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1
Safety
Check
Verify There
Is No Main Burner
Flame
Limit
Switch
NO
Closed?
YES
Rollout
Circuit
NO
Closed?
L
I
YES
G
H
T
Low
O
Pressure
NO
F
Switch
F
Open?
YES
Inducer ON
at Ignition
Firing Rate Speed
Low
Pressure Switch
Closed Within 150
Seconds?
YES
Pre-Purge
15 Seconds
H.S.I. ON
20 Seconds
Gas Valve
Energized
C
A
L
L
Ignition Trial Begins
Heat Fan On Delay
(H.S.I. ON)
Timer Started
F
O
R
1
Flame
S
Sensed Within
T
4 seconds?
S
T
A
G
YES
E
H
H.S.I. OFF
E
A
T
Wait For Ignition
Stabilization Delay
Set Target Firing Rate
Based on Thermostat
Signals Present
2
– OR –
Call For 2nd Stage Heat
Call For Heat Satisfied
Fig. 9. S9240F sequence on Light Off and Call for 1st Stage Heat cycle (2-stage thermostat).
S9240F1004 MODULATING HOT SURFACE IGNITION INTEGRATED FURNACE CONTROL
1. Light Off and Call for 1st Stage Heat (2-Stage Thermostat)
De-Energize
Inducer ON
Gas Valve
(Max Speed)
Inducer ON
(Max speed)
De-Energize
Gas Valve
Circulator ON
(Mid Speed)
High
Error Code Flashes
Pressure
After 5 Seconds
Switch
Open?
Low Pressure
Switch Opens
YES
YES
Pressure Switch
Calibration
NO
Calibration
Successful?
Wait
5 minutes
Interpurge
(15 Seconds)
Gas Valve
De-energized
NO
Unsuccessful
Trial?
H.S.I. OFF
1
SOFT LOCKOUT IS RESET AUTOMATICALLY AFTER ONE HOUR WITH A CALL FOR HEAT ACTIVE,
OR BY CYCLING THE CALL FOR HEAT, OR BY CYCLING POWER TO THE CONTROL.
2
HARD LOCKOUT IS RESET BY CYCLING POWER TO THE CONTROL.
3A
Circulator OFF After
Heat Fan OFF Delay
(Low Heat Speed)
Error Code
Circulator ON
Flashes
(Max Speed)
Rollout
Error Code
Circuit
Flashes
Closes?
NO
Error Code Flashes
NO
After 5 Seconds
High Pressure
Switch Opens
4
Soft Lockout:
Calibrations
NO
YES
Attempted?
NO
NO
5th
Post-Purge
YES
(20Seconds)
19
YES
Limit
Closes Within 3
NO
Minutes?
Circulator OFF After
Heat Fan OFF Delay
(High Heat Speed)
Soft Lockout:
Error Code
Flashes
YES
Inducer OFF
After Post-Purge
Circulator OFF After
Heat Fan OFF Delay
Hard Lockout:
Error Code
2
2
Flashes
flashes
Call
For
NO
Heat?
YES
Error Code
Flashes
Circulator OFF After
Heat Fan OFF Delay
Soft Lockout:
Inducer OFF
Error Code
1
Flashes
1
NO
Call For
Heat
Ends?
YES
Circulator
On?
YES
NO
1
M28154
69-2088—01
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