E20
Immergas
Firmware Integrity Error
Thermostat displays E20 and indicates a firmware or software error; device may reboot repeatedly
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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
Interrupted firmware update, Corrupted firmware image, Internal flash memory fault, Incompatible firmware version loaded
How to Fix / Troubleshooting
Safety: Do not disconnect power during firmware updates.
- Step 1 – Attempt recovery update: Using the Immergas app or service interface, check if a recovery or reinstallation of firmware is offered and follow the instructions.
- Step 2 – Stable power: Ensure the thermostat has a stable power supply during the update (no timers or switches in series).
- Step 3 – Do not interrupt: Allow the update to complete fully, even if the screen appears frozen for several minutes.
- Step 4 – Service replacement: If E20 remains and the thermostat cannot boot normally, the unit must be replaced by an authorized technician.
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Repair Difficulty
Hard
4/5
Required Part
Immergas thermostat main PCB
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