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CAT-5 buried, exposed to sun

Discussion in 'Electronic Design' started by Joerg, Feb 3, 2007.

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  1. Joerg

    Joerg Guest

    Well, the frost out here took its toll. Need to re-plumb and relocate a
    sprinkler valve. Poof ... phssssst. Anyhow, like most engineers I've got
    lots of CAT-5 sitting on two spools doing nothing. I know, I know, it's
    not what you are 'sposed to use outdoors but it'll save me a drive into
    town.

    What happens to CAT-5 outdoors when part of it is buried in the soil and
    another part is exposed to the sun? Regular stuff, not plenum rated.
    It's going to get 24V, not much current, probably 250mA or so and I can
    parallel all the pairs. Any experience?

    BTW, I have in the past used indoor telephone line outdoors and it
    lasted forever. But that was much older technology, four non-twisted
    wires in a gray jacket. Then I had non-stranded electricians wire as an
    antenna, high up there, looked like new after 15+ years. Amazing.
     
  2. Short term its ok, but long term you should use outdoor rated cable. Sun and
    water will deteriorate the jacket.

    Cheers
     
  3. Rich Grise

    Rich Grise Guest

    The grey plastic jacket will dry out and crack, and the part underground
    might rot. It could last up to maybe five years, depending on how harsh
    the weather and stuff is, but if you're going to be burying it anyway, how
    hard would it be to bury a piece of PVC pipe and thread the cable through
    it? For the part exposed to the sun, one, put it in the shade ( ;-) ), and
    see if you can get some white vinyl tape and cover it up. That way, the
    tape will take the weather and the cable "should" last. ;-)

    Or, for that matter, extend the PVC to cover the otherwise exposed part.

    Or, if that's too much of a PITA, then just buy the proper wire -
    BUT! If it's not for permanent, then just lay it there. ;-)

    Have Fun!
    Rich
     
  4. Joerg

    Joerg Guest

    Yeah, I was thinking about wrapping electrical tape around the whole
    run. It's just 30ft or so. Can't lay it in PVC because this is very
    rocky and uneven terrain.

    Interestingly, when taking off the old valve there was electrical tape
    around a cable splice. It looked like the cheap stuff and I know it's
    been there 25+ years. Had a real hard time getting it off. Not cracked
    at all and it stuck like glue.
     
  5. Probably be fine. You could run it inside hose for extra protection.
     
  6. Joerg

    Joerg Guest

    Maybe I'll just wrap the whole run with electrical tape. Beats a
    round-trip into town. And I want to get it over with, I hate those
    plumbing projects :)
     
  7. Ross Herbert

    Ross Herbert Guest

    The old garden hose conduit method sure works for rocky terrain. It is
    certainly waterproof :)
     
  8. MassiveProng

    MassiveProng Guest

    No, but it will probably be fine. Electrically at least. You will
    have to change it out in a few years (if your smart) as the jacket
    will degrade, and you could then get electrical issues.

    POTS drop line lasts forever too. It has a creosote impregnated
    jacket. Nothing gets in or out.
    Yes, the run could last over a decade, but I'd still change it out
    for plenum rated or the like in a few years. Hell, get larger gauge
    teflon twisted pair power wiring! We used to buy it by the spool at
    16Ga, Black and White twisted pair teflon, with a shield and a teflon
    oversheath.

    Mil spec stuff. Excellent noise rejection, and great stuff to wire
    up anything AC fed with. There are even little terminations that heat
    shrink over the sheath, attach a shield lead to the shield, and seal
    off the shield and wires inside from the world outside. A heat gun
    shrinks it up, and solders on the shield lead in one operation.

    The finished cable assembly has two main AC lines and a small shield
    wire to tie to the chassis. Very quiet realm for your sensitive
    circuitry to operate in without disturbance. Twists stay tight, and
    there is another shield on top of that.

    THAT would last 50 years easily. Oh yeah... The wire itself is
    premium grade SPC (Silver Plated Copper).

    A little under a buck a foot. Short quantities would likely nearly
    double that.

    Still not bad for what you get.

    I think Reynolds made it.
     
  9. I use cat5 for my sprinkler system (24vac). One section is buried,
    proabably 10meters. Its been there for around 5 years now, never had a
    problem with it. It is that cheap that if/when it rots, i will just
    yank it up and replace it.

    There is also a meter or so exposed to sun light, and it is still
    going strong.

    I have used no precautions to keep the ends out of water, in fact I
    would be surprised if the outer insulation is not full of water.

    I use one pair per valve, and the total run would be 30meters or so.
     
  10. There's a kind of tape called self amalgamating. It bonds together over
    time.
     
  11. The stuff that phone guys use for indoor wiring is almost always rated
    for outdoors. Most of the time, they run it on the outside of buildings
    so its not worth carrying indoor only cable and then having to splice
    it, etc.
     
  12. (known to some as Joerg)
    scribed...

    <snippety-two>

    Unless it is explicitly designed and rated for outdoor (direct
    burial) and sunlight exposure, you can expect a fairly short lifetime as
    the PVC jacket gets progressively turned into brittle dust where the sun
    gets to it, and where water seeps in over a few month's time
    underground.

    If you must use standard CAT-5 cable outdoors, you should run it
    through conduit that is explicitly rated for direct burial.

    Ideally, you need to use cable that is itself rated for direct
    burial and sunlight. PVC won't cut it -- Outdoor and direct-burial
    telephone cables use a high-density polyethylene outer jacket.

    You should be able to find the appropriate stuff at
    telecommunications or electrical suppliers.

    I'd say you were extremely lucky with that older cable.


    Happy hunting.
     
  13. (known to some as Joerg)
    scribed...

    Won't help. Electrical tape itself will break down, both
    underground and when exposed to sunlight.

    If you're serious about doing this right, and saving yourself a
    replacement job down the road, use the correct materials to start with.
     
  14. mpm

    mpm Guest

    "There is nothing more permanent than something temporary."

    But in this case, I agree.
    Trenching through rock is no fun.

    -mpm
     
  15. Jim Thompson

    Jim Thompson Guest

    I'd put the CAT-5 inside some of that (1/2" I think) drip tube. It's
    flavor is undesirable to the desert rodents we have around here. I
    couldn't keep my pool controls alive until I did that.

    ...Jim Thompson
     
  16. Joerg

    Joerg Guest

    This was regular indoor line I used. It amazed me.
    Then the PVC water lines would become the limiting factor in MTBF.


    The cigarette manufacturer ? SCNR...
     
  17. Joerg

    Joerg Guest


    Good! That's what I am planning to do.
     
  18. Joerg

    Joerg Guest

    Won't fit around the rocks here, way too stiff. We only have foxes. The
    kits dig and play when they are young, and occasionally knock over the
    firewood stack. But they never chew anything up. They are actually quite
    behaved compared to most puppy dogs. They also don't relieve themselves
    in the middle of a flower bed but always go into a corner.
     
  19. Jim Thompson

    Jim Thompson Guest

    I have several inches of decorative crushed granite on the yard, so I
    just scrape back a few inches away from the edge of the house, lay
    down the tubing, then sweep the granite over it.

    ...Jim Thompson
     
  20. MassiveProng

    MassiveProng Guest


    That was the old stuff. The newer stuff is the polyethylene
    jacketed stuff the other guy described.
     
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