20
Table 2. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and TS=Thermostat
Alert
Code
Inverter
Flash
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notifications
Component or System Operational State and Troubleshooting Tip
How to clear alert code
271
Service
Urgent
GF Low Press
Switch Open
The furnace is in Watchguard mode. The furnace low pressure switch is open. This is a five strike
condition during a single demand.
•
Check pressure (inches w.c.) of low pressure switch closing during a heat call.
•
Measure operating pressure (inches w.c.).
•
Check for blocked cold end heater box (CEHB), or condensate drain or drain strainers at outlet
of CEHB and cracked hoses.
•
Check for cracked hoses.
•
Check levelness of unit.
NOTE:
Check Service Manual and Service and Application Note
“Condensing Furnace
Pressure Switch Troubleshooting” for additional information.
Automatically clears on successful igni-
tion.
272
Service
Urgent
GF Low Press
Switch Open
Run Mode
The furnace low pressure switch is open during run mode. The system will go into Watchguard
mode.
•
Check operation of low pressure switch to see if it is stuck open during a heat call.
•
Measure operating pressure (inches w.c.).
•
Inspect vent for blockages, and combustion air inducer for correct operation and restriction.
•
Check for blocked cold end heater box (CEHB), or condensate drain or drain strainers at outlet
of CEHB and cracked hoses.
•
Check for cracked hoses.
•
Check levelness of unit.
NOTE:
Check Service Manual and Service and Application Note
“Condensing Furnace
Pressure Switch Troubleshooting” for additional information.
Automatically clears when a heat call ends
successfully.
273
Service
Urgent
GF Flame Fail In
Run Mode
The furnace flame is going off during a heating cycle. The system will go into Watchguard
mode.
•
Check micro-amperes of flame sensor using thermostat or control diagnostics.
• Clean or replace sensor.
•
Measure voltage of neutral to ground to ensure good unit ground.
• Clean face of burner assembly.
Automatically clears when a heat call ends
successfully.
274
Service
Urgent
GF Primary
Limit Switch
Open
The furnace limit switch has been open for more than three minutes. The system will go into
Watchguard mode. In Lennox Smart Zoning zoning systems, the limit trips will place the system
into central mode.
•
Check for high gas pressure.
•
Low supply air due to being plugged or restriction in system (example: dirty air filter or blockage
in duct work).
•
Check for proper firing rate on furnace.
•
Check for non-functioning zone dampers.
NOTE:
Refer to Service and Application Note ACC-14-01 - Lennox Smart Zoning
®
and SLP98 -
Insufficient
Zone Heating and Alert Code 250 Issues for corrective actions.
Automatically clears when a heat call ends
successfully.
