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OCPD sizing for RV sites in RV park

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    OCPD sizing for RV sites in RV park

    I'm looking in 551, but not seeing how to size the OCPD for each site.
    The reason I'm asking is that today I was troubleshooting a power issue at a site that was a 30/20.
    I wasn't able to find the breaker for the site (nothing was labeled) so I used my circuit tracer and it led me to a 2-pole 60 .

    turns out the adjacent site was the other half of the breaker.
    I was expecting to find a 1-pole 30 but there were none.
    Then I thought maybe there'd be a 2-pole 30 and maybe the 2 sites would be sharing the neutral.

    I was surprised to see a 2-60. Would this be normal?
    What would determine how to size the OCPD for sites?

    #2
    I see 551.73 talking about calculated load,
    A 30/20 would be 3600 VA, that's 30 amps.
    551.74 Overcurrent Protection says to refer to 240.

    still not sure why a 60 was used.
    Am I missing something?

    Comment


      #3
      Originally posted by sw_ross View Post
      I see 551.73 talking about calculated load,
      A 30/20 would be 3600 VA, that's 30 amps.
      551.74 Overcurrent Protection says to refer to 240.

      still not sure why a 60 was used.
      Am I missing something?
      210.21 and 210.23 Nothing in 551 exempts us from article 210 it just modifies it. (90.3)
      Comments based on 2017 NEC unless otherwise noted.

      Comment


        #4
        Originally posted by tortuga View Post

        210.21 and 210.23 Nothing in 551 exempts us from article 210 it just modifies it. (90.3)
        That concept was my first thought,

        Then I got wondering that the 30/20 has individual OCPD's for each receptacle in the box (a 30 & 20) so I wondered if there was something in the code that allowed that assembly to be protected at a higher setting, but I'm not finding it.

        Comment


          #5
          If there are OCPD's in the box like this, then yeah the 60A breaker is a feeder and your good to go. Click image for larger version

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          Comments based on 2017 NEC unless otherwise noted.

          Comment


            #6
            Originally posted by tortuga View Post
            If there are OCPD's in the box like this, then yeah the 60A breaker is a feeder and your good to go. Click image for larger version

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            How is that value calculated?
            I guess there's something that I'm missing...

            Comment


              #7
              I guess I can understand the concept of a 30/20 (with 2 OCPD's) being supplied with a feeder.
              The feeder OCPD being sized based on the conductor size of the feeder.

              So then, is there a minimum size feeder/OCPD for this 30/20?
              Is there anything wrong with 10/2 and a 30-amp breaker?

              Comment


                #8
                Originally posted by sw_ross View Post
                I guess I can understand the concept of a 30/20 (with 2 OCPD's) being supplied with a feeder.
                The feeder OCPD being sized based on the conductor size of the feeder.

                So then, is there a minimum size feeder/OCPD for this 30/20?
                Is there anything wrong with 10/2 and a 30-amp breaker?
                Yes to 10AWG as 551.73 is for sizing RV site feeders and states 3600 VA for a 30/20 120V site. Depending on voltage drop I would tend to go way over that.
                Comments based on 2017 NEC unless otherwise noted.

                Comment


                  #9
                  Originally posted by sw_ross View Post
                  I see 551.73 talking about calculated load,
                  A 30/20 would be 3600 VA, that's 30 amps.
                  551.74 Overcurrent Protection says to refer to 240.

                  still not sure why a 60 was used.
                  Am I missing something?
                  You need a minimum supply that can handle 3600 VA to that site, nothing wrong with supplying it with more if you wish. You said adjacent site was also on the 60 amp breaker. Have to presume there is 60 amp conductors involved as well - leaves room to add more if anything.

                  I've installed 200 amp feed through pedestals on 200 amp feeder, last unit definitely didn't need a 200 amp supply.
                  I live for today, I'm just a day behind.

                  Comment

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