[Tfug] CMP *in* ductwork?

[Bexley Hall]

Hi Harry,

--- On Mon, 9/10/12, Harry McGregor <micros at osef.org> wrote:

> Personal soap box....
> 
> I *HATE* CMP aka Plenum cabling.
> 
> US building codes are based on visible smoke, and CMP
> cabling has Teflon in it to increase the temp at which it
> gives off visible smoke.
> 
> Personally I prefer the .eu way, which is more worried about
> bad things in the smoke then the amount or when the smoke
> starts (ie low halogen cabling).

Ha!  I would never have considered the "optical" properties of
the smoke to be important!  I figured the prohibition against
smoke was to prevent nasty chemicals from killing folks in the
edifice -- even if flame was not present.  (When they say most
deaths are caused by smoke, I'm pretty sure its the chemicals
*in* the smoke that are doing the killing!)

[And, of course, the self-extinguishing requirement consequential
to the runs that CMR/CMP makes without fire stops as deterrents
so the wire doesn't act as an accelerant propagating the fire
unimpeded by the absence of those fire stops!]

So, why the emphasis on *visible* smoke?  So fire fighters can
*see* the bodies of the victims of the invisible noxious fumes??
Or, is "visible" just considerably easier to test for??!  <frown>

> In either case, I have seen CMP cabling run inside duct
> work, don't know if I would recommend it with evap or heavy
> heating loads....

Something is nagging at my memory suggesting this is not kosher.
Perhaps a local addition to the code in one of the (many) places
I've lived?  (I recall one place insisted all residential wiring
was run in EMT -- even indoors, etc.!)

The only runs in question were those intended to support the
future addition of motorized baffles at each air outlet.  So,
it might be wiser to just run those down the outside of the
ductwork *now* (vs. through the ductwork in the future!)
and not have to worry about getting from the inside of the 
duct (where the wire would be located) to the outside of the
duct (where the actuator would be located).

Or, maybe just skip it, entirely!  This house isn't big enough
that the extra control would make a realistic difference in
the HVAC!  (but, it would have been useful as a test bed)

Thanx!
--don