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Discussion Starter · #1 ·
Hi all, Urgent question because my electrician will be finished by Tuesday and then I have to run my low voltage. So................


I have a soffit that is designated for my LV cables, which are: speaker wire, couple of cat 5E, and a bunch of RG6.


Well Friday, my electrican ran electrical wiring thru part of this soffit. Even after I requested he not do this, grrrr. This electrical wire now runs parallel to my planned LV runs for about 2 feet in the soffit.


I asked him to move the electrial run down a few feet and in the wall.


He just rolled his eyes and said "It's no big deal, as long as you stay at least 6 inches away and only cross the electric at 90 degrees, there will be no EMI."


Is this true? Am I over reacting? Man, I just hate not knowing enough to sort these contractor's BS lines from the truth. But I will hate it even worse if this house is built and all the video suffers from EMI.....


I'm almost certain I had read here on the forum to stay at least 12 inches away (naturally, all my frantic searches turned up zip.... and I know I've read about this here). Anyway, do you think this will be a problem?


I was planning to run an electrical conduit for future use, would the PVC conduit help shield from the electric wire? Should I run my current cables thru the conduit and then run another for future use?


Sorry for the rambling, stress levels are rising.


Thanks for your advice on this.
 

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PVC will no provide any shielding, other than physical. However, the 6" separation for a couple of feet will not be problematical. It's not like at 12", there's no interference, and then suddenly, at 6", there's all kinds of interference.


If you think about it, there are plenty of places within your equipment where power wires are within a few inches of signal wires, some unshielded even, and the signals don't get polluted. Over-reacting? A little, maybe. Don't sweat it.
 

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Discussion Starter · #3 ·
Thanks Larry,


I've enjoyed reading your posts in this forum and appreciate your response to my questions!


I just didn't know how long a parallel LV and electric run can be and not affect the LV signals.


For my own education and future reference:


If you absolutely had to run parallel cables of LV and electric separated by 6 inches, at what distances would you start to be concerned? I'm just looking to add your advice to my ever expanding "rule-of-thumb" list. :D


Thanks again



Quote:
Originally posted by Larry Fine
PVC will no provide any shielding, other than physical. However, the 6" separation for a couple of feet will not be problematical. It's not like at 12", there's no interference, and then suddenly, at 6", there's all kinds of interference.


If you think about it, there are plenty of places within your equipment where power wires are within a few inches of signal wires, some unshielded even, and the signals don't get polluted. Over-reacting? A little, maybe. Don't sweat it.
 

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Paraphrased from EIA/TIA-569A, Pathways and Spaces Standard:


quote:

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Voice and data telecommunications cabling should not be run adjacent and parallel to power cabling-even along short distances-unless one or both cable types are shielded and grounded. For low-voltage communication cables, a minimum 5-inch distance is required from any fluorescent lighting fixture or power line over 2 kVA and up to 24 inches from any power line over 5 kVA*. In general, telecommuni-cations cabling is routed separately, or several feet away from power cabling

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Translated, this means you should try to maintain at least a 5 inch distance between power and audio/video as the load limit for a 20A circuit (80% load per NEC) is less than 2 kVA. Further is always better, if you cannot avoid doing this, at least minimize the length that they run together and ensure the audio/video cable is a shielded model where appropriate.
 

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Discussion Starter · #5 ·
Thanks Chris,


That's exactly what I wanted to know. Between you and Larry, I'll sleep much better tonight! One less thing to worry about.......... :D


Quote:
Originally posted by mysphyt
Paraphrased from EIA/TIA-569A, Pathways and Spaces Standard:


quote:

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Voice and data telecommunications cabling should not be run adjacent and parallel to power cabling-even along short distances-unless one or both cable types are shielded and grounded. For low-voltage communication cables, a minimum 5-inch distance is required from any fluorescent lighting fixture or power line over 2 kVA and up to 24 inches from any power line over 5 kVA*. In general, telecommuni-cations cabling is routed separately, or several feet away from power cabling

--------------------------------------------------------------------------------


Translated, this means you should try to maintain at least a 5 inch distance between power and audio/video as the load limit for a 20A circuit (80% load per NEC) is less than 2 kVA. Further is always better, if you cannot avoid doing this, at least minimize the length that they run together and ensure the audio/video cable is a shielded model where appropriate.
 

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PP, different signal levels are susceptible to interference at different distances/current levels, etc. In order of least to most sensitive to induced noise (in my opinion):


Other power lines

Speaker

RF (RG-type)

CAT-5, etc.

Phone

Line-level video

Line-level audio
 

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Larry::

How about line level video and audio through RG. Would that change the susceptibility??
 

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Discussion Starter · #8 ·
Larry,


I'm mostly concerned about the LL Video and LL Audio.... I'm running Belden RG6 Tri-shield for both. Would you consider this cable acceptable for the "low-voltage communication cables" mentioned in the EIA/TIA-569A, Pathways and Spaces Standard that Chris posted? I should be able to stay at least 8 inches away on the parallel portion of my run, but will need to cross 3 maybe 4 electric lines at 90 degrees and only a couple of inches away. Also remeasured those parallel runs....... they are closer to 4 ft. long! grrrr.


Thanks


Brett



Quote:
Originally posted by Larry Fine
PP, different signal levels are susceptible to interference at different distances/current levels, etc. In order of least to most sensitive to induced noise (in my opinion):


Other power lines

Speaker

RF (RG-type)

CAT-5, etc.

Phone

Line-level video

Line-level audio
 

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Well, first of all, RG-59 is just as good at AV as RG-6, and is more flexible and easier to attach RCA's to. Also, I still believe that audible interference will not be a problem. There's theory, where "the farther, the better" rules, and then there's reality, where "let's not get ridiculous" reigns supreme.


For each of my mains, my DefTech's, I ran two (bi-wire) speaker lines, one RCA cable for the powered sub (not RG, just a good, no-name shielded audio cable), and a regular NM (Romex®) cable for the sub amp) down between a pair of studs (8' or more) with no physical separation between them at all.


This is an existing room, by the way, so I didn't even have access to the stud bays to staple the NM to one side, and the audio cables to the other. I mounted a receptacle in an old-work box for the amp, and the speaker wires and the RCA in a low-voltage (no back) old-work box less than a foot away.


In addition, the audio and power wiring for the amps, the fluorescent lights (on when listening to music), the projector, the satellite, etc., are all haphazardly draped above my suspended ceiling. In the wall behind the stack, the feeder for the sub-panel shares the same space as the aforementioned cables.


My setup is dead-quiet at idle.
 

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if your concerned about interferance you can buy shielding tape and cover them for the run they are close.. but if the cat5/6 is shielded which it should be and is in cat6 you wont have to worry about it. i had my ham neighbor come over with his meters and was listning for interferance and even the CF lights hardly made any noise.. we did find one dimmer that had some problems but it was about 15 years od and we replaced it.. he was also an electrician for years
 

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Pen, shielded CAT-5, 5e, and 6 is rare. It's the twisting and proper termination that render the noise-rejection capability.
 

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That and it's secret to high speed transfer for Category 5, enhanced, or 6. How's life PixelPusher? If you did go the conduit route copper pipe would do better than PVC for shielding. It is best to separate low volt soft wire 18" away from romex. There are times, however, when romex and low volt almost touch because of the way it is pulled. You can't get around it at times. Those are the places to shield. If you are prewiring this low volt yourself try to keep the LV away as much as you can and shield the areas that touch, or almost touch. I am surprized folks still OEM 59, RG59: has less shielding than RG6 and a smaller dielectric (stinger). It is used best for transfer of video signal only.

www.swhowto.com
 

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Our office uses modular furniture where all the wiring is in troughs at the base of the panels. A/C is barely separated from Cat5e data and Cat3 voice cables as they wind through the desks for over 50 feet. Doesn't seem to be any interference, although we don't carry video. I would consider what the electrician's wires in your soffit are powering. If they go to lighting circuits you are probably OK. If they feed your furnace blower, sump pump, or an arc welder, I would get concerned.
 

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Discussion Starter · #14 ·
Thanks for the advice everyone! These last few weeks have been fairly stressful as I've watched all my wiring options get consumed by other trades!! After rough framing, I started planning my low voltage runs. Not just for the HT, but the entire house. Just as I thought I had it all outsmarted............ HVAC guys arrive and run main air returns and duct work right where I figured I'd go. No problem, switch to plan run B. Wow, how did those plumbers know I'd want to use that joist.....? Ok, minor setback, now switching to plan C, (and at least another 20 ft, per run). But wait, the worst was: Hello electricians, who just ignored my little note to them in permanent ink on the soffit ("Plz, no electric runs, reserved for Low Voltage. Thank you"). Even spoke to the Head electrician as he was marking up the house and whose response was a friendly "No Problem!". Now I realize that really meant "Yea, Whatever!" So what do I get in the soffit? After further review, there are actually 2 runs, each over 4 ft long. One of the runs was tacked on the backside a 2x4, so I didn't spot it initially. The full length of the wall is 22' and now over 8' has electric........grrrrr And they've run wire just about everywhere I wanted to run LV.


Anyway, thanks to all of your tips and reassurances, I think I can still get most of my wiring completed and stay at least 6 - 8 inches from any electrical runs. Of course my most important run (HT line level audio and video) will now have to cross 4 different romex runs..... at least all will be at 90%.


Does anyone know if there are any code issues with running LV in the same hole as plumbing PVC? It would be really easy to run several vertical runs in some of the holes that are a bit larger than the PVC. I have to keep everything to code since this is a new build and the general contractor was already very nervous about me running my own LV. Anyway, I start my wiring on Friday, should be interesting.......... to say the least.
 

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Thats low volt. We are last in line, they take the ideal wire runs because they know we are not required to prove ourselves with a 5 year apprenticeship and a test. It is against code to run any wire, soft, or romex right next to hot water pipes and HVAC hot air returns. PVC is safer than metal pipe, but try to just make your own holes by pounding out the perforated TGI boards. It is your castle you do not want a fire or your left channel suddenly going out and you have to retro another line in. And general contractors may make you rewire runs they see unsafe. Wire tie it at the home run and label everything.
 

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Discussion Starter · #16 ·
yep, I kinda figured it would be frowned upon to share the same hole as PVC, but didn't think it would be dangerous. Guess I better pick up that biggo auger bit on the way to the house! Thanks again.
 

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Auger bit and Milwaukee Hole-Hog, don't leave Home Depot without it.:)
 

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Why fight it? If you asked him not to, and he did, make him move it! I agree with everything said here, that it probably won't make a difference, but it's a helluva lot easier to fix now than later! How long could it possibly take him...an hour, maybe 2? I say move it...for peace of mind at least.
 
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