Generation 2: (SG1200WIFI, SG2000LED, CO2200LEDMAX)
Turn off the heater.
Hold the button with the 3 wavy lines / WiFi button / temperature wheel while turning the heater back on.
When you see the display reset (the LEDs on the display will blink), you can release both buttons.
The heater will start with the default temperature set to 22°C.
