DIY Home Improvement Forum banner

Running network wiring in a cold air return vent?

51K views 26 replies 9 participants last post by  J187 
#1 ·
Hi All.

Basically, I'm in the midst of laminating a bedroom above a porch. I've taken out the carpeting and have had to insulate it with some 'stuff it' at the base of the floor/walls as well as bought some nice felt underpad which will keep cold air out for the most part.

I also think this is the perfect time to run network cabling from this room and other rooms on this floor to the basement to setup a 'wired' home.

In order to minimize the damage I will cause to existing walls and drywall when running cable, I have found a 'cold air return' area on the top floor, which actually has at least one electrical wire inside stapled to the wall. I figured I could strategically use this 'vent' area to run more cabling down into the basement.

I couldn't stick my head in there, but I used an interesting technique (in case you want to know). I held a powerful flashlight with one hand and stuck in my camcorder to 'film' what was in between the wall with the other hand. That helped me figure out and see what was down there. This method worked pretty well to at least see what was going on :)

Does anyone have any opinions on my plan to run cable to this vent and run it down to the basement? I followed the vent from the top floor to the main floor to the basement and it appears to me to be 'ok'. I might have to find a way to drill a hole to allow the wires to get through.

Any feedback would be appreciated!
 
See less See more
#3 ·
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.
 
#5 ·
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.
 
#7 ·
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!
 

Attachments

#13 ·
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!
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.
 
#16 ·
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
 
#19 ·
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.

 
#18 ·
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.
 
#20 · (Edited)
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.
 
#23 ·
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.
 
#24 ·
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.
 
#25 ·
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.
 
#27 ·
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.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top