With some units, the basic setting of the thermostat was made incorrectly by the manufacturer.

The ST620 then switches on the heating when the temperature is higher than the one set. This is actually the temperature that you select, where the thermostat should switch off the heating. The thermostat is set to cool and closes the contact when it should open it.

Here are the instructions on how to change the basic setting:

  1. Call up Service in the menu
  2. Enter the code: "372"
  3. Change COOL mode to HEAT mode by turning the touch ring.


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