Lennox S40 - Page 71

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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
427 21
Service
Soon/Service
Urgent
OU Inverter DC Peak
Fault
The inverter has detected a DC peak fault condition.
• If condition (55A or higher) is detected, outdoor unit will stop (compressor and fan) – service soon
condition.
• Anti-short cycle is initiated.
• If peak current (55A or higher) occurs 10 times within an hour, system will lockout – service urgent
condition.
• Inverter LEDs will ash code 21.
• If the unit is a Lennox 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.
Inverter ash code 21.
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.
To clear, disconnect
and reconnect power
to outdoor control.
428 22
Service
Soon/Service
Urgent
OU Inverter High Main
Input Current
The inverter has detected a high main input current condition.
• If condition is detected, outdoor unit will stop (compressor and fan) – service soon condition.
• Anti-short cycle is initiated.
• If condition occurs 10 times within an hour, system will lockout – service urgent condition.
• Inverter LEDs will ash code 22.
• Refer to the unit service documentation for detailed troubleshooting procedures.
Inverter ash code 22.
The sequence is:
• Red LED: Two Flashes
• Green LED: Two Flashes
NOTE: Inverter normal operations with no error code present is as follows. Red LED is ON and Green LED
is OFF.
To clear, disconnect
power to outdoor unit
and restart.