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2. Call for 2nd Stage Heat (2-Stage Thermostat)
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
Pressure Switch
Closes Within
10 Seconds?
YES
Adjust Circulator To
Appropriate Speed
3A
Wait for Call for Heat Satisfied
1
SYSTEM WILL ALWAYS LIGHT ON LOW FIRE, EVEN IF 2ND STAGE CALL FOR HEAT IS IN PLACE.
SPECIAL MODULATING MODE HAS NOT BEEN SELECTED.
2
2
3
IF THE HIGH PRESSURE SWITCH DOES NOT CLOSE WITHIN 5 ATTEMPTS, THE SYSTEM WILL
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).
S9240F2051 MODULATING INTEGRATED FURNACE CONTROL
Increase
Error Code
NO
Inducer Speed
Flashes
if Not at Maximum
19
Wait 5
3
Minutes
M33120
M33120
69-2807—01
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