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?
oh oh pick me pick me i know the answer. you cannot run the wire like you propose. in an air handling space you may only run wires perpendicular to the duct. not sure what code off hand but it is code.
According to the 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.
The trick here is that all of these conduits need to be fastened at certain intervals, that can be difficult inside of a duct that's too small to crawl through.
No, it is not Kosher to run a circuit through the duct.
the biggest reason is:
anything is a duct or plenum space must be plenum rated. That means it is specifically designed to not emit above a determined level of toxic fumes when exposed to fire.
anything is a duct or plenum space must be plenum rated. That means it is specifically designed to not emit above a determined level of toxic fumes when exposed to fire.
This is 100% correct. Nothing to do with securing the wire. You can run appropriate wires through a plenum, but what you're talking about is a DUCT, and you just can't use a duct as a conduit.
Very bad idea. Hypothetically, if you were to do this, how would they clean the ducts? It would wreck the wire. Find another way to route the wire.
Great points guys but I think and I may be wrong but the OP is considering using a cold air return for the wiring path.... here in the north we see this on a regular basis for new home construction..... This is not a duct.... typically a void.... Interesting that this is against code in the US.
Great points guys but I think and I may be wrong but the OP is considering using a cold air return for the wiring path.... here in the north we see this on a regular basis for new home construction..... This is not a duct.... typically a void.... Interesting that this is against code in the US.
yes, that is a duct. A cold air return duct. Just because is uses the floor and 2 floor joists and a sheet of metal for the walls of the duct, it is still a duct.
The problem is if for some reason there would be a fire, the non-rated plastic in the duct, plenum, void, whatever you want to call the space used to confine a column of air and directs it to another area, would transport the smoke deveopled from the heated/burned plastic to other area of the building.
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.
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?
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:
[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.
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........."
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.
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.
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.
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?
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?
The OP originally asked about running Romex through a joist cavity being used as a cold air return. I'm trying to accomplish a similar task. Someone else said that it could be done if it is in a conduit or MC type cable.
Is this accurate? Is there any electrical cable rated for plenum use? (BX / MC, etc...)?
The OP originally asked about running Romex through a joist cavity being used as a cold air return. I'm trying to accomplish a similar task. Someone else said that it could be done if it is in a conduit or MC type cable.
Is this accurate? Is there any electrical cable rated for plenum use? (BX / MC, etc...)?
If it were me and I needed to cross a cavity that is being used as a duct or plenum (trying to avoid that argument again), I would use a piece of EMT large enough to comfortably put the NM through it and seal the ends of the EMT to the studs/joists with a fire caulk. While this is not necessary, I believe it provides for the best installation as the NM, if exposed to excessive heat, will not gas off toxic fumes into an air handling space and where the stud/joist is penetrated, there will be no air leakage.
in the code section concerning duct and plenums, MI and MC (only that type with a continuous smooth or corrugated outer sheath without a non-metallic outer layer (in other words, not the typical MC with the spiral wrap metal sheath as well as any MC that has an outer non-metallic sheath) is allowed as well as solid metal conduits (FMC has very limited and specific uses allowed but not as a general wiring method.)
in "other spaces used for environmental air", basically, the material needs to be listed for use in a plenum air space.
If that doesn't make sense. let me know. I realize it is confusing as written but trying to avoid excessive verbiage.
But nm in the space enclosed by joists and the ceiling of one story and the floor of the next can be used as a raceway for nm, can it not, as long as the space isn't being used for routing air for heating or cooling, yes? I did that for cable to a ceiling fan and light, while stapling the cable half way up the side of a joist.
correct. the problem comes in when the cavity is being used as an air transfer space that could conceivably cause toxic gases to be spread throughout the building should the plastic sheath be exposed to excessive heat.
But nm in the space enclosed by joists and the ceiling of one story and the floor of the next can be used as a raceway for nm, can it not, as long as the space isn't being used for routing air for heating or cooling, yes? I did that for cable to a ceiling fan and light, while stapling the cable half way up the side of a joist.
Wow! Now I know why I joined this chatroom. Gret stuff people.
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