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I am building a new house and am planning to hardwire network cables into each room.

Can I run CAT5/6 cables parallel to electrical wires without introducing any general safety issues or losing much in connection quality?

Wiring runs for up to 25 metres from patch panel and distribution board in garage to rooms.

My research indicates that is should be fine if they are in separate conduits or if the CAT cables are shielded.

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While a shielded Cat5/6 cable is designed to protect itself from outside interferance, it isn't recommended to run them side-by-side to your electrical wiring. Typical is to run electrical down one stud and the Cat5/6 down a different stud. Basically do the same as you would for telco.

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  • Thanks for the answer. Apologies for my ignorance; do you mean conduit with "stud"?
    – Martin
    Commented Jan 16, 2012 at 9:18
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    I believe he's suggesting using a different stud; not the other side of the same one, for (e.g.) 16" of separation, not 1-1/2".
    – JRobert
    Commented Jan 16, 2012 at 16:33
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    That makes sense. I'm from South Africa and we build using bricks and mortar. No wood at all. So the wiring and cables place inside PVC pipes and are then covered with concrete
    – Martin
    Commented Jan 17, 2012 at 13:04
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    archive.org/details/gov.law.nfpa.nec.2011 While this is a link, and therefore link rot may set in, the NEC is available for download through Archive.org. 800.133(A)(2) states that Communications wires and cables shall be separated by at least 50mm (2 in.) from conductors of any electrical light, power, Class 1 non-power-limited fire alarm or medium-power network-powered broadband communications circuits. Exceptions are if separate raceways or conduit are used for separating the communications cables/wires from the power conductors.
    – Fiasco Labs
    Commented Nov 4, 2012 at 18:12
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    While Ethernet falls under low power communications and 800 rules, running POE (Power Over Ethernet) will change its classification to Class 2 or Class 3 power and require consulting 725 rules for its installation.
    – Fiasco Labs
    Commented Nov 4, 2012 at 18:23
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You want to keep low voltage and high voltage separate so that stray nails, screws, and staples installed by less attentive individuals in the future can't puncture the cables and turn your low voltage wire into high voltage. There is always a chance some idiot is going to stick something electrically conductive where he ought not, and he probably shouldn't pay with his life for the mistake. (Nor should the home owner employing the idiot.) That's good to keep in mind even outside of construction/home improvement situations.

I have no idea what code actually says, but conduit is probably sufficient for the task, and shielded cable isn't. Distance would be the best option.

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    800.133(A)(2) states that Communications wires and cables shall be separated by at least 50mm (2 in.) from conductors of any electrical light, power, Class 1 non-power-limited fire alarm or medium-power network-powered broadband communications circuits. -> Their concern is not with electrical interference, merely power safety. More distance is better.
    – Fiasco Labs
    Commented Nov 4, 2012 at 18:14
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    Electrical interference are not their problem. It actually still is a problem, but it just won't kill you.
    – Nelson
    Commented Sep 24, 2020 at 5:19
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I'm not sure how much the separation needs to be. One thing I found says 24" unless things are shielded. If one or the other is shielded by metal conduit then you could use 12". If both are shielded 6". It was all alphabet soup. I could not find a official standard.

Data cables, coax, and low voltage in general should not run parallel to mains power. While people mention the need to avoid interference, the main thing to watch out for is induction. Interference will be annoying to equipment, but stray voltages will be destructive.

I had someone run coax along 120 AC in my house. It ruined a few cable boxes, a network router, and at least one motherboard. Once I moved the coax over a few feet these problems went away.

So two feet for parallel runs with any required crossings happening at 90 degrees is the rule I personally use.

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  • The router and mobo were damaged by lightning strikes. The circuit was heavily loaded and would often trip during thunder storms. It had a GFCI breaker. Once the coax was moved away these problems ceased. 6 months of problems became 10 years or no more damaged equipment.
    – Andrew
    Commented Mar 25, 2015 at 0:08
  • It make a lot of sense that induction is an important problem, thanks.
    – Olivier 'Ölbaum' Scherler
    Commented May 22, 2016 at 18:11
  • The general guideline I've followed for parallel AC and data wires is about 1 inch per 10 volts. So one foot away for 110/120, and two feet of separation for 220/240. Empirically and anecdotally, that has worked well in my homes (I've rewired a few for myself now) and the small office where I provided that guidance to the electrician we hired for the remodel. The audio engineer there didn't complain, and I didn't notice any data issues with the network I managed, for whatever that's worth.
    – dannysauer
    Commented May 11, 2020 at 15:45
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As others have mentioned, there could be some interference. Most likely there is not a safety issue here if you are running parallel to standard plastic-sheathed NM / romex wire, but you may see reduced speeds. It's certainly not against code. You should at least use CAT 5e over CAT 5, as it is shielded better and can almost work at Gigabit speeds. CAT 6a would be your best bet, but probably a little overkill for you. When I built, I ran 5e in my house, and tried to keep it away from the the electrical as much as I could. There was some crossover and parallel runs, but it was kept at a min and I have been getting near gigabit speeds.

Note, manufactures have been using the term CAT6e, which does not appear to be a true spec. Seems like they are loosely using that as CAT6 with extra shielding. CAT6a on wikipedia.

Here is an article I found: differences between cat5 cat5e cat6 and cat6e cables

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  • why the downvotes?
    – mohlsen
    Commented Jan 18, 2012 at 3:53
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    There is no such thing as cat 6e. There is CAT 6 and 6a.
    – Steven
    Commented Jan 18, 2012 at 3:57
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    also, it is in part a safety issue. and you should always be incredibly hesitant to dismiss something as not being a safety issue.
    – Jay Kominek
    Commented Jan 18, 2012 at 4:19
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    didn't realize 6e was not a "true standard", although if you google it everyone sells it. Updated that to clarify. Also changed the safety comment.
    – mohlsen
    Commented Jan 18, 2012 at 13:31
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Its very simple; just don't put your Ethernet cables near any of power cables. Run your data cables 10" to 12" from your power cables. For future updates, put your cables inside conduit so that you can pull more cables or replace cables in the future.

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    The actual separation is about 4-inches, iirc. This information can be found but it's been a while since I installed mine. You can run data cables closer but only if they are perpendicular to the electric lines. Of course, the farther away the better.
    – Rob
    Commented Nov 4, 2012 at 14:19
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    You might want to motivate your answer with explanations, like others did here.
    – Olivier 'Ölbaum' Scherler
    Commented May 22, 2016 at 18:10
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I was told if the cable was rated at the same voltage as your power.you could even run them in the same pipe. Plus cat5 is twisted which also reduces electromagnetic interference. I actually had to put data and power in the same pipe for a fuel station

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    While twisted wiring reduces the impact of EM interference, my concern is if high voltage ever gets into low voltage wiring. Connectors and devices attached to low voltage/data connections do not expect high voltage over those connections. One short from a nail that misses a stud from the hot wire to the low voltage wiring, and you'll fry some devices at best, or electrocute a person at worst.
    – BMitch
    Commented Sep 10, 2013 at 1:10
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I work in the cctv/security area. A bloke I work with ran the cat 5e utp next to a 3 phase cable for only 2-3 meyers(yes, I know) it fried the ipcamera. When I went to inspect, i touched the metal plug of the camera and it almost threw me off the ladder. I thought I connected it to 220vAC instead of 12dc. Don't do it. The whole thing apparently becomes a capacitor and it shocks like hell. Hope it helps!

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I think not a good idea, every power cable creates an electromagnetic field http://en.wikipedia.org/wiki/Electromagnetic_induction which will influence the other cables at least will lead to disturbances and errors.

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    What does your program for calculating voltage drop in industrial pumping stations have to do with running data wiring through a wall?
    – Niall C. ♦
    Commented Jan 17, 2012 at 19:07
  • I've edited out the irrelevant part of the answer.
    – ChrisF ♦
    Commented Jan 18, 2012 at 9:52
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    Inverse square law says that the fields decrease rapidly with distance. The strength of the fields is dependent on the voltage and amperage in the power cables. Higher current requires greater separation.
    – Fiasco Labs
    Commented Nov 4, 2012 at 17:40
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Any cat cable that isn't S/FTP or F/FTP is going to cause problems if you simply want the outlets to be relatively close to the electrical ones (6" or so between the two), specially in the long run.

You don't want to go cheap with ethernet cables and this is important as there are good reasons for it.

Same thing goes with doors and windows of the house when you are buying or building a new one, or just want to change them as it's time for it after so many years... that's right, you don't go cheap.

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Be sure to use cables rated for in-wall Riser (CMR) use. That's a safety issue in the event of a fire. Use Plenum is rarely required in homes.

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    Plenum (CMP) is only required if the cable is installed in a plenum space. Riser (CMR) is required for between floors so long as the space is not used for environmental air. The only differences really are plenum is self-extinguishing and low-smoke.
    – gregmac
    Commented Jan 18, 2012 at 0:06
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    Also, this is not a very good answer to the actual question, and would have been better as a comment.
    – gregmac
    Commented Jan 18, 2012 at 0:07

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