at a temper ucts are described. ature at the unit corresponding to a pressure of 16.7 psia UNIT VENTILATORS (218.5 F). The standard air rating of the unit is the delivery in cubic-feet per minute, converted to standard air at 70 F. The term unit ventilator denotes an assembly, the principle functions of which are to heat, ventilate, and cool a space by the introduction of outdoor air in quantities up to 100 percent of its rated capacity. The heating medium may be steam, hot water, gas, or electricity. The essential elements of a unit ventilator are fans and motor, heating element, dampers, filters, and outlet grilles (or diffusers), all encased in a housing. Unit ventilators are used primarily in schools, meeting rooms, offices and other areas where the density of occupancy indicates the need for controlled ventilation. The typical unit is equipped with a system of control that permits the heating, ventilating, and cooling effect to be. varied while, The anemometer air rating is peculiar to school venti lation. It originated as a convenient field measurement for checking air quantities, and is the basis of rating for venti lation requirements under some state and local building codes. The anemometer rating (air capacity) is obtained by averaging the air velocities obtained by an anemometer (propeller or averaging type) held over equal subdivisions of the outlet grille at a distance of 2 in. from the grille, and multiplying the average velocity by the gross area of the grille. The anemometer rating is based on the final temper ature of the air leaving the grille while the unit is delivering outdoor air and recirculated air in the proper proportion and the heating element is supplying heat as specified. This the fans are operating continuously. In normal operation, the discharge air temperature from a unit is-varied in ac cordance with the room requirements. When heating is required, the air delivered is above room temperature. When the heat generated within the room by occupants, lights, sun, etc., is sufficient to cause overheating, the temperature of the air delivered is below that of the room. It is customary to equip unit ventilators with control.devices that prevent the delivery of air at a temperature low enough to cause discomfort. Classification The various types of unit ventilators can be classified according to the three following methods: I.Heating Medium. Four-types of heating elements are used: (a) steam, (b) hot water, (c) gas-fired, and (d) electric. 2. Type of Unit. Under this classification there are three basic types to be considered: (a) Floor-mounted type, (b) ceil ing-mounted type, and (c) auditorium type which are used in vertical, horizontal, or inverted positions. Figs. 1 and 2 show typical floor-mounted units. Fig. 3 shows a typical ceilingmounted unit, 'while Fig. 4 shows a typical auditorium-type unit in horizontal position. 3. Arrangement of Elements. Unit ventilators may be of the (a) draw-through, or (b) blow-through arrangement. Fig. 1 shows a typical draw-through unit and Fig. 2 shows a typical blow-through unit. Ratings of Unit Ventilators Unit ventilators are customarily cataloged with two rat ings: the standard air rating and the anemometer air rating. The standard air rating is obtained in accordance with the ASHAE Standard Code for Testing and Rating Steam Unit Fig. 1.... Typical Floor-Mounted Unit Ventilator-- Draw-Through Type 213 x'