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jheavner 10-07-2008 09:18 AM

low-voltage and electrical wiring sharing same stud space
 
When I moved into my house I started pulling runs of low-voltage wire (CAT-5e, RG6, and speaker wire). My house is relatively small and there is only one interior wall that is shared on the first and second floor. There is only one space between studs that doesn't have either electrical or HVAC and it's not on a 16" center but more like an 8".

I might be running new electrical wiring from the basement to the attic and this space is easily accessible. Is there a way to let my low-voltage live harmoniously with the electrical? Can I use conduit? Do I even need to worry about it? I would be running up to four 14/2 lines.

Different area...the spaces where I want to put in-wall speakers have either HVAC or electrical in the same wall space. For the HVAC, the duct terminates on the first floor and does not extend to the second floor. I was planning to run the speaker wire through the hole cut for the ductwork (not inside the duct). Is this ok? The actual speaker would be 5' or 6' above where the duct terminates.

ScottR 10-07-2008 10:56 AM

I've run all sorts of wires in relatively close proximity (RG6 for cable, CAT5/6 for net, 120v, speaker), and I've never had a serious problem on any. (There's a lot of argument here, I know. Your milage may vary, as has mine from time to time). However, since you'll be sealing this in a wall and it will be a pain to troubleshoot and move the cables around once you have the walls up and the speakers/etc in...

If you're running just comm in that 8" space, put it in conduit (ditto with a second conduit for speaker wire if you're putting it in that space). If you were to put the 120v in conduit, then you'll have to obey NEC rules about wire in conduit (you won't be able to use "Romex"), and that will add time and expense to your project. Hence I'd leave that out of conduit, but your comm is still sheilded. And the conduit should be metal and should be grounded.

As far as running speakers and spkr wire near HVAC ducts, I see no problem.. I just wouldn't put the cable right up against the duct (if you can avoid it), to prevent it from heating up (if you have forced hot air), and/or to prevent the insulation from becoming brittle/moist when cooling. And in the same vein, if the duct outlet is too close to the speaker, AND one day your system pumps out humid air, AND you have a paper cone speaker.. I guess that could be bad.

I'm also thinking that some duct joints may be sharp or abrasive, so be careful when installing the wire.

^^^ IMHO. There may be code that's relevant here of which I'm not aware.

And just as a side note, I read this page on speaker wire recently. I think this gentleman must have gone mad while writing the page, but it seems really thorough.. Maybe useful to you?

http://www.roger-russell.com/wire/wire.htm

Edit: BTW, I've been installing datacomm professionally for years. In commercial installs, yes, I always install as far away from electrical wiring as practical -- same for fluorescent lights, motors, and other such equipment. This is because in office buildings runs are much longer and potential sources for interference are more numerous than in residential. If you're doing 100-200ft runs of CAT5e, so long as you don't run it right past your garbage disposal or washing machine you should be fine.

Marvin Gardens 10-07-2008 11:15 AM

Running data lines next to power lines is not recommended according to the IEEE specs. It is recommended that Cat 5 be at least 6 inches away from 120 and 12 inches from 240. Cat 5e running gigabit will need to be at least 12 inches and 24 inches respectively.

Any data lines can be affected by the magnetic field created by power lines. Data lines include speaker wires, phone lines, cable, Ethernet, or anything that is carrying organized pulses that need to be read at the other end. The only thing that is not affected is fiber.

Shielding does make a difference from what I hear. Kind of like a Farady Cage but I have no experience with shielded data lines as all mine are UTP.

If you are running Cat 5e at 10bt speeds then there is less problem but I don't figure you are installing Cat 5e to run at Cat 3 speeds.

So I guess the short answer is no, this should not be done.

Think of different routes. It doesn't have to be on the inside wall. You could even put some conduit on the outside and go into the attic and then to drops to the rooms you need from the attic.

Or get plenum rated Cat 5e and put it in the duct work. I have done that before. It is easy to pull also. While you are at it pull some speaker wire and your RG6.

ScottR 10-07-2008 12:14 PM

Some fire codes do not allow cable/wire in ducts. So check the rules in your area. I would not run any wire inside of ducts for the following reasons:

First off, even plenum-rated cable (CMP) will burn (it is more fire resistant than CM however), the fumes just won't be as toxic as non-plenum-rated. So if your cable were to ignite in a duct, the moving air would push the fire into all rooms serviced by those ducts.

Second, I'd be concerned that the cable, especially where it bends, would act as a trap for dust (you shouldn't have dust in your ducts if properly filtered, but still), and you could get buildups around the cable.

I'd also be concerned that the heat/cool cycles would deteriorate the cable sheath prematurely. Not sure if this is a wholly valid concern, but I'd like not to find out the hard way.

Finally, you'd run into the problem of how to bring the cable in and out of the ducts. I'd imagine that you'd have to cut holes in the duct work here and there. Properly sealing those holes would be another concern.

Annnyway, the NEC section on communications wiring in ducts (800.154(A)) refers to 300.22(B). Looks to me that network cable can't be run in ducts without some kind of raceway surrounding it. Someone correct me if I'm wrong.

Also, power and comm cables/wires should be at least 2 in. apart according to the NEC.

jheavner 10-07-2008 12:29 PM

Couple of follow up questions for you guys...

Do I need "riser rated" CAT-5e if I'm going from my basement to my attic? It's less than 40' and probably less than 30'. I would think I don't but better to double check.

The only reason I was considering putting electrical in that run was because I have ready access to that space. The walls are up and this is all remodel. I would really like to avoid using that channel for anything except low-voltage. I have another path that I think I can use but it will be going by my other front speaker. I can probably get the speaker and wire at least 12" from the electrical. What's my downside here? Just buzzing on the speaker due to magnetic field influence? Can I drill one hole for the 3 or 4 romex lines and "bundle" them together? Do I need to staple or otherwise attach the romex in a vertical installation? Am I ok running these romex lines together or do they need separation?

Thanks guys. That was an interesting read on the speaker wire. I pretty much had the same opinions. I've been using an in-wall 14 gauge speaker wire for my runs and all are less than 50'. That was the biggest two-wire gauge HD sold that was in-wall.

ScottR 10-07-2008 01:49 PM

Quote:

Do I need "riser rated" CAT-5e if I'm going from my basement to my attic? It's less than 40' and probably less than 30'. I would think I don't but better to double check.
As far as the NEC is concerned, no. 800.154(B)(3) permits CM and CMX ("regular" 4-pair CAT5/6) to be run in risers in 1- and 2-family dwellings. Again, not sure about fire code.

Quote:

I can probably get the speaker and wire at least 12" from the electrical.
That should be good. I don't think you'd hear interference unless you have a heavy motor or some weird load on the lines even if they were closer than 12". If you're doing lighting, I've gotten noise from dimmers, but that should only matter if your lines are near the dimmer, not the wires.

By code you do need to staple the romex something like every 4 or 6 feet (I have the online version of the NEC in front of me, but it's a PITA to browse through so not sure -- I'm also not an electrician, BTW). But in remodel jobs where wire is pulled in wall cavities, I don't think anyone opens the drywall to staple the wire.

As far as running the romex together, I did a search for "cable bundle" here, and this seems to be your answer (both complex and simple):

http://www.diychatroom.com/showthrea...t=cable+bundle

jheavner 10-07-2008 02:31 PM

Quote:

Originally Posted by ScottR (Post 169352)
That should be good. I don't think you'd hear interference unless you have a heavy motor or some weird load on the lines even if they were closer than 12". If you're doing lighting, I've gotten noise from dimmers, but that should only matter if your lines are near the dimmer, not the wires.

Well...there are 3 dimmer switches in a triple gang box on the other side of the wall in the same cavity that the speaker wire will pass along. Perfect. I guess I'll have to pull it and see what my results are like.

From the reading, I'm going to interpret my bundling as being okay. I won't be able to attach it without opening the walls so that might be an issue. Dunno.

Marvin Gardens 10-07-2008 06:27 PM

The basic principle for data lines is that they don't like magnetic fields. The higher the voltage the higher the magnetic field.

Cat 6 is a much higher frequency and more suceptable to magnetic fields since much of the data runs outside the wire. Cat 7 is even faster and only comes shielded for that reason.

I have heard 60 cycle buzz on speakers where they ran the wire in the same hole as the house wiring. With speaker wire they say that 2 inches is fine and if you have to cross house wiring then do so at 90 degrees. I have whole house stereo and volume controls in all the rooms and the wire does get close to the house wiring with so many wires. I don't have any buzz that I can hear and have exceptional hearing.

rgsgww 10-07-2008 06:40 PM

It shouldn't be a problem, if your worried about the dimmer, hook a small speaker up and put the wire near the dimmer, hear for 60 hz.
Use compression connectors on the rg/6, not those crimp or twist ons...

What might the romex power? If it is home entertainment you might want to go for a 20 amp.

Don't buy romex at the big box stores, it is ALOT cheaper at some warehouses. Go calling around and find a price on romex and data cables first.

I would use solid twisted pair for the networking wires, there is less packet loss, the only con is that it likes to kink up somtimes and the price is slightly more, but not much.

InPhase277 10-08-2008 09:07 PM

Quote:

Originally Posted by Marvin Gardens (Post 169442)
The basic principle for data lines is that they don't like magnetic fields. The higher the voltage the higher the magnetic field.

Don't want to come in this late in the game, but I just read this. Not being nitpicky but the above statement is not true. Voltage has nothing to do with magnetic fields. The current is what matters.

And as far as NM goes, the code most certainly allows it to be within metal conduit for physical protection. I wouldn't do it unless I had to, and it must be grounded. But definitely allowed. See 334.15. I know this is for exposed work, but it may fit what you are doing, especially for noise reduction in your LV.

chris75 10-08-2008 09:31 PM

Quote:

Originally Posted by Marvin Gardens (Post 169442)

Cat 6 is a much higher frequency and more suceptable to magnetic fields since much of the data runs outside the wire. Cat 7 is even faster and only comes shielded for that reason.

Why would you even use cat 6 or 7? Nothing supports it...

Quote:

Originally Posted by Marvin Gardens (Post 169442)
I have heard 60 cycle buzz on speakers where they ran the wire in the same hole as the house wiring.

So did they actually run CL2 or CL3 speaker wire?

Quote:

Originally Posted by Marvin Gardens (Post 169442)
With speaker wire they say that 2 inches is fine and if you have to cross house wiring then do so at 90 degrees. I have whole house stereo and volume controls in all the rooms and the wire does get close to the house wiring with so many wires. I don't have any buzz that I can hear and have exceptional hearing.

I've done tons of houses and the stereo guys run the their stuff pretty close to mine, its not an NEC issue, and most likely not a audio issue either, just some audio phile bone heads wetdream. :)

theatretch85 10-08-2008 09:39 PM

As far as dimmers affecting surrounding LV wiring....

My high school theater still to this day has an issue with the work lights being dimmed (connected via a dimmer rack). There is a noticeable buzz in the sound system when the lights are not at 100% or at 0% (any where in between). Only affected by one or two channels of "work lights" which are simply 500 watt halogens. The dimmers are of course in a dimmer rack in a well ventilated room off the stage, no where near the sound equipment which is up in the booth. As far as I know, there is no crossing of paths of the dimmer cabling and the audio cabling. And, everything is all in conduit (since it is a commercial like setting). None of the stage lighting on the same fly line has the same effect, heck none of the stage lighting anywhere in the theater have that same effect.

chris75 10-08-2008 09:42 PM

Quote:

Originally Posted by theatretch85 (Post 169910)
As far as dimmers affecting surrounding LV wiring....

My high school theater still to this day has an issue with the work lights being dimmed (connected via a dimmer rack). There is a noticeable buzz in the sound system when the lights are not at 100% or at 0% (any where in between). Only affected by one or two channels of "work lights" which are simply 500 watt halogens. The dimmers are of course in a dimmer rack in a well ventilated room off the stage, no where near the sound equipment which is up in the booth. As far as I know, there is no crossing of paths of the dimmer cabling and the audio cabling. And, everything is all in conduit (since it is a commercial like setting). None of the stage lighting on the same fly line has the same effect, heck none of the stage lighting anywhere in the theater have that same effect.

That could be a grounding issue.

ScottR 10-08-2008 10:35 PM

Quote:

Originally Posted by chris75
Why would you even use cat 6 or 7? Nothing supports it...

...yet? :)

CAT6 will do 1gbps with less packet loss than CAT5e, esp. over longer runs. Not a bad idea to install. Now, I don't see a need for CAT7 / 10gbps in the average home anytime in the next 5-10 years, but if you have the bucks there's no harm in putting it in the walls for the future.

chris75 10-09-2008 03:06 PM

Quote:

Originally Posted by ScottR (Post 169918)
...yet? :)

CAT6 will do 1gbps with less packet loss than CAT5e, esp. over longer runs. Not a bad idea to install. Now, I don't see a need for CAT7 / 10gbps in the average home anytime in the next 5-10 years, but if you have the bucks there's no harm in putting it in the walls for the future.


Nothing takes advantage of cat6, and when something finally does take advantage of cat 6/7, there will be a better technology out by then anyhow, save your money folks. :)


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