Document k9bDkgadKpavdM93414L2y1Db

C. A. Dunham Company Specialties, Heatinn the steam supplied to the radiators is varied to suit the changing weather con ditions. This is the basic principle of the Dunham Differential Vacuum Heat ing System. (Fig. 1083A). The heating profession has long realized that there is a large amount of heat wasted in mild weath er because buildings are overheated. The cause of this waste in steam heated systems is that most all of them are oper ated on and limited in their operation to pres sures above atmospheric, even in mild weather. Fig. 1076A. Relation oj Beat Lose and Heat Emission to Temperature Difference This illustration shows how the room temperature is maintained uniformly under changing weather conditions.-by varying the steam pressure so that the heal given off by the radiator equals the heat lost by the building. ` Steam pressures ranging from a few ounces to 2 or 3 lb. afford but a to balance the heat loss of the building and small operating range of steam tempera maintain the desired temperature. The tures to meet changes in weather condi building temperature will increase above tions. That is steam at a relatively con that desired, resulting in excessive heatloss stant pressure is usually supplied to the from the building structure. This is gener radiators regardless of what the outside ally termed overheating and represents a weather may be. direct waste of fuel. Government weather The heat output of the radiators will reports show that extreme weather prevails therefore, be entirely too high in mild during about 5 per cent of the average weather, when only a fraction of the radia heating season when the system must be tion installed would actually be required operated at full rating. This leaves 95 per Dunham Company Specialties, Heating r cent of the heating season when the heat output of the system must be reduced if fit. unjf0rm room temperature is to be main- ta Da^ly weather reports' show that the temperature rises and falls quite rapidly 0ver the greater portions of the country. Temperature changes of. 40 deg. per day occur each winter in the Chicago area, while daily changes of 20 deg. are but 1/ slightly higher than normal. To this varia tion in heat demand must be added the T-^^joijng effect of wind, if a true picture of the great fluctuations in heating require ments is wanted. The graph, Fig. 1288, shows the.official maximum and minimum temperatures at. Chicago for each day of the heating season of 1928-29. It clearly shows the tempera ture fluctuations for that season and also the extreme limits of temperature recorded in the previous 54 years. During that year, there was a total of 131 hours when the temperature was 10 deg. or lower, with but 35 hours of this at zero or below. The heat ing season was but 0.4 deg. warmer .than the average since the year 1900. Fuel Saving of 25 Per Cent or More Compared with Ordinary Types of Steam Heating Systems , On buildings changed over to the Dun ham Differential Vacuum System the per formance records show actual fuel savings of 25 per cent or more compared with pre vious system. The charts and illustrations on this and the following page tell this story in a non technical way. Fig. 1066C, Steam Table Applied-- This drawing gives a comparison of the properties of steam as used in the ordinary type heating system and the Dunham Dif. ferential Vacuum System. The Ordinary System Has-- (1) Operating range zero to 5 lb. gauge pressure or higher. - (2) Temperature range 212 deg. fahr. to 227.1 deg. fahr. (3) Volume per pound steam 26.79 to 20.42 cu. ft. The Dunham Differential Vacuum System Has-- -. (1) Operating range 25 in. vacuum to 5 lb. gauge pressure or higher. (2) Temperature range 133.22 deg. fahr. to 227.1 deg:.fahr. (3) Volume per pound steam 145 to 20.42 cu. ft. By comparing the steam volumes and temperatures used in the two types of systems an index to the flexibility of each is obtained. The extreme flexibility of the Differential System eliminates overheating and reduces the heat lost through-open windows. Fig. 1288. Average Temperature for Chicago Healing Season 19S8-1929 = Ifi.t deg. (1) Maximum and minimum daily temperatures for 1928-29. (2) Normal daily temperature from 54-year record. (3) Hightest temperature on record. (4) Lowest temperature on record. (5) 65 deg. temperature base for degree-day calculation. Comparison of steam pressures, volumes and corresponding 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. 807