York 92% GF9 User's Information, Maintenance And Service Manual

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York 92% GF9 User's Information, Maintenance And Service Manual Manual pdf 5 page image

035-17737-003 Rev. A (0504)Unitary Products Group 5SECTION II: SERVICE AND MAINTENANCEMANUALSAFETY SECTIONThe following safety rules must be followed when servicing thefurnace.FURNACE MAINTENANCE SECTIONThe furnace should be cleaned and adjusted by a certified dealer orqualified service contractor once a year or before the start of everyheating season. The following items must be cleaned and serviced orreplaced if there are signs of deterioration.1. The vent terminal.2. The furnace vent and combustion air intake passageways. Shouldit be necessary to service the vent/air intake system, the manufac-turer recommends this service be conducted by a qualified serviceagency. The operation of this appliance requires the reassemblyand resealing of the vent/air intake system.3. The furnace burners, ignitor and flame sensor.4. The condensate collection and disposal system. If any disassem-bly of components containing flue or vent gases is required, aqualified service agency must perform the service.SEQUENCE OF OPERATIONThe following describes the sequence of operation of the furnace. Referto Figure 1 for component location.Continuous BlowerCooling/heating thermostats have a fan switch that has an ON andAUTO position. In the ON position the thermostat circuit is completedbetween terminals R and G. The motor will operate on the speed tapwire that is connected to the cooling terminal on the control board.Intermittent Blower - CoolingCooling/heating thermostats have a fan switch that has an ON andAUTO position. In the AUTO position the thermostat circuit is completedbetween terminals R and G when there is a call for cooling. The motorwill operate on the speed tap wire that is connected to the cooling termi-nal on the control board. The fan off setting is fixed at 60 seconds forSEER enhancement.Heating CycleWhen the thermostat switch is set on HEAT and the fan is set on AUTO,and there is a call for heat, a circuit is completed between terminals Rand W of the thermostat. When the proper amount of combustion air isbeing provided, the pressure switch will close, the ignition control pro-vides a 17-second warm-up period, the gas valve then opens, the gasstarts to flow, ignition occurs and the flame sensor begins its sensingfunction. The blower motor will energize 30 seconds after the gas valveopens, if a flame is detected. Normal furnace operation will continueuntil the thermostat circuit between R and W is opened, which causesthe ignition system and gas valve to de-energize and the burner flamesto be extinguished. The vent motor will operate for an additional 15 sec-onds and the blower motor will operate for the amount of time set by thefan-off delay jumper located on the control board. See Figure 6. Theheating cycle is complete, and ready for the start of the next heatingcycle.If the flame is not detected within 7 seconds of the gas valve opening,the gas valve is shut off and a retry operation begins. If the flame is lostfor 2 seconds during the 10-second stabilization period, the gas valve isshut off and a retry operation begins. During a retry operation, the ventmotor starts a 15 second inter-purge and the ignitor warm-up time isextended to 27 seconds. If the flame is established for more than 10seconds after ignition during a retry, the control will clear the ignitionattempt (retry) counter. If three retries occur during a call for heat, thefurnace will shut down for one hour. If at the end of the one hour shutdown there is a call for heat, the furnace will initiate a normal start cycle.If the problem has not been corrected the furnace will again lockoutafter three retries.A momentary loss of gas supply, flame blowout, or a faulty flame probecircuit will result in a disruption in the flame and be sensed within 1.0seconds. The gas valve will de-energize and the control will begin arecycle operation. A normal ignition sequence will begin after a 15 sec-ond inter-purge. If during the five recycles the gas supply does notreturn, or the fault condition is not corrected the ignition control will lock-out for 60 minutes.During burner operation, a momentary loss of power for 50 millisecondsor longer will de-energize the gas valve. When the power is restored,the gas valve will remain de-energized and the ignition sequence willimmediately restart.ELECTRIC SHOCK, FIRE OR EXPLOSION HAZARDFailure to follow safety warnings exactly could result indangerous operation, serious injury, death or propertydamage.Improper servicing could result in dangerous operation,serious injury, and death or property damage.• Before servicing, disconnect all electrical power to the fur-nace.• When servicing controls, label all wires prior to disconnect-ing. Reconnect wires correctly.• Verify proper operation after servicing.FIGURE 6: Typical Heat/Cool Speed Tap ConnectionsPARKPARKHI COOLHEATEACL1XFMRHUMNEUTRALSRED - LOW SPEEDYELLOW - MED. LOW SPEEDBLACK - HIGH SPEEDBLUE -MED. HIGH SPEEDFAN OFFADJUSTMENTJUMPERY/Y2 W R G C