1
Thermostat calls for heat.
-Prior to energizing blower, ignition module checks safety circuits for normal switch positions:
a) Vent temp switch normally closed.
b) Intake pressure switch normally closed.
c) Exhaust pressure switch normally open.
If the vent temp switch is open, the control waits
indefinitely
for temp switch to close (green light stays on).
If the exhaust pressure switch contacts are closed (not in normal position), the ignition module will wait 45 seconds for
pressure switch contact to open before energizing blower. If after 45 seconds and pressure switch contacts do not open,
the ignition module locks out with the PURGE light flashing indicating pressure switch fault.
2
Blower energizes.
3
Pressure switch proves blower/vent system operation.
If the N.O. contacts of the exhaust pressure switch do not close within 5 minutes of the blower being on,
the control locks out with the PURGE light flashing indicating pressure switch fault.
4
Blower pre-purge period (5 seconds) indicated by the PURGE LED on the module.
5
Igniter warm up (18 seconds), indicated by the IGNITER LED on the module.
6
Trial for ignition (4 seconds, three trials).
a) Flame establishing period (2.5 seconds) gas valve and igniter on, indicated by the IGNITER and VALVE LED
on the module.
b) Burner on, flame proving period (1.5 seconds, looking for minimum of 1 micro amps), indicated by the FLAME
& VALVE LED on the module.
7
Steady state operation.
Ignition module monitors:
- Thermostat circuit.
- When thermostat opens, gas valve is shut down and post purge begins.
- Safety circuit.
- If vent temp switch opens, gas valve is shut down, system will post purge and wait for switch to close before
attempting re-ignition.
- If either pressure switch opens, Gas valve is shut down, Blower is shut down for 30 seconds after which blower
is re-energized and system attempts re-ignition starting at pressure switch proving mode.
-Flame sensor circuit.
- If flame is lost, gas valve is shut down, system will post purge and system attempts
re-ignition starting at pressure switch proving mode.
Thermostat satisfies.
Burner off.
Blower post purge (15 seconds).
9
8
10
For models prior to CF serial numbers
For models prior to CF serial numbers
10
10
