[KwartzLab] plenum vs non-plenum
ben at kwartzlab.ca
Fri Sep 7 11:16:38 EDT 2012
Hey are you gonna be at the party tonight? I found a box with about
180ft of Cat5e plenum if you want it.
On 9/5/2012 11:03 AM, Darcy Casselman wrote:
> Sweet! I like free... :D
> On Wed, Sep 5, 2012 at 10:58 AM, Ben Brown <ben at kwartzlab.ca> wrote:
>> I'll have a look, I may still have some plenum kicking around here you
>> can have for free. I have cat5e as well, if you ever need some.
>> On 9/5/2012 10:49 AM, Darcy Casselman wrote:
>>> Hm, that's not a bad idea. There are a couple places I need to cross
>>> over heading ducts, which gave the idea of fire-rated cable more
>>> practical appeal.
>>> PrimeSpec looks like it only sells spools of 1000', which is way more
>>> than I need. And $185 is somewhat more than I want to pay.
>>> On Wed, Sep 5, 2012 at 9:23 AM, Kevin Martin <kpmartin at thinkage.ca> wrote:
>>>> Indeed the question is what is a plenum. The word (as far as building trades
>>>> are concerned) originates in ventilation terminology, and applies to spaces
>>>> such as that above a drop ceiling when it forms part of the ventilation
>>>> system. In commercial buildings the space above the drop ceiling is often
>>>> used as the air return to the HVAC unit. It also applies in residential work
>>>> to the wall and floor cavities that form part of the cold air return on a
>>>> forced air heating system.
>>>> Wiring in such spaces which could generate plentiful smoke would be a safety
>>>> concern because it could quickly get dispersed throughout the building.
>>>> The Ontario Building Code defines: "Plenum means a chamber forming part of
>>>> an air duct system."
>>>> 22.214.171.124. Wiring and Cables: (2) "Where a concealed space in a floor or
>>>> ceiling assembly is used as a plenum, electrical wiring and cables within
>>>> the plenum shall conform to Sentence 126.96.36.199.(1)." Section 188.8.131.52 then goes
>>>> into a long-winded description of the fire ratings of the materials that
>>>> form the plenum itself as well as stuff like wiring that happens t run
>>>> through a plenum.
>>>> If the space above the drop ceiling is closed and not part of the HVAC
>>>> system, it would not count as plenum space, any more that the sealed
>>>> cavities within a wall between each pair of adjacent studs would.
>>>> That being said I have never seen any special provision for regular power
>>>> wiring when it passes through a wall cavity that happens to form part of the
>>>> cold air return in a residential heating system, although it would seem to
>>>> me that the same hazard would exist. This may just be a case of endemic lax
>>>> application of regulations. Or perhaps this only occurs in walls, which are
>>>> not covered by 184.108.40.206 (2).
>>>> In any case if you only need a few short runs in true plenum space, you
>>>> could enclose them in conduit (some of the provisions of 220.127.116.11(1) allow
>>>> for this). This is essentially the solution used for power cables in plenum
>>>> spaces, where one sees conduit and/or armoured ("BX") cable. This might be
>>>> cheaper and/or simpler than buying all plenum cable or buying two types of
>>>> cable and having to splice them.
>>>> -Kevin Martin
>>>> the Papertrail Handmade Paper & Book Arts
>>>> New Dundee ON
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