Document 8R60DOVYy1xMm8Bw58jaydLEo

222 CHAPTER 14 I960 Guide adding moisture to the air in the room. Tests" show that Ml average evaporative' rate of about 0.235 lb per (hr) (sq ft of water surface) may be obtained from such pans when a radiator is steam heated and the relative humidity in tin* 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 l/ = B -- R Baseboard Heating Systems Installation Guide No. 500 (Institute of Boiler and Radiator Manufacturers, 1957, 1st ed.). *A. P. Krats and W. 8. Harris: A Study of Radiant Base* board Heating m the I - B ~ R Research Home (University of^Dlinois, Engineering Experiment Station Bulletin No. 358, * l = B = R Testing and Rating Code for Finned-Tube (Commercial) Radiation (Institute of Boiler and Radiator Manufacturers, 1958,3rd ed.). `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 (This code was withdrawn in 1956.)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. S. Department of Commerce, CS 140-47,1947). *C. Brabble: The heating effect of radiators (ASHVE Transactions, Vol. 33, 1927, p. 33). * A. C. Willard, A. P. Krats, M. K. Fahnestock, S. Konzo: Investigation of heating rooms with direct 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. Konzo: Investigation of Various Factors Affecting the Heaping of Rooms with Direct Steam Radiators (University of Illinois, Engmeerina Experi ment Station Bulletin No. 223). *1 -- B ~ R Testing and Rating Code for Baseboard Radia tion (Institute of Boiler and Radiator Manufacturers. May 1957,3rd 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, Engineering Experiment Station Bulletin No 24 10371 , ' wcciuj>. vuuipaiauve tests oi radiator nmsnes (ASHVE Transactions, Vol. 33, 1927, p. 41). H. Allen: Heat loss from direct radiation (ASHVE Transactions, VoL 26, 1920, p. 11). F. Hratz: Humidification far 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 Rkfort No. 928--The application of the eupatheoscope for measuring the performance of direct radiaters and convectors in terms ol 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. PubHc Health Service Report, Reprint No. 953, September 5, 1924, p. 2293). C.-E. A. Window and Leonard Greenburg: The thermointegrator--a new instrument for the observation of thermal interchanges (ASHVE Transactions, Vol. 41, 1935, p. 149). C.-E. A. Window, A. P. Gragge, Leonard Greenburg, I. M. Moriyama, and E. j. Rodee: The calibration- of the thermomtogrator (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 Ventihtors: Classification, Ratings, Capacity, Requirements, Application, Control, Location, Exhaust Vents, Window Downdraft Prevention, Mechanical Cooling; Unit Heaters: Cfazsrficafion, Application, Heating Medium, Type, Location, Sound Level, Ratings, Control, Piping, Maintenance. UNIT ventilators and unit heaters are discussed in this Ventilators} This code requires OF entering air temper 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 prodor grille on the outlet, and dry saturated steam at a temper ucts are described. UNIT VENTILATORS ature at the unit corresponding to a pressure of 16.7 psia (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 ate 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: 1. 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: (o) Floor-mounted type, (b) ceUxng-mounted type, and (c) auditorium type which are used in vertical, horizontal, or inverted positions. Figs. 1 and 2 show typical floor-motmted units, fig. 3 shows a typical cedingmintnted unit, while Fig. 4 shows a typical auditorium-type unit in horizontal position. 3. Arrangement of Elements. Unit ventilators may be of the (o) 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 223