York ZR Series Installation Manual

Also see for ZR SERIES: Technical guide Wiring diagrams Installation manual

Contents

275864-YIM-F-0213Johnson Controls Unitary Products 51Shut Down1. Set the thermostat to the lowest temperature setting.2. Turn “OFF” all electric power to unit.3. Open gas heat access panel.4. Turn gas valve clockwise to “OFF” position (See Figure 30).Checking Gas Heat Input1. Turn off all other gas appliances connected to the gas meter.2. With the furnace turned on, measure the time needed forone revolution of the hand on the smallest dial on themeter. A typical gas meter usually has a 1/2 or a 1 cubicfoot test dial.3. Using the number of seconds for each revolution and thesize of the test dial increment, find the cubic feet of gasconsumed per hour from the Gas Rate - Cubic Feet PerHour Table 25.If the actual input is not within 5% of the furnace rating (withallowance being made for the permissible range of the regulatorsetting), replace the orifice spuds with spuds of the proper size.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 - it varies widely from city to city.)EXAMPLEBy actual measurement, it takes 13 seconds for the hand on the1-cubic foot dial to make a revolution with just a 300,000 Btuhfurnace running. Read across to the column in the table above,headed “1 Cubic Foot”, where you will see that 278 cubic feet ofgas per hour are consumed by the furnace at that rate. Multiply278 x 1050 (the Btu rating of the gas obtained from the localgas company). The result is 292,425 Btuh, which is close to the300,000 Btuh rating of the furnace.Manifold Gas Pressure AdjustmentSmall adjustments to the high-fire gas flow may be made byturning the pressure regulator adjusting screw on the automaticgas valve.Adjust as follows:1. Remove the cap on the regulator. It's located next to thepush-on electrical terminals.2. To decrease the gas pressure, turn the adjusting screwcounterclockwise.3. To increase the gas pressure, turn the adjusting screwclockwise.NOTE: The correct manifold pressure for these furnaces is3.65 IWG ± 0.3.Adjustment Of Temperature RiseThe temperature rise (the difference of temperature between thereturn air and the heated air from the furnace) must lie within therange shown on the CSA rating plate and the data in Table 11.After the temperature rise has been determined, the CFM canbe calculated as follows:After about 20 minutes of operation, determine the furnacetemperature rise. Take readings of both the return air and theheated air in the ducts (about 6 feet from the furnace) wherethey will not be affected by radiant heat. Increase the blowerCFM to decrease the temperature rise; decrease the blowerCFM to increase the rise (See SUPPLY AIR DRIVEADJUSTMENT).NOTE: Each gas heat exchanger size has a minimumallowable CFM. Below this CFM, the limit will open.Figure 28: Proper Pilot Flame AdjustmentTable 25: Gas Rate Cubic Feet Per HourSeconds forOne Rev.Size of Test Dial1/2 cu. ft. 1 cu. ft.4 450 9006 300 6008 228 45010 180 36012 150 30014 129 25716 113 22518 100 20020 90 18022 82 16424 75 15026 69 13828 64 129Burner Assembly BracketFlame Sensor Bulb1/8” Gap BetweenCarry-over Tubeand Flame Sensor BulbCarry-over Tube