Shield Lov-Voltage Lines From Power Lines - Page 1
Forum section: electronics / projects

author: Helmanfrow
author_rank: Contributor
timestamp: February 12, 2022, 11:37:37 pm
content: I'm doing all the low-voltage wiring for a home we're renovating. This includes Cat6, Cat6a, Cat3, RG6 and 4-conductor station wire.Due to limited space the 'wiring closet' will almost certainly share wall space with the main electrical panel/load center, sitting directly below it.The electrical wiring comes in from the attic and drops into the wall cavity behind the load center.Wiring will pass through holes in the plywood wallboard and terminate in the panel. I left this out of the drawing because I'm lazy.The low voltage wiring will also come from the attic and will have to enter the same wall cavity, albeit on the opposite side of a stud to most of the electrical.I'm worried about the roughly five-foot span across which the low-voltage lines will run parallel to all the power wiring only inches away.EMI/RFI can wreak havoc on data lines and I'd like to minimize the effect.Installing a grounded metal channel seems like it might do the trick.I can do this in one of three ways:1) 2" EMT.Pros:a) Available at retail outletsb) probably an effective shieldCons:a) Expensiveb) Heavy2) Fashion a channel from HVAC sheet metal.Pros:a) Plenty of scrap material to work withCons:a) reworking sheet metal.3) Build a cardboard channel lined with aluminum foil.Pros:a) Cheep and cheerfulb) Easy to construct and installCons:a) How to tie to ground?I guess my question is: Will aluminum foil be effective in shielding my data lines?Drawings are from as-built SketchUp model.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 13, 2022, 03:18:18 am
content: Just spacing them apart a few inches is sufficient. You can also opt for shielded cables as additional protection, but that shouldn't be necessary.

author: Helmanfrow
author_rank: Contributor
timestamp: February 13, 2022, 04:50:30 am
content: Quote from: NiHaoMike on February 13, 2022, 03:18:18 amIf it was one power line I'd probably be okay with that but ALL of the power lines? Does EMI/RFI not increase in proportion to the amount of current flowing through a point in space?P.s. the Cat6a is S/FTP and the my RG6 has both served and foiled mylar shields. I'm less worried about those and more about the UTP cables, which will be more common throughout the house.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 13, 2022, 08:00:46 am
content: EMI is due to signals generated by loads, not the load current itself. Indeed the most common source of noise is the machine-gun-fire burst of spikes generated when an inductive load is turned off by mechanical contact (so, switches and relays).Anything that's ran through walls, should already be rated for this kind of noise. Ethernet for example has noise filtering methods (it's twisted pair, and transformer coupled, among other things), and most protocols have auto-retry to mitigate data loss.Adding shields, without proper (RF) grounding design, is likely to do little, and could well make things worse. Don't worry about it. Distance is your friend here!Tim

author: jonpaul
author_rank: Super Contributor
timestamp: February 13, 2022, 08:30:01 am
content: Bonjour, Ethernet is very well protected against CM noise as mentioend.Various tyoes and grades of cable have better properties, eg twist pitch of each pair and overall outer shield.Cat 5, 5e, 6, 7 etc need to be checked.If the mains woroign in in EMT, the Etherneet is aleray well isolated.We never had any with 100baseT on ordinary old CAT5.Jon

author: Terry Bites
author_rank: Super Contributor
timestamp: February 13, 2022, 09:44:25 am
content: https://www.truecable.com/blogs/cable-academy/running-ethernet-and-power-cable#

author: jonpaul
author_rank: Super Contributor
timestamp: February 13, 2022, 11:15:07 am
content: https://www.ni.com/en-us/support/documentation/supplemental/06/field-wiring-and-noise-considerations-for-analog-signals.htmlhttps://www.newark.com/wcsstore/ExtendedSitesCatalogAssetStore/cms/asset/pdf/americas/common/techarticles/easy-automation/Belden_Industrial_Ethernet_WP.pdfhttps://www.belden.com/blogs/broadcast/the-strange-world-of-cat-5e-and-cat-6/https://slidetodoc.com/the-history-of-category-cables-steve-lampen-multimedia/

author: Helmanfrow
author_rank: Contributor
timestamp: February 13, 2022, 06:36:53 pm
content: Quote from: Terry Bites on February 13, 2022, 09:44:25 amYes, I found this chart in my own research and I was loosely basing my concerns on it.

author: Helmanfrow
author_rank: Contributor
timestamp: February 13, 2022, 06:41:08 pm
content: Excellent, thanks!