The reason fan speed went to 0 was due to that TO accidently entered 0 when change fan speed. When enter a new value, make sure the actual value was in the box you entered. If the mouse moved, the value field goes back to 0, then if you pressed ENTER, it would go to zero. We will in the future to change it to make it securer. But at the mean time, TO needs to eb careful with this. In case fan went to 0 for the He loop, please tune off heater or set it to manual with 0 or low power value first before recovering the fan.