Carrier 59SC5B Installation, Start-up, Operating And Service And Maintenance Instructions

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66The NATURAL GAS manifold pressure adjustments in Tables18 and 19 compensate for BOTH altitude AND gas heatingvalue. DO NOT apply an additional de--rate factor to thepressures show in Table 18 and 19. The values in this tableare NOT referenced to sea level; they are AS--MEASUREDAT ALTITUDE.The heating content of natural gas at altitude may alreadyprovide for a reduction in capacity of the furnace. Be sure toobtain the expected in--season gas heating value of the gasfrom the gas supplier BEFORE making any adjustments forcapacity or altitude. Refer to Table 18 and 19. Noadjustments to the furnace may be necessary at altitude forcertain gas heating values.Refer to the instructions provided in the factory--specifiedLP/Propane conversion kit for instructions for setting gasmanifold pressures for LP/Propane applications.NOTICEIn the USA., the input rating for altitudes above 2000 ft. (609.6M)must be reduced by 2 percent for each 1000 ft. (304.8M) above sealevel. Refer to Table 18 or 19 . The natural gas manifold pressuresin Table 19 adjust for BOTH altitude and natural gas heating value.In Canada, the input rating must be reduced by 5 percent foraltitudes of 2000 ft. (609.6M) to 4500 ft. (1371.6M) above sealevel. The natural gas manifold pressures in Table 18 adjust forBOTH altitude and natural gas heating value.NOTE: For Canadian altitudes of 2000 to 4500 ft. (610 to 1372M), use USA altitudes of 2001 to 2000 ft. (611 to 914 M) in Table18 or 19.To adjust manifold pressure to obtain the proper input rate, first,determine if the furnace has the correct orifice installed. At higheraltitudes or different gas heat contents, it may be necessary tochange the factory orifice to a different orifice. Tables have beenprovided in the furnace installation instructions to match therequired orifice to the manifold pressure to the heat content andspecific gravity of the gas. To do this:1. Obtain average yearly gas heat value (at installed altitude)from local gas supplier.2. Obtain average yearly gas specific gravity from local gassupplier.3. Find installation altitude in Table 18 or 19.4. Find closest natural gas heat value and specific gravity inTable 18 or 19. Follow heat value and specific gravity linesto point of intersection to find orifice size and manifoldpressure settings for proper operation.5. Check and verify burner orifice size in furnace. NEVERASSUME ORIFICE SIZE. ALWAYS CHECK ANDVERIFY.If orifice hole appears damaged or it is suspected to have beenredrilled, check orifice hole with a numbered drill bit ofcorrect size. Never redrill an orifice. A burr--free and squarelyaligned orifice hole is essential for proper flame characteristics.NOTICE6. Replace orifice with correct size, if required by Table 18 or19. Use only factory--supplied orifices. See EXAMPLE 1.EXAMPLE 1: 0 -- 2000 ft. (0 -- 609.6M) altitudeHeating value = 1050 Btu/cu ft.Specific gravity = 0.62Therefore: Orifice No. 44Manifold pressure: 3.4--in. w.c. (847 Pa)(Furnace is shipped with No. 44 orifices. In this example, all mainburner orifices are the correct size and do not need to be changed toobtain proper input rate.)NOTE: To convert gas manifold Table pressures to Pascals,multiply the in. w.c. value by 249.1 Pa/in. w.c. (1 in. w.c. = 249.1Pa).