# Thread: wire layout, cat5 and power lines

1. Junior Member
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## wire layout, cat5 and power lines

I am reading alot on interference of power lines running parallel to low voltage communication signals (I.E. Ethernet cable).

I read that you cant run the parallel and if you do , cross at 90 degrees.

I also read that they should be in separate stud cavities, and if the same, uses a gang box with a divider.

I also read to have them separated by 16'.

I know that there is the National Electrical Code but it is not something i can get for free.

How can i find out what the code and and what the official regulations are and what is the best for me to run my cat5 cabling inside the wall that is regualtion apporiate?

How/where can if find the local regulations?

2. ## Re: wire layout, cat5 and power lines

Originally Posted by pgkool
I am reading alot on interference of power lines running parallel to low voltage communication signals (I.E. Ethernet cable).

I read that you cant run the parallel and if you do , cross at 90 degrees.
True --- communication cabling shouldn't run parallel within close proximity of electrical wiring and when need to cross over at 90 degree.
The reason being ---- electricity emits a Electrical Magnetic Field ( EMF ) in a somewhat circular fashion when current flows through the conductors. This creates an inductive interference known as Electrical Magnetic Interference ( EMI ) when the communication cable runs parallel in close proximity. When crossing at 90 degree the EMI is 90 degrees out of phase which has minimal effect on the communication cable.

But what is close proximity ?
The level of EMF and subsequent EMI from the electrical lines is dependent on the power level of the electricity. In most cases the distance of a few inches or a foot can be far enough separation from a single 120 volt line --- but, the further the safer.

I also read that they should be in separate stud cavities, and if the same, uses a gang box with a divider.
It would always be a good idea to run the communication cable in a separate cavity.
I'm not sure what you mean about using a gang box with a divider --- if you mean that the communication cable is in a gang box with 120 volts -- no it shouldn't be.

I also read to have them separated by 16'.
Not sure where you got that --- that's pretty extreme --- they can be separated by a single wood stud between 2 bays.

I know that there is the National Electrical Code but it is not something i can get for free.

How can i find out what the code and and what the official regulations are and what is the best for me to run my cat5 cabling inside the wall that is regualtion apporiate?

How/where can if find the local regulations?
Bottom line --- from real world applications there is a lot of common sense to running communication cabling like those mentioned ----- keep a reasonable separation between cables ---- cross power cables at 90 degrees and things shouold be just ducky.

I'm not sure if you are looking for regulations pertaining to residential --- if so there really aren't any when it comes to voice/data/video wiring ( low voltage ).
If you are talking about commercial spaces --- then some local jurisdictions have guidelines for voice/data/video cabling. That information would be available from the local AHJ.

3. ## Re: wire layout, cat5 and power lines

There is very little to worry about with residential wiring. The magnetic field around a wire is dependent on the direction of current flow. With residential wiring you have two wires, hot and neutral, running very close to each other with the current in one always running in the opposite direction of the other and the magnetic fields created pretty much cancel each other out. Noise spikes on the line can have some affect especially with single line or low voltage DC signals such as coax if the jacket is not grounded or speaker wire. Network cables are different, they are made up of twisted pairs that operate differentially. One wire has 5VDC on it and the other has 0 VDC, when a bit is sent the 5 VDC has to go to 0 and the 0 VDC line has to go to 5 VDC to be read as a bit. It is very difficult to induce a signal that will affect these twisted pairs. A few millimeters of separation is all that is required.

Generally speaking data and power cables are separated in different runs and boxes to prevent shorts between the two. 120 VAC on a network cable can cause a lot of damage.
Jack

4. ## Re: wire layout, cat5 and power lines

A simple non-contact voltage tester will indicate how strong and how far the EMF is from an electrical cable.

Bottom line --- don't run the VDV cables right beside or on top of electrical lines.
I see too many hacks cable tie the VDV cables to electrical lines ---- not good practice.

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## Re: wire layout, cat5 and power lines

Originally Posted by canuk
A simple non-contact voltage tester will indicate how strong and how far the EMF is from an electrical cable.

Bottom line --- don't run the VDV cables right beside or on top of electrical lines.
I see too many hacks cable tie the VDV cables to electrical lines ---- not good practice.
I believe they have been called "trunk slammers" by posters on this board.
I also agree to think the OP meant to type 16" and not 16'. As in the distance apart in two cavities or bays when Romex and Cat5e are running parallel. Which I think is more than an ample distance, along with the other posters.
And Romex and coaxial cable or Cat 5e can and do share a double gang box, but separated by an approved divider, in todays world. But I too would rather mount two separate boxes instead, and do in most cases. You see that alot when mounting combo wall boxes for flat screen installs.
I will try and do some code sluthing on this, but that may take a day or two.
Last edited by Ernie_Fergler; 03-18-2010 at 04:17 PM. Reason: spellin

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## Re: wire layout, cat5 and power lines

Originally Posted by canuk
I'm not sure what you mean about using a gang box with a divider --- if you mean that the communication cable is in a gang box with 120 volts -- no it shouldn't be.
Sorry, Like Ernie said, i ment a gang box with a approved divider. I think i will be safe and move it to another stud cavity.

Originally Posted by Ernie_Fergler
I also agree to think the OP meant to type 16" and not 16'. As in the distance apart in two cavities or bays when Romex and Cat5e are running parallel. Which I think is more than an ample distance, along with the other posters.
I appologize, I did mean 16 inches.

Thankyou all for your tremendous help!

I am trying to rewire my phone line with UTP cat6 cabling and adding a network cable for ethernet with UTP cat6.

My problem is My DSL has shown alot of disconnects when i wired the phone line in the same gang box as power. (armature mistake) I want to do it right this time.

Should i be using shielding cableing?

I need to cross over a bundle of power wires from my fuse box (~10+ power lines). I am getting the gist that this may not be smart as it is not JUST one power line. I really have very limited other options unless i route the wire up to the attic and drop it from there.

As Jack said, ethernet is differential so there might not be as much to worry about, but i hear there is issues with cross talk (NEXT), but what about the phone line? Is there is a signal integrity issue with the switching frequency of AC?

7. ## Re: wire layout, cat5 and power lines

Originally Posted by pgkool
Sorry, Like Ernie said, i ment a gang box with a approved divider. I think i will be safe and move it to another stud cavity.

I appologize, I did mean 16 inches.

Thankyou all for your tremendous help!

I am trying to rewire my phone line with UTP cat6 cabling and adding a network cable for ethernet with UTP cat6.
There's no performance advantage using cat6 for the phone and in most cases for ethernet unless large bandwidth is a concern.

My problem is My DSL has shown alot of disconnects when i wired the phone line in the same gang box as power. (armature mistake) I want to do it right this time.
Yes --- it' possible to get increased noise margins and packet losses on the DSL if the cable and power line are/were tied together.

Should i be using shielding cableing?
There should be no need for shielded cable.

I need to cross over a bundle of power wires from my fuse box (~10+ power lines). I am getting the gist that this may not be smart as it is not JUST one power line. I really have very limited other options unless i route the wire up to the attic and drop it from there.
Best to avoide the mess of electrical wires

As Jack said, ethernet is differential so there might not be as much to worry about, but i hear there is issues with cross talk (NEXT), but what about the phone line? Is there is a signal integrity issue with the switching frequency of AC?
Cross talk is pretty much a non issue ---- that's the reason the pairs of wires are twisted within the cat6 cable --- cat6 has more twists than any other category cable.

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## Re: wire layout, cat5 and power lines

Well i talked to a Signal Integrity Expert at my company (perks of working for a engineering firm) and he assured be that because Ethernet and your regular Phone Line are "TRUE DIFFERENTIAL" and the use of twisted pair cabling, you can run them parallel to power and have no issue. (so this does not include RG6 TV cable)

But to be on the safe side, im going to cross at 90 degrees and try my best to steer clear of power, aka separate gang boxes atleat one stud cavity away.

THANKYOU all for your input, i think you all reiterated this information, but i just wanted to sum it up for people who read this in the future.