Honeywell S9240F2051 - Page 19

S9240F2051 MODULATING INTEGRATED FURNACE CONTROL
19 69-2807—01
Fig. 10. S9240F IFC sequence on Call for 2nd Stage Heat cycle (2-stage thermostat).
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2. Call for 2nd Stage Heat (2-Stage Thermostat)
M33120
1st Call
for High
Fire?
Wait for Call for Heat Satisfied
2 Stage
Thermostat
2nd Stage
Recognition Delay
(30 Seconds)
YES
Inducer ON
(High Fire Speed)
Increase
Inducer Speed
if Not at Maximum
High
Pressure Switch
Closes Within
10 Seconds?
NO
Error Code
Flashes
NO
YES
Wait 5
Minutes
3A
2
Adjust Circulator To
Appropriate Speed
M33120
SYSTEM WILL ALWAYS LIGHT ON LOW FIRE, EVEN IF 2ND STAGE CALL FOR HEAT IS IN PLACE.
SPECIAL MODULATING MODE HAS NOT BEEN SELECTED.
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.
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2
3
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