The adjustable mechanical thermostat for the heater can be sensitive if subjected to frequent up and down temperature adjustments. There is rarely anything saved by setting the temperature down if it is still to be raised again later. Therefore, avoid adjusting the thermostat once the desired heat has been reached, as this can otherwise contribute to large temperature variations starting to appear. If this happens, it may be possible to recalibrate the thermostat. In practice, 6 degrees is then a limit for what can be calibrated. If calibration is needed, follow the instructions below.
Calibrate thermostat SDH-20, SDH-30
Turn the thermostat knob down to 0 degrees (counter-clockwise).
Pull out the thermostat knob and you will see the red seal which can be scraped off and under there is an adjustable screw.
Note! If it needs to be calibrated more than 6 degrees, the thermostat probably needs to be replaced.
Note that there is also a digital thermostat that can be installed for this heater. The advantage of it is accuracy in temperature and setting options.