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S9240F1004 MODULATING HOT SURFACE IGNITION INTEGRATED FURNACE CONTROL
2. Call for 2nd Stage Heat (2-Stage Thermostat)
1
SYSTEM WILL ALWAYS LIGHT ON LOW FIRE, EVEN IF 2ND STAGE CALL FOR HEAT IS IN PLACE.
2
SPECIAL LENNOX MODULATING MODE HAS NOT BEEN SELECTED.
IF THE HIGH PRESSURE SWITCH DOES NOT CLOSE WITHIN 5 ATTEMPTS, THE SYSTEM WILL
3
OPERATE AT LOW FIRE FOR THE REMAINDER OF THE CALL FOR HEAT REQUEST.
Fig. 10. S9240F IFC sequence on Call for 2nd Stage Heat cycle (2-stage thermostat).
69-2088—01
2
1
2 Stage
2
Thermostat
1st Call
for High
Fire?
YES
NO
2nd Stage
Recognition Delay
(30 Seconds)
Inducer ON
(High Fire Speed)
High
Increase
Pressure Switch
NO
Inducer Speed
Closes Within
if Not at Maximum
10 Seconds?
YES
Adjust Circulator To
Appropriate Speed
3A
Wait for Call for Heat Satisfied
Error Code
Wait 5
Flashes
Minutes
20
3
M28155
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