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Fiber over rooftop !

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    Fiber over rooftop !

    99% of my work is cat5E data, in interior retail environment. ( rarely have to run exterior circuits ) But on occasion have used 1 -1/2 EMT on rooftop conduit supports to run between structures. Have a customer interested in connecting structures 20 feet apart with a fiber circuit, but doesn't want it on the deck (due to foot traffic and re-roofing in the near future) Am I stuck with running suspension wire or anyone suggest a product they have had success with?

    #2
    I don't know how you would use conduit as a means to run cable between two buildings roofs unless it was only a couple of feet.

    As to your question, you would use a cable designed for aerial installation- that would be a cable with a built-in messenger wire, commonly called figure 8.

    I suppose that if the bulk of the run is up and down the sides of the buildings and inside with only 20 feet aerial you could run a messenger then ty-rap (with outdoor cable ties) the cable to it.

    If it will be difficult to reach the entire run down the side of the building to install straps, a quick and dirty way is to use figure 8 and continued the messenger, attached at the top and bottom with tension to support the cable. Where you don't need the messenger you strip it off.

    -Hal

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      #3
      Thanks !
      Problem is, I am using delicate fiber optic cable and so have to support the conduit that protects it. Usually lay on durablok support directly on the roof. But customer wants it suspended if possible between 2 structures (an outside wall and an atrium ). cheersClick image for larger version

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        #4
        Originally posted by Limeydal View Post
        Thanks !
        Problem is, I am using delicate fiber optic cable and so have to support the conduit that protects it. Usually lay on durablok support directly on the roof. But customer wants it suspended if possible between 2 structures (an outside wall and an atrium ). cheers[ATTACH=CONFIG]21054[/ATTACH]

        To protect against bending/flexing in the wind, with potential kinking forces, you could run an EMT (or heavier) sleeve, supported as necessary by a messenger wire. To keep the conduit sheath straight in the vertical plane (for appearance as much as function) you might need to suspend the wire in a catenary curve with ties of varying length down to the conduit.

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          #5
          It is in a sheltered location, so that may be the way to go !
          See "Gripple" have some interesting products ,that may make this easier,with an easy adjust clevis hanger system ,to support the EMT
          (Will need to brush up on my math skills to calculate that catenary though )

          cheers

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            #6
            Originally posted by Limeydal View Post
            It is in a sheltered location, so that may be the way to go !
            See "Gripple" have some interesting products ,that may make this easier,with an easy adjust clevis hanger system ,to support the EMT
            (Will need to brush up on my math skills to calculate that catenary though )

            cheers
            BTW, before you spend too much time brushing up on your math, consider that there are two different hanging support curves to consider:

            For a chain or wire that is supporting only its own weight, the curve of a stretched wire is a catenary. That applies to free hanging transmission lines between towers and is needed to calculate the sag for a given span and tension.

            For a chain or wire that is instead supporting a load much greater than its own weight and that load is constant per unit length along the full length of the span (like a bridge deck or maybe EMT containing a possibly heavy cable) the curve of the support wire is a simple parabola. The equations are much simpler to derive and apply, although you would probably end up using a set of tables anyway.

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              #7
              Originally posted by GoldDigger View Post
              For a chain or wire that is instead supporting a load much greater than its own weight and that load is constant per unit length along the full length of the span (like a bridge deck or maybe EMT containing a possibly heavy cable) the curve of the support wire is a simple parabola.
              To clarify, that's constant load per unit horizontal length, right? Because if it is per unit length of the chain or wire, that would be back to the catenary case, right?

              Cheers, Wayne

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                #8
                Originally posted by wwhitney View Post
                To clarify, that's constant load per unit horizontal length, right? Because if it is per unit length of the chain or wire, that would be back to the catenary case, right?

                Cheers, Wayne
                Yup.

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