E20
Trane
Humidity Accessory Communication Error
Thermostat displays E20 and dehumidification or humidification functions are disabled
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Disconnected Trane whole-home dehumidifier or humidifier, Miswired dehumidifier/humidifier control terminals, Failed accessory control board, Incompatible accessory type selected in thermostat setup
How to Fix / Troubleshooting
Safety: Turn off power to any connected humidifier or dehumidifier before servicing.
- Step 1 – Verify accessory presence: Confirm that a Trane whole-home humidifier or dehumidifier is actually installed. If not, disable the accessory in the thermostat installer setup.
- Step 2 – Inspect wiring: At the indoor unit and accessory, check the HUM, DHUM, or dedicated accessory terminals. Ensure low-voltage wires are secure and not shorted.
- Step 3 – Check accessory power: Confirm the humidifier/dehumidifier has power at its disconnect or plug.
- Step 4 – Confirm configuration: In installer setup, select the correct accessory type (on/off, powered, or communicating Trane unit).
- Step 5 – If E20 persists: The accessory control board or communication module may be faulty and should be tested or replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Trane Whole-Home Dehumidifier or Humidifier Control Board
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