York DNH 030 Installation Manual

Also see for DNH 030: Technical guide Installation manual

York DNH 030 Installation Manual Manual pdf 13 page image

282911-YIM-B-0807Unitary Products Group 13SEQUENCE OF OPERATIONThe unit is controlled by a conventional heating/cooling ther-mostat common to this class of equipment.HEATINGThe control board begins a call for heat when W1 is ener-gized (connected to R). The control ignores W2 until pilotignition has been established.The control checks to see if the pressure switch is open. If thepressure switch is closed, the control board flashes "3" on theLED and waits indefinitely for it to open. When the pressureswitch is sensed as open, the control begins pressure switchproving period. If the call for heat is lost, the control goesback to Standby.PRESSURE SWITCH PROVINGThe control board energizes the induced draft motor (Highspeed for 2 stage model) and waits for the low pressureswitch to close. When the low pressure switch closes, thecontrol begins Pre-purge period. If the call for heat is lost, thecontrol de-energizes the inducer without post-purge andreturns to standby.If the low pressure switch does not close within 10 seconds ofinducer energizing, the control board flashes "2" on the LED.If the pressure switch does not close within 5 minutes ofinducer energizing, the control shuts off the inducer for 30seconds, then energizes the inducer for another 5 minute tryto close the pressure switch. This cycle continues indefinitelyuntil either the pressure switch is proved closed, or the callfor heat ends.PRE-PURGEThe control board monitors the low pressure switch andensures it remains closed during pre-purge. If the pressureswitch opens, the control goes back to pressure switch prov-ing mode. The control waits for a 15 second pre-purgeperiod, then begins the ignition trialIGNITION TRIAL PERIODThe control board energizes the pilot gas valve and sparkoutputs for an 85 second Ignition trial. The control de-ener-gizes the spark when flame is sensed and enters a flame sta-bilization period.If flame is not established within the ignition trial period, thecontrol de-energizes the spark and gas valve and begins aninter-purge period before attempting another ignition trial.If the call for heat is lost during an ignition trial period, thecontrol immediately de-energizes spark and gas. The controlruns the inducer motor through a post purge period beforede-energizing.If the pressure switch is lost during an ignition trial period, thecontrol immediately de-energizes spark and gas. The controlbegins pressure switch proving before an inter-purge and re-ignition attempt.PILOT FLAME STABILIZATION PERIODThe control board de-energizes the spark output, and waitsfor a 2 second flame stabilization period before energizing themain gas valve.If flame is lost during the flame stabilization period, the con-trol board counts it as a flame loss and retries ignition or locksout flashing a "5" on the LED.HEAT BLOWER ON DELAYThe control board waits for 30 seconds and then energizesthe indoor blower heat speed. Blower on delay time begins atthe start of flame proving period in the trial for ignition.If the thermostat demand for heat is removed, the control de-energizes the gas valve, energizes the blower on heat speedand initiates a post-purge and heat blower off delay.MAIN BURNER OPERATIONHigh heat warm-upTwo stage models run high heat for the first 60 seconds fol-lowing Pilot Flame Stabilization period regardless of W2demand. If W2 is not energized at the end of this 60 secondperiod the control de energizes the high gas output and stepsthe inducer to low speed. If W2 is energized the controlremains on high heat.There is no high heat warm-up on single stage modelsLow heatThe control board keeps the pilot gas valve, main gas valveand induced draft motor energized while continuously moni-toring the call for heat, low pressure switch, and flame status.If the call for heat (W1) is lost, the control de-energizes thegas valve and begins post purge.If low pressure switch opens, the control de-energizes thegas valve and begins pressure switch proving mode.If flame is lost, the control de-energizes the gas valve within2.0 second and counts the flame loss. If flame has been lostmore than 16 times within the same call for heat, the controlboard locks out flashing "5" on the LED. If flame has beenlost less than 16 times, the control attempts re-ignition after a300 second inter-purge period.High heatIf the W2 terminal was energized more than 1 second beforeW1 at the start of the call for heat, and remains continuouslyenergized through the call for heat, the control considers it tobe connected to a single stage thermostat and implements a10 minute Auto staging feature. The 2nd stage thermostatcall is ignored until 10 minutes into steady heat (9 minutesafter high heat warm-up ended).