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Electronics tech needs help with wire sizing for AC and elevator

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    #16
    Originally posted by RobertKLR View Post
    There are two feeders to the building in question, one comes straight from the switchgear building (13.2KV) to a transformer for the 208 power but the hvac and elevator are fed from another building across the street which has 460vac.
    That kind of makes sense.

    I wonder why they did not just set another xfmr in there instead of running 480 from another building? Not that it matters much at this point. Probably to save a buck or two.

    About the only thing you can do is up size the breaker to the max allowed for the wire you have. But I am not thrilled with the idea of suggesting you do it given that you could potentially kill yourself trying it due to lack of knowledge on how to do so in a safe way. Not knowing how to do it right might also cause you to do it wrong in a catastrophic way that might not kill you but might create serious damage.
    Bob

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      #17
      Originally posted by RobertKLR View Post
      The elevator and hvac are on the same breaker but the hvac serves the entire 3 story 70+ yr old building. This is also the OI&T building and when the hvac system stops that old building heats up fast.

      I'll add the building power is 120 and 208. That's why the 460 had to be brought in from the nearby building. This is the VA, there is no rhyme or reason to why they do things the way they do.
      pretty sure this an NEC and A17 violation

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        #18
        Originally posted by Ingenieur View Post
        pretty sure this an NEC and A17 violation
        That would have been my guess. But I wonder if what he meant was that they are on the same feeder, and not the same branch circuit.

        It's still a code violation if you don't have adequately sized feeders.

        There is so very little we know about this installation from what he is telling us.
        Bob

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          #19
          It's an NEC violation for the disconnecting means of an elevator circuit to be disconnected by any other means than the elevator system. In fact you cannot even run the HVAC for the elevator on the same branch circuit of an elevator, it must have it's own branch circuit. So if that breaker is the only OCPD in the elevator system, then it is the BRANCH OCPD for the elevator and that alone disallows the use of that same circuit to be used by both systems. If on the other hand the 70A breaker is a FEEDER, not a branch OCPD, then there must be branch OCPDs somewhere down stream of this 70A breaker for BOTH the elevator AND the HVAC. If so, but it is the FEEDER that is tripping, not the branch OCPDs, then something was incorrectly sized.
          __________________________________________________ ____________________________
          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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            #20
            I really appreciate the comments and there has been some good advice in them. I've summarized some of the comments in an email to the chief engineer and safety director. I then went to the union and requested they also push for a contractor to assess the situation.

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