Document 3NKebVdR01wjYm14EMnqywmj0

C. A. Dunham Company Specialties, Heating !i By furnishing steam at this wide range of tem peratures, it is possible to vary the heat output of the radiation thus pre venting overheating. For instance, in mild weather, steam is supplied at a low temperature, therefore the radiator will give off only a slight amount of heat (in fact one can hold his hand on the radiator). As the weather gets colder higher temperature steam is furnished until finally in severe weather there may be a pressure on the radiation instead of the high vacuum used in mild Fig.l Heat Co.nthol.--Tto illustration shows how the room temperature is maint&ined uniformly under changing weather conditions, by varying the steam pressure so that the heat given off by the radiator equals the heat lost by the budding. weather. See Figs. 1 and 2. It is generally known that water boiling at sea level will generate steam at 212 deg, while-up iii the higher altitudes where the atmospheric pressure is less, water will boil at much lower temperatures. See Fig. 3. For instance, in Denver which is at an altitude of 5279 ft. above sea level the water will boil and generate steam at about 199.7 deg. fahr. The same pressure conditions are dupli cated in the boiler and system, of the Dif ferential Vacuum Steam Heating System. The temperature of the steam is governed by the Dunham control equipment and tne Dunham Differential Vacuum Pump wfiich removes the air from the system because a relatively constant differential in pressure between the radiator and the return is maintained, so that the air and water will constantly flow out of the radia tors. The steam is induced to completely' fill them. Due to this " Differential" com plete circulation is obtained and the radia tors throughout the building are heated uniformly. The "cooler" steam gives a "mild heat," which prevents overheating. This is more healthful, and less destructive to decorations and furniture, than the "hot" steam used in ordinary types of systems. This system is simple, easy to design and install and very economical in opera thereby reducing the pressure on the water . tion. in the boiler, or causing the steam to ex The system was in the transition process pand through Reducing Valves when they from theory to practical application for are used. many years. There was involved in this The term "Differential" is applicable j problem a complete revolutionizing of the art of heating with the Srcm WiMUtt I Vfcn*gPtL&3Tt*M. _ .KEwnm 9mm, Or nwwfrfftM] altering of Mechanical Appliances so as to func tion under the new condi tions. There are many out standing advantages in such a system. First and foremost it affords a solution of the problem of preventing waste of fuel through over heating of buildings in cluding loss from exces sive window ventilation in mild weather when only a minimum amount of heat Fig, S 1 is required. The Steam Table Applied:--Comparison of steam pressures, volumes and cor responding boiling points. Steam is produced at lower temperatures and circulated just as easily at 20 in. of vacuum as at 2 to 3 lb. gauge pressure. Mild weather consti tutes approximately 95 746 G A. Dunham Company Specialties, Heating per cent of the heating season in most localities. Curves (3) and (4) are the highest and lowest temperatures recorded during this Past experience indicates that this sys period. tem will effect a fuel saving of 25 per cent or more compared with previous types of steam heating systems. A heating system must be designed with sufficient radiation to heat the building satisfactorily on the coldest winter day. The Dunham Differential Vacuum Curve (4) governs what heating engineers Heating System fully meets the needs of a term the "design basis" for a heating climate where variations in temperature system in or around Chicago. Now note occur during the heating season. how curve (3) reveals the demand for a Fig. 4 clearly shows how . marked the flexible heating system--one which will not daily fluctuations in outdoor temperature overheat in mild weather, and yet will pro may be. These changes may be as high vide ample warmth when lowest tempera as 40 deg. within a period of 24 hours. tures are encountered. Weather Bureau Note the wide variations in the daily temperatures, as shown by the heavy ir regular curve marked (1). This curve is an actual picture of each day's maximum and minimum temperature^ during the i heating season of 1926-27. Curve (2) indicates the average mean I temperature over a period of 54 years. \ records show that there were but 35 hours when temperatures were zero and lower during the winter of 1926-27 and but 131 hours when the temperature dropped to 10 deg. above zero or lower. On March 16,1927, temperature in Chicago soared to 71, yet during March in other years there have been days when zero temperatures were reached! 10Q-- 10 20 31 10 20 30 10 20 31 (0 20 31 10 20 26 10 20 31 10 20 30 10 20 31 October ! No/embcrI December I January I February! March I April I May Fig. < Official temperatures for Chicago's winter weather, season 1926-27. a record typical of a large portion of the country- Method of I [eat Control The principal function of this system is sufficient flow of Sub-Atmospheric Steam. This method to prevent excess heat losses from a build and method B are used in the "D" series system. ing by maintaining a uniform desired tem (b) Automatic Control, by the additional function of an perature in the building and no more. automatic valve controlled from one or more Room Ther There are three distinct methods of accomplishing this: I j mostats. This automatic valve takes the place of the larger of the Sub-Atmospheric Reducing Valves. (o) ManualControl, using two Dunham Sub-Atmospheric 1 (c) Automatic operation, as used in the "DH" series Reducing Valves, adjusting these so as to furnish a uniform I system and also in the "D" aeries, in which the boiler is controlled by a Room Thermostat.