Document 9Jm3dGqkqEdJRG68VKK3kLDQ3

American Society of Heating and Ventilating Engineers Guide, 1932 been developed to meet the requirements of the newer architecture of modern building construction and are based on well established engineer ing principles of control for occupancy, wind and sun effect, zone demands, etc. Descriptions of these systems will be found in the catalog section of The Guide. 14S Chapter 9--Steam Heating Systems and Pipe Sizes TEMPERATURE CONTROL The heating surface installed in buildings must emit sufficient heat to maintain the desired temperature in the coldest weather. For higher out side temperatures, the radiators will be of greater capacity than required, and overheating will result unless the heat output is reduced. The amount of heat delivered by a steam radiator can be reduced by any one of the following three methods: 1.. By lowering the pressure and thus the temperature of the steam. 2. By admitting steam to the radiator intermittently and thus reducing the length of time it is filled with steam. 3. By restricting the flow of steam into the radiator. Vacuum or Pressure Control If large buildings are controlled by a single thermostat, the heating surface should be carefully balanced against the heat losses of the build ing. The heat emission of the radiators may then be varied according to the heat losses of the structure by varying the pressure or vacuum on the system. The higher the vacuum the lower will be the temperature, and thus the temperature in the radiator will be reduced. This method is sometimes supplemented with thermostatically operated valves in rooms Table 11. Maximum Allowable Capacities of Up-Feed Risers for Two-Pipe Low Pressure Steam Based on A. S. H. V. E. Research Laboratory Tests CT Ftp* Sob Inches Velocity Per per Second Pressure Drop Ounces per 100 Ft. Sq. Ft. Radiation Capacity B.t.u. per Hour Lb. Steam per Hour AB 34 20 l 23 m 27 i'A 30 2 35 2'A 38 3 41 m 42 4 43 C -- 1.78 1.57 1.48 1.33 1.16 0.95 0.81 0.71 D 40 74 151 228 438 678 1129 1548 2042 E 9550 17,900 36,500 55,200 106.100 164,100 273,500 375,500 495,000 F. 10.0 18.45 37,65 57.0 109.5 169.4 282.2 . 387.0 510.5 INSTRUCTIONS FOR USING TABLE 11 1. The capacities given in this table should never be exceeded on two-pipe risers. 2. Capacities based on M lb. condensation per square foot equivalent radiation and: actual diameter of standard pipe. 3. All pipe should be well reamed and free from constrictions. Fittings should be! up to size. (See Tables 7 and 8). 149