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Posted By: George Little Cold Air Returns - 09/13/05 01:36 PM
When installing NM cable in a dwelling unit, do the inspectors require metal wiring methods in CA returns?
Posted By: Joe Tedesco Re: Cold Air Returns - 09/13/05 02:43 PM
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.
Posted By: George Little Re: Cold Air Returns - 09/13/05 05:00 PM
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.
Posted By: Ryan_J Re: Cold Air Returns - 09/13/05 05:20 PM
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]
Posted By: gfretwell Re: Cold Air Returns - 09/13/05 06:07 PM
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]
Posted By: Redsy Re: Cold Air Returns - 09/13/05 11:57 PM
gfretwell,

What about the "hot" water heater?
Posted By: gfretwell Re: Cold Air Returns - 09/14/05 12:52 AM
We keep it outside.
Posted By: Redsy Re: Cold Air Returns - 09/14/05 11:48 AM
Why does hot water need to be heated, anyway?
Posted By: George Little Re: Cold Air Returns - 09/14/05 01:09 PM
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?
Posted By: renosteinke Re: Cold Air Returns - 09/14/05 03:16 PM
As luck would have it, there is a new pic in the Photo forum that illustrates this issue.
Posted By: Redsy Re: Cold Air Returns - 09/14/05 08:44 PM
It was a pun as in "cold air return".

I guess I'm not as funny as I thought!
Posted By: gfretwell Re: Cold Air Returns - 09/16/05 01:15 AM
You were going toward Bill Engvall and I was going more Jeff Foxworthy. [Linked Image]
Posted By: iwire Re: Cold Air Returns - 09/17/05 11:28 AM
Quote
BTW a Florida guy would ask why you are "returning" cold air?

When you have it in abundance you want to return it as much of it as you can. [Linked Image]
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