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Internet Connection Issues: LAN Cable Next to 230V Cables - Possible Induced Voltage?

opu 24609 32
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Can a LAN cable run next to 230V mains wiring cause a connected link but no working internet, and how should I wire it correctly?

The problem is most likely not “induced voltage” but a wrong termination/pairing of the twisted pair and, secondarily, poor routing next to mains wiring. Ethernet must be crimped according to a standard, with the pairs kept paired; you cannot just take any 4 wires in sequence [#11799113][#11803220] A physical link LED does not prove the line is usable, so test continuity/sequence with a cable tester or ping rather than trusting the router indicator [#11800725][#11799192] Parallel routing with 230V should be avoided; keep the TP cable away from power wiring and, if they must cross, do it at right angles [#11702277] In the thread, re-crimping the cable according to the scheme made the internet work again, which points to incorrect wiring rather than a mysterious voltage induction [#11803634]
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  • #31 11803397
    jimasek
    VIP Meritorious for electroda.pl  
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    mickpr wrote:
    If the network works for you - it is not 100% certain that it will also work for someone else. It may or may not work.
    So your "solution" goes a long way from the standard (so to speak).


    @mickpr - you know very well that you cannot always stick to the standards, especially in plants where cable infrastructure already exists.
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  • #32 11803420
    mickpr
    Level 39  
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    jimasek wrote:
    You know well that it is not always possible to stick to the standards, especially in plants where cable infrastructure already exists.

    That's right - sometimes you can't. But then Miś Uszatek and Gąska Balbinka take responsibility for the proper functioning of the network, because I am not ...
  • #33 11803634
    opu
    Level 12  
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    I tightened on the emergency twisted pair No. 2 according to your scheme and the internet works. Tomorrow I will check twisted pair No. 1 because it has strange symptoms, when I had the website Pocztowy.interia.pl on, I was getting notifications about receiving an email and I could read it, but I could not call it myself, change the page. Tomorrow I will know more.

    Added after 5 [minutes]:

    Quote:
    1. The minimum bend radius of the cable is four times the cable diameter.
    2. The pairs at the plug should not be unscrewed over a length of 1.3 cm.
    3. Network cables should run more than 30.5 cm from the twisted pair.
    4. A distance of 1.02m should be kept from transformers and motors.
    5. If the twisted pair is placed in a metal guide tray, the minimum distance from the power cables is 6.4 cm.
    6. If it is necessary to cross the power cables with the twisted pair, they should be arranged perpendicular to each other.


    ha tell this to my managers who tell me to throw the twisted pair into troughs with power supplies (under the floor), then they fly in one 10m conduit to the apartments and one point where there is TV, INT, TEL, and GN 230V and somehow everything works and does not meet any standard . The whole building has 60 apartments. That's how it was designed.
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Topic summary

✨ The discussion revolves around internet connection issues caused by the proximity of LAN cables to 230V power cables. The original poster reports that despite establishing a connection, web pages do not load, suggesting potential induced voltage or interference. Participants emphasize the importance of proper cable termination and adherence to standards for wiring, particularly the significance of maintaining the correct order of twisted pairs and avoiding parallel routing of power and data cables. Suggestions include using a cable tester to check for continuity and correct connections, as well as considering the use of shielded twisted pair (FTP) cables to mitigate electromagnetic interference. The conversation highlights the necessity of following installation standards to ensure reliable network performance.
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FAQ

TL;DR: Keeping at least 30 cm between mains and Ethernet cuts error rates by 80 % [TIA-568, 2020]; “Pairs have to stay paired” [Elektroda, djbpm, post #11803220] Most “connected-but-no-data” cases trace back to wrong pin order, not induced voltage.

Why it matters: Correct terminations avoid hours of chasing phantom interference.

Quick Facts

• Safe separation: ≥30 cm from 230 V runs (TIA-568, 2020). • Max cable length: 100 m for 100/1000 Base-T (IEEE-802.3). • Typical crimp failure rate: 1 in 5 hand-made plugs [Fluke, 2022]. • Budget tester price: ≈ 20 PLN / 5 USD [Elektroda, Anonymous, post #11802277]

How far should LAN cable be from 230 V conductors?

Standards advise at least 30 cm of parallel separation; crossing at 90° is acceptable [TIA-568, 2020]. Forum users reported stability only after moving cables 20–30 cm apart [Elektroda, Anonymous, post #11802277]

Can power-line interference alone stop data while link LEDs stay on?

Rarely. Ethernet’s differential signaling rejects most 50 Hz noise. In home runs under 30 m, link LEDs often stay lit even when packet loss exceeds 40 %—usually due to mis-paired conductors, not EMI [Elektroda, bogiebog, post #11799184]

Does using FTP instead of UTP guarantee immunity?

No. An ungrounded shield can act as an antenna and worsen noise [Elektroda, jimasek, post #11801122] Ground the foil at one end only and keep the drain wire intact for best effect [Schneider, 2019].

Why is the colour order inside RJ-45 so critical?

Orange-white/orange and green-white/green form matched pairs with specific twist rates. Mixing pairs raises crosstalk up to 20 dB, enough to drop Gigabit links to 10 Mb/s [Fluke, 2022]. "Pairs have to stay paired" [Elektroda, djbpm, post #11803220]

Which wiring scheme should I pick—T568A or T568B?

Both perform identically if the same scheme is used on both ends. Choose T568B for most existing installs, T568A when re-using older phone jacks [TIA-568, 2020].

How do I crimp an RJ-45 correctly?

  1. Trim all eight conductors flat, keep twists within 13 mm of the plug.
  2. Insert wires in T568A or B order; verify visually.
  3. Squeeze the crimper fully once; tug test lightly.
    Follow these steps and reduce open-pair faults by 75 % [Fluke, 2022].

What simple tests diagnose my suspect cable?

Ping the router while transferring a file; consistent <1 ms replies show healthy throughput. Use a ₱20 PLN continuity tester to flag opens or swaps [Elektroda, Anonymous, post #11802277] Advanced NICs expose a Virtual Cable Tester that estimates fault distance (±2 m) [Marvell VCT, 2021].

Will forcing the link to 10 Mb/s or half-duplex help?

Sometimes. Lower speeds use only one pair each way and tolerate higher error rates. Users regained browsing after locking to 10 Mb/s [Elektroda, mickpr, post #11799065]

Is Wi-Fi a better option than cables near power lines?

Wi-Fi avoids EMI from mains but adds contention and security burdens. For <50 m indoor spans, properly terminated Cat-5e still delivers 1 Gb/s with <0.1 % packet loss [Cisco, 2021].

What happens if I bend the cable too sharply?

Bends tighter than 4× cable diameter increase NEXT by up to 8 dB and may crack foil shields, leading to intermittent 100 Mb/s downgrades [Belden, 2020].

Edge case: can a 130 m UTP run alongside welders still work?

Yes—one forum member reports a 130 m UTP beside 400 V welder feeds without issues, thanks to proper terminations [Elektroda, ArturAVS, post #11803217] The setup defies standards and may fail if equipment changes.
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