Occupancy sensors and A/C vents

[rhamer]

I am interested in anybodys experience with the 360Deg PIR units and their placement relative to heating and cooling vents.

My new house has both heating and cooling vents in the roof and when you add lights and PIR's they all seem to be fighting for the same space.

I am concerned about placing the PIR units near the heating and cooling vents, as the sudden change of air temperature may trigger them.

Any thoughts on minimum spacing?

Regards

Rohan

[UncleDick]

Couple of points:

I have had internal PIR's mounted within a metre or so of their respective loads and had no problem with my worry (which is why I did it to see) that the globe going on or off would trigger the PIR.

I visited a problem site where (amongst other problems) the house owner complained that every night when he got up to pee, as soon as he turned the light on in the bathroom, the outside lights would turn on (honest). Turned out that the bathroom light also triggered a ducted exhaust fan and the duct exeted (yes you guessed it) a foot or so in front of the out door PIR that controlled the external lights.

Unfortunatly every installation is different but in general moving air at different temp to background (>5C difference typically) will tend to trigger PIR's. I have seen this in outdoor (hot air over a sun warmed drive being blown away by sea breezes) at 10+ metre range and indoor (A/C ducts - cieling and wall mount) at 2-3 metre range.

You won't really know until you try and then it will be too late.

On a different tack are you sure you want PIR's in the living areas (where HVAC are normally placed)? My experience is that it seems like a good idea at the time but is a pain in the proverbial to live with. I had to fix up a site where the original installer had sold the owner of the idea of having a 'totally automatic house' with no light switches - just PIR's in every room. Just walking down the hall lit up every adjoining room like a christmas tree and when they sat still enough in a room (reading or watching TV etc) the 'kin lights kept going out. Even if he had provided enable/disable/on/off switches remembering what was what would have been a task,

For that and other reasons this became a mamoth re-wiring operation (solid walls chased to new switch possitions and output units moved from the (Hot) roof to a cooler possition.

PIR's are great for Garages, Halls, Corridors, Toilets (not Bathrooms), Laundries, walk in Pantry's and Robes, store rooms etc. But not living areas

[Frank Mc Alinden]

Hi Guys

Unfortunatly every installation is different but in general moving air at different temp to background (>5C difference typically) will tend to trigger PIR's


From previous experience (long time back) in the security industry i recall sensors looking for a 2 degree change in temp before triggering...Remember putting a pir next to an air con in a computer room thinking it would false alarm like crazy..But because the temp was reasonably constant it never did....

I use Pulnix ceiling mount sensors connected to Genesis Alarm panel and have Genesis outputs connected to aux inputs of my cbus system....Works quite well for occupancy detection.........

Just walking down the hall lit up every adjoining room like a christmas tree and when they sat still enough in a room (reading or watching TV etc) the 'kin lights kept going out

Yes my family love it when the lounge lights ramp down and go out....;-)
But i keep saying we are saving a fortune ;-)
Frank