Effective: January 2020
2 F-35-53-CE
SEQUENCE OF OPERATION / FLAME
RECOVERY / SAFETY LOCKOUT
Power Up
During power up the LED shall briefly flash ON for around 1.2
seconds, then turn OFF to indicate normal operation.
Start-Up - Heat Mode
When a call for heat is received from the thermostat, 12 VDC to
TH, then control will begin a pre-purge delay. Following the pre-
purge period, the gas valve is energized and sparking com-
mences for the Trial for Ignition (TFI) period.
When flame is detected during the TFI, the sparking process is
terminated and the gas valve remains energized. The thermo-
stat and burner flame inputs are constantly monitored to assure
proper system operation. When the thermostat is satisfied and
the demand for heat ends, the gas valve is immediately de-
energized.
A post-purge delay ensures the unit is ready for the next call for
heat.
Failure to Light - Lockout
SINGLE TRIAL MODEL
Should the burner fail to light, or a flame is not detected during
the TFI period, the gas valve will de-energize and the control
will go into lockout. The diagnostic LED will indicate the fault
code for ignition lockout. (3 Flashes)
MULTI TRIAL MODEL
Should the burner fail to light or the flame is not detected
during the TFI period, the gas valve will de-energize. The con-
trol will then go through an inter-purge delay before an addi-
tional ignition attempt. The control attempts two additional
ignition trials before de-energizing the gas valve and entering
lockout. The diagnostic LED will indicate the fault code for igni-
tion lockout. (3 Flashes)
Flame Failure
FLAME FAILURE - RECYCLE MODE (Standard)
With the “Recycle after Loss of Flame” option, upon loss of
flame, the gas valve is de-energized and the control proceeds
to inter-purge before attempting to relight the flame. Multi-try
models permit three tries for ignition including inter-purges. If
the burner relights, normal operation resumes. If the burner
does not relight, the control will enter lockout.
FLAME FAILURE - RE-IGNITION MODE
If the established flame signal is lost while the burner is operat-
ing, the control will respond immediately energizing the H.V.
spark for the TFI period in an attempt to relight the flame. If
the burner does not light within the TFI, the gas valve will
immediately de-energize and single try models will enter lock-
out. On multi-try models, a new TFI sequence will begin after
an inter-purge delay. Multi-try models perform two additional
attempts to light the burner before de- energizing the gas valve
and entering lockout. If the burner relights, normal operation
resumes.
Combustion Airflow Faults
If the airflow signal is lost, or the hi-limit opens during heat
mode, the gas valve is immediately de-energized and the
blower stays on. If the switch closes again, a normal ignition
sequence will resume. If not and this condition persists for
more than five minutes, the control will enter lockout with the
blower off.
Lockout Recovery
Recovery from lockout requires a manual reset by either reset-
ting the thermostat, or removing power for a period of 5 sec-
onds. On models with non-volatile lockout, reset must be by
using the reset switch with 12VDC power maintained.
