Wired networking through ventilation ducts


#1

Soaked in as much as I could from Google, and I learned that plenum-rated cables are required for installation through any type of ventilation ducts to prevent toxic emissions due to cable burning. Some people say that for residential applications it doesn’t matter, while others keep pushing for plenum. Thing is, plenum cables cost hundreds of dollars and don’t seem to come in anything shorter than 500 feet (I’d need about 1/20 of that size).

I’m just wondering if anyone has any further opinions about this, particularly if you’ve done it with a regular ethernet cable. I live in Canada so there will be several hours of heating per day during the winter. I won’t be running the cable near the furnace.

Thanks.


#2

Well, there’s nothing that prevents it from being done, but the issue is that several fire codes require it to be used to pass inspection. But that probably wont affect a residential location.


#3

If you only need 25ft worth of cable, my question for you is why would you want to run it through ventilation ducts in the first place? It’s relatively easy to drill holes into drywall and then fish the wire down through the wall, and any additional distance that you would need to run horizontally along a wall can be covered with Taperwire. Running cables through ventilation ducts is only needed when you have to run lengths in excess of 100 feet, typically in a building where going through the walls by other means would be near impossible.


#4

Totally agree with Earlyberd - if you don’t want to buy Plenum rated stuff because of cost, just don’t run it through the ducts. There’s normally already cabling runs for electric that live outside the ducts, and you can test with short cables first to see if they need to be shielded or not.
Some smaller computing shops will sell you cable by the yard/meter, but they almost certainly won’t have plenum rated cable sitting around.


#5

I don’t know how helpful this would be in your case, but when I was in my parents’ house, I ran 100 feet of regular cat-5e ethernet cable through the return air vents. Technically, the cable didn’t go into the vent, but was run beside the holes in the floor (in between walls) to get a cable from the 2nd floor down into the basement. My thinking was, even if it had to go through the return air vent instead of beside it, it was just room temperature anyways.


#6

Do this. As a bonus you’ll learn how to run cable in the process.


#7

Thanks for the advice.

The reason I’m considering the ventilation method is because there’s a vertical duct along the wall in the lower floor room that leads nicely to the other source above. If I do any drilling, the cable would be following what is essentially the same path right next to the duct. Even the vents are in the perfect spots. Plus I figure it would be a lot easier to get the bottom end of the cable out of a vent instead of a small drilled hole.

Sorry if my descriptions don’t make sense. I’m not familiar with housing regulations and those things. I can take some photos if it would help.


#8

Is this happening in your house? If so, you don’t really need to worry about plenum rating… it’s normally only a worry at a workplace, where suing people is the norm.


#9

… though I would make a mental note to remove the cable if you move out :wink:


#10

Yes, this’ll all be taking place at home. But in Canada the heat will be running constantly in the winter months and there will certainly be some contact between the cable and duct walls and metal vent covers. I’m not too worried about lawsuits or passing inspections, but I sure don’t want to be responsible for a health or fire hazard. Do typical HVAC ducts ever get hot enough to damage common cable insulation?


#11

Alright, it turns out I just can’t do this. The ducts are much narrower than I thought and it’s really dangerous getting my hand in there. I can’t seem to move the cable toward the vertical duct I was talking about, either. And even if I could direct it there, I guess I would have no idea whether or not I’ve succeeded in doing so. It’s not like I can see anything through the upper floor’s vent opening.

Once I drill the proper holes in the drywall, how do I retrieve the cable through the hole on the lower floor? Ideally, I’d like for the holes to be as small as possible. Is there anything in the walls that could obstruct the cable while I’m lowering it?

Sorry for all the questions. I’m just frustrated because 3S comes out in a couple hours and I thought I would have this done in time.

Edit: Here’s a photo if anybody has any opinions about what to do. The vertical duct is at the left and the brown rectangle I drew on the ceiling is roughly where the vent is on the ground on the above floor. Sorry for it being sideways. I tried rotating it in an image editor but it keeps uploading like that.

http://img41.imageshack.us/img41/978/img0232rt.th.jpg