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Tapping a Starter or Breaker for CPTs

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    Tapping a Starter or Breaker for CPTs

    When they tap a 3PH starter or circuit breaker for control power transformers or any other transformer for auxiliary loads, how do they actually make the bus tap? with a multi lug connector bolted to the bus?



    #2
    Depends on a number of things. If there is bus bar after the breaker you can drill and tap it. If it is wire, you can use splitter blocks, or get some breaker lugs with listed tap-off screws on them. Some starters have tap points on the line lugs. Lots of different ways to skin that cat.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

    I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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      #3
      do they make these taps line or load side, usually?

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        #4
        Originally posted by designer82 View Post
        do they make these taps line or load side, usually?
        Tapping the line side of the breaker? Possibly, but why would you do that? If you tap the line side, the breaker will not disconnect power to the CPT when you open the breaker, forcing you to add ANOTHER disconnect for the control power primary.

        Here's an example of what I was referring to; the small screw on the surface is for tapping off for the CPT primary. These are for ABB breakers, other breaker mfrs offer them as well. The key however is that the lugs must be LISTED for this purpose, you can't (legally) do it on your own.
        Click image for larger version

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        Square-D's version for PowerPact breakers:
        Click image for larger version

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        The alternative that I have used is to attach a short bus bar to the load side of the breaker, then drill and tap that bar for the CPT primary connections.
        __________________________________________________ ____________________________
        Many people are shocked when they discover I am not a good electrician...

        I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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          #5
          I'm trying to tap this starter like shown. Have you seen this done? Maybe there's issues against doing this

          I could even tap it ahead of the breaker and add another breaker, it doesn't matter.
          Attached Files

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            #6
            Originally posted by designer82 View Post
            I'm trying to tap this starter like shown. Have you seen this done? Maybe there's issues against doing this

            I could even tap it ahead of the breaker and add another breaker, it doesn't matter.
            Almost all combination starters are done that way. usually the tap is done on the line side of the starter (contactor) because they generally have lugs on them for doing this. 4160V though, that's a different story. Assuming that's a Draw-Out breaker, it likely has tap lugs available for the breaker terminals.
            __________________________________________________ ____________________________
            Many people are shocked when they discover I am not a good electrician...

            I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

            Comment


              #7
              Originally posted by Jraef View Post

              Almost all combination starters are done that way. usually the tap is done on the line side of the starter (contactor) because they generally have lugs on them for doing this. 4160V though, that's a different story. Assuming that's a Draw-Out breaker, it likely has tap lugs available for the breaker terminals.
              Thank you

              That auxiliary tap would be a 75KVA transformer though with #1/0 conductors. Wouldn't be for control voltage, it would be for a pump motor for a chiller chilled water pump.

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                #8
                Originally posted by designer82 View Post

                Thank you

                That auxiliary tap would be a 75KVA transformer though with #1/0 conductors. Wouldn't be for control voltage, it would be for a pump motor for a chiller chilled water pump.
                75kVA is just a little larger than the average control power transformer usually is
                I live for today, I'm just a day behind.

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