Is an ethernet cable threaded inside a metal conduit is more protected from electromagnetic interference?

Question

I am at the end of a renovation, and only now  I discovered that it is not recommended to run ethernet cable in parallel and closely to power cables, even if they are in separate conduits, but I may have the option to improve the safety and the data integrity: As you can see in the photo there are 3 pvc conduits runs parallel to each other. Each with a diameter of 16mm. In one is threaded a telephone cable, in the other a cat 7 ethernet cable and in the third a 240V power cable.( I dnot know in what order) On the left side there is an additional 50mm in diameter flexible PVC conduit also parallel and closely to the three conduits, but it is empty.I estimate that there is  2-3 cm between the cables. (not between the conduits) I have the option to cancel the cat7 that is threaded inside the 16mm conduit, and thread a new cat7 cable inside a flexible metal conduit (that protects low voltage cables from electromagnetic) and thread the metal conduit into the flexible 50mm PVC conduit (conduit within a conduit) Is it worth making this change? (I am thinking of a future option that maybe I will increase the network speed, and even if there is a lot of amperage in the power cable which increases the strength of the magnetic field)     And another question: can there be an interference to the telephone cable as well because it is run parallel near to the power conduit? It is not shielded and not a twisted pairs, but I can replace it with a more high quality cable, and also transfer it in the 50mm conduit. Thanks in advance for any answers

Answer 1

You discovered wrong. Ethernet runs at 100MHz and up, your line voltage at 60Hz is virtually DC at that frequently difference.

With that said, you should still run your data cables in conduit. Not for interference concerns, but so that in 2040 you can easily replace the cat5 with something new for our 20K ultra VR direct brain video or whatever is the deal then. Plastic Smurf tube is fine, it doesn't need to be metal.

Answer 2

Speaking as somebody who's spent much more time messing around with networks and power cables than with bricks and beams: keep them moderately separated but don't go full paranoid.

Power cables are substantially more robust than network cables, have different failure modes, and are tested differently by people with different skills and equipment.

Network cables are invariably twisted pair and sometimes screened, which will reject what is known as "common mode" interference. Untwisted cable, as shown for example in Best way to stick a very long Ethernet cable semi-permanently to walls? is not intended for high-speed networks and should be avoided (this photo https://upload.wikimedia.org/wikipedia/commons/f/ff/Ams-ix.k.root-servers.net.jpg shows that type of untwisted cable in its intended use as a low-speed console connection).

Network interface cards have isolation circuitry, but this can be overwhelmed (inductors driven into saturation, insulation damaged) by noise of sufficient amplitude.

Power cables can often have substantial amounts of switching noise on them (e.g. from an induction hob), which can easily be sufficiently high in frequency to result in a measurable network degradation. Note that I'm saying measurable here, not necessarily detectable "by eye".

An extreme case of this is a nearby lightning strike which can result in fried network equipment, although the ingress for that is usually a computer's power supply (hence the recommendation that stuff be disconnected during storms).

There is a slim possibility that network traffic could be "sniffed" by putting monitoring equipment on the power lines. This is a VERY slight risk compared with other ways your personal data could be exfiltrated.

Broadly speaking, high-frequency noise and cross-coupled data will travel between several houses etc., until stopped or at least attenuated by the inductance of a power distribution transformer (normally described as "at the end of the street").

The "keep them separate and cross at right angles" rule applies to 'phone lines and low-speed data cables, i.e. the sort of thing that was run for substantial distances before about 1990. These days, as I've said, keep them moderately separated but there's much less need to go full paranoid.

Answer 3

It's not the problem it's made out to be.

Ethernet is running at millions of frames per second. Power is 60 frames per second.

Imagine we stretch that time frame out by a factor of 86400*60. Now, the AC frequency is akin to the rising and setting of the sun, and the Ethernet is akin to ships passing light-gun signals. Does the sun interfere with that? Of course not, it is massively, glacially too slow to affect that.

One conduit for telecomm is fine.

In those conduits, one conduit should get all telecomm - phone, ethernet and coax/cable TV if that is present.

The large conduit should be reserved for big power, or for water lines or whatever the original layer envisioned.

Consider fiber-optic.

If you're really that worried about it, maybe fiber-optic is for you. It has the merit of being immune to EM interference, but also, it can be placed in AC power conduits if the optic line is entirely non-conductive.

Answer 4

Let's talk interference for a second. Some other answers have dismissed EMF as a concern, but it's worth noting something on the subject.

Most networks today are 1GB or less. That equipment is ubiquitous, as is the cable. Very few people are running 10GB networks because

1. You need far better cable than Cat5e (or even Cat6)
2. The equipment is much more expensive
3. Very few people need bandwidth on that scale. I mean, most WiFi still struggles to top 300MB (0.3GB) and virtually nobody complains about that

If you're just running a 1GB network (which is probably 99% of DIYers), you're probably fine as-is. Metal is slightly better to limit EMF interference, and 1GB networks are fault-tolerant enough to where you probably wouldn't notice it. In fact, most devices aren't making a lot of EMF interference on electrical wires to begin with (which is why "powerline" Ethernet devices are a thing).

If you think you'll be running a 10GB network anytime soon, you'll want to rethink that and place the cables elsewhere, since you'll be paying a LOT for that extra shielding and even the minor EMF coming off electrical wires could cause interference.

The better solution here would be fiber, which doesn't use EMF. That equipment isn't that much more expensive than straight Ethernet, and the fiber itself has come down in price to reasonable levels. For comparison (late 2020 pricing), 100ft Cat5e is about $14, and 100ft two-channel fiber is $35 currently on Amazon (prices subject to change)

Answer 5

One thing rarely mentioned is the interference from the Ethernet cables to other devices.

In theory, this should be prevented by conformity testing, but in practice, it's not too uncommon to find devices with appropriate conformity labels being sold, which, when combined with particular cables, tend to radiate like crazy. The situation with not-very clear standards for Ethernet cables, and optimistic cable labeling adds to the issue.

As a result of the what I mentioned above, it might happen that you, for example, have interference to FM radio, or low VHF over the air TV. To make issue even more insidious, the "regular" users of network equipment in general aren't going to be capable of easily detecting interfering devices, so you usually won't find any comments about that in equipment reviews.

Putting the cables into metal conduits is one of the things which might help mitigate such issues, if they pop up in the future. Of course, if you don't watch terrestrial TV, and don't listen to terrestrial radio, then these potential issues won't be very interesting to you.