Flow Rated Fans – How Do They Regulate?
Bathroom-style fans like Panasonic’s WhisperGreen units regulate their speed to ensure consistent airflow as restriction varies downstream. Does anyone know how this works exactly? I’m assuming it would use a pressure sensor on the exit side of the fan and have programmed speed values for differing levels of restriction, but that’s just me guessing.
The reason I ask is, what happens to the flow rate if there’s a restriction introduced on the intake side of the fan? These fans are probably designed to have nothing more than the included cover restricting them, so what happens if you want to filter the incoming air? If a filter was to introduce a significant pressure drop at the fan intake, would it detect this and compensate?