I have some 1/2" PEX-AL-PEX left over and thinking about using it as conduit for ~20' ethernet or phone cable. Pipe is appropriately orange.
Will the aluminium layer provide RF shielding? (assuming I manage to ground it)
Is this a bad idea?
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2It’s good that you mention grounding. Ungrounded, a shielded cable can suffer worse interference than an unshielded cable.– Craig TullisCommented Jun 10, 2018 at 16:52
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Also grounding both ends of a shield can make things worse, ground exactly one end.– TysonCommented Jun 10, 2018 at 17:46
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1@Craig is absolutely correct about ungrounded shielded cable introducing more crosstalk/noise than unshielded cable. If the shield isn't grounded, it can create capacitive crosstalk in addition to inductive crosstalk.– BillDOeCommented Jun 10, 2018 at 20:25
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1@jsotola Ethernet cable is not necessarily already shielded. The still-typcial Cat5e UTP (unshielded twisted pair) cable is not shielded. Each (balanced signal) wire pair is twisted together to mitigate crosstalk with other pairs, but shielding is different. Cat6 can be had shielded (STP) or not (UTP). Cat 6a is shielded, and Cat7 is shielded more heavily (each individual wire pair is shielded in addition to the a shield around the entire bundle). But it is not universally true that Ethernet cable is shielded.– Craig TullisCommented Jun 10, 2018 at 20:37
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@Tyson are you positive that is the universal advice? I've seen conflicting information. But either way, if you have a properly terminated STP cable, the grounding strip in the cable is typically going to be in contact with the metal sheath on the RJ connectors on both ends, those metal plugs will be in contact with both of the switches that the cable is plugged into, and both of those switches will be grounded.– Craig TullisCommented Jun 10, 2018 at 20:46
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4 Answers
If you are located in the US and this is going to be subject to inspection according to the National Electrical Code, then you need to use a listed raceway. Pex tubing or any other plumbing pipe is not listed for use as an electrical raceway.
If you just want some physical protection for the Cat 5 cable then PVC electrical conduit will perform nicely. Save your scrap pex for a plumbing project.
Good luck!
answered Jun 11, 2018 at 14:39
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4At least in my jurisdiction, data cables are functionally unregulated. Because there's minimal safety risk with them, they can be run more-or-less however you want.– HariCommented Jun 11, 2018 at 18:56
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2@ThreePhaseEel Yes, but as I said, my jurisdiction chooses not to regulate data cables. It's possible that the OP is in a similar jurisdiction, so it may not need to comply with anything– HariCommented Jun 12, 2018 at 17:35
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Once you use a chapter 3 wiring method (conduit) to protect the communication wiring you now also fall under chapter three permitting and inspection. For decades we have run the conduit for the phone company because of this. Otherwise, Article 800 is the controlling article for communication wiring. Commented Jun 12, 2018 at 17:41
Because this is an indoor run, I'm not entirely sure why conduit would be helpful, except in eventually pulling more cables, as you mention. That said, I pulled CAT6 through 3/4" PEX, and that was difficult. If you have 1/2", you're not likely going to be able to pull it through at all if it's terminated, and you probably can't get any more cables in there afterward.
Overall, I don't see a point to it.
If you wanted to do it, you could. You could probably use a PG fitting to connect it to boxes on either end. Keep pull tape in the PEX so you can pull more easily in the future. It helps to have twice the length of the run so you can hold it on either end, attach your cable, and pull without losing the pull tape on either end.
Meh. You might get some benefit in the shielding department but it's a lot of hassle for not a lot of gain. Phone lines don't need much, if any, shielding. Ethernet is internally shielded to meet the needs of the signal inside (i.e. this little bit of conduit won't bump you from Cat5e to Cat6).
The only way I would do this is if you have an open wall and want to be able to run wires later. But 1/2" PEX will hold maybe one wire at best. Still not much to be gained there either. If you want conduit, PVC conduit is stupid cheap.
answered Jun 11, 2018 at 20:08
No separate RF shielding is needed for typical installations with twisted pair Ethernet (e.g., CAT 5) cabling. Phone cable also doesn't generally need RF shielding. I would actually recommend using the same cabling (but separate physical cables) for phone & Ethernet cabling. Phones don't need the top quality of CAT 5 (CAT 3 is more than adequate) but for 20' it is easier just to do everything the same way - just the connectors/jacks on the ends are different.
answered Jun 10, 2018 at 17:02
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