Wiring through joists w/ Hot Air Ducts

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I'm in the process of buying a house and the lower level is an unfinished basement. There is NM cable drooping unsupported under the joists to single bulb light fixtures. Naturally I want to get this fixed as soon as possible. I've been told to just staple the wire to the bottom of the joists, but I believe this violates NEC 334.15(C). Even if it didn't, it would look awful and possibly cause problems someday when I finish the basement.
So the solution is to drill holes in the joists and rewire. However, there is a hot air duct (uninsulated) that runs parallel to and between the joists that the wiring has to cross.
How should this be handled? Does NM cable have to protected from the potentially hot duct? Should it be run in a conduit? How should I route the cable around the duct?
Thanks -T
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Stapling the wire up with the proper staples is done every day and is the accepted method of straping NM. As to the bottom of the joists, I would not. Every time I put something on the bottom of a joist I had to move it. Drill a 3/4 inch hole in the center of the joist and run the cable there. NM should never touch something hot. A couple of inches clearance is fine.
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Not when it *crosses* the joists, it's not. The NEC _specifically_prohibits_ that practice. Stapling NM that runs parallel to a joist, to the face of that joist, is fine.

And how does he get around the duct?
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I had a house like that. The "duct" was the space between the joists with sheet metal nailed to the bottom of the joists. I hired an electrician to wire from one side to the other. He went all the way around the cellar, said there was no other way to cross the duct.
Bob
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Must be a recent code change in your area or overkill. Those types of ducts are usually return air so temp is not a concern. There wouldn't have been any problem drilling a hole on each side and running the romex straight through. Caulk the holes when done.
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"Clark W. Griswold, Jr." <73115 dot 1041 at compuserve dot com> wrote in message wrote:

While the NEC does allow one to pass a Romex type cable straight through a cold air return as described, a safer method, and also permited by code, would be to install a 1/2" EMT with a connector attached at each end (to serve as bushings) and pass the Romex through the conduit.
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then the conduit has to be bonded
wrote:

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So use PVC

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wrote:

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| | |> then the conduit has to be bonded| | Short sections of EMT, as applied in this case, are not required to be | bonded. If one is really concerned about bonding the EMT, then extend one | end of the EMT to a metal box mounted on the next joist, run the cable into | the box and ground the EMT and the box with the Romex equipment ground wire. | While a conduit isn't required in the first place in this case, it makes for | a better installation because the EMT would not allow toxic fumes from the | Romex cable to enter the cold air return duct......a PVC conduit would just | add to it.
What about a ceramic conduit? They used to make those a long time ago. It was called K&T. So we can just adapt the tubes to be larger, hold a whole cable instead of one wire, and run through a duct instead a single joist. Maybe glass (not fiberglass) would also work.
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Have you ever tried to stretch ceramic conduit? ;-)
I suspect you'd get into trouble with this practise, because the thermal insulation value can be quite high. K&T materials simply aren't approved anymore.
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Chris Lewis, Una confibula non set est
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|> What about a ceramic conduit? They used to make those a long time ago. |> It was called K&T. So we can just adapt the tubes to be larger, hold a |> whole cable instead of one wire, and run through a duct instead a single |> joist. Maybe glass (not fiberglass) would also work.| | Have you ever tried to stretch ceramic conduit? ;-) | | I suspect you'd get into trouble with this practise, because the thermal | insulation value can be quite high. K&T materials simply aren't approved | anymore.
Why would it need to be stretched? You just drill a hole in each joist that is the wall of the duct, and slip the conduit across from one to the other, and fasten it in place so it can't slip out. Now you have a path through the ductway that is isolated from the duct itself.
This is not a long path. Select a tube wide enough to allow air to flow through it (between the two ends, not into the duct) with the cable to be used.
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I was referring to the "just adapt the tubes to be larger" remark. If there ain't one stock, you'd have to make the tube yourself. That seems a bit overkill ;-)
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|> |> What about a ceramic conduit? They used to make those a long time ago. |> |> It was called K&T. So we can just adapt the tubes to be larger, hold a |> |> whole cable instead of one wire, and run through a duct instead a single |> |> joist. Maybe glass (not fiberglass) would also work.| |> | Have you ever tried to stretch ceramic conduit? ;-)| |> Why would it need to be stretched? | | I was referring to the "just adapt the tubes to be larger" remark. If there | ain't one stock, you'd have to make the tube yourself. That seems a bit | overkill ;-)
That was in reference to the smaller (narrower and shorter) tubes used in old K&T wiring, vs. the wider (for a whole cable) and longer (to go between two joists to cross the duct) we'd need.
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In Canada, the CEC does not permit you to do that. Hint: if the wire ever overheats, it's injecting noxious fumes _directly_ into your air handling. I'm surprised the NEC permits it.
[That said, I _have_ seen it in older homes at least.]
There's an exception for teflon coated wire (certain types of CAT-5 for example). And conduit of course. If you use EMT, you could probably get away with strapping it to the ducting for ground.
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|> While the NEC does allow one to pass a Romex type cable straight through a |> cold air return as described, a safer method, and also permited by code, |> would be to install a 1/2" EMT with a connector attached at each end (to |> serve as bushings) and pass the Romex through the conduit.| | In Canada, the CEC does not permit you to do that. Hint: if the wire | ever overheats, it's injecting noxious fumes _directly_ into your air | handling. I'm surprised the NEC permits it. | | [That said, I _have_ seen it in older homes at least.] | | There's an exception for teflon coated wire (certain types of CAT-5 for | example). And conduit of course. If you use EMT, you could probably | get away with strapping it to the ducting for ground.
I wouldn't trust ducting for ground. How about a PVC conduit throught the duct?
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If the wire overheated or in case of a fire, you'd get toxic fumes in the plenum from the PVC and shortly thereafter, from the romex too. That's why (we) ban bare romex in air plenums in the first place - toxic fumes from plastic sheathing...
Given it's only a short sleeve buried _inside_ the ducting, as long as it had the proper bushings at either end, I doubt that an inspector would care if it was grounded or not.
Better still, use a PVC conduit sleeve to route the wire _under_ the plenum. Just don't go _through_ the plenum. The PVC conduit is sufficient physical protection for bridging the joists, even without the sheet metal on the bottom of the plenum.
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|> | There's an exception for teflon coated wire (certain types of CAT-5 for |> | example). And conduit of course. If you use EMT, you could probably |> | get away with strapping it to the ducting for ground.| |> I wouldn't trust ducting for ground. How about a PVC conduit throught |> the duct?| | If the wire overheated or in case of a fire, you'd get toxic fumes in | the plenum from the PVC and shortly thereafter, from the romex too. | That's why (we) ban bare romex in air plenums in the first place - toxic | fumes from plastic sheathing...
So what non-metallic can be used?
| Given it's only a short sleeve buried _inside_ the ducting, as long as | it had the proper bushings at either end, I doubt that an inspector | would care if it was grounded or not.
But if the code requires it be grounded, then this is not the course I would take.
| Better still, use a PVC conduit sleeve to route the wire _under_ the plenum. | Just don't go _through_ the plenum. The PVC conduit is sufficient physical | protection for bridging the joists, even without the sheet metal on the | bottom of the plenum.
Then you're committing space between any future ceiling finish and the joists, in which case the crossmember could do the job, too.
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Essentially none. Consumer-available non-metallic conduit is pretty well all PVC. Almost all plastics have a noxious fumes issue anyway.

For the most part you'd be at least strapping the bottoms of the joists for a ceiling finish, no matter how you routed the wire, so, you're losing that 3/4" of headroom anyway.

True enough.
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snipped-for-privacy@nortelnetworks.com (Chris Lewis) wrote:

A little bit of reality goes a long ways in this situation. While I wouldn't run romex for any length inside a plenum, crossing 18" of floor joist is not a major threat to the occupants of the building. If there is enough flame to burn through the plenum and vaporize 18 inches of plastic, the occupants have far worse problems to deal with.
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