Lennox Error Code 274

Priority condition: Service Urgent The furnace limit switch has been open for more than three minutes. The system will go into Watchguard mode. In iHarmony 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 - iHarmony and SLP98 - Insufficient Zone Heating and Alert Code 250 Issues for corrective actions.