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Old 05-11-2008, 10:20 PM   #16
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Running wire through a cold air return?


Ok, now that the issue is thoroughly clouded, do we all at least agree that he can't use this cold air return non-duct thing as a raceway, and can only run wires across it?

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Old 05-11-2008, 10:22 PM   #17
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Running wire through a cold air return?


Ok, my 2 cents. First of all, the OP stated that the referenced joist bay runs half the legth of his house. The Code limits concealed spaces to 10' vertical and 10' horizontal. Under normal conditions, this bay would have blocking to limit any concealed space to 10' or less. As this is not the case, we are left to assume that this joist bay was specifically designated to carry the return air and by definition is a plenum.

Whether or not it is "finished" is not germaine to the original question, but raises another question regarding it's fire-resistance. There are 1000's of homes all over the western US with HVAC units sitting on garage platforms which also serve as the return air plenum, but they are always lined with sheet rock and this joist bay probably should have been too as it can serve as a conduit for flame, smoke, and combustion gases (see the other thread regarding fire stops and fire blocks).

As the joist bay was designed to carry that return air, the previous post stating:

Quote:
[2005 NEC, 300.22 (B), MC cable, EMT, IMC, and rigid can be run in "ducts or plenums specifically fabricated to transport environmental air." Type NM cable (Romex) is not allowed inside of a duct.
would seem to apply.

Last edited by MacRoadie; 05-11-2008 at 10:49 PM.
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Old 05-11-2008, 10:42 PM   #18
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Running wire through a cold air return?


Its bad business to do that...The answer is no... My Uncle a master electican said a good electican wouldn't do that anyway...
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Old 05-11-2008, 11:16 PM   #19
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Running wire through a cold air return?


Quote:
Originally Posted by Silk View Post
Sorry it is "Other Space Used for Environmental Air". It does not have to be either a duct or a plenum.

The code states that a duct or a plenum is "specifically fabricated to transport environmental air"

A stud or joist cavity is not fabricated to transport environmental air, it is something that is "altered to be able to transport environmental air.

If it is either a duct or a plenum, then there would be no need for Section 300.22(C) because what it covers wouldn't exist.

Section 300.22(C) exception specifically addresses this type of situation
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.
It says that Section 300.22 does not apply to this situation. The section is titled "Wiring in Ducts, Plenums, and Other Air-Handling Spaces".

The exception says this section does not apply to this situation, therefore we cannot call it a duct or a plenum, by the NEC rules.

P.S. -- I was wrong about calling it an "other air-handling space", because if it doesn't apply to this section, it cannot even be referred to as that, because that is part of the section.
silk, did you notice that that exception follows 300.22(C) that starts out with:

Quote:
(C) Other Space Used for Environmental Air This section applies


I read that as the exception refers to THAT section, not the entire group of sections.

and to:

Quote:
The code states that a duct or a plenum is "specifically fabricated to transport environmental air"

where does it state that?

and to:

Quote:
A stud or joist cavity is not fabricated to transport environmental air, it is something that is "altered to be able to transport environmental air.
you are right. a joist cavity is not fabricated to transport air. It would leak a whole lot but adding the 4th side is altering yes, but isn't altering a synonym for specially fabricating?
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Old 05-12-2008, 06:53 AM   #20
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Running wire through a cold air return?


Quote:
Originally Posted by nap View Post
where does it state that?

Right Here:

(B) Ducts or Plenums Used for Environmental Air. Only wiring methods consisting of Type MI cable, Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering shall be installed in ducts or plenums specifically fabricated to transport environmental air. Flexible metal conduit shall be permitted, in lengths not to exceed 1.2 m (4 ft), to connect physically adjustable equipment and devices permitted to be in these ducts and plenum chambers. The connectors used with flexible metal conduit shall effectively close any openings in the connection. Equipment and devices shall be permitted within such ducts or plenum chambers only if necessary for their direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires shall be permitted.

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Old 05-12-2008, 07:04 AM   #21
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Running wire through a cold air return?


Now that you guys have made me dig through old boxes in order to find the last handbook that I bought which is a 1999, maybe this should put the arguement to bed.

I will try to photocopy it, here goes:
Attached Thumbnails
Running wire through a cold air return?-page-1.jpg   Running wire through a cold air return?-page-2.jpg  
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Old 05-12-2008, 07:19 AM   #22
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Running wire through a cold air return?


OK, I screwed that up. The second image is the first page, the first image is the second page.

The explanation for Section 300.22(C) reads as:

Section 300.22(C) applies to other spaces used to transport environmental air that are not specifically manufactured as ducts or plenums,....................... and on, and on (I'm tired of typing)

The expanation for Section 300.22(C)exception reads as:

The exception to Section 300.22(C) permits cable to pass through joist or stud spaces of a dwelling unit, as illustrated in figure 300.19. The joist space is covered with sheet metal and used as a cold-air return for a forced warm-air central heating system.

Now to explain further. The NEC Handbook is written by the NFPA, which is the same people that write the NFPA 70, which is what we refer to as the Codebook. So I believe that we can all agree that if we are arguing semantics of NFPA 70, that the handbooks interpretation is the correct one, as it is written by the same people to explain their intentions.

To summarize: If we are going to be reciting code on what is a duct or a plenum, we cannot use our own interpretation of what that is. We must use the NFPA codebook and their associated clarifications in the NFPA 70 Handbook.
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Old 05-12-2008, 07:25 AM   #23
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Running wire through a cold air return?


Quote:
Originally Posted by Lansing View Post
Its bad business to do that...The answer is no... My Uncle a master electican said a good electican wouldn't do that anyway...

I am a master electrician, I have many freinds that are master electricians, and we are all "good" electricians. The only difference is that we know the code.

If I had a dime for everybody who had an uncle or a brother-in-law or a monkey's uncle who is supposed to be a master electrician that told me how I'm suppposed to do something............... I would be the richest man in the world!

I just wish people would refrain from the " my uncle says........."
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Old 05-12-2008, 07:29 AM   #24
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Running wire through a cold air return?


[quote=nap;122585]

. Here is an excerpt from a poster on Mike Holts forums concerning this:



Doesn't make him right but it does make him on my side.
[quote]


Just because somebody posted their opinion on a Mike Holt Website doesn't mean that Mike Holt agrees with them or you, he has more than likely never read 99% of the postings, he just hosts the site and pays the bills
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Old 05-12-2008, 08:27 AM   #25
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Running wire through a cold air return?


[quote=Silk;122631][quote=nap;122585]

. Here is an excerpt from a poster on Mike Holts forums concerning this:



Doesn't make him right but it does make him on my side.
Quote:


Just because somebody posted their opinion on a Mike Holt Website doesn't mean that Mike Holt agrees with them or you, he has more than likely never read 99% of the postings, he just hosts the site and pays the bills
Remember, I didn't say he was right GW gets to cite such people all the time. Why can't I?

I am a licensed electrician myself so I do not argue from a point of ingnorance either. I do respect the handbook and will accept their interpretation. It wasn't that I wasn't truly acccepting yours either silk. Just that I disagreed with some of your interpretation such as this:

Quote:
Quote:
The code states that a duct or a plenum is "specifically fabricated to transport environmental air"

where does it state that?
and your reply of:

Quote:
covering shall be installed in ducts or plenums specifically fabricated to transport environmental air.
it still does not state that the consctuct we are speaking if is not a plenum or duct. It simply states that that section refers to ducts or plenums that are specifically constructed to carry air. My position is that it is a duct but the code does not consider it so for the purposes defined within this section because of the type of construct. Regardless how it is built or the rejection of my thought that it is a construct specifically built for the purpose, it is still a duct by virtue of its use. You know, if it walks like a duct and it talks like a duct, its a duct. I know it is beating a dead horse but bottom line, it is a duct, just not within the codes definition of one specifically built for the purpose.





So, bottom line; the OP still cannot do what he asked if he could do and we are all more clear on the rest of the code as well



Quote:
I just wish people would refrain from the " my uncle says........."
Hey, if you can't count on family, who can you count on? Mi famiglia is always backin' me up.

Oh, forget I said that. I don;t really have any famiglia. Nope. none. No such thing.
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Old 05-12-2008, 08:41 AM   #26
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Running wire through a cold air return?


Quote:
Originally Posted by nap View Post

Remember, I didn't say he was right GW gets to cite such people all the time. Why can't I?

.

It's all good

But who is GW?
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Old 05-12-2008, 12:03 PM   #27
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Running wire through a cold air return?


Quote:
Originally Posted by Silk View Post
I am a master electrician, I have many freinds that are master electricians, and we are all "good" electricians. The only difference is that we know the code.

If I had a dime for everybody who had an uncle or a brother-in-law or a monkey's uncle who is supposed to be a master electrician that told me how I'm suppposed to do something............... I would be the richest man in the world!

I just wish people would refrain from the " my uncle says........."
My Uncle John was never a monkey's uncle but your intitled to your opinion on him though I bet you would never say that to his face...But what about my answer?? was it right or wrong ??or do you even know ??
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Old 05-12-2008, 12:14 PM   #28
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Running wire through a cold air return?


Quote:
Originally Posted by Silk View Post
It's all good

But who is GW?
our beloved (cough, cough) president. He has a lot of yes men telling him he is doing right and well. Doesn't mean he really is.

lansing: silk was not calling you a monkey (therefore your uncle would be a monkey's uncle). He was simply stating how often many people tell of somebody they know that is, (whatever) and they must be right.

bottom line:

it is ok and acceptable to run NM across the type of air "duct" we were discussing but it is not acceptable to run in lengthwise inside of it.

In a residential setting, this is a normal situation as a floor or wall stud cavity is often used to direct air throughout areas of the house, especially when there are multiple floors and/or a basement. The code does allow the NM to be run though (crossways) those areas. I don;t like that they do allow it but they have more money than me so what I want does not always matter.
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Old 05-12-2008, 02:47 PM   #29
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Running wire through a cold air return?


interesting post. (nice work silk)

it's only a house, and any good electrician (excluding monkeys) will know how to run a stupid cable anywhere in that building! forget the "whatever" and just run the cable somewhere else.

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Old 05-12-2008, 08:07 PM   #30
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Running wire through a cold air return?


Quote:
Originally Posted by beezlebub03 View Post
Hi,

I'm planning to run a new 15 amp circuit to a new ceiling fan in my living room while minimizing destruction of my walls and ceilings. I just realized I have a cold air return that runs half the length of my house and could serve as a good, obstruction-free conduit for running wiring where I need it to go. This cold air return isn't a traditional metal vent. It's merely an un-insultated joist bay in my finished basement. I'm assuming there's no unusual temperature variation - there's just room temp air being pulled through this joist bay towards the furnace.

Anybody have any idea if it's kosher to run electrical wiring through something like this?

thanks.
Back to the OP... WHY are you running a new 15a circuit to add one lousy measly little ceiling fan? You dop know these things use all of 100-150 watts, right?


Last edited by LawnGuyLandSparky; 05-12-2008 at 08:08 PM. Reason: My reasons are my own...
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