Lennox S40 - Page 60

60
Table 21. Lennox S40 Smart Thermostat Alert Codes and Troubleshooting
E2A=Errors to Action, GF= Gas Furnace, AH=Air Handler, IU=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OU=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system,
SRS=Smart Room Sensor, TS=Thermostat , IAQ- IAQ Monitor and WE=Wi-Fi Extender
Alert
Code
Inverter
Flash
Code
Priority
Condition
Actual Displayed Alert
Text Under dealer control
center > Notications
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 ve 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 H-13-07 “Condensing Furnace Pressure
Switch Troubleshooting” for additional information.
Automatically clears on
successful ignition.
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 H-13-07 “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 ame is going off during a heating cycle. The system will go into Watchguard mode.
• Check micro-amperes of ame 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 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 lter or blockage in duct
work).
• Check for proper ring rate on furnace.
• Check for non-functioning zone dampers.
NOTE: Refer to Service and Application Note ACC-14-01 - iHarmony
®
(Smart Zoning) and SLP98 -
Insufcient Zone Heating and Alert Code 250 Issues for corrective actions.
Automatically clears
when a heat call ends
successfully.