Appropriate conduit for several data cables underground over 300' run

Question

I have done some searching around but have not found anything definitive, and/or my background is weak in this area and I may be understanding poorly.

I will have 2-4 PoE cables that will be run underground a distance of up to 300ft. There will be no sources of interference near the cables. There will most likely be 4 cables, with the possibility of others in the future.

My guess was that I would want a 2" conduit to run these through. I have seen it suggested that PVC be used for this, which I assume refers to some flexible PVC conduit, which I have not found in 2" x 300ft variety, if I remember correctly, or it is too expensive.

I have also seen Carlon's Carflex Liquidtight conduit (https://carlonsales.com/carflexliquidtightnmconduitparts.php), but these appear to be expensive for my basic needs and the 2" conduit Edit Meant to say that the 2" conduit only goes up to 100'

Currently, it appears that the cheapest solution would be to run each cable in its own 3/4"-1" PEX tubing, but I would rather leave room for further cable(s) in the future, and a separate conduit for each cable is awkward. I understand that direct burial with appropriately shielded cable is also an option but I would rather allow, again, for addition of cables, but also cable replacement, without unearthing the trench.

I wonder if anyone has any recommendations for materials or specific products.

edit devices are going to be PoE cameras

Answer 1

Speaking as someone who does a LOT of data cables...

Pray to your deity of choice regarding (lack of) lightning nearby. The extent to which I prefer fiber optic for outside data runs is influenced by years of dealing with copper outside data runs, and the failures resulting - but few, if any, cameras are set up for power + fiber optic, so you'll want a nice POE-friendly surge suppressor at the point where these cables enter your building, tied into the building grounding/earthing system. Else you will have burnt out data ports, almost certainly, eventually.

As already mentioned, don't even think of putting non-wet-rated cable in exterior conduit. It may work for a while, but it will fail, usually at "not a good time." I personally prefer a "dry gel" cable and tend to get stuff which purports to be direct burial, but I run it in conduit as I hate digging trenches twice, and I trust rodents to chew on direct burial cables.

You can not bother to glue the joints at all, or you can glue the joints with great care. If the conduit is PERFECTLY waterproof, it will still fill with water, as moist air will enter and moisture will condense, and stay in the conduit. All outside conduits are defined as wet locations, and all cables in them must be wet rated, or failures will be expected.

Run 2" conduit if you like, but it's going to be massive overkill for four 4-pair data cables unless you get some absurdly thick jackets. Nice to have more room than you need, but there is a point of absurdity. Two examples of 24AWG Cat 5e direct burial in stock are right around 0.25" diameter for a net area of 0.05 square inches each - roughly equivalent to 6AWG wire, where (less than) 40% fill would be 1" (rigid) schedule 80 conduit, (or 3/4" schedule 40, but I prefer 80 by a large margin.) So 1-1/4" would be more than generous sizing and cost you quite a bit less. Where things are more unknown, 2" is nice just because if you don't know, you don't, but if 4 data cables is it, 2" is, IMHO, Massive Overkill. Save your money for something you actually need... Like those POE surge suppressors (not cheap, but inexpensive as compared to the equipment you will lose otherwise.)

Most "real" POE devices work just fine at 100 meters on 24Ga cable from the 48V POE power supply - the device power supply is generally flexible and expects to be able to work on a short cable at full voltage or a long cable at lower delivered voltage, and most are not power hogs anyway. Early "half-baked" POE systems varied a lot more wildly, as may things which ARE powerhogs and outside the "real" POE standards.

Answer 2

The upside of data cables is there's no limit to how many you can run in one conduit -- no 310.15(b)(3) thermal current limits (PoE may change that), and no 225.30(D) limits on multiple circuits. Really, your problem is all about the ease of pulling multiple cables this long distance, especially given the delicacy of Ethernet. Larger diameter conduit and fewer bends helps a lot with this.

If your notion is that PoE has no distance limit, you will want to very, very, carefully research the particular power needs of your devices, and revisit that assumption.

When we talk about "PVC conduit" we mean 10 foot sticks. You don't buy it in reels. The problem with reels (far as NEC is concerned) is that the stuff has to be fairly flexible to go on a reel, and if it's flexible, it's going to lay down with lots of bends. Those bends, added together, will exceed the 360 degrees allowed between pulling points. This rule is entirely about practicality of pulling, so it applies to you.

Liquidtight is a lost cause. You don't keep water out of conduit by NASA-tier conduit sealing and gluing and anti-condensation humidity control forever. You presume it is 100% filled with water 100% of the time, and use cable rated for that.

I would go one of two ways.

Two conduits

One for data cables, and the other for the inevitable mains power. (Low-voltage is out of the question at these long distances). Given my fondness for stepping up mains AC for long distances, I would probably use 1" for the mains power and 2" for all data (for easy pulling without rending the cables).

The big downside of this is that you have to be serious about conduit cover for the mains wiring... PVC would need to have at least 18" of dirt over top of it (so a 21" trench).

Rather Fat low voltage wire

Go all-in with low voltage <30V, and just use some really fat wire to endure the voltage drop. If you're contemplating #8 copper or larger, it's time to switch to aluminum wire. In this case you'd have all powered devices draw from the same pair of wires. Which would be fused at the source for appropriate thermal limits. It could also be DC, which removes the issue of crosstalk between power and data (not that that's much of an issue).

Then, because it is low voltage, you get to put it in the same conduit as ethernet.