Document 0qKNOoKdxEJpL0dBa0Zj6mxYV

372 CHAPTER 15 1951 Guide surface) are rated in square feet (steam) on the basis of heating surface with limitations set for grate area, furnace volume, and furnace height. The residential boilers (defined as those having not more than 177 sq ft of heating surface) are rated from tests of oil-fired boilers, with limitations in relation to heating surface and testing conditions. Stoker-fired, and gas-fired residential boilers are rated (SBI Net Rating) not in excess of the oil-fired' rating. Hand-fired residential boilers are rated (SBI Net Rating) not greater than 14 times the heating surface. Tables 1 and 2 show the SBI ratings of residential and commercial steel boilers, respectively. The Institute of Boiler and. Radiator Manufacturers has adopted a Code5 for rating cast-iron heating boilers, based upon performance obtained under controlled test conditions. This Code applies to all sectional cast-iron heating boilers except those of magazine-feed type. The Gross I = B = R Output is obtained by test, and is subject to certain limiting factors. For hand-fired boilers, the number of boilers of a series-to be tested, the minimum overall efficiency, the minimum time limit (the time an Available Fuel Charge will last when burned at a ratewhich will produce the Gross I = B = R Output), the chimney area and height, and the draft in the stack are all subject to the limits established in the Code. Tests are run using anthracite coal of standard specification. Bituminous coal and coke ratings are the same as for anthracite coal. For automatically-fired boilers, the number of boilers of a series to be tested, the flue gas temperature and. analysis, the minimum overall efficiency, the draft loss through the boiler, and the heat release in the combustion chamber are subjected to limitation by the Code.6 Auto matically-fired boiler ratings are established by oil-fired tests using gun type oil burners and commercial grade No. 2 fuel oil. Stoker-fired and gas-fired ratings (where no A.G.A. Rating is published) are based on the Gross I=B=R Output obtained by oil-fired tests. The Net I = B = R Rating is determined from the Gross I = B = R Output by applying specified Piping and Pickup Factors which range from 2.36 to 1.40 for hand-fired boilers, and from 1.56 to 1.288 for automaticallyfired boilers. In both cases, the factor decreases as. the boiler size in creases. Table 3 is abstracted from the I = B = R Rating Tables in the Code and illustrates the relationship between Net I = B = R Rating and Gross I = B**R Output. The American Gas Association has adopted a method of rating gas designed boilers upon performance under tests. This method is described in Approval Requirements for Central Heating Gas Appliances. The Heating, Piping and Air Conditioning Contractors National As sociation has adopted a method, based on their physical characteristics for rating boilers that are not rated in accordance with the SBI or I = B = R Codes. Ratings are expressed on a Net Load basis in square feet of steam radiation. BOILER EFFICIENCY The term efficiency, as used for guarantee of boiler performance, is usu ally construed as follows: 1. Solid Fuels. The efficiency of the boiler alone is the ratio of the heat absorbed by the water and steam in the boiler per pound of combustible burned on the grate, to the calorific value of 1 lb of combustible as fired. The combined efficiency, of boiler, furnace and grate is the ratio of the heat absorbed'by the water and steam in the boiler per pound of fuel as fired, to the calorific value of 1 lb of fuel as fired.' Heating Boilers, Furnaces, Space Heaters 373 . Tabus 3. I=B=R Rating Tabus Net 1~B=R Batika HakxhFibxd ' Autouatio-Fxhsd Sq Ft Steam 1000 Bta Piping Factor Piping and Pickup Factor Grass I=B=R Output 1000 Bta .Time Available Fuel Will Lest, Hr Maximum Stack He^htb Minimum' Piping- 8tack and Areal* Pickup* Sq la. Factor Gras 1=8=11 Output 1000 Bta- Mimmtim Stack ' Areab Sq In. Maximum Allowable Draft Lea 1 - i in 700 1450 2200 29S0 3100 3250 3400 3550 3700 23 1.300 1.275 -><cn 168.0 1.248 4 1360 2.341 1268 120J. 1139 5 56.6 140.5 217.7 ms 359.4 6 7.50 6.77 642 5.99 5.73 1.236 2.084 425.1 5.50 1.225 2.039 489.4 5.32 1.215 1001 552 . 5.15 1.205 1.967 614. . 4.99 348 1.198 1.939 675 : 445 384 1.190 1.914 735 420 1.182 1.891 794 456 1.177 1.872 854 492 1.169 1.855 913 528 1.162 1.837 970 4.73 4.60 4.49 4.41 444 564 1.158 1.821 1027 (600 1.152 1.805 1083 636 1.148 1.789 1138 672 1.142 1.774 1192 708 1.139 1.759 1245 . 4.29 4.24 4.19 4.1S 4.11 744 1.136 1.744 1298 4.07 780 1.132 1.730 1349 4.03 816 1.129 1.717 1401 .-4.00 852 1.128 1.704 1452 . 4.00 888 1.122 1.691 1502 4.00 3350 4000 4200 4400 4600- 924 960 10081056 1101 1.121 1.120 1.120 1.120 1.120 1.678 1.666 1.650 1.634 1.620. 1550 1599 1663 1726 1788 4.00 4.00 4.00 4.00 4.00 4300 5000 5200 5400 5600 1152 1200 1248 1296 1344 1.120 1.120 1.120 1.120 1.120 1.605 1.590 1.577 1.564 1.552 1849. 1908 1968 2027/ 2086 4.00 4.00' 4.00 4.00 4.00 5800 6000 6200 6400 6600 1392 1440 1488 1536 1584 1.120 1.120 1.120 1.120 1.120 1.539 1.526 1.514 1.502 1.491 2142 2197 2253 2307 2362 4.00 4.00 4.00 4.00 4.00 7 29.0 33.0 36.5 39.5 42.0 8 50.0 500 50.0 50.0 54.0 9 10, 1460 1448 1425 1407 1.492 37.4 92.9 146.4 198.9 250.7 11 50.0 . 50.0 50.0 50.0 ` 50.0 44.0 46.0 47.5 49.0 505 68.5 . 82.0 95.5 110.0 . 122.5- 1.478 1.466 L454 1.444 1.434 3014 3514 401 451 499 50.0 52.0 63.0 734 84.0 52.0 53.0 54.5 -S5.S ' 56.5 135.0 147.0 160.0 - 172.0 185.0 1.424 .1.416 1.408 1.401 . 1494 547 595 642 689 736 * 95.0 105.0 115.0 125.0 1354 58.0 59.0 600 . 61.0 62.0 196.0 207.5 219.0 231.0 ' 242.0 1.388 1482 1476 1.369 1464 783 829 875 920 966 145.0 155.0 165.0 1734 1834 63.0 64.0 64.5 654 66.5 253.0 264.0 275.0 286.0 296.0 1.359 1454 1449 1.344 1439 1011 1056 H01 1145 1189 1924 2024 , 2114 221.0 230.0 67-5 68.0 694 70.0 70S 306.0 315.0 326.0 337.0 349.0 1435 1431 1425 1420 1414 1234 1278 1336 1394 1451 239.5 249.0 2614 274.0 2854 71.5 72.S 73.0 74.0 744 358.0 367.0 376.0 385.0 393.0 1410 1.305 1401 U97 1.294 1509 1566 1624- 1681 1739 297.0 308.0 3184 3294 3394 75.5 76.0 77.0 77.5 78.0 .402.0 409.0 .417 425 . . 431 1.291 1.290 1.289 1.288 1.288 17971858 1918 1978 2040 350.0 359.0 369 377 386 12 0444 0.051 0.058 0065 047: 0478 0.084 0.090 0496 0.102 0.108 0.113 0.118 ,0.124 . ai30 0.136 0.141 0.146 0.152 0.1S7- . 0.162 0.167 0.172 0.178 0.183 0.188 0.192 0.200. 0406 :-- ; --... --, . ... . --- 6800 7000 7500 8000 8500 1632 1680 1800 1920 2010 9000 9500" 10000 11000 12000 2160 2280 2400 2640 2880 13000 14000 13000 16000 17000 3120 3360 3600 3840 4080 18000 4320 19000 4560 20000 4800 1.120 1.120 1.120 1.120 1.120 1.480 1.470. 1.44V 1.426 1.409 2415 2470 2605 2738 2874 ` 4.00 4.00 4.00 4.00 4.00 79.0 ' 79.5 . 81.5. 83.0 85.0 438 446 464 481 497 1.120 1.120 1.120 1.120 1.120 1.400 1.400 1.400 1.400 1.400 3024 ' 3192 3360 3696. 4032 4.00 4.00 4.00 4.00 .4.00 ' ' 874 515 89.0 > 535 91.5 555 95.0 ` 595 99.0 634 1.120 1.120 1.120 1.120 1.120 1.400 1.400 1.400 MOO 1.400 4368 4704 5040 5376 5712 4.00 4.00 4.004.00 4.00 . 103.0 106.5 109.5 1124 115.5 673 712 751 789 827 1.120 1.120 1.120 1.400 -6048' 1.400 6384 1.400 6720 4.00 4.00' 4.00 '1184 120.0 1200 863 899 900 1.288 1488 1.288 1.288 1.288 2102 2164 2318 2473 2628 - 1.288 1.288 1.288 1.288 1.288 2782 2937 3091 3400 3709 1.288 1488 1.288 1.288 1.288 4019 4328 4637 : 4946 S25S 1488 1.288 1.288 5564 5873 6182 395 405 426 446 467 486 504 522 560 596 633. 668 704 740 776 810 844 877 __ __ -- ,..... , ____ . ,, ____ -- --r b blades pickup allowance and correction for difference between test and operating conditions. 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