plenums: do's and don'ts FREE cabling and networking Helpdesk
 Question by Bill Thomas posted 17 Jan 2006
 plenums: do's and don'ts
A few questions recently came up about plenums.
1. If I use plenum-rated cable, am I allowed to run the cable through the inside of an air return duct to get cable from the second floor of my house to my basement?
2. Am I allowed to place electronics above a plenum drop ceiling in a business? I'm thinking about things like a UPS or a Power over Ethernet splitter. If I install a hidden camera in a ceiling, are the video wires that come attached to the camera supposed to be plenum-rated?
3. Am I allowed to use those white plastic tie wraps to hang wire above a plenum ceiling? I read on that the answer is no.
Thank you.
 Answer by Joseph Golan posted 17 Jan 2006
Dear Bill,

1. You would need to contact the AHJ (Authority Having Jurisdiction) to see if it is legal to do this. Plenum rated cable is primarily used to run in return-air plenum space such as a drop ceiling for example.
2. Any material installed in a return air plenum space is subject to the same legalities as cable. So in general if the equipment is not designed and designated for use is a return-air plenum then the answer would be no (PVC plastics etc. make this the most likely reason why they would not be acceptable). This includes all equipment and cables.
3. The cable ties used in a plenum rated space must also be designed for that installation, I cannot comment on your reference but in general any material not approved for use in a plenum rated space is forbidden.

Joseph Golan, RCDD

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