Technical information
29
Servicing should only be performed by a Qualiî‚żed Service Technician
START UP/ FLAME RECOVERY/ SAFETY LOCKOUT
START UP - HEAT MODE
When a call for heat is received from the thermostat supplying 24 volts to TH/W, the control will reset, perform
a self check routine, flash the diagnostic LED once in the first two seconds, and a pre-purge delay begins.
Following the pre-purge period, the gas valve is energized and sparks commence for the trial for ignition
period. The VFD high speed signal remains de-energized until flame is detected.
When flame is detected during the trial for ignition, the sparking process is terminated and the VFD high
speed signal is energized after a 5 second dwell period. The thermostat and burner flame are constantly
monitored to assure the system continues to operate properly. When the thermostat is satisfied and the
demand for heat ends, the gas valve and VFD speed signals are de-energized immediately.
FAILURE TO LIGHT - LOCKOUT
MULTI TRIAL CONTROL
Should the burner fail to light, or if flame is not detected during the first trial for ignition period, the gas valve is
de-energized. The control then goes through an interpurge delay before another ignition attempt. The control
will attempt two additional ignition trials before going into lockout and the valve relay will be de-energized
immediately. This ignition control has an automatic reset. If the thermostat is still calling for heat after 15
minutes the control will automatically reset and attempt to ignite the burner.
FLAME FAILURE- RECYCLE MODE
This control has the "recycle after loss of flame" function, upon loss of an established burner flame, the gas
valve is de-energized and the control proceeds to interpurge before attempting to relight the burner. The
ignition control will allow three tries for ignition including inter-purges. If the burner relights, normal operation
resumes. If the burner does not relight, the control will go into lockout as described in "failure to light".