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Thread: Question about running ethernet cable

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    Question about running ethernet cable

    I'm replacing the cable run to my shop and using buriable Cat6 because the old cable had condensation in the conduit. I was told by my electrician that that condensation in an underground conduit is common.

    I can't figure out why a pvc conduit would sweat. Is this true?
    Last edited by Robert Engel; 12-02-2019 at 10:24 AM.

  2. #2
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    Connections in electrical PVC conduit are not necessarily water tight. Moisture in the conduit can enter through those joints, or from condensation of water vapor that enters from either end of the conduit. Wire or cable that is rated for wet locations must always be used when pulling in underground conduits.

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    Moisture can condense as the temperature changes and unless that conduit is really deep where the ground temp is stable, yes, it's possible for condensation to form just from whatever air is in there, augmented by what Frank mentions...any moisture that infiltrates after installation.

    That said, even in conduit, using the direct burial type of cable is a "best practice" for this and since it's easy to buy pre-terminated, direct burial Ethernet rated cables, it's a no-brainer, IMHO. That's what I ran to my shop. The cable is in PVC conduit down the wall of our home and transitions to being inside black poly water pipe from the house to the shop slab.
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    Robert, not sure where you are located but if you have lighting strike risk, look at pulling a pre terminated multi mode fiber cable instead. Gigabit copper to fiber media converters are about $80-100 a pair on amazon and you can get 100-250’ fiber cable for $75-100. That way you won’t have any lighting concerns or moisture concerns again. Good luck.

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    Quote Originally Posted by Chris Fairbanks View Post
    Robert, not sure where you are located but if you have lighting strike risk, look at pulling a pre terminated multi mode fiber cable instead. Gigabit copper to fiber media converters are about $80-100 a pair on amazon and you can get 100-250’ fiber cable for $75-100. That way you won’t have any lighting concerns or moisture concerns again. Good luck.
    I had the same thought though I have no experience with fiber. It seems conventional wisdom that fiber is more expensive to install but more trouble-free so cheaper to maintain once installed.

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    Quote Originally Posted by Robert Engel View Post
    ...I was told by my electrician that that condensation in an underground conduit is common.
    An electrician told me the same thing - they usually find water in buried PVC conduit.

    When I ran underground power to my shop (250') I also ran a smaller conduit and pulled two ethernet cables, one for use and a second for a spare. I think I used Cat5e. The cable was rated for direct burial but I put it in conduit for physical protection. (If in the same trench as power the two need to be separated)

    BTW, I also ran a spare 2" conduit, empty except for a rope. Just in case.

    JKJ

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    Quote Originally Posted by Curt Harms View Post
    I had the same thought though I have no experience with fiber. It seems conventional wisdom that fiber is more expensive to install but more trouble-free so cheaper to maintain once installed.
    Fiber is simple really. If you donít abuse the cable, donít make any sharp bends in it and protect the ends which are ceramic, itís not much different than a copper cable. I have been in the networking space for work for 25+ years now so I donít know the low end type of gear sold on amazon but ratings wise this media converter looks like a goof fit. Grab a pair of them and an LC to LC multimode fiber cable what ever length you need and you should be good to go. LC refers to the plug style on the fiber cable and multimode refers to the type of fiber cable. Multimode can be run at least 220 meters and can go up to 550 meters on higher quality multimode fiber at gigabit speed. Also if you go with the higher quality OM3 or OM4 fiber you can use the same cable for 10 gigabit speed down the road. If you have any questions on networking please ask.

    sample media converter (you need one for each side)
    https://www.amazon.com/Converter-SFP-Transceiver-550M-ipolex/dp/B0716XT1QT

    sample om3 fiber cable
    https://www.amazon.com/Meter-Multimode-Duplex-Fiber-Optic/dp/B006KSXHC4

    sample drawing of how this plugs in. You can have switch/router or wireless router plugged in on the shop side as well.
    A47E0B63-FBCE-4B38-8922-E5ED31B48993.jpeg

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    fiber undergrond

    Quote Originally Posted by Chris Fairbanks View Post
    I think the OP, Robert, wanted to replace his existing ethernet cable due to water in the conduit. I see the fiber you referenced is not recommended for underground use in conduit or for direct burial. I saw direct burial OM3 fiber on Amazon at a much higher price.

    JKJ

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    Quote Originally Posted by John K Jordan View Post
    I think the OP, Robert, wanted to replace his existing ethernet cable due to water in the conduit. I see the fiber you referenced is not recommended for underground use in conduit or for direct burial. I saw direct burial OM3 fiber on Amazon at a much higher price.

    JKJ
    Yes, water infiltration can cause problems with fiber cable. Use the stuff approved for wet locations.

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    Buried electrical conduit collects water when there is an air pressure difference between the ends (even a very slight difference). The air will flow through it and moisture in the air will condense on the cooler below ground conduit walls. Over time, the conduit can become nearly full of water.

    I once ran a test with two conduits running parallel to each other under ground. I sealed both ends of one and left the other with both ends open. Both of these conduits were PVC and fully glued together at every joint. Even the end caps were glued onto the sealed conduit. Two Summer months later, when it came time to pull the wires, the open conduit had a significant amount of water in it and had to be blown out. When the sealed ends of the other conduit were opened and we blew it out, there was no significant water in it at all. After this, when we ran conduit under ground and didn't expect to install the wiring for extended periods, we always sealed the ends of the conduit. Blowing them out isn't hard, but messy and time consuming. Installing the wiring/cabling in dry conduit is much easier. You should always use cabling that is rated for moist areas when running it under ground, even when placing it in conduit as it will eventually fill with water again if the air can flow through it
    .

    Charley

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    Quote Originally Posted by Charles Lent View Post
    Buried electrical conduit collects water when there is an air pressure difference between the ends (even a very slight difference). The air will flow through it and moisture in the air will condense on the cooler below ground conduit walls. Over time, the conduit can become nearly full of water.
    Too true. There doesn't even have to be a pressure differential. As long as the buried conduit is below the dew point of the ambient air, the humidity will collect & condense.

    On one of our projects, the telco had to blow a line in a 4" conduit to pull in they're service cable. They hooked the blower up inside & a geyser of water shot about 20' in the air out at the pedestal. Quite impressive. I suspect that was mostly ground water that had seeped in.

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    If the two ends of the conduit are not exactly the same height there will be a thermosyphon effect constantly drawing in air. Same for any wind at all.
    Bill D.

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    Expanding on this question, where to find direct burial fiber cable (but don't mind running conduit)? I have a mechanic shop 150 yards from the house, and a dock 200 yards from the house. I'd like to put in trouble free (as possible) wifi extensions to both, from the house. Both are line of sight, but I'll be doing a lot of trenching anyway.

    From what I've read, that Google found, knowing next to nothing about this stuff to start with, it sounds like fiber is a better answer than antennas.

    The dock is on the end of a point, a couple of hundred yards long, that we will be renting out for weddings, and would like to make wifi available over those few acres. There is a restroom house about right in the middle that houses the main electrical panel (that feeds a sub at the dock), and is in line of sight from the house.

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    Tom, fiber is likely the ideal choice for these runs because the distance limitations on fiber are substantially longer (even for multi-mode) than for copper and wireless hits a performance wall that may not be acceptable, depending on what you intend to use the network for. And yes, direct burial rated is what you want, but putting it in some form of conduit is always a best practice because it adds a little more protection and allows "easy" replacement or addition of other low- or no- voltage needs in the future. Use pre-terminated fiber since terminating fiber requires special equipment and skills and use fiber to copper transceivers to move between the mediums. Just be sure to acquire fiber and transceivers with the same connectors...there are multiple types with LC and SC tending to be the most common. You have to match them across your infrastructure. If you intend to use something like an Ethernet switch out in one of the buildings and/or your primary location that already has provisions for fiber, match that connector type for obvious reasons.
    Last edited by Jim Becker; 12-08-2019 at 1:52 PM.
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  15. #15
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    Thanks. That's a good start on useful information. I usually put long runs of wire, and such, in black poly pipe, since it comes in long, continuous lengths. I can even use one really old black poly line, already in the ground, that was a water line going to that restroom building from uphill-was part of an old campground.

    I might just put an antenna to the mechanic shop. I like to watch youtube videos when I'm getting ready to work on something. Speed is not really much of a concern with that one, but I'll have a trencher here anyway, doing the other stuff, so could just run a wire there too.

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