York Predator Z series Installation Instructions Manual

Contents

5370596-YIM-C-0518Johnson Controls Ducted Systems 516. If necessary, adjust the low pressure regulator asdiscussed in the section “Manifold Gas PressureAdjustment”. Be sure not to under-fire the furnace on firststage. If in doubt, it is better to leave the first stage of thefurnace slightly over-fired (greater than 70% input). RepeatSteps 1-6.NOTE: To find the Btu input, multiply the number of cubic feetof gas consumed per hour by the Btu content of the gasin your particular locality (contact your gas company forthis information as it varies widely from area to area).EXAMPLEBy actual measurement, it takes 46 seconds for the hand on a 1cubic foot dial to make a revolution with a 80,000 Btuh furnacerunning. To determine rotations per minute, divide 60 by 46 =1.30. To calculate rotations per hour, multiply 1.30  60 = 78.Multiply 78  1 (0.5 if using a 1/2 cubic foot dial) = 78. Multiply78  (the Btu rating of the gas). For this example, assume thegas has a Btu rating of 1050 Btu/ft. 3 . The result of 81,900 Btuhis within 5% of the 80,000 Btuh rating of the furnace.Manifold Gas Pressure AdjustmentThis gas furnace has two heat stages. Therefore, the gas valvehas two adjustment screws located under a plastic protectivecover. The second stage (100% input) adjustment screw isadjacent to the “HI” marking on the valve and the first stage(60% input) adjustment screw is located adjacent to the “LO”marking on the valve (See Figure 30).Manifold pressure adjustment procedure.Adjust second stage (100% input) pressure first, then adjustfirst stage (70% input) pressure.1. Turn off all power to the unit.2. Using the outlet pressure port on the gas valve, connect amanometer to monitor the manifold pressure.3. Remove plastic cap covering HI and LO pressureadjustment screws.4. Turn on power to the unit.5. Set thermostat to call for second stage heat and startfurnace.6. If necessary, using a screwdriver, turn the second stageadjustment screw (adjacent to the “HI” marking on thevalve) clockwise to increase manifold pressure orcounterclockwise to decrease manifold pressure. Be surenot to over-fire the unit on second stage.7. After the high manifold pressure has been checked, adjustthe thermostat to call for first stage heat.8. If necessary, using a screwdriver, turn the first stageadjustment screw (adjacent to the “LO” marking on thevalve) clockwise to increase manifold pressure orcounterclockwise to decrease manifold pressure. Be surenot to under-fire the unit on first stage.9. Once pressure has been checked, replace the plastic capcovering the HI and LO pressure adjustment screws.NOTE: When using natural gas, the manifold pressure forsecond stage (100% input) should be 3.5 IWG ± 0.3.The manifold pressure for first stage (60% input) whenusing natural gas should be 1.5 IWG ± 0.3.Table 27: Gas Rate Cubic Feet Per HourSeconds forOne Rev.Size of Test Dial1/2 cu. ft. 1 cu. ft.10 180 36012 150 30014 129 25716 113 22518 100 20020 90 18022 82 16424 75 15026 69 13828 64 12930 60 12032 56 11334 53 10636 50 10038 47 9540 45 9042 43 8644 41 8246 39 7848 37 7550 36 7252 35 6954 34 6756 32 6458 31 6260 30 60