Safety: Disconnect from mains before working on sensors or the control board.

E20 suggests that one or more temperature sensors are reading outside the expected range for the firmware.

Verify sensor part numbers: Check that any recently replaced NTC sensors are the correct De Dietrich parts for your model and zone.
Inspect wiring: Ensure that upper and lower zone sensors are not swapped at the PCB and that connectors are in the correct sockets.
Compare readings: With a multimeter, measure resistance of each sensor at the same temperature and compare. Large discrepancies indicate a faulty or incorrect sensor.
Replace incorrect or faulty sensors: Install the correct NTC sensors and reconnect them to the proper terminals.
Board compatibility: If the issue started after a board replacement, confirm that the board firmware matches the model and sensor set. Replace with the correct board if necessary.
Re-test: Restore power and monitor temperature readings and operation to ensure E20 does not return.

Display shows E20 and the unit may show abnormal temperature readings or freeze bottles unexpectedly.

Possible Causes