[KwartzLab] plenum vs non-plenum
Bob DeGregory
bob.degregory at gmail.com
Wed Sep 5 14:15:17 EDT 2012
Thanks Kevin for adding the appropriate details to my oblique questioning
of the need for plenum cable.
Also, Darcy wrote: "There are a couple places I need to cross over heading
ducts" which brings us to the point of further discussion.
1) Traversing heating ducts is a slightly different "use case" than running
cable through plenum space. Since I'm too lazy to xref the appropriate
building code provisions, I will wing it with the statement that when
traversing heating ducts you simply need to provide "separation". In
practice, with residential power wiring I've seen electricians simply
insert a scrap of drywall between their cable and the heating (supply) duct
that needs to be traversed. I suspect that this is mostly to satisfy
inspection requirements. What I see much more frequently are avoidance
strategies like artful bending of cables.
2) Care must be taken when going the conduit route as only certain conduit
is ``plenum rated``. Basically if you`re going to run through return air
space using conduit, you`ll need to use EMT because PVC conduit isn`t
plenum rated. (can you see a trend developing with PVC)
3) Speaking from personal experience, I know that there`s non-plenum-rated
coaxial cabling running through my cold air returns because I took Rogers
up on an offer to wire a bunch of cable drops for free and they didn`t use
plenum cable. I don`t loose any sleep over the worry that one or two cable
runs in air return ducts will be a concern if a fire erupts at 3 a.m.
For illustration purposes here`s a composite picture showing the various
types of electrical conduit. The green section in lower right corner shows
EMT but I failed to label it.
[image: Inline image 1]
On Wed, Sep 5, 2012 at 12:00 PM, <discuss-request at kwartzlab.ca> wrote:
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> Today's Topics:
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> 1. Re: plenum vs non-plenum (Kevin Martin)
> 2. Re: plenum vs non-plenum (Darcy Casselman)
> 3. Re: plenum vs non-plenum (Ben Brown)
> 4. Re: plenum vs non-plenum (Darcy Casselman)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 5 Sep 2012 13:23:26 +0000
> From: Kevin Martin <kpmartin at thinkage.ca>
> To: KwartzLab Public Discussion List <discuss at kwartzlab.ca>
> Subject: Re: [KwartzLab] plenum vs non-plenum
> Message-ID:
> <F0D86D0652C5F74AB56B6E448926881431A13AD4 at Exchange.thinkage.ca>
> Content-Type: text/plain; charset="iso-8859-1"
>
> 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."
> 9.34.1.5. 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 3.6.4.3.(1)." Section 3.6.4.3 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 9.34.1.5 (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 3.6.4.3(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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> ------------------------------
>
> Message: 2
> Date: Wed, 5 Sep 2012 10:49:47 -0400
> From: Darcy Casselman <dscassel at gmail.com>
> To: KwartzLab Public Discussion List <discuss at kwartzlab.ca>
> Subject: Re: [KwartzLab] plenum vs non-plenum
> Message-ID:
> <CAA=
> K3WfaNYkbn4-XWf-TMZCcLsmPe0w3KdaSTW8_7ouZS1he5w at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 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.
>
> Darcy.
>
> 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."
> > 9.34.1.5. 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 3.6.4.3.(1)." Section 3.6.4.3 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 9.34.1.5 (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 3.6.4.3(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
> >
> >
> > _______________________________________________
> > Discuss mailing list
> > Discuss at kwartzlab.ca
> > http://kwartzlab.ca/mailman/listinfo/discuss_kwartzlab.ca
> >
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 05 Sep 2012 10:58:14 -0400
> From: Ben Brown <ben at kwartzlab.ca>
> To: discuss at kwartzlab.ca
> Subject: Re: [KwartzLab] plenum vs non-plenum
> Message-ID: <50476886.8020503 at kwartzlab.ca>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 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.
>
> Ben
>
> 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.
> >
> > Darcy.
> >
> > 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."
> >> 9.34.1.5. 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 3.6.4.3.(1)." Section 3.6.4.3 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 9.34.1.5 (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 3.6.4.3(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
> >>
> >>
> >> _______________________________________________
> >> Discuss mailing list
> >> Discuss at kwartzlab.ca
> >> http://kwartzlab.ca/mailman/listinfo/discuss_kwartzlab.ca
> >>
> > _______________________________________________
> > Discuss mailing list
> > Discuss at kwartzlab.ca
> > http://kwartzlab.ca/mailman/listinfo/discuss_kwartzlab.ca
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 5 Sep 2012 11:03:19 -0400
> From: Darcy Casselman <dscassel at gmail.com>
> To: KwartzLab Public Discussion List <discuss at kwartzlab.ca>
> Subject: Re: [KwartzLab] plenum vs non-plenum
> Message-ID:
> <CAA=
> K3WfKJrFYpPFwQm7+ikvpxXQ4HgxSFOakh911EKUKbVS2gw at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 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.
> >
> > Ben
> >
> > 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.
> >>
> >> Darcy.
> >>
> >> 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."
> >>> 9.34.1.5. 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 3.6.4.3.(1)." Section 3.6.4.3
> 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 9.34.1.5 (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 3.6.4.3(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
> >>>
> >>>
> >>> _______________________________________________
> >>> Discuss mailing list
> >>> Discuss at kwartzlab.ca
> >>> http://kwartzlab.ca/mailman/listinfo/discuss_kwartzlab.ca
> >>>
> >> _______________________________________________
> >> Discuss mailing list
> >> Discuss at kwartzlab.ca
> >> http://kwartzlab.ca/mailman/listinfo/discuss_kwartzlab.ca
> >
> >
> > _______________________________________________
> > Discuss mailing list
> > Discuss at kwartzlab.ca
> > http://kwartzlab.ca/mailman/listinfo/discuss_kwartzlab.ca
>
>
>
> ------------------------------
>
> _______________________________________________
> Discuss mailing list
> Discuss at kwartzlab.ca
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>
>
> End of Discuss Digest, Vol 30, Issue 6
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