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Largest 120/208 volt service

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    #16
    Originally posted by brantmacga View Post

    That sounds like a fun project; I have zero experience with buildings of that size. Is the 480 for HVAC and common area/exterior lighting?
    Yes the 480Y/277 is for the chillers, HVAC, elevators, fans, pumps, etc.

    Originally posted by mbrooke View Post

    I might have done it the same way. If 208 makes the bulk of the load it makes sense IMO. Hate to see a 225kva step down on every floor.
    IMO the flaw is that instead of that (208 volt vertical risers) we have 4160 step-up and 4160-208Y/120 step down transformers for the apartment power anyway. All of the 480 is derived from huge transformers as well. It is nice to run a single 2.5" riser the height of the building and end up with 1000 amps at 208Y/120 on the other end.
    Rob

    Moderator

    All responses based on the 2017 NEC unless otherwise noted

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      #17
      Not one of my jobs, I got an email from a friend asking if I knew where he could get an 8000A disconnect from. He was in Russia on a job that was to be done to BS7671 but using 208/120V ? ? ? ?

      Don’t ask me why, because I don’t know.

      6300A was the best I could come up with.
      My first answer was “why don’t you use 3.3kV?”
      “They want the whole site has to be 208/120V.”
      “Telemecanique can gang disconnects.”

      What size the cables did they used? I dread to think.
      [COLOR=#000000]The reports of my death are greatly exaggerated.[/COLOR]

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        #18
        Originally posted by infinity View Post

        Yes the 480Y/277 is for the chillers, HVAC, elevators, fans, pumps, etc.



        IMO the flaw is that instead of that (208 volt vertical risers) we have 4160 step-up and 4160-208Y/120 step down transformers for the apartment power anyway. All of the 480 is derived from huge transformers as well. It is nice to run a single 2.5" riser the height of the building and end up with 1000 amps at 208Y/120 on the other end.
        How is metering handled? Is electric included for tenants?
        Ethan Brush - East West Electric. NY, WA. MA

        "You can't generalize"

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          #19
          208 Volt, 3 phase, 4000-amp at a hospital in Brooklyn, NY. And it was probably 50+ years old. The reported fault current was 200kA. There were five 1000 kVA transformers network-connected on the other side of the wall in the basement of the facility.

          I was doing data collection for an arc flash study and couldn't 't find the current-limiting fuses that were shown on the drawings. So I took 40 nuts off the cover off a 3' by 4' protruding enclosure. The cover was held by 4 captive studs. When I popped the cover off to inspect it, I found the 4000-amp, 208 Volt busbar was about 3/4' from the face of the cover. It scared the bejeezus out of me, but it made sense. There wasn't the need for much clearance because it was just 208 Volts.

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            #20
            Originally posted by mayanees View Post
            208 Volt, 3 phase, 4000-amp at a hospital in Brooklyn, NY. And it was probably 50+ years old. The reported fault current was 200kA. There were five 1000 kVA transformers network-connected on the other side of the wall in the basement of the facility.

            I was doing data collection for an arc flash study and couldn't 't find the current-limiting fuses that were shown on the drawings. So I took 40 nuts off the cover off a 3' by 4' protruding enclosure. The cover was held by 4 captive studs. When I popped the cover off to inspect it, I found the 4000-amp, 208 Volt busbar was about 3/4' from the face of the cover. It scared the bejeezus out of me, but it made sense. There wasn't the need for much clearance because it was just 208 Volts.
            How did you end up dealing with 200ka fault current?

            What you describe is typical, not the exception in NY.
            Our comedian shamelessly joked about a blackout. Talk about dark humor.

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              #21
              Originally posted by mbrooke View Post

              How did you end up dealing with 200ka fault current?

              What you describe is typical, not the exception in NY.
              4000-amp KRP-C fuses with 300 kAIC

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                #22
                Originally posted by electrofelon View Post

                How is metering handled? Is electric included for tenants?
                There is a separate sub-metering system, each apartment feeder is monitored by a current sensor that feeds a metering panel. That is connected to the building BMS through a CAT6 cable.
                Click image for larger version

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                Rob

                Moderator

                All responses based on the 2017 NEC unless otherwise noted

                Comment


                  #23
                  Originally posted by infinity View Post

                  There is a separate sub-metering system, each apartment feeder is monitored by a current sensor that feeds a metering panel. That is connected to the building BMS through a CAT6 cable.
                  Click image for larger version

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                  Is that in the same building as this?

                  Attached Files
                  Our comedian shamelessly joked about a blackout. Talk about dark humor.

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                    #24
                    Originally posted by mayanees View Post

                    4000-amp KRP-C fuses with 300 kAIC


                    I'm going to look those up, I need them.
                    Our comedian shamelessly joked about a blackout. Talk about dark humor.

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                      #25
                      Originally posted by mbrooke View Post

                      Is that in the same building as this?
                      Nope.
                      Could be this guy, BTW much better sub-metering system.

                      Click image for larger version

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                      Rob

                      Moderator

                      All responses based on the 2017 NEC unless otherwise noted

                      Comment


                        #26
                        Originally posted by electrofelon View Post

                        Me too. Seems like taking service at MV and distributing that around rather than sending that much 208 around from one (or 4) locations would be more efficient.
                        Depends on who is going to maintain things. Not as many people are trained to work with medium voltage, and those that are typically want more pay than those that aren't. But one has several things to look at before making such decision. Already too many general maintenance guys in some places that probably shouldn't mess with electric as is, they certainly don't need to even have a chance at doing anything with medium voltages.

                        I live for today, I'm just a day behind.

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                          #27
                          Originally posted by infinity View Post

                          Nope.
                          Could be this guy, BTW much better sub-metering system.

                          Click image for larger version

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                          Wish all panels looked like that good
                          Our comedian shamelessly joked about a blackout. Talk about dark humor.

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                            #28
                            Originally posted by mbrooke View Post
                            What is the largest 120/208 volt Y service you've ever encountered in your career?
                            4,000 amp. 120/208
                            ~New signature under construction.~
                            ~~~~Please excuse the mess.~~~~

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