On Friday, April 16, 2021 at 4:07:05 PM UTC-4, wrote:
On Fri, 16 Apr 2021 11:27:38 -0700 (PDT), Dean Hoffman
wrote:

On Friday, April 16, 2021 at 12:56:08 PM UTC-5, wrote:
If I were to install a new door-bell transformer and/or a new receptacle for security system, is it acceptable to install these devices above a drop ceiling in the basement and then cover them up ?

Transformers don't put off very much heat, but there still a danger ?

Thanks
Sid.

My initial thought would be no. Someone might have to trouble shoot your doorbell system someday. And the rules for the wiring would be different for the supply and load side of the transformer. I'm curious what Fretwell had to say.
Things above a T bar ceilings are considered "accessible" but they
need to be supported by structure. Most doorbell transformers go in a
box KO and as long as the box is properly attached it is OK. The other
issue might be the cable itself if this space is used for return air.
Then everything needs to be plenum rated.
That is the most frequent violation other than loose cables laying on
the tiles. They need to be supported too. They do make clips for that.
(attach to the ceiling support wires).

And I;m sure there are millions of them installed there already. Very common
for the transformer to be installed on a metal box fastened to a joist in the
basement. Then someone comes along and finishes the basement and puts
in a drop ceiling. Any heat from the transformer is insignificant and there is
still plenty of airspace around it.