Lennox SLP98UHV Installation Instructions Manual page 62

Troubleshooting: Heating Sequence of Operation (Continued)
IGNITION AND CALL FOR HEAT WITH SINGLE-STAGE THERMOSTAT
4
Safety
Check
Verify There
Is No Main Burner
Flame
Limit
NO
Switch
Closed?
YES
Rollout
NO
Circuit
Closed?
L
I
G
YES
H
T
O
Low
F
Pressure
NO
F
Switch
Open?
YES
Combustion Air Inducer ON
at Ignition at 70% rate speed
Low
Pressure Switch
Closed Within 150
Seconds?
YES
Pre-Purge
15 Seconds
Ignitor ON
20 Seconds
Gas Valve
Energized
IgnitionTrial Begins
Indoor Blower On
C
Ignitor ON Delay Timer Started
A
L
L
F
Flame
O
Sensed Within
R
4 seconds?
H
E
A
T
YES
Ignitor OFF
Wait For Ignition
Stabilization Delay
Set to
Low Firing Rate
Move to Mid Firing Rate
and High Firing Rate after
2nd and 3rd Stage Delays
(based on DIP Switch selections)
Indoor Blower OFF After
Heat OFF Delay
(Low Heat Speed)
De-Energize Combustion Air
Gas Valve
Inducer ON
(100%)
Combustion Air
Inducer ON
(100%)
De-Energize
Gas Valve
Indoor Blow­
er ON
(70%)
High
Error Code Flashes
Pressure
After 5 Seconds
Switch
Open?
Low Pressure
Switch Opens
YES
YES
Pressure Switch Calibration
NO
Successful?
Calibration
Wait
5 minutes
Interpurge
(15 Seconds)
NO
Gas Valve
De-energized 5th
NO
Unsuccessful
Trial?
Ignitor OFF
1
2
Call For Heat Satisfied
3B
Indoor Blower
Error Code ON
Flashes
(100% Speed)
Rollout
Error Code
Circuit
Flashes
Closes?
NO
Combustion Air Inducer
Error Code Flashes
NO
After 5 Seconds
High Pressure
Switch Opens
4
Soft Lockout:
Calibrations
NO YES Error Code
Attempted?
NO
Post-Purge Combustion Air
YES
(20 Seconds)
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 CON­
TROL.
HARD LOCKOUT IS RESET BY CYCLING POWER TO THE CONTROL
Page 62
YES
Limit
NO
Closes Within 3
Minutes?
Indoor Blower OFF
After Heat OFF Delay
(High Heat Speed)
Soft Lockout:
Error Code
Flashes
YES
OFF After Post-Purge
Indoor Blower OFF After
Heat OFF Delay
Hard Lockout:
Error Code
2
Flashes
flashes
Call
For
NO
Heat?
YES
Flashes
Blower On?
Indoor Blower OFF
After Heat OFF Delay
Soft Lockout:
Error Code
Inducer OFF
1
Flashes
1
NO
Call For
Heat
Ends?
YES
Indoor
YES NO
1