Top of pole mount conduit routing



  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Top of pole mount conduit routing
    Macaw wrote: »
    Item # 2
    "do you want us to weld a cap in the top of the pipe so it does not fill up with water?"
    That is what they do with all (most?) of their big signpost installations. Good idea I figure so I present it to the forum.

    (I replied to this once, but I guess I failed somehow to post it.)

    I would.

    I have opened up junction boxes at the bottom of parking lot lighting poles and had a gallon of water pour out - so I know that water gets in somehow. Condensation? Dunno. Maybe your welder guys can answer that question. Either way, a properly welded cap has GOT to be better in the long term than a plastic plug.

    If it were me, I would also hole-saw and tap for a 1/2" pipe plug - as low as possible and still be above grade - and then goop up the plug with Led-Plate before installing it so I could take it out easily later. I would use one of the pipe plugs with a square head:

    Then add an item to the annual maintenance list: R&R Drain Plug.

    EDIT: As to the welded on cross-pieces...

    I've seen gate guys placing poles to hold the hinges for some great huge wrought iron gates in Beverly Hills. Since I had to place conduits before the concrete was poured, I got a good close up look at them.

    The poles they set had rebar welded to the bottom sections (the 6' or so that was in the concrete). The poles were (IIRC) 8" and the chunks of rebar were something like 1" dia. x 18" long. The rebar stuck out all over the pole like a Christmas tree. I would say in the bottom 6' of the pole there were maybe 30 or so sticking out. They also had a grid of rebar welded to the bottom, in a pattern like this: # Those 4 bars were probably 6' long themselves.

    So, again if it were me, I would say thanks to the welders for the extra cross pieces and be glad to have them. Maybe not required, but it can't hurt so what the hey.

    EDIT 2: I just remembered another time. I had a buddy who worked for a sign company. They were installing an enormous sign at an auto dealership and one day I passed by and saw his truck there so I stopped in to check it out.

    There were two poles for the sign. They were round and in 3 sections. The sections looked like a telescoping antenna - each fitted into and welded into the one below.

    The poles were probably...oh 36" dia. x 120' long, of which I guess maybe 20' was in the ground. The footing was gigantic - something like 30' deep by 40' x 60'. Huge. And it was filled with a thick fat rebar assembly. The round poles were welded to that rebar assembly.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Top of pole mount conduit routing
    dwh wrote: »
    There is a special silicone for electrical connections; dielectric silicone - usually sold as a form of grease but I've seen it as an RTV as well.

    Wirenuts that are factory-filled, will normally be filled with dielectric silicone grease, but some are filled with a NoAlox type compound. ...


    Best regards,

  • MacawMacaw Solar Expert Posts: 36
    Re: Top of pole mount conduit routing

    Wow- Thanks DWH for your expert opinion. And thanks to everyone for your helpful responses.

    Darn it! No matter how hard I try, I STILL learn something new every day.

    That is a good idea to have a drain plug or in other words an inspection port near the base of the mast. My 10 inch diameter mast is sized for the limit of safety factor at 90 miles per hour using 42 ksi structural steel. If I drill a big hole then my safety factor is reduced. Of course there is lots of margin in that safety factor so we might sweep the stress concentration under the rug. The highest stress is at the top of the concrete, right where you want the inspection port. Recon why it works out like that. :)

    In summary, I agree that welding the top of the structural pipe support closed with no air vent is the way to go, and, that welding some sort of anti-rotation feature and maybe even some anti-pull-out prongs at the base of the mast is the prudent approach for the top-of-pole mount structural support.

    After all, if I can get a decent lift coefficient in a 90 MPH breeze, then my 12 Evergreen panels should at least be able to pull 5000 pounds straight up with no problem.
  • MacawMacaw Solar Expert Posts: 36
    niel re: Top of pole mount conduit routing

    Regarding condensation inside the pipe support- I agree that there will be an annual, seasonal and daily cycle of rain (sprinkles) and evaporation inside of the steel pipe support.

    After spending much time considering the details of condensation in a crawlspace, and evaluating vented versus sealed crawlspace technologies, I recon that for the life of the pipe, venting is not important. But if there is no vent then will the Oxygen run out after a while so oxidization stops on the inside of the pipe?

    (the thread that goes on, and on, and on...)
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Top of pole mount conduit routing

    "But if there is no vent then will the Oxygen run out after a while so oxidization stops on the inside of the pipe?"

    good question and i'm not qualified to answer that one.

    "(the thread that goes on, and on, and on...) "

    that bunny's got nothing on us in any way.:p
  • halfcrazyhalfcrazy Solar Expert Posts: 718 ✭✭✭
    Re: Top of pole mount conduit routing

    Has any one ever asked DPW what they recommend for the pipe capped or not?
  • russruss Solar Expert Posts: 593
    Re: Top of pole mount conduit routing

    Lack of oxygen does not necessarily stop corrosion - İn the iron ore business we found that in an atmosphere with no available oxygen but with moisture available, iron would react with the moisture to make hydroxides. A slower reaction but very much there. Still corrosion potential
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