Document Z46b7KjVrdLkj3Jp1m9g18mNV

378 CHAPTER 18 1949, 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 on tests for 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 Code6 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 over-all efficiency, the minimum time limit (the time an Available Fuel Charge will last when burned at a rate which 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 over-all efficiency, the draft loss through the boiler, and the heat release in the combustion chamber are subjected to limitation by the Code6. 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 1= 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 automatically fired 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 based upon performance under tests. This is described in Approval Requirements for Central Heating G'as Appliances. .The Heating, Piping and Air Conditioning Contractors National As sociation has adopted a method of rating boilers based on their physical characteristics for those 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 guarantees 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 (lie 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 Id of fuel as fired. Heating Boilers, Furnaces, Space Heaters 379 Table 3: I=B=R Rating Table Net I~B=R Batxno Hawd-Fihkd Autohatio-Fiam) 8q Ft ghwn 1000 Bta Piping Factor Piping and 'ickup* Factor Groea /== Output 1000 Btu Time Available Fuel Will Last, Hr Maximum Stack He^fhtb Minimum Stack Areab Sq In.; Piping ' and Pickup* Factor Gross I=B=R Output 1000 Bta - Minimum Stack Areab Sq In. Maximum Allowable Draft * Loss 12345 24.0 1500 2.360 56.6 1.293 1341 1405 1268 217.7 132.0 1.260 1201 2905 700 168.0 1.248 1139 359.4 6 750 6.77 652 5.99 5.73 1450 1.236 240 0 '1.225 276 1.215 348 1.198 2.084 1039 1001 1.967 1.939 425.1 489.4 552 614 675 550 552 5.15 4.99 455 1.914 735 1.891 794 1.177 1.872 854 1.855 913 2200 528 1.162 1.837 970 4.73 4.60 4.49 4.41 454 2950 364 <600 672 *708 1.158 1.142 1.139 1.821 1.805 1.789 1.774 1759 1027 1083 1138 1192 1245 ' 4.29 4.24 4.19 4.15 4.11 3250 3700 744 780 816 852 888 , 1.136 1.132 1.129 1.128 1.122 1.744 1.730 L717 1.704 1.691 1298 1349 1491 1452 1502 4.07 4.03 4.00 - 4.00 4.00 4000 4200 4600 924 960 1008 1056 1104 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 4800 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 1.120 1440 1.1201488 , . 1.120 1536" 1.120 1584 1.120 1.539 1-526 1-514 1.502 1.491 2142 2197 2253 2307 2362 440 4.00 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 1.400 1.400 1.400 1.400 3024 3192 3360 '3696 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 L120 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 1.120 1.120 1.400 6048 1.400 6384 1.400 6720 440 4.00 4.00 .7 294 33.0 365 . 395 . 4X0 8 504 504 50.0 50.0 54.0 . 9 1.560. 1548 1525 1.507 1.492 10 37.4 9X9 146.4 198.9 250.7 11 12 50.0 0544 50.0 50.0 50.0 50.0 44.0 46.0 475 49.0 505 . 685 82.0 95.5 1104 1225 1.476 1.466 1.454 1.444 1.434 3015 3515 401 451 499 50.0 0.078 : 52.0 63.0 735 84.0 52.0 1354 53.0 147.0 545 160.0 555 17X0 565 . 1854 1.424 1.416 1.408 1.401 1594 547 595 642 689 736 95.0 105.0 1155 125.0 135.0 0.108 0.118 0.130 S8.0 196.0 1588 783 145.0 0.136 59.0 2075 1582 829- 155.0 60.0 2194 1576 875 165.0 0.146 ; 61.0 2314 1569 920 ' 1735 0.152 624 242.0 1564 966 1835 63.0 64.0 64.5 655 665 253.0 2644 273.0 286.0 2964 1559 1.354 1.349 1544 1539 1011 1056 1101 1145 1189 192.5 20X5 211.5 221.0 230.0 0.162 0.167> 67.5 68.0 . 69.0 704 705 306.0 315.0 326.0 337.0 3494 1535 1531 1525 1520 1514 1234 1278 1336 1394 1451 239.5 249.0 261.5 274.0 2855 - 0.188 ----- . 715 358.0 725 367.0 73.0 3764 74.0 3854 745 3934 755 76.0 77.0. 775 : 78.0 40X0 409.0 417 425 , . 431 79.0. 795'. 815 83.0 85.0 438 446 464 .481 .497 87.0 ' 89.0 915 95.0 99.0 515 535 555 595 634 1510 1505 1501 1.297 1.294 1509 1566 16241681 1739 1591 1590 1.289 1588. 1588 1797 18S8 1918 1978 2040 1.288. 1.288 1.288 1.288 1588 2102: ! 2164 2318 2473 2628 1588 1588 1588 1588 1.288 2782 2937 3091 3400 3709 297.0 308.0 3295 350.0 386 395 446 467 486 504 - ----- ` ------ . '__ -- ------ . ----- __ ----- . --a-- . _t-- --. ____ .-- ---- -- -- 103.0 1065 1095 1125 1155 N 673 712 751 789 827 1588 1.288 1.288 1588 1588 4019 ' 4328 . 4637 4946 S255 ` 633 .704 776 ___ : ---- ---- --- -- 118.0 863 1588' 5564 810 ___ ; 120.0 . 899 : 1588 5873 844 1204 900 1588 6182 877 * Includes pickup allowance end correction for difference between test and operating conditions. b To be specified in catalog. -