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What wire is acceptable for use in underground conduit to transmit Data/Communication? Does it need to be shielded? Are there any specifications listed in the National Electric Code? Thanks!

Gary Stephen Jouas
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  • Is it being routed with a power circuit? – Ed Beal Jul 02 '20 at 20:09
  • The distance and amount of data could be helpful too (for example - 150 feet, 50 megabit home internet) - that can influence what kind of cable you should get in practice, even if it's not relevant for code compliance. – Khrrck Jul 02 '20 at 20:35
  • https://diy.stackexchange.com/questions/8159/what-is-the-proper-way-to-run-category-6-underground might be relevant but may need updating for 2020. – Khrrck Jul 02 '20 at 20:37
  • I suggest you get hold of a copy of TIA-EIA-586, a spec for building cabling. – SteveSh Jul 02 '20 at 20:55
  • Are you interested in copper or fiber? Copper comms runs between buildings require primary protectors at each end as per NEC 800.90(A) unless you can prove to your AHJ that lightning's an infrequent enough event where you're at that your interbuilding circuit isn't at serious risk of being fried by a nearby bolt – ThreePhaseEel Jul 03 '20 at 01:21

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If you are using it in outdoor conduit, it needs to be wet rated. Shielding is not required, and may offer little if any benefit, or detriment, for that matter. NEC says little indeed as it it is considered "Low Voltage" communications cable, but there are requirements for minimum burial depth to the top of the conduit, for instance. That is assuming you are using a conduit dedicated to communications/network wiring. There are also things related to the insulation type (outdoor-only insulation can only be routed a maximum of 50 feet inside a building, while "indoor/outdoor" insulation removes that limit (related to smoke and fumes in a burning situation.)

My professional advice as a low-voltage / network / telephone professional is to use fiber optics (also wet rated) when running between buildings, as it solves many repetitive problems that wired networking between buildings is prone to. One of the problems it can solve (if using "all dielectric" cable with no conductive members) is cohabitation with power wiring, but that is a poor idea from a "physical abuse of the fiber" point of view in any case.

When fiber is not an option, I frequently use "direct burial" Cat5e in conduit, since it's a conveniently available form of outdoor-rated cable, but I don't believe in direct burying anything I might want to work for more than a month or two (conduit resists rodent teeth and rocks much better than cable sheaths do.)

Ecnerwal
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  • As an added benefit, conduit makes it easy to replace failed cables without any digging. – FreeMan Jul 02 '20 at 21:13
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    With data cables, "obsolete" comes faster than "failed" in most cases, assuming you did choose the correct cable type. – Ecnerwal Jul 02 '20 at 21:16
  • Another fiber benefit is that you don't need primary protection at each end of the run....that's probably the biggest issue with running copper between buildings, even, as there are very few properly rated primary protectors for network service. – ThreePhaseEel Jul 03 '20 at 01:22
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    And the main reason I strongly prefer it - having blown more than a few "ethernet surge protectors" when thunderstorms came to call. Moving to fiber made that a non-issue. The length available going from 100 meters to 4000-10000 meters was also useful (I do single-mode when I do fiber.) – Ecnerwal Jul 03 '20 at 02:14