Shielding network cable from parallel high-voltage cable?

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Old 05-28-14, 01:45 PM
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Shielding network cable from parallel high-voltage cable?

I'm running power (60 amps, 4 gauge, teck) to a shed in my yard. I've dug my 18" trench already. I'm wanting to find a way to also run networking cable (Cat6 shielded) to my shed.

Because of the density of the ground (mostly rock and clay) I really want to avoid digging another trench - or digging this one deeper/wider.

I'm looking for a way that I can bury the two together in the same trench (Cat6 in it's own conduit) without the power cable interfering (electromagnetic interference).

Would PVC conduit wrapped in foil tape work? Does anybody know of a solution that would work? If I was forced to either deepen or widen the trench to separate the two cables, does anybody know how far apart the two need to be kept?
 
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Old 05-28-14, 02:10 PM
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Welcome to the forums.

I have run both in separate conduits in the same trench with no ill effects.

If you were really concerned you could run the network cable in 1/2" IMC (Intermediate Metal Conduit) which is a threaded aluminum conduit.
 
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Old 05-28-14, 03:27 PM
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In normal practice you need to keep at least 12" of separation between unshielded network cable and parallel electrical cable. If you don't want to do the wider/deeper trench, you can either run STP (shielded Cat5/Cat6) but that requires special terminations at both ends, or do as PJ said and just lay IMC for the network cable.
 
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Old 05-28-14, 04:31 PM
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Smile

Thanks guys. I'm starting to feel confident running the two side-by-side.

I am using shielded Cat6 cable, so I know I'm off to a good start. But my gut is saying I should go the extra mile just to be safe.

Is there a reason you both recommended IMC instead of EMT? Just checking my local hardware stores it looks like EMT is all that's available.
 
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Old 05-28-14, 04:38 PM
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IMC is aluminum and won't rust. EMT is steel and will rust quickly when buried.

The other choice is 1/2" galvanized pipe but it's heavier and more expensive.

You didn't list where you're from but most home improvement stores have galvanized and some also carry aluminum.
 
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Old 05-28-14, 08:40 PM
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Keep in mind when using STP, (since I doubt your whole network will be done with shielded/grounded patch panels, jacks, and plugs) you must at the very least connect the shield/drain wire to solid earth ground at both ends, otherwise it will not reject interference.

If you were to just terminate it in standard unshielded jacks or RJ-45's and leave the shield/drain floating, the shielding will act as a resonant antenna, and re-radiate the interference into the wires - it would be as if there's no shielding at all.
 
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Old 05-29-14, 09:26 AM
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Thanks, JerseyMatt. I will make sure my jacks are grounded.

EMT here (Alberta, Canada) doesn't seem to come in a direct-bury form (at common hardware stores). Raintight is the closest I can find.

I think I'm forced to use pipe, unless there is some way I can add EMI shielding to PVC, or ensure the my EMT setup is suitable for direct-burial.

If I go with pipe, what do I need to do to make sure it stays sealed and won't crack? The winters up here can get pretty brutal and the ground frost definitely causes things to shift.
 
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Old 05-29-14, 10:02 AM
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Why not go the wireless route?
 
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Old 05-29-14, 10:13 AM
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If I were doing it, I would trust the design of the Cat6 cable to provide significant EMI resistance. For me, some dropped packets while using the table saw wouldn't be worth the time/cost involved with running EMT/IMC.

You can also obtain some of the separation vertically. Run the power at 18" per code requirements, then run the network at 12" deep.

And as always when you're running underground services, take some pictures and keep them with your house stuff. In 10 years, you'll likely forget where the conduits are run
 
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Old 05-29-14, 11:09 AM
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Yeah exactly.. The shielded/grounded Cat6 should do fine given even a few inches of dirt separation. I wouldn't bother with metal pipe either.

As for the freezing issue, I'm not sure what your local codes dictate but you'd either have to go below the frost line (could be up to 4 feet down up there) or install heavier pipe (schedule 80) and put in expansion joints where it comes above ground. That will give it room to heave and contract, and the heavier pipe is less likely to crack.
 
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