Document RxOQVgJRmmZdoqBoYvOxMXmn

412 CHAPTER 16 1957 Guide tested, the flue gas temperature and analysis, the minimum overall effi ciency, the draft loss through the boiler, and the heat release in the com bustion chamber are subjected to limitation by the code.5 Oil-fired boiler ratings are established by tests using gun-type oil burners and commercial grade No. 2 fuel oil. Stoker-fired ratings are based on the Gross I--B = R Output obtained by oil-fired tests. Gas-fired ratings for boilers having gross outputs greater than 300,000 Btu per hour, where -no A.G.A. Rating is published, are based on the Gross I = B = R Output obtained by oil-fired tests. Gas-fired ratings for boilers having gross outputs less than 300,000 Btu per hour, where no A.G.A. Rating is pub lished, are established by gas-fired tests with atmospheric, single-porttype burners using natural or manufactured gas or a mixture of these two Table 2. SBI Net Rating Data fob Table 2 Steel Boilers--Oil-Fired* SBI Net Rating Steam Btuh (2) Water Btuh (3) Minimum Furnace Volume Cu Ft Minimum Heating Surface Sq Ft (4) (5) 275 66,000 74,000 320 77,000 87,000 400 96,000 108,000 550 132,000 149,000 2.5 2.9 3.6 5.0 16 19 24 32 700 900 1100 168,000 216,000 264,000 189,000 243,000 297,000 6.4 8.2 10.0 41 53 66 1300 1500 1800 312,000 360,000 432,000 351,000 405,000 486,000 11.8 13.6 16.4 77 88 106 2200 2600 3000 528,000 624,000 720,000 594,000 702,000 810,000 20.0 23.6 27.3 129 153 177 3500 4000 4500 5000 840,000 960,000 1,080,000 1,200,000 945,000 1,080,000 1,215,000 1,350,000 31.8 36.3 40.9 45.4 206 236 265 294 * Stoker-Fired and Gas-Fired SBI Net Rating not greater than .oil-fired rating. Hand-Fired NefcSBI Rating (Steam) not greater than 14 times the square feet of heating surface.. * gases. The A.G.A. Output Rating of a gas-designed boiler may be used in determining the Net I=B = R Rating. The Net I = B = R Rating is determined from the Gross 1= 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 steam boilers, and from 1.333 to 1.288 for. automatically-fired hot w;ater boilers. In all cases, the factor decreases as the boiler size in creases. Table 3 is abstracted from the 1951 I = B = R Boiler 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 rates gas-designed boilers at 80 percent of the A.G.A. Input Rating. These ratings are determined by Per: formance tests described in the A.G.A. Approval Requirements for Central Heating Appliances. The Heating, Piping and Air Conditioning Contractors National As- T a b le 3. --B --R B o il e r R a t in g T a b leI ii