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Sequence of Operation and Troubleshooting Flow Chart
1
Safety
Check
Verify There
Is No Main Burner
Flame
Limit
Switch
Closed?
YES
Rollout
Circuit
Closed?
L
I
G
YES
H
T
O
Low
F
Pressure
F
Switch
Open?
YES
Combustion Air Inducer
ON at 70% Rate Speed
Low
Pressure Switch
Closed Within 150
Seconds?
YES
Pre −Purge
15 Seconds
Ignitor ON
20 Seconds
Gas Valve
C
Energized
A
L
L
Ignition Trial Begins
Indoor Blower Delay
F
(Ignitor ON)
O
R
1
S
Flame
T
Sensed Within
S
4 seconds?
T
A
G
E
YES
H
E
Ignitor OFF
A
T
Wait For Ignition
Stabilization Delay
Set Target Firing Rate
Based on Thermostat
Signals Present
OR
2
Call For 2nd Stage Heat
Figure 54. Ignition and Call for Low Fire with Two-Stage Thermostat
31-5000723 Rev. 0
Combustion Air
De−Energize
Inducer On
NO
Gas Valve
(100% rate
speed)
Combustion
Air Inducer
On (100% rate
speed)
De−Energize
NO
Gas Valve
Indoor Blower
ON (70%)
Error Code Flashes
Pressure
NO
After 5 Seconds
Low Pressure
Switch Opens
YES
Pressure Switch
Calibration
NO
Calibration
Successful?
Wait
5 minutes
Interpurge
(15 Seconds)
Timer Started
Gas Valve
De−energized
NO
Unsuccessful
Ignitor OFF
1
2
3A
Call For Heat Satisfied
Indoor blower OFF
After
Heat OFF Delay
(Low Heat Speed)
Indoor Blower
Error Code
Flashes
ON (100%)
Rollout
Error Code
Circuit
Flashes
Closes?
NO
High
Error Code Flashes
NO
Switch
After 5 Seconds
Open?
High Pressure
Switch Opens
YES
4
Calibrations
NO
YES
Attempted?
NO
NO
5th
Post-Purge
YES
(20Seconds)
Trial?
SOF T LOCKOU T IS RESE T AUTOMATICALLY AFTER ONE HOUR WITH A CALL FOR HE AT ACTIVE,
OR B Y CYCLING THE CAL L FOR HE AT, OR B Y CYCLING POWER TO THE CONTROL.
HARD LOCKOU T IS RESE T BY CYCLING POWER TO THE CONTROL.
Page 69
YES
Limit
NO
Closes Within 3
Minutes?
Indoor Blower OFF
After Heat OFF Delay
(High Heat Speed)
Soft Lockout:
Error Code
Flashes
YES
Combustion Air
Inducer OFF
After Post-Purge
Indoor Blower OFF After
Heat OFF Delay
Hard Lockout:
Error Code
Flashes
2
2
flashes
Call
For
NO
Heat?
YES
Soft Lockout:
Error Code
Flashes
Indoor blower OFF
After Heat OFF Delay
Combustion Air
Soft Lockout:
Error Code
Inducer OFF
Flashes
1
1
NO
Call For
Heat
Ends?
YES
Indoor
Blower
ON?
YES
NO
1
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