The extract fan with a humidity sensor, I mentioned in an earlier thread and the logic of its operation. It has a PIR, which normally triggers the fan into running, but...
Should it also begin to run or be triggered by rising humidity, or simply continue to run if the humidity is high, if it is already running? I still have the leaflet from when I installed it, but it doesn't mention this point at all.
All the ones I have encountered, simply run continuously when they detect humidity above their trigger threshold.
The PIR trigger however may be fed into a run on timer, to keep it running for a period of time after a detection.
John Rumm presented the following explanation :
Thanks and yes - the PIR once triggered has a timer setting. I have that set on 20 minutes run on after triggered.
Mine runs all the time but at about 40% speed. It ramps up to about 65% if the light comes on. If the humidity goes up it ramps up to 85% until the humidity drops. All programmable.
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