Document 5b3pnbY5DgKpYDybNZYom4Xpe

358 CHAPTER 15 1950 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 Eating) 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 wall last when burned at a rate which will produce the Gross I -- B = RfhUput), 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.5 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. Eating is published) are based on the Gross 7= 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 1= 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 6ot7er 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. Boilers, Furnaces, Space Heaters 359 Table 3. I=B=R Rating Table NrtI~B = R Rating Sq Ft Steam ------- I *iping I actor 1000 Bta *'ipu ig and. Pickup I'actor ('*X=}1rB0iat0=p0sBut Btu Hand-Fibed Time Available fuel Will Last, Hr Anrimtim Stack Be^btb ] Amiriirm Stack Ateab Sq In. We* and *ickup factor Automaito-Feed 3roa I=B=B Output 1000 Bta 1ASintaimckiim Areab Sq Id. ] [axmnm k JlovaMe -Draft * Lam 100 250 400 550 700 850 1000 1150 1300 14S0 1600 1750 1900 2050 2200 2350 2500 2650 2800 2950 3100 3250 3400 3550 3700 2 24.0 60.0 96.0 132.0 168.0 3 1.300 1.293 1.275 1.260 1.248 4 2-360 2.341 2.268 2.201 2.139 5 56.6 140.5 217.7 2904 359.4 204.0 240 0 276 312 348 1.236 1.225 1.21$ 1.205 1.198 2.084 2.039 2.001 1.967 1.939 425.1 489.4 552 614 675 384 420 456 492 528 1.190 1.182 1.177 1.169 1.162 1.914 1.891 1.872 1.855 1.837, 735 794 854 913 970 564. 4600 636 672 MSS 1.152 1.148 1.142 1.821 1.805 1.789 1.774 1027 1083 1138 1192 708 1.139 L7S9 4245 744 1.136 1.744 1298 780 816 852 1.132 1.730 1349 1.129 1.717 1401 1.128 1.704 1452 888 1.122 1.691 1502 6 740 6.77 642 5.99 5.73 540 542 5.15 .4.99 445 4.73 4.60 4.49 4.41 444 4.29 444 4.19 4.15 4.11 4.07 4.03 4.00 4.00 4.00 3850 4000 4200 . 4400 4600 924 960 1008 1056 1104 1.121 U20 1.120 1.120 1.120 1.678 1.666 1.650 1.634 1.620 1550 1599 1663 1726 1788 440 4.00 4.00 4.00 4.00 4800 5000 5200 5400 ' 5600 1152 1200 1248 1296 1344 1.120 1.120 1.120 1.120 1.120 1.605 1.590 1477 1.564 1452 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 .1426 1.514 1.502 1.491 2142 2197 2253 2307 2362 4.00 *40 ` 4.00 4.00 4.00 6800 ' 7000 7500 8000 8500 1632 1680 1800 1920 2040 1.120 1.120 1.120 1.120 1.120 1.480 1.470 1.447 1.426 1.409 2415 2470 2605 2738 2874 4.00 4.00 4.00 4.00 4.00 9000 9500 10000 11000 12000 2160 2280 2400 2640 2880 1.120 1.120 1.120 1.120 1.120 1.400 3024 1.400 3192 1.400 . 3360 1.400 3696 1.400 4032 4.00 4.00 4.00 4.00 4.00 13000 14000 15000 16000 17000 3120 3360 3600 3840 4080 1.120 1.120 1.120 1.120 1.120 1.400 1.400 1.400 1.400 1.400 4368 4704 5040 5376 5712 4.00 4.00 ' 4.00 4.00 4.00 18000 4320 19000 4560 20000 4800 1.120 1.400 1.120 . 1.400 1.12C 1.400 6048 6384. 6720 - 4.00 4.00 4.00 7 29.0 33.0 364 39.5 , 42.0 . 44.0 46.0 47.5 49.0 SG4 52.0 53.0 54.5 55.5 56.5 58.0 59.0 60.0 61.0 62.0 63.0 64.0 64.5 654 664 67.5 68.0 69.0 70.0 ' 70.5 714 72.5 73.0 74.0 , 75.5 76.0 77.0 774 78.0 79.0 79.5 81.5 83.0 85.0 87.0 89.0 91.5 95.0 99.0 103.0 106.5 109.5 1124 1154 118.0 120.0 120.0 8 9 10 50.0 1460 37.4 50.0 1448 92.9 50.0 1425 146.4 50.0 1407 198.9 54.0 1.492 250.7 11 12 50.0 0444 50.0 0451 sao 0.058 50.0 0465 50.0 0472 684 810 954 110.0 1215 135.0 147.0 160.0 1710 185A) 1.478 L466 1.454 1.444 1.434 1.424 1.416 1.408 1.401 1494 3014 3514 401 451 499 547 595 642 689 736 50.0 52.0 63.0 734 844 95.0 105.0 115.0 125.0 135.0. 0478 0.084 0.090 0496 0.102 0.108 0.113 0.118 0.124' 0.130 . 196.0 2074 219.0 231.0 242.0 1488 1482 1476 1.369 1.364. 783 829 875920 966 145.0 1554 1654 1734 183.5 0.136 0.141 0.146 0.152 ' 0.157 253.0 264.0 275.0 2863). 296.0 1459 1.354 1.349 1444 1439 1011 1056 1101 1145 1189 1924 2024 2114 2214 230.0 0.162 0.167 0.172 0.178 0.183 306.0" 315.0 326.0, 337.0 349.0 358.0 367.0 3763) 385.0 393.0 1435 1431 1425 1420 1414 1234 1278 1336 1394 1451 1410 1.305 1401 1.297 1.294 1509 1566 1624- 1681 1739 2394 249.0 2614 2744 2854 2974 3084 3184 3294 339.0 0.188 a 192 0.200 0406 1, 402.0 409.0 417 425 431 1491 1.290 1.289 1488 1.288 17974 1858 1918 . 1978 2040 350.0 3594 369 . 377' 386 :------ 438 446 464 481 497 1.288 ' 1488 1488 1.288 1488 2102 2164 2318 2473 2628 395 405 426 446 467 , 515 535 555 595 634 1488 1488 1488 1.288 1.288 2782 2937 3091 3400 3709 486 504 522 560 596 673 712 751 789 827 1488 1.288 1.288 1.288 L28S 4019 4328 4637 4946 5255 633 668 704 740 776 ---_ 863 899 . 900 1488 1.288 1488 5564 810 5873 ' 844 6182 . 877 -------- Includes pickup allowance and conccUdn for difference between test and operating conditions. bTobe specified in catalog.