# Running network wiring in a cold air return vent?



## handy man88 (Jan 23, 2007)

I guess in theory, that works. Just make sure when you're pulling cable that the cable doesn't get ripped by the jagged edges of the ducting hole that you just drilled through.


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## jwhite (Mar 12, 2006)

Per code, you are not allowed to run wires inside duct work, unless the wires are needed for the proper operation of the HVAC system.

This is intended to limit the wiring inside a duct because if it catches fire it will flood the rest of the home with poision gasses.


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## joed (Mar 13, 2005)

The wire must be FT6 rated to run in ductwork. That is it won't burn or give off toxic gases that will spread through the ventilation system.


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## jwhite (Mar 12, 2006)

If in the USA, even plenum rated wire is not allowd in the duct work, unless it is needed for proper operation of the HVAC system. This does not mean that the t-stat wire can be snaked in there cause it is easier. If there is nothing in the section of the duct where the wire is running that requires wiring, do not run wires in there.


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## RippySkippy (Feb 9, 2007)

Make sure to use plenum grade cable you'll be fine, and be very careful when pulling through metal.


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## mcvane (Mar 19, 2007)

*wires will actually not be in duct work...*

Hi All.

Apologies if I didn't say it a bit clearer, but the wires actually won't be in the ducts themselves. Our HVAC furnace system has (in addition to the typical ducts which blow in warm or cool air depending on season) additional vents which are supposed to be the cold air returns (from what people seem to call it).

Basically, it allows the air to flow through the house. I would be running the cables through this cold air return, which actually 'sucks' air through the house, which then feeds into the furnace and pushes air out. Where these air passages are, there is simply the wooden frame and drywalls of the typical floor. I will attach a few pics to illustrate.

This particular section appears to go from the upper floor to the main floor to the basement.

How does this look to you?

Thanks in advance!


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## space_coyote (Nov 12, 2006)

I ran some speaker wires through mine if it makes you feel any better...I ran them next to the thermostat wire that was already there.

As far as code goes, I have no idea...


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## mcvane (Mar 19, 2007)

space_coyote said:


> I ran some speaker wires through mine if it makes you feel any better...


Thanks for your input...I do feel a lot better...


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## joed (Mar 13, 2005)

Same rules apply for cold air returns as hot air ducts. The air still goes through the furnace and gets dispersed around the house. You don't toxic fumes from combustion being spread around the house.


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## jwhite (Mar 12, 2006)

space_coyote said:


> I ran some speaker wires through mine if it makes you feel any better...I ran them next to the thermostat wire that was already there.
> 
> As far as code goes, I have no idea...


Yup, duhhhh huuuhh... I was speeding, but I was speeding right next to another guy who was speeding... ahuh a huh....

Explain it to the judge.


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## jwhite (Mar 12, 2006)

mcvane said:


> Thanks for your input...I do feel a lot better...


 
You should not feel any better from knowing that some other person hacked it up and his house has not burnt down YET>

If you really think that your job is worth doing, then it is worth doing right.

Wires cannot be run in duct work.

Notice I did not put anything after the . in my previous line.


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## jwhite (Mar 12, 2006)

mcvane said:


> Hi All.
> 
> Apologies if I didn't say it a bit clearer, but the wires actually won't be in the ducts themselves. Our HVAC furnace system has (in addition to the typical ducts which blow in warm or cool air depending on season) additional vents which are supposed to be the cold air returns (from what people seem to call it).
> 
> ...


Thanks for the lesson in HVAC terminology. I have been doing HVAC controls for over 10 years. I know what a supply duct is, what a cold air return is, and a bunch more stuff about the systems too... 

When a hole is cut in the wall to allow air flow, and then the air is channeled later to or from the unit, it does not matter that the walls of the duct are wood and drywall.. they become the duct. The duct is the channel for the air, not the material use to make them.

Wires may not be run inside the ducts.


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## jwhite (Mar 12, 2006)

Let me add that I could care less who hacked it up before and hasnt been killed by it yet. That does not make it the right way.


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## RippySkippy (Feb 9, 2007)

In duct work, plenum grade...still


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## mcvane (Mar 19, 2007)

*thanks for all the input*

Thanks for all your advice and especially, professional advice from jwhite.

I don't claim to be a professional or certified contractor, just simply a do-it-yourselfer, which is why I went into such graphic detail about my question. Sometimes it's easier to explain it in 'baby' terms so that there are no misinterpretations. I was not intending on giving anyone a lesson in HVAC systems.

Thanks


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## HouseHelper (Mar 20, 2007)

Article 830.154(B) in the NEC states that plenum rated network cable (type BLP or CMP) IS allowed in ducts or plenums for low power, network powered broadband communication cabling.


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## J187 (May 19, 2006)

I also concur that the wires should be kept out of the duct if they are straight networking wires. Is there anything from preventing you from simply running the wires through the walls other than it is just a bit more work. My house had zero networking and zero coaxial wire run anywhere when I bought it. I ran network cable and coaxial cable through the whole house through the walls fromt he attic down. Originating at a 3db forward gain, 8 output drop amplifier. It took a little bit of time but I was able to locate good locations to drop the lines down between studs by following the existing receptacle wiring. I didn't need to repair or patch a single wall. However, its really not much of a problem if you do, short of matching paints... I guess my point is, my opinion is to take your time and do it right. You live in your house, its worth not cutting corners.


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## jwhite (Mar 12, 2006)

HouseHelper said:


> Article 830.154(B) in the NEC states that plenum rated network cable (type BLP or CMP) IS allowed in ducts or plenums for low power, network powered broadband communication cabling.


I agree that they are. If they are needed for the proper operation of the Air handling system. I do this every day for a living. I am an HVAC controls contractor.


*(B) Ducts, Plenums, and Other Air-Handling Spaces. 
*Cables installed in ducts, plenums, and other spaces used for environmental air shall be Type BLP. Type BLX cable _installed in compliance with 300.22 _shall be permitted.

300.22 (B) *
(B) Ducts or Plenums Used for Environmental​*​​wiring methods consisting of Type MI cable, cable employing a smooth or corrugated impervious
sheath without an overall nonmetallic covering, metallic tubing, flexible metallic tubing, intermediate conduit, or rigid metal conduit without an nonmetallic covering shall be installed in ducts or specifically fabricated to transport environmental metal conduit shall be permitted, in lengths
1.2 m (4 ft), to connect physically adjustable and devices permitted to be in these ducts chambers. The connectors used with flexible shall effectively close any openings in Equipment and devices shall be permitted within or plenum chambers only if necessary for their upon, or sensing of, the contained air. Where devices are installed and illlumination is necessary facilitate maintenance and repair, enclosed gasketed- luminaires (fixtures) shall be permitted.​
​


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## burdman (Apr 17, 2007)

Can I place PVC pipiing in the cold air return and run the wires through the pvc pipiing? My cold air return is enclosed by drywall on the left and right side, and by 2x4 on the top and the bottom is open to the basement. I would make the hole to the for the pvc piping as close to the size as the PVC piping(hopefully I can make a hole the same size) so there are no gaps. Your help would be greatly appreciated.


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## jwhite (Mar 12, 2006)

Polly vinyl chloride conduit gives off chlorine gas when it burns. It is about the worst thing you can put in a duct.


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## J187 (May 19, 2006)

You do not have access from above??


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## burdman (Apr 17, 2007)

I can go around the cold air return. I just did not want to do it that way but it looks like it is the only option I have. I will create a channel with PVC piping for the wires around the cold air return. I think this will make it easier later on if I have to run more wires.


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## HouseHelper (Mar 20, 2007)

I'll say again: plenum (-P) rated cable for communication systems (Article 800) and low-power network systems (Article 830) is allowed in a cold air return (plenum space).

Article 90.3 states that NEC Chapter 8 covers communication systems and is not subject to the requirements of Chapter 1-7, except where the requirements are specifically referenced in Chapter 8.

800.154(A) states that cables installed in ducts, plenums, and other spaces used for environmental air shall be Type CMP. It also states that *other* types of communication wiring may be installed, if done in compliance with 300.22.

The first sentence of 830.154(B) states that cables installed in ducts, plenums, and other spaces used for environmental air shall be Type BLP. The second sentence refers to Type BLX cable, not BLP.

Is it confusing and ambiguous? Of course, it is the NEC. But based on what is in the 2005 codebook, it is permissible to use plenum rated communication and low powered network cable in a duct or plenum.


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## burdman (Apr 17, 2007)

Say I do decide to run the wires in the cold air return. I will need to make a hole in the 2X4 that is at the top of the cold air return. I will then need to make another hole just underneath the grill(still within the cold air return) to have the cables exit. I am not to worried about the hole underneath the grill but as for the on I am making in the 2X4 at the top of the cold air return. Do I need to seal it with something so no air is pulled in? If so, what can I use? I will post pictures tonight if it may help.


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## HouseHelper (Mar 20, 2007)

You will need to seal both penetrations with fire caulk, available in tubes for a caulk gun from a good hardware or big box store.


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## J187 (May 19, 2006)

If you have access to drill through the top plate and you dont' mind cutting the wall, why don't you avoid the cold air return alltogether and just simply fish the cable inside the wall? If you cut a hole in the bottom of the wall - where you would place an "old work" electrical box and a coaxial face plate afterwards, and drill through the top plate above, as long as you 

a. Drill and cut within the 14.5" space between the studs
b. have no blocking between them

then it won't be hard at all to retrieve the end of the wire through the hole and you will have a nice, clean, safe run and not have to repair anything at all afterwards. Maybe you have a good reason not to do this, but I would think its your best bet.


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