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Motion detection in plenum

Motion detection in plenum

(OP)
Hi,
I thought I would seek out suggestions on a challenge we have been trying to figure out for the last couple of weeks. Our client wants to put motion detection (of some sort) in the ceiling space above suites within their building (a data center).
The challenge we have is the ceiling space is a plenum and there doesn't seem to be any plenum rated devices suitable for this purpose. We can build a box around the sensor but this voids the operation of most types. We found an RF device which we could put in a drywall enclosure but this is a 2.4 GHz device which they will probably push back on as it could interfere with Wifi.
Our only viable option so far is a (plenum rated) fiber optic cable which would detect motion if disturbed. this would work but will be costly and difficult to install insitu.

does anyone have any insights into this? any brilliant suggestions?

RE: Motion detection in plenum

I found a few plenum rated by googling "motion detection in plenum".
Good lick,
Dave

RE: Motion detection in plenum

(OP)
I think you'll find those are plenum rated back boxes. I thought it was that easy at first too/
I'd be happily proven wrong with a link!

RE: Motion detection in plenum

(OP)
This looks promising. We will contact the manufacturer to confirm as we have seen similar claims only to dig into it and find the housing is plenum rated but the device as a whole is not. i.e. it can back into a plenum but the whole device can not be contained within a plenum (as we are planning for).

RE: Motion detection in plenum

What are the requirements for that? Seems to me that having a plenum rated casing should be an adequate barrier; for anything worse, having the guts be plenum rated is kind of pointless.

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RE: Motion detection in plenum

(OP)
The normal installation of these sensors is flush mounted on a ceiling with only the housing/back box projecting into the ceiling space/plenum behind. Our requirement is to put the whole device in the plenum as it is presence in the plenum (not the room) that we are interested in. The big red flag on the above linked cut sheet is the material being listed generically as "plastic". Plastic is not normally allowed in plenums unless it is plenum rated (normally stated)
the RF sensor we found which can be boxed into drywall while still detecting presence in the plenum was a really good compromise at first - it could tecnically be removed from the plenum while still detecting within it. When we realized that the 2.4 GHz operational frequency would impinge on wifi bands this became less rosy.
I thought I would punt the question out to the crowd to see if anyone knew of any other sensor which might be able to be adapted in a similarly novel way.

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