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Diam.
(in.)
Table 1.8.15C: Approximate Stack Capacities (MBH)
(Based on Atmospheric Boiler with Draft Hood)
5 7 10 12 15 20 25 30 35 40 45 50 60 70 80 90 100 125 150 200
6 100 120 140 150 170 200 220 250 270 280 300 320 350 380 400 430 450 510 550 640
7 130 160 190 210 240 270 310 340 360 390 410 430 480 510 550 580 620 690 760 870
8 180 210 250 280 310 360 400 440 480 510 540 570 620 670 720 760 810 900 990 1140
9 220 270 320 350 390 450 510 560 600 640 680 720 790 850 910 970 1020 1140 1250 1450
10 280 330 400 430 490 560 630 690 750 800 850 890 980 1060 1130 1200 1260 1410 1550 1790
12 400 480 570 630 700 810 910 1000 1080 1150 1220 1290 1410 1520 1630 1730 1820 2040 2330 2580
14 550 650 780 860 960 1110 1240 1360 1470 1570 1660 1750 1920 2070 2220 2350 2480 2770 3040 3510
16 720 850 1020 1120 1250 1450 1620 1770 1920 2050 2170 2290 2510 2710 2900 3070 3240 3620 3970 4590
18 910 1080 1290 1420 1590 1830 2050 2250 2430 2590 2750 2900 3180 3430 3670 3890 4100 4590 5030 5810
20 1130 1340 1600 1750 1960 2260 2530 2770 3000 3200 3400 3580 3920 4240 4530 4810 5070 5670 6210 7170
22 1370 1620 1940 2120 2370 2740 3060 3360 3630 3880 4110 4340 4750 5130 5480 5820 6130 6860 7510 8680
24 1630 1930 2300 2530 2820 3260 3650 4000 4320 4610 4900 5160 5650 6110 6530 6920 7300 8160 8940 10330
26 1910 2260 2710 2960 3320 3830 4280 4690 5070 5420 5750 6060 6640 7170 7660 8130 8570 9580 10490 12120
28 2220 2630 3140 3440 3850 4440 4970 5440 5880 6280 6660 7030 7700 8310 8890 9430 9940 11110 12170 14060
30 2550 3010 3600 3950 4420 5100 5700 6250 6750 7210 7650 8070 8840 9540 10200 10820 11410 12760 13970 16140
32 2900 3430 4100 4490 5020 5800 6490 7110 7680 8210 8710 9180 10050 10860 11610 12310 12980 14510 15900 18360
34 3270 3870 4630 5070 5670 6550 7320 8020 8670 9270 9830 10360 11350 12260 13110 13900 14650 16390 17950 20730
36 3670 4340 5190 5670 6360 7350 8210 9000 9720 10390 11020 11620 12730 13750 14700 15590 16430 18370 20120 23240
48 6530 7730 9230 10120 11310 13060 14600 16000 17280 18470 19600 20660 22630 24400 26130 27710 29210 32660 35780 41320
54 8260 9780 11690 12810 14320 16530 18480 20250 21870 23380 24800 26140 28640 30930 33070 35080 36970 41340 45290 52290
60 10200 12070 14430 15810 17680 20410 22820 25000 27000 28870 30620 32280 35360 38190 40830 43310 45650 51040 55910 64560
72 14700 17390 20780 22770 25460 29400 32870 36000 38890 41570 44100 46480 50920 55000 58800 62360 65740 73500 80510 92970
NOTE: The above vent input capacities in MBH (thousands of Btu/hr) are sea level ratings for double wall or insulated vents allowing for a system K factor of
7.5. Apply the correction factors for altitude, other k-factors and boiler draft control correction factors.