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#95429 - 09/13/05 09:36 AM Cold Air Returns  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
When installing NM cable in a dwelling unit, do the inspectors require metal wiring methods in CA returns?


George Little

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#95430 - 09/13/05 10:43 AM Re: Cold Air Returns  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Quote
See 300.21(C)

Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such
spaces.


Joe Tedesco, NEC Consultant

#95431 - 09/13/05 01:00 PM Re: Cold Air Returns  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Joe- the issue that seems to have come up is the wording "passing through" versus "terminating in" the CA. If it passes through the CA perpendicular to the long dimension I don't see a problem but when you start installing boxes it's debatable. I'm curious how this forum feels about it.


George Little

#95432 - 09/13/05 01:20 PM Re: Cold Air Returns  
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
I think the code prohibits it. I also think that it is a silly prohibition. The IRC allows anything, other than gas piping, to be installed in a plenum. For example, I could run a 4" ABS lengthwise through a plenum, and that wouldn't matter. I can't do this with 14-2 NM cable, however. [Linked Image]


Ryan Jackson,
Salt Lake City

#95433 - 09/13/05 02:07 PM Re: Cold Air Returns  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,105
Estero,Fl,usa
The "passing through" language is meaningful.
When you install a box in a return plenum, the box becomes a return air register. It is just like the dumb idea of PCs "breathing" through the diskette drive.
They end up packed with dirt.
In a dwelling that dirt could be combustible.

BTW a Florida guy would ask why you are "returning" cold air? That is the supply side. [Linked Image]


Greg Fretwell

#95434 - 09/13/05 07:57 PM Re: Cold Air Returns  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
gfretwell,

What about the "hot" water heater?


#95435 - 09/13/05 08:52 PM Re: Cold Air Returns  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,105
Estero,Fl,usa
We keep it outside.


Greg Fretwell

#95436 - 09/14/05 07:48 AM Re: Cold Air Returns  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
Why does hot water need to be heated, anyway?


#95437 - 09/14/05 09:09 AM Re: Cold Air Returns  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Hot water needs to be heated for cleaning dishes as in a restaurant. They are called booster heaters and are used to increase the temperature to a higher level to meet health department requirements,

How did we migrate to this from derating NM cable?


George Little

#95438 - 09/14/05 11:16 AM Re: Cold Air Returns  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
As luck would have it, there is a new pic in the Photo forum that illustrates this issue.


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