Turn off the heater using the main switch on the side.
Turn the heater back on.
Press and hold the gear button (bottom right) until you see "FR" in the display. Before "FR" appears, it will show "CH" and "CO", but keep holding until you see "FR".
After this, the heater will restart and should eventually stop at 22 degrees. The heater is now reset to factory settings
Generation 3
Updated over a month ago