Lennox Error Code E111 indicates Line voltage polarity reversed. 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
Line voltage polarity reversed
Unknown
Line power wiring reversed
Reverse line‑power wiring; system resumes normal operation 5 seconds after fault recovered
Power supply wiring
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: