Lennox Error Code 427

Priority condition: Service Soon/Service Urgent The inverter has detected a DC peak fault condition. • If condition (55A or higher) is detected, outdoor unit will stop (compressor and fan) – moderate condition. • Anti-short cycle is initiated. • If peak current (55A or higher) occurs 10 times within an hour, system will lockout – critical condition. • Inverter LEDs will flash code 21. • If the unit is a XP20 or XP25 variable capacity heat pump, this error may occur entering or exiting a defrost cycle as the compressor restarts after the 30 second compressor shift delay. If the unit was manufactured prior to serial number 5817F and has frequent alert code 427, then compare the inverter part number to the latest part number listed in the unit repair parts. Units produced after serial number 5817F which is listed on the unit name plate have an inverter with updated software that includes compressor current slope logic to reduce the potential of alert code 427 instances from occurring during defrost. Replace the inverter with the latest inverter if necessary. • Refer to the unit service documentation for detailed troubleshooting procedures. NOTE: Serial number format on unit name plate is PPYYMNNNNN (PP = Manufacturing Plant, YY and M represents the year and month made. Priority condition: Service Soon/Service Urgent Inverter flash code 21. Priority condition: Service Soon/Service Urgent The sequence is: • Red LED: Two Flashes • Green LED: One Flash NOTE: Inverter normal operations with no error code present is as follows. Red LED is ON and Green LED is OFF.