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    Voltage Drop & Feeder Sizing

    Need some input here, have to install a 200 Amp, single phase service for a remote cell tower with a 400 ft underground feed in PVC to the utility transformer. When I read Sec 215.2 Informational Note No. 2 is states we are to design the feeder to a maximum of a 3% voltage drop which results in 500 MC copper conductors. It also goes on to say a 5% VD to the farthest outlet. If I plug in 5 %, I can use 4/0 copper conductors. Per Code, am I allowed to use the 4/0 conductors?

    #2
    Informational notes are not enforceable; they are not "code." So to disregard them is not a "code violation." The real question is whether the equipment at the far end of the line will operate properly at a lower voltage.
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

    Comment


      #3
      Originally posted by chicagosparky View Post
      Need some input here, have to install a 200 Amp, single phase service for a remote cell tower with a 400 ft underground feed in PVC to the utility transformer. When I read Sec 215.2 Informational Note No. 2 is states we are to design the feeder to a maximum of a 3% voltage drop which results in 500 MC copper conductors. It also goes on to say a 5% VD to the farthest outlet. If I plug in 5 %, I can use 4/0 copper conductors. Per Code, am I allowed to use the 4/0 conductors?
      Voltage Drop is based upon the amps of the load. The equipment might be rated higher.

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        #4
        The client always requests a 200 amp MCB, but the actual loads only total up to 60 amps since it's just radios for the most part.

        Thanks.

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          #5
          I would use the 60 amps for the VD calculation and size according to that as long as the conductors are still good for at least 200 amps.
          Rob

          Moderator

          All responses based on the 2017 NEC unless otherwise noted

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            #6
            No idea how cell towers actually work, but with 5G expecting to roll out over the next several years, is it possible your client wants the voltage drop calc'd assuming max load on the conductors so there isn't an issue adding more equipment to towers in the near future?
            I'm offended.

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              #7
              Just a quick comment: Be careful with oversimplified voltage drop calculations only factoring resistances and not the reactance component as they will give false results.

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                #8
                We wired power and ground for a cell site on top of a 10-story apartment building. The copper wire sizes were spec'ed, as was the RGS conduit, so there was no debate as to size.

                We only had use of an elevator twice taking stuff up, and once coming down. The rest of the time, we had to take stairs . . . from the basement. My knees were quite angry at me.
                Master Electrician
                Electrical Contractor
                Richmond, VA

                Comment


                  #9
                  Originally posted by infinity View Post
                  I would use the 60 amps for the VD calculation and size according to that as long as the conductors are still good for at least 200 amps.
                  thats what I do.
                  Comments based on 2017 NEC unless otherwise noted.

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