Carrier 59SC2C Series Installation, Start-up, Operating And Service And Maintenance Instructions

Also see for 59SC2B: Product data

65AdjustmentsFIRE HAZARDFailure to follow this warning could result in personalinjury, death and/or property damage.DO NOT bottom out gas valve regulator adjusting screw.This can result in unregulated manifold pressure and resultin excess overfire and heat exchanger failures.! WARNINGFURNACE DAMAGE HAZARDFailure to follow this caution may result in reduced furnacelife.DO NOT redrill orifices. Improper drilling (burrs,out--of--round holes, etc.) can cause excessive burner noiseand misdirection of burner flames. This can result in flameimpingement of heat exchangers, causing failures. See Fig.59.CAUTION!For proper operation and long term reliability, the Furnace inputrate must be within +/--2 percent of input rate on furnace ratingplate, or as adjusted for altitude.The gas input rate on rating plate is for installations at altitudes upto 2000 ft. (609.6M).The NATURAL GAS manifold pressure adjustments in Table21 compensate for BOTH altitude AND gas heating value.DO NOT apply an additional de--rate factor to the pressuresshow in Table 21. The values in this table are NOT referencedto sea level; they are AS--MEASURED AT 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 21. No adjustments to thefurnace may be necessary at altitude for certain gas heatingvalues.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 19. The natural gas manifold pressures inTable 21 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 21 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 3000 ft. (611 to 914 M) in Table21.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 21.4. Find closest natural gas heat value and specific gravity inTable 21. Follow heat value and specific gravity lines topoint of intersection to find orifice size and manifold pres-sure 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 as shown inTable 21. Use only factory--supplied orifices. See EX-AMPLE 1.EXAMPLE 1: 0 -- 2000 ft. (0 -- 609.6M) altitudeHeating value = 1050 Btu/cu ft.Specific gravity = 0.62Therefore: Orifice No. 44(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.)Manifold pressure: 3.4--in. W.C. (847 Pa).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. =249.1 Pa).1. Adjust manifold pressure to obtain proper gas input rate.See Fig. 58.a. Turn gas valve ON/OFF switch to OFF.b. Remove manifold pressure tap plug from gas valve.c. Connect a water column manometer or similar device tomanifold pressure tap.d. Turn gas valve ON/OFF switch to ON.e. Manually close blower door switch.f. Jumper R and W thermostat connections on control to startfurnace. See Fig. 38.g. Remove regulator adjustment cap from gas valve pressureregulator and turn adjusting screw (3/16 or smaller flat--tipped screwdriver) counterclockwise (out) to decrease in-put rate or clockwise (in) to increase input rate. See Fig.58.DO NOT set manifold pressure less than 2.8--in. W.C. (697Pa) or more than 3.8 in. W.C. (947 Pa) for natural gas. Ifrequired manifold pressure is outside this range, change mainburner orifices to obtain manifold pressure in this range.NOTICEh. When correct input is obtained, replace cap that concealsgas valve regulator adjustment screws. Main burner flameshould be clear blue, almost transparent See Fig. 66.59SC2C