Everyone,
As part of a limited remodel, we’re installing a whole house audio system. For one room, running the speaker wire through the ceiling/walls would be particularly difficult and require cutting holes in the ceiling and walls. The room was previously (recently) remodeled so we’re trying to avoid that at all costs. There is a HVAC duct in that room. If we ran the wire through part of the duct (for about 10 feet) until we clear the inaccessible area, it would save substantial time and effort. This duct carries hot and cold air (it is not a return vent). We’re using high quality in wall rated wire. Aside from sound quality issues, are there any safety issues in doing this? (Wire Melt/Fire)
As usual, thanks for any input. Breaktime is a great resource.
Frank R.
Replies
Legally, the cable must be plenum-rated cable -- certified to not support combustion and not emit dangerous smoke in a fire. You also have the problem that the cable is apt to rattle in the ducts, and the cable is in danger of getting cut on sharp edges as the duct vibrates.
No electrons were harmed in the making of this post.
Dan,
Thanks a lot for the response. You saved me days of work. I will use plenum rated Monster Cable.
Frank R.
You might also want to run the speaker cable in conduit, to help reduce any interference that might occur. Probably overkill, but just a thought.
Just for kicks, take a piece of plenum speaker or cat 5 wire and a piece of regular and throw a match to it. I have done it and could not tell a nickels worth of difference. I do know you pay 3 to 4 times more for plenum cable
Well, mostly you're paying for the printing on the outside, but there is a difference in off-gasing in a fire, if nothing else. The gas thrown off by regular hot insulation is quite toxic.--------------
No electrons were harmed in the making of this post.
Everyone,
Thanks for the input. It is not a long run, so I'll get the plenum cable.
Thanks again.
Frank R.
Whooaa wait a minute,can you say FIRE! I just got home and read this, my NEC Handbook is at work, but I know that you cannot run any type of wiring in any ductwork, except to cross the duct in a return duct, like a panned joist bay. The vibration of the metal duct when air is flowing thru it will destroy the insulation and cause a short or possible fire, depending upon voltage, in fact you cannot even lay cable of any type on top of ducts, or have any non protected contact with ductwork.
Plenum rated cable is not to be used in ductwork, but above a suspended ceiling where the building uses the "plenum" ceiling as a return duct. There is a huge difference between plenum and non-plenum rated cable, you can't tell by holding a match to it. It is the fumes that are generated when burned that is different, plenum cable is nowhere near as toxic as non-plenum cable and don't forget that the ductwork will distribute these fumes throughout the building.
BTW, I am a Licensed Master Electrician with 30 years experience, and would never, ever run wiring thru a duct, cut the ceiling.
Bigman, I just looked in my NEC ad there are about 12 sections that deal with wiring in ducts, ....
in fact there are too many to even bother addressing this postDanH , it appears that ....some...wiring is acceptable but that stuff looks like power-limited cable and fiber..installed.in raceways through the ducts, or"
in other words what I should have said, ...you can not run cable " IN " the duct"
This is one example.
Edited 10/17/2005 8:51 am by Tim
I spent 20 years doing custom A/V sales and installs. Never put a a/v cable in a duct, in addition to all the other concerns raised, which are valid, if your audio amplifier fails, it could pass 120v ac direct to the speaker wire. Now you are very close to having 120v ac on your ducts. Want that risk?
Find an experienced low voltage contractor, you won't believe the number of wire pulling and fishing tricks they have.
Good luck.
Thanks Guys. I'll find another way.
Frank R.