warning - Nordyne

to remove any dirt and lint that may have accumulatedin the compartment or on the blowerand motor. Dirt and lint can create excessiveloads on the motor resulting in higher thannormal operating temperatures and shortenedservice life.Heat Exchanger and Burner MaintenanceThe furnace should operate for many yearswithout excessive soot buildup in the fl ue passageways,however, the fl ue passageways,the vent system, and the burners should beinspected and cleaned (if required) by a qualified serviceman annually to ensure continuedsafe operation. Particular attention must begiven to identify deterioration from corrosion orother sources.SYSTEM OPERATIONINFORMATIONProper maintenance is most important to achievethe best performance from a furnace. Followthese instructions for years of safe, trouble freeoperation.• Do not place combustible materials on oragainst the furnace cabinet or the ventpipe.• Do not store gasoline or any other flammablevapors and liquids in the vicinity ofthe furnace.• Change or replace the air filters monthlyduring any period when the circulatingblower is operating regularly.• Always replace the doors on the furnaceafter servicing. Do not operate the furnacewithout all doors and covers in place.• Avoid operating the furnace when windowsand doors are open.• Be sure that the thermostat is properlyinstalled and is not being affected by draftsor heat from lamps or other appliances.Sequence of OperationOperating sequences for the heating, cooling,and fan modes are described below. Refer tothe wiring diagrams (Figures 29) and the voltagefi eld wiring diagram (Figure 26).Heating Mode:1. On a call for heat the thermostat closes,applying 24 VAC to the W terminal on thecontrol board.2. The control board checks for continuity onthe 24 VAC limit control circuit (over-temperaturelimit switch, fl ame rollout switches andblocked vent switch in series). If an open limitis detected the control board will energizethe inducer and the conditioned air blower.All other system functions will be inoperableuntil the limit circuit closes. While the limitis open, the red LED will pulse at a rate of1 blink per unit time.3. The furnace control checks for continuityacross the pressure switch (24 VAC). If thepressure switch is closed the heat modesequence will not continue. If it remainsclosed for 10 seconds the red LED will blink3 times repetitively until the fault conditionclears.4. The inducer is energized.5. The pressure switch will close. If the pressureswitch does not close after 10 secondsthe fault LED will blink 2 times repetitivelyand the inducer will continue to run until theswitch is closed.6. The inducer will pre-purge for 30 secondsand then the igniter will start its warm-up asfollows:Initial Power up: After 30 seconds of igniterwarm-up the gas valve (24 VAC) will thenopen. The igniter circuit will stay energizedfor 3 seconds after the gas valve opens.After Initial Power up: The control has aprogrammed adaptive ignition feature whichvaries the warm-up period as follows: If ignitionis successful the warm-up is reducedby 3-seconds on each subsequent call forheat until ignition failure occurs. Upon ignitionfailure, the warm-up is increased by3-seconds on the next try. If successful, thetiming remains fi xed at this level. In general,whenever ignition failure occurs the warm-upinterval is increased by 3-seconds on thenext try. And if successful, it remains there.Minimum and maximum warm-up time limitsare set at 6 and 54-seconds, respectively.7. The furnace control must prove fl ame viathe fl ame the fl ame sensor 5 seconds afterthe gas valve opens. If fl ame is sensed, allburners are on and the igniter cools off. Ifno fl ame is sensed, the gas valve closes immediatelyand the inducer continues to run.38