Sequence Of Operation And Troubleshooting Flow Chart; Ignition And Call For Low Fire With Two-Stage Thermostat - Lennox G71MPP SERIES Unit Information

A − 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 Call For Heat Satisfied
IGNITION AND CALL FOR LOW FIRE WITH TWO−STAGE THERMOSTAT
Combustion Air
De−Energize
NO
Inducer On
Gas Valve
(100% rate speed)
Combustion
Air Inducer
On (100% rate
speed)
De−Energize
NO
Gas Valve
Indoor Blower
ON (70%)
High
Pressure
Error Code Flashes
NO
Switch
After 5 Seconds
Open?
Low Pressure
Switch Opens
YES
YES
Pressure Switch Calibration
NO
Successful?
Calibration
Wait
5 minutes
Interpurge
(15 Seconds)
Timer Started
Gas Valve
De−energized
NO Unsuccessful
Ignitor OFF
SOF T LOCKOU T IS RESE T AUTOMATICALLY AFTER ONE HOUR WITH A CALL FOR HE AT ACTIVE,
1
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.
2
3A
After
Indoor blower OFF
Heat OFF Delay
(Low Heat Speed)
Error Code Indoor Blower
Flashes
ON (100%)
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)
Trial?
Page 56
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
2 2
Flashes
flashes
Call
For NO
Heat?
YES
Error Code
Flashes
Indoor blower OFF
After Heat OFF Delay
Combustion Air Soft Lockout:
Error Code
Inducer OFF
1
Flashes
1
NO
Call For
Heat
Ends?
YES
Indoor
Blower
ON?
YES NO
1