Running wires through old ductwork?
Hi, all… my wife and I are embarking on our second rehab project. This house has a gravity-fed heating system in poor repair, which we’re planning on removing (if we can find someone willing to remove the massive furnace in the basement — it’s reminiscent of Mike Mulligan and his Steam Shovel). Since we probably can’t re-use the ducts and/or registers, we’re probably going to replace the heating system with a new baseboard or radiant system.
The plaster walls are in great shape, but all of the wiring needs to be replaced (knob and tube and only 30 amp). In an effort to disrupt the walls as little as possible, does anyone know whether it’s code-acceptable to run wires (both electrical and various low-voltage) through the heat system ducts if we’re no longer going to be using them for heating?
I found another post in Breaktime (linked below) that said I would need “plenum” wire, but I wasn’t sure if that just applied to low voltage wire.
Here’s the link:
http://forums.taunton.com/n/find/findRedir.asp?webtag=tp-breaktime&mg=C9F1B1C6-EF95-4A1D-98D7-E2469064FB65
Thanks in advance.
Replies
If the ducts were sealed at both ends (or possibly even one end) then they should be OK for wiring, the only issue being protecting the insulation from cuts from the metal. But the inspector will have the last word, of course.
If plenum cable is required, it would generally be required for both high and low voltage cables. The reason for the special cable is to protect occupants from the fumes of burning insulation.
i feel for you,it's 10 pm and i just got home from fishing wires and busting holes in plaster all weekend,it's hard to have this much fun and still be legal! anyway first of all i had to remove a gravity flow furnace that was about 42"dia. x 5' tall.when it came time to remove it i didn't have a clue what to do,but after looking at it you could just unscrew the "big round part" and then all that was left was the burner assembly to carry out of the basement. i'm not sure what you would gain by using the ducts for chase's . you probably only have 1 duct per room and you'll have 4-8 plug in's to wire in. on my deal i've been able to feed the first floor pretty much from the basement and the 2nd from the attic. biggest problem has been the first floor lights,unfortunately theres a few holes broke in the clg for access,but i can't figure out any easier way. good luck larry
yeah, that's a good point. I'm just worried about the second floor since there is no attic to access (it's a 1.5 story house), so we'd probably have to bust some holes in the walls. The walls are paint over wallpaper, and that seems to be a pretty hard texture to reproduce.
My suspicion is that abandoned ductwork is not an approved raceway for romex, because you can't know whether or not there are sharp edges in there damaging the wire as it's pulled in. You could probably get away with armored cable.
Good point. I just called the town's electrical inspector, and he first said no, but when I mentioned armored cable, he said "maybe" and that he'd come check it out.
If he approves armor cable, go to a supply house and get a roll of mc cable. Available in 12/2 w grd. and 12/3 w grd. amoung others wire gauges. Ask the guys at the counter about a cable cuttere and the correct throat insulators, as well as box connectors. Good stuff. Beats the heck out of fishing wire throogh Greenfield.
Dave
I will. What's MC cable?
spiral wound metal jacket, gotta neat little cutter with a crank handle for slitting it, and then bend and snap..then ya need little inserts for the cut end..anti shorts. Cool stuff to use for a change from the normal.
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As a complete aside from the question raised in this thread... Plenum wire is an interesting situation for those looking for uniform regulations between Europe and the U.S. For plenum wiring, the U.S. calls for wire coatings that, if I remember correctly, have a high ignition temperature. However, when the fire is hot enough to burn the coating, the coating (such as Teflon) gives combustion products that are unacceptable to the countries of the European Union. The European Union, on the other hand, will not accept wire coated with materials such as Teflon that release halogens and have performance standards for their wire coatings that otherwise do not meet the more stringent standards of the U.S.
For those wanting to pursue the minutia of this situation, there is an NFPA paper which refers to the status of wire coatings at:
http://www.turi.org/business/NFPA_Symposium_Paper-FINAL1.pdf
You're not telling us that fire safety codes are based on anything but the soundest recent research, are you? Maybe something like ... politics?