Document zomnkjKdp54dE8REp1R4eMKMR

American Society of Heating and Ventilating Engineers Guide, 1926-27 As a check on the sizes of hot water mains, Table 60 will'-give safe sizes for gravity systems fed from roof tanks set not less than 20 ft. from the water line in tanks to the highest fixtures. Table'60. Gallons per Maximum Hour 500 750 1000 1250 1500 1750 2000 2500 3000 Sizes of Hot Water Mains Size of Hot Water Main, Inches 2 23^ 2H 3 3 3^ 3H 4 4 106 Chapter VII STEAM AND HOT WATER HEATING BOILERS THE boiler is one of the most important parts of any heating system and its selection, as to type, size, rating, capacity, draft require ments, firing periods, kinds of fuel, principles of operation, efficiency and construction, should be made with great care. TYPES OF BOILERS Boilers used for heating, may be classified according to their construc tion as Sectional, either round cast-iron or rectangular cast-iron with horizontal or vertical sections respectively; Fire Tube, embracing steel firebox, or brick-set return tubular; and Water Tube, with either horizontal or vertical tubes and suitable drum arrangements. The most general use for heating falls in the first two of the three classifications given. For the small installations the round pattern cast-iron sectional boiler predomi nates, although certain designs of small steel boilers with fire-tubes and coil water tubes are also used to some extent. In the larger installations, the rectangular vertical section cast-iron boilers and the steel fire-tube boilers of the firebox pattern are used; the makes of either are numerous, and many detail differentiations in construction are to be noted. For the small installations, it is customary to choose a design of boiler with such a disposition of flue passages as will give the maximum contact of flue gas with the indirect heating surface without unduly restricting the gas travel. For this the round sectional cast iron boilers are well fitted, and they are largely used for reason of their resistance to corrosion, pitting and other forms of deterioration. They are generally compact, requiring a minimum amount of floor space, low head room (low water line), and have a small water capacity. On account of their sectional construction and the usual practice of being shipped knocked down and assembled on the job, they are easily handled through small openings at any stage of construction. Their design also facilitates the removal and replacing of damaged parts as well as an increase or decrease in capacity by the addition or removal of sections. Most sectional boilers are comparatively cheap in first cost but the labor of assembling is a factor which must be considered. There are other forms of the boilers in the smaller sizes well adapted for heating small buildings, which embrace vertical section cast-iron con struction, steel vertical tubular, and steel firebox construction, which have merit for particular classes of service. The features that are of Compiled especially for The Guide by C. W. Obert. New York, E. A. May, Chicago and E. R. Fish, St. Louis, Mo. 107