I have a question that relates to a doorbell install that you folks have
been helping me with, along with another transformer install that I have
to do for a AC system. The transformer that had been spec'd out a couple
of years ago for the AC system called for a JBOX with a extension to give
it depth and the transformer would mount directly inside of the box with
the low voltage terminals sticking out, visible and easy to work on. I
want to find the same setup for my doorbell install as the device will be
in a home run closet that is drywalled! It is impractical to rip open the
wall to install on the side of a JBOX. It is easier to just cut in a
retro box that I can dedicate to the transformer and then pull Romex or
THNN from a nearby outlet. What type of transformer fits inside of a JBOX
and what size jbox do I get. I know that I have seen applications in the
past, where the transformer is sticking right out of the box. Can someone
help me with this. I am confused. If I was given bad info re the AC
transformer that it will be a pain to rip out that box and reposition.


One method would be to install an extension ring on an existing box.
Install the transformer in a KO on the exposed extension ring.


*I had the same thought. They make a four inch square box that will mount
onto a in-wall outlet box. You will need to go to a electric supply company
to get it. Check out the Raco/Hubbell web site to get a part number. One
thing though is if you would be mounting this onto a plastic box you would
need to connect a ground wire onto the metal box using a G clip.

Most of the transformers that I see and install for doorbells and furnace
control are mounted on the exterior of electrical boxes with the line
voltage leads going into a knockout. The only exception is factory
installed transformers that are mounted directly inside of equipment.