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How close can unshielded CAT 5e/6/6a cables be in parallel to 110V power lines in rooms of common residential/commercial buildings before interference becomes an issue?

If proximity between the two should be avoided, would it still be an issue if the ethernet cable only comes near the power line at the heads/plugs?

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    It's more of a safety issue than a signal integrity issue. Power is 60Hz (in the US), ethernet is in the MHz, so very unlikely to interfere with each other. Now if a live power line touches an ethernet circuit... google: etherkiller – Ricky Beam Mar 12 '18 at 19:04
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Apr 1 '18 at 22:34
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Ron's pointed out the possible legal problems - here in Germany this isn't even a problem but running power and data in parallel for some length can cause errors or increase the error rate.

When I run them together on a tray I keep them apart at least 10 cm, better 20 cm - tie the power to one edge of the tray and data to the other.

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You need to ask the AHJ (Authority Having Jurisdiction), such as your local fire or building inspector. Those are the guys who will make the final determination, and they can fine you and shut the building down until violations are remediated.

When running cabling, you should also consult the ANSI/TIA-569-C Commercial Building Standard for Telecommunications Pathways and Spaces. Here is an overview document, and what it says about that:

Power Separation

Co-installation of telecommunications cable and power cable is governed by applicable electrical code for safety. In addition, the following precautions should be considered in order to reduce noise coupling from sources such as electrical power wiring, radio frequency (RF) sources, large motors and generators, induction heaters, and arc welders;

  • Increased physical separation
  • Electrical branch circuit line, neutral, and grounding conductors should be maintained close together (e.g., twisted, sheathed, taped,
    or bundled together) for minimizing inductive coupling into
    telecommunications cabling
  • Use of surge protectors in branch circuits can further limit the propagation of electrical surges.

Use of fully enclosed, grounded metallic raceway or grounded conduit or use of cable installed close to a grounded metallic surface will also limit inductive noise coupling.

The NEC (National Electric Code), NFPA 70, also has much to say about cabling. It has been adopted by all 50 states and most local jurisdictions. It doesn't just deal with power lines; there is quite a bit of it which deals with low-voltage (network) cabling.

  • Our electricians who will be laying the wires for us are well versed in the safety related codes. So I am not as concerned with the local legal requirements. Would you have any advise for me from the signal interference perspective? – Argyll Mar 12 '18 at 18:21
  • That's covered by ANSI/TIA-569. If you meet the legal requirements, you should be OK. – Ron Maupin Mar 12 '18 at 18:23
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    @Argyll, by the way, you are not letting electricians run your network cabling, are you? You should have a certified cable installer do that, and perform the cable category test suite, correcting any out of spec cables, and provide reports for each cable installed. See this answer for the basic tests required. – Ron Maupin Mar 12 '18 at 18:27
  • One of the electricians actually is a certified cable installer. (And they come in the correct journeyman to apprentice ratio in my locale.) But he has only worked with cat5 before. I should check in with him. Thank you for the info! – Argyll Mar 12 '18 at 19:38
  • I will second not letting electricians run data. While in my local area, electricians are technically qualified to run data cabling, I have quite a few horror stories that scale up to the fiber terminations at one location being done with a "very sharp utility knife" and polished on a plaid shirt that was "guaranteed to be good enough for our purposes" by those installing it. Getting a professional data cabling installation company is always highly recommended whenever possible. – YLearn Mar 14 '18 at 4:13

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