Effective: October 2018
4 06-237172-002
SEQUENCE OF OPERATION / FLAME
RECOVERY / SAFETY LOCKOUT
START UP - HEAT MODE
When a call for heat is received from the thermostat supplying
24 volts to TH the following sequence occurs in the order listed:
1. The green power LED is illuminated.
2. The control resets and then performs a self check routine,
flashing the red diagnostic LED once in the first two sec-
onds.
3. The control begins a pre-purge delay.
4. Following the pre-purge period, the control energizes the
gas valve.
5. The control enables the high voltage spark output for the
trial for ignition period.
6. When the control detects the presence of flame during the
trial for ignition, the control terminates the sparking pro-
cess.
7. The thermostat and burner flame are constantly monitored
to assure the system continues to operate properly.
8. When the thermostat is satisfied and the demand for heat
ends, the main gas valve is de-energized immediately and
the green LED turns off.
FAILURE TO LIGHT - LOCKOUT
SINGLE TRIAL MODEL
Should the burner fail to light, or if the flame is not detected
during the trial for ignition period, the control performs the fol-
lowing actions:
1. The control enters ignition lockout.
2. The main gas valve is de-energized immediately.
3. The diagnostic LED indicates the fault code for lockout.
MULTI TRIAL MODEL
Should the burner fail to light, or if the flame is not detected
during the first trial for ignition period, the control performs the
following actions:
1. The main gas valve is de-energized.
2. The control then goes through an interpurge delay before
another ignition attempt.
3. The control attempts two additional ignition trials before
going into lockout and the main gas valve relay is de-ener-
gized immediately.
4. The diagnostic LED indicates the fault code for lockout.
LOCKOUT RESET
Recovery from lockout requires a manual reset by either recy-
cling the thermostat or removing 24 volts for a period of 5 sec-
onds. On models with automatic reset, if the thermostat is still
calling for heat after one hour the control will automatically reset
and attempt to ignite the burner.
CE versions have an option for non-volatile lockout. In this
case, only the external RESET input must be used to recover
from an ignition lockout.
FLAME FAILURE RESPONSE
RE-IGNITION MODE (STANDARD)
If the established flame signal is lost while the burner is operat-
ing, the control will respond within 0.8 seconds (max) by ener-
gizing the HV spark for the programmed TFI period in an
attempt to relight the burner. If the burner does not light within
the TFI, the gas valve is de-energized immediately and on
multi-try models a new TFI sequence begins.
If the burner does not relight, the control will lockout as previ-
ously described in “Failure to Light - Lockout”. Multi-try models
will make 2 more attempts to light the burner. If the flame is re-
established, normal operation resumes.
RECYCLE MODE (OPTIONAL)
With "recycle after loss of flame", upon loss of flame, the main
gas valve is de-energized within 0.8 seconds (max). After the
flame recycle delay, the control attempts to relight the burner.
Multi-try models 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 - Lockout”.
CHECKOUT
Test the gas control system after any service or component
changes to the appliance using the following method:
1. Perform a visual check of all piping, burners, and venting.
Check all wiring for integrity and proper electrical and
ground connections. Verify the burner is properly
grounded.
2. With the gas supply and thermostat off, turn on power to
the appliance.
3. Turn the thermostat to a setting high enough to initiate a
call for heat. Verify the ignition control proceeds through
the operating sequence to a safety shutoff (lockout) condi-
tion. (The burner will not light because the gas is shut off)
4. Turn off the thermostat.
5. Turn on the gas supply, and purge the gas lines of air.
Check for gas leaks on all joints upstream of the gas valve
with a soap solution.
6. Turn the thermostat to a setting high enough to initiate a
call for heat. Verify the ignition control proceeds through
the operating sequence to a normal run (burner lit) condi-
tion. Confirm there are no gas leaks downstream of the
gas valve using a soap solution.
7. Turn the thermostat setting down below the room tem-
perature. Verify the burner flame goes out.
WARNING
Risk of Explosion or Fire
Verify there are no gas leaks by using a rich
soap and water solution on all joints and
pipe connections. Never use a match or
lighter to test for the presence of gas. Fail-
ure to test properly before operation can
lead to explosion or fire and may result in
severe injury or death.
