York International DFAA User's Information, Maintenance And Service Manual

York International DFAA User's Information, Maintenance And Service Manual Manual pdf 8 page image

107273-UUM-C-03068 Unitary Products GroupTo Replace Blower Wheel:1. Turn off all power to the burner before servicing.2. Disconnect the burner motor wires.3. Remove the bolts securing the blower motor to thehousing.4. Remove the blower motor and wheel.5. Remove the existing wheel.6. As shown at right, slide the new blower wheel onto the shaft.• Slide blower wheel toward motor until the bottom rim is 1/8” fromthe motor face.• Rotate the wheel until the set screw is centered on the flat of themotor shaft.• Tighten the set screw to secure the wheel.7. Install the motor on the burner housing. Tighten the bolts. Recon-nect the motor wires.8. Restore power, start the burner, and perform combustion tests.Refer to “Set combustion with instruments.”Check / Adjust ElectrodesCheck the electrode tip settings. Adjust if necessary to comply with thedimensions shown in Figure 10. To adjust, loosen the electrode clampscrew and slide / rotate the electrodes as necessary. Securely tightenthe clamp screw when finished.UOIL FURNACE SEQUENCE OF OPERATIONThe following describes the sequence of operation of the furnace. Referto Figure 1 for component location.Continuous BlowerDFAA cooling/heating thermostats have a fan switch that has an ONand AUTO position. In the ON position the thermostat circuit is com-pleted between terminals R and G. The motor will operate continuously.DFAH models are heating only.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 until the call for cooling is removed by the thermostat.Heating CycleWhen the thermostat switch on a DFAA is set on HEAT and the fan isset on AUTO, (DFAH has no manual fan operation), and there is a callfor heat, a circuit is completed between terminals R and W of the ther-mostat. There is a 10 second delay to allow the burner motor to comeup to speed at which time the primary control provides power to the igni-tion transformer, the solenoid valve on the oil pump opens and fuel oilstarts to flow to the nozzle, ignition occurs and the flame sensor beginsits sensing function. The blower motor will energize after the air temper-ature at the fan control is above 110° F, if a flame is detected. Normalfurnace operation will continue until the thermostat circuit between Rand W is opened, which causes the ignition system and oil pump sole-noid valve to de-energize and the burner flames to be extinguished.The blower motor will operate until the fan switch is below 90° F. Theheating cycle is complete and ready for the start of the next cycle.If the flame is not detected within 15 seconds of the primary control, itwill turn off the oil burner. There will be 3 retries before the primary con-trol will lockout. If the flame is lost for 2 seconds during the 15 secondstabilization period, the ignition transformer is energized and a retryoperation begins. If flame is not detected within 15 seconds during theretry, the primary control will go into recycle mode. Once the primarycontrol locks out the reset button must be pressed before an ignitionretry occurs.A momentary loss of fuel oil, flame blowout, or a faulty cad-cell detectorwill result in a disruption in the flame and be sensed within 1.0 seconds.The oil pump solenoid valve will de-energize and the primary control willbegin a recycle operation. A normal ignition sequence will begin after a15 second inter-purge. If during the three recycles the fuel oil supplydoes not return, or the fault condition is not corrected the primary con-trol will lock out.During burner operation, a momentary loss of power for 50 millisecondsor longer will de-energize the primary control. When the power isrestored, the primary control will remain de-energized and the ignitionsequence will immediately restart.TYPICAL PRIMARY CONTROL SEQUENCE OFOPERATION1. STANDBY - The burner is idle, waiting for a call for heat. When acall for heat is initiated, there is a 2-6 second delay while the con-trol performs a safe start check.2. VALVE-ON DELAY - If applicable, the ignition and motor areturned on for a 15 second valve-on delay.3. TRAIL FOR IGNITION (TFI) - The fuel valve is opened, if applica-ble. A flame should be established within the 15 second lockouttime (30 seconds on some models).4. LOCKOUT - If flame is not seen at the end of the TFI or is seenduring valve-on delay or postpurge, the control shuts down onsafety lockout and must be reset. If the control locks out threetimes in a row, the control enters restricted lockout. Follow theinstructions on the front to reset it.5. IGNITION CARRYOVER - Once flame is established, the ignitionremains on for an additional 10 seconds to ensure flame stability. Ifthe control is wired for intermittent duty ignition, the ignition unitstays on the entire time the motor is running.6. RUN - The burner runs until the call for heat is satisfied. The signalis then sent to burner motor-off delay, if applicable, and it is shutdown and sent to standby.7. RECYCLE - If the flame is lost while the burner is firing, the controlshuts down the burner, enters a 60 second recycle delay, and thenrepeats the above ignition sequence. If flame is lost three times ina row, the control locks out to prevent cycling with repetitious flameloss due to poor combustion.FIGURE 10: Electrode SettingsLabel all wires prior to disconnection when servicing controls.Wiring errors can cause improper and dangerous operation.Verify proper operation after servicing.1/16"Nozzle-to-tipSpacing5/32"GapEND VIEW SIDE VIEW5/16” abovenozzle center