Re: Short Plenum Run Question

[Frank Olson <Use_the_email_links@xxxxxxxxxxxxxxxxxxxxxx>]

robertlbass@xxxxxxxxxxx wrote:
> Please DO NOT run any cables inside air ducts except those which are
> required for the operation of the ducts themselves.  An example of an
> acceptable cable would be one used to power a damper.  No other cables,
> including plenum rated cables, are permitted in the air ducts.

In Canada, damper motors are wired with mineral jacketed cable or
armoured BX.  There are also restrictions with respect to how much cable
can be exposed.  Check with your local building codes and your AHJ to be
on the safe side.


>
> Plenum cable is permitted in a plenum air return, but that is not a
> duct.  Plenum spaces are sometimes found above the ceiling in
> commercial office buildings.  Instead of running a complete system of
> return ducts, grates are installed in the ceiling and room air passes
> though them on its way back to the furnace or A/C unit.  Because these
> spaces are the only place wires can be run in such structures, you are
> allowed to use plenum cable in them.  The interior of an air duct is
> not considered a plenum for running cables.  Significantly stricter
> rules apply.


In addition to Robert's coments, building codes may allow you to run
standard FT-4 as well (for communications and network).  In Vancouver
(for instance) you don't need to run plenum rated wire in a plenum if
the total length of the wire run (from panel to device) doesn't exceed 9
meters.  Some would interpret this part of the code to mean the total
*exposed* length of wire inside the plenum, but I've always believed
it's better to err on the side of "safety".  What's really interesting
is that the wire wholesaler we use doesn't sell FT-4 jacketed CAT5 or
CAT6.  He only carries the plenum rated stuff.

It's always best to check with both your local codes and your AHJ before
you start any project like this.  Your family is worth the few minutes
this is going to take.