What It Means
- ID Invalid Size Unit Code
Lennox Equipment not specified
Lennox Equipment not specified Error Code 203
Equipment not specified:
Causes & actions from Lennox
How it shows
- iComfort S30 alert: 203
Priority condition: Service Urgent The unit size code for the indoor unit has not been selected or set incorrectly. • Verify that the correct unit size code is configured. Unit size codes for furnace and air handler are listed in the system component configuration guide or installation instruction. • Remove the thermostat from the system while applying power and set the unit size code per instructions provided in the indoor unit installation instruction.
Applicable models & manual sources
- iComfort S30
ID Invalid Size Unit Code
Disclaimer: This information is for general reference. Code wording and instructions vary by model. Always follow the service manual for your exact unit.
What should you check next?
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