Document Ed6OEZYz1ZpJeB72ZXQeeOeDR

American Society of Heating and Ventilating Engineers Guide, 1926-27 is so small that the least unfavorable condition or interference practically puts the chimney out of commission. At best the head produced by chimneys up to 64 ft. in height is so. small that the draft is frequently affected by surrounding conditions making the draft a doubtful one. 'Chimneys over 64 ft. in height are not usually so affected, 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 unfavor able weather conditions, 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: )P 7.9 r8 where P = draft pressure in inches of water. H = height of chimney in feet. T0 = absolute temperature of outside air. Ts = 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 : Table 61. Chimney Sizes Warm Air Furnace Capacity in Leader Pips 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. In. Round Flue Inside Diameter of Lining In. Effec tive Area Sq. In. Height in Ft. from Grate 790 590 973 8Mxl3 7xllJ-<! 81 70 1000 690 1140 900 1490 13x13 llKxllK 127 99 900 1490 8Hxl8 6%xl6^ 110 100 1100 1820 1700 2800 13x18 HMxi6 183 156 1940 3200 2130 3520 18x18 15^x15% 248 195 2480 4090 20x20 17Kxl7k 298 234 3150 5200 4300 7100 4600 7590 20x24 17x21 357 278 5000 8250 24x24 21x21 441 5570 9190 24x24* 576 380 5580 9200 6980 11500 7270 12000 24x28* 672 468 8700 14400 28x28* 784 531 9380 15500 10150 16750 30x30* 900 616 10470 17250 28x32* 896 635 11800 19500 14700 24300 17900 29500 10 12 15 18 20 22 24 27 30 33 36 *Dimensions below are for unlined rectangular.flues. 1See also Code of Minimum Requirements for Heating and Ventilating of Buildings. 112 SJi 79 c o I-2 113 cr o 177 2 jo o-q 52 254 c"w 314 5.2 | c 41 u 380 aSt) 452 m2 b>2afa2 573 707 855 1018 g.Hx. ,, r = &> C'o-e American Society of Heating and Ventilating Engineers Guide, 1926-27 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) 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 of Chimney in Inches for Horizontal Return Tubular Boilers Height of Stack in Feet--For Sea Level and 0 deg. fahr. Outside Temp. Assumed Fric. jjon Loss in Stack 0.1 in. per 100 ft. Nominal H. P. 15 20 25 30 35 40 50 60 75 90 100 115 125 150 175 200 210 225 250 100% Rating 13 14 16 17 18 19 20 21 23 . 25 26 27 28 30 32 33 34 35 36 150% Rating 14 16 18 19 20 21 23 24 26 28 29 31 32 34 36 38 38 40 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._6_5 ___ ___ ___ ___ ___ -- 100% Rating 21 26 35 43 52 60 69 78 86 95 104 112 __ __ 150% Rating 22 ' 28 37 46 56 65 74 84 93 102 112 _12_1 200% Rating 25 30 41 51 61 71 81 91 101 111. 122 132 __ Rating............ Efficiency____ CO,.. ........... Data on Which Tables are Based 100% 65% 8% 150% 200% 65% 63%. 9% 10% Stack Temp, deg. fahr................. Lbs. of Gas.................. 450 -500 85 77 550 73 Average Friction Loss Through Boilers Per Cent Ratings.......... 100 150 200 250 300 Loss Ins., Water...... ....... 0.1 to0.3 0.2 to0.6 0.3 to0.9 0.5 to 1.4 0.7 to 1.9 Friction loss through boiler varies according to construction. -- -- For Furnace Draft.--Allow 0.15 for forced draft. For Natural Draft 0.35 iri. 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. Cross sectional area should be 20 per cent larger than that of stack. 113