UHA S TANDARD U NIT H EATER I NSTALLATION O PERATION AND SERVICE MANUAL30 of 5911.2 Begin Start-Up11.2.1 Before Operating the HeaterTo ensure that all the controls are in safe workingorder, operate the heater for the first time with theisolating gas valve turned off and power supplyturned on.1. Turn off the isolating gas valve.2. Turn up the thermostat above roomtemperature. The automatic ignitionsequence will now begin as describedon Page 30, Figure 12.There will be no ignition of the burner and lockoutwill occur, which proves the controls are operatingcorrectly.Figure 12: Automatic Burner Control SequenceBurner Sequence for Ignition ControlFlame SignalStart Gas ValveIgnition SparkThermostat 24 VSHUT DOWNRUNSTARTts = 10 SecondsSignals Output By ControlRequired Incoming SignalsFlue BlowerPressureSwitchPCNONC30 Seconds Purge**Purge time begins at pressure switch change over.Axial Fan30 Seconds Delay 90 Seconds Delay30 Seconds Post PurgeIf at any stage the flame fails, the control will retryfor ignition. The control has four trials for ignitionbefore a one hour lockout.
