Lennox Error Code E250 indicates Limit switch circuit open. Start by checking the most common and safe items identified in the troubleshooting section. If the code returns after those checks, professional diagnosis is recommended.
Easy
Limit switch circuit open
Unknown
Limit switch open due to overheating or airflow blockage
Check proper firing rate on furnace; ensure no blockage in heater; check proper air flow; if limit not closed within 3 minutes, unit goes into 1‑hour soft lockout; resumes normal operation after fault cleared
Limit switch, air flow components (filters, blower), heat exchanger
Call an HVAC technician if the error persists after completing the recommended basic troubleshooting steps or if the system repeatedly locks out.
Disconnect power before inspecting the equipment. Never bypass safety devices or operate the system if you suspect unsafe conditions.
Learn more about the furnace components and operating conditions commonly associated with diagnostic error codes: