Document x5wykLaxZ80xRpMEZaqjNRvb0

American Society of Heating and Ventilating Engineers Guide, 1925-26 reliable, because as a rule the chimney is designed by an engineer and must be well built to sustain such a heavy load and the height is such as to produce considerable head or force to offset unfavorable weather con ditions, etc. Chimneys in this class produce about 0.009 in. draft per ft. of height in zero weather with 600 deg. in the stack according to the formula: where P = H (TM-) \ io *8 / P = draft pressure in inches of water. H = height of chimney in feet. To = absolute temperature of outside air. rs = absolute temperature of stack gases. For low-pressure heating boilers, water heaters and warm air furnaces conservative modern practice in the matter of chimney sizes is in accord ance with the_ accompanying schedule, Table 61: 61.Table. Chimney Sizes Warm Air Furnace Capacity IN Leader Pipe Sq. In, Steam Boiler Capacity Sq. Ft. OF Radia tion Hot Water Heater Capacity Sq. Ft. OF Radia tion Nominal Dimen sions of FireClay Lining In. Rectangular Flue Actual Inside Dimensions of Fire Clay Lining In. Actual Area Sq. In. Effec tive Area Sq. InJ Round Flue Inside Diameter of Lining In. Effec tive Area Sq. In. Height in Ft. from Grate 790 590 973 8)4x13 7x11)4 81 70 35 1000 690 1140 900 900 ' 1490 1490 13x13 8)4x18 UKxn% 6^x16^ 127 no 99 100 10 79 1100 1820 12 113 40 1700 2800 13x18 11)4x16)4 183 156 1940 3200 15 177 2130 3520 18x18 15J4xl5J4 248 195 2480 4090 20x20 . 17)4x17)4 298 234 45 3150 5200 18 254 50 4300 7100 \ 20 314 5000 8250 24x24 21x21 441 4600 7590 20x24* 480 326 55 . 5570 9190 24x24 576 380 60 5580 9200 22 380 6980 11500 24 452 65 7270 12000 24x28 672 468 8700 14400 28x28 784 531 9380 15500 27 573 10150 16750 30x30 900 616 10470 17250 28x32 896 635 11800 19500 30 707 70 14700 24300 33 855 17900 29500 36 1018 Dimensions below are for unlined rectangular flues. 106 American Society of Heating and Ventilating Engineers Guide, 1925-26 Chimneys recommended for larger boilers 15 to 250 hp. are propor tioned in accordance with the report made by a joint Committee of the American Boiler Manufacturers Association and Stoker Manufacturers Association and approved by these organizations. The sizes are given in Table 62) Table 62. Height of Stack for Average Installations (Sea Level) i . Forced Draft Stokers Per Cent Rating................................. Draft Furnace....................................... Friction Loss (Boiler)........................ Friction Loss (Breeching)................... Total Draft Required................... ..... Height of Stack (Ft.)........................... 100 0.15 0.18 0.10 0.43 80 150 . 0.15 0.4 0.10 0.65 112 200 0.15 0.65 0.10 0.90 145 250 0.15 .0.9 0.10 1.15 178 300 0.15 1.20 0.10 1.45 220 Diameter op Chimney in Inches for Horizontal Return Tubular Boilers Height of Stack in Feet--For Sea Level and 60 DEG. FAHR. OUTSIDE TEMP. ASSUMED FRIC TION Loss in Stack O.lrn. per 100 ft. Nominal H. P. 15 20 . 25 3Q 35 40 50 60 75 90 100 115 125 150 175 200 210 225 250 100% Rating .. 150% Rating 13 14 14 16 16 18 17 19 18 20 19 21 20 23 21 24 23 26 25 28 26 29 27 31 28 32 30 34 32 36 33 38 34 38 35 40 36 41 200% Rating 17 18 20 21 22 23 25 27 29 31 33 34 35 38 40 43 44 45 47 Draft at Base of Stack 0.12 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 -- 100% Rating 21 26 35 43 52 60 69 78 86 95 104 112 -- 150% Rating - 200% Rating 22 28 37 . 46 56 65 74 84 93 102 112 121 25 30 41 51 61 71 81 91 101 111 122 132 -- Data on Which Tables are Based j Rating............ Efficiency___ 100% 150% 200% 65% 65% 63% Stack Temp, deg.fahr...... . 450 500 550 1 CO,................ 8% 9% 10% Lbs. of Gas............ 85 77 73 Average Friction Loss Through Boilers Per Cent Rating....... . 100 150 200 250 300 Loss Ins., Water............ 0.1to0.3 0.2to0.6 0.3to0.9 0.5tol.4 0.7tol.9 Friction loss through boiler varies according to construction. . For Furnace Draft.--Allow 0.15 for. forced draft. For Natural Draft 0.35 in. or higher should be used depending upon rate of combustion and fuel used. For Breeching Friction Loss.--Allow 0.05 in. for each right angle bend and 0.1 in. per 100 ft. of length. Lross sectional area should be 20 per cent larger tliau that of 6tack. 107