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480/277 WYE service to 120/240 Single phase

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    #76
    Originally Posted by PVfarmer

    1.you can't physically have the power going out to grid from the main 3 phase meter and then back to a separate single phase meter

    Why not? The wiring arrangement would be the same as the single phase service with two meters, except the 3 phase meter would have the extra POCO conductor going to it.

    2. Yes, line-side would simplify things- but Im not sure if line-side input is OK when the meters have to be "cold".

    Sure, why not?

    3. If the PV output meter is PV-side of the PV disconnect it would be cold. (Line-side would be the dotted red line in the 2nd diagram.)
    Sorry, I've lost track of which diagram you are referring to, so I'm having trouble following you. But if I understand correctly you just want to do the following (forgive the ASCII art):

    Service --- 3 phase disconnect -- 3 phase PV production meter -- PV source
    |
    ------- 1 phase disconnect -- 1 phase consumption meter -- 1 phase loads

    ////
    1. I don't think the wiring would be the same- with single phase, it's two meters side by side, with L1 and L2 from the grid connected to L1 and L2 of each meter- so power would go out one meter and right back in thru the other.
    With 3 phase, I *think* you have one main 3 phase service meter that goes with the 3 (or single) POCO xfmr- so the power is being stepped down, and all three phases are metered, then the additional single phase customer gets 2 lines of that three phase for their single phase. It depends where the two wires for single phase are connected- if they're before (grid side) the 3 phase meter then it'll work- if they're after the 3 phase meter, it won't work.

    2. I meant OK as in with the POCO. There *would* be two disconnects, the 100A main and the PV shut-off-so...you'd think it would be OK.

    3. Not sure what the | means there.
    But this diagram- if the PV was connected to grid at the red line (line side), and the larger green meter was at the green arrow, you'd be measuring the two loads as one.
    But I'm trying to get two separately metered bills on the same service.
    Click image for larger version

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      #77
      Originally posted by PVfarmer View Post
      With 3 phase, I *think* you have one main 3 phase service meter that goes with the 3 (or single) POCO xfmr- so the power is being stepped down, and all three phases are metered, then the additional single phase customer gets 2 lines of that three phase for their single phase. It depends where the two wires for single phase are connected- if they're before (grid side) the 3 phase meter then it'll work- if they're after the 3 phase meter, it won't work.
      Unless your POCO is weird, they will let you connect the service for the single phase meter before the 3 phase meter. What use is it to meter the power twice?

      Originally posted by PVfarmer View Post
      3. Not sure what the | means there.
      That's just a vertical line, - is a horizontal line. I'm showing two different connections to the POCO service wires. In practice, I think you'd typically bring your service entrance conductors into a gutter/tap box, make your connections there, and then come out of the gutter separately to the three phase disconnect/meter and to the single phase disconnect/meter.

      Originally posted by PVfarmer View Post
      But this diagram- if the PV was connected to grid at the red line (line side), and the larger green meter was at the green arrow, you'd be measuring the two loads as one.
      Yeah, that doesn't make sense, so don't do that. You're making this much more complicated than it needs to be. If you want to meter the consumption and the production separately, just arrange your meters so that one measures only production, and the other measures only consumption. That should fly with the POCO, assuming they are on board with this meter them separately idea.

      BTW, this isn't really anything I have any experience with, I'm just trying to hopefully bring some order to a cluttered thread.


      Cheers, Wayne

      Comment


        #78
        Originally posted by wwhitney View Post
        You're making this much more complicated than it needs to be.
        Somebody else said that... Oh, yeah; it was me.

        Comment


          #79
          Originally posted by wwhitney View Post
          Unless your POCO is weird, they will let you connect the service for the single phase meter before the 3 phase meter. What use is it to meter the power twice?

          That's just a vertical line, - is a horizontal line. I'm showing two different connections to the POCO service wires. In practice, I think you'd typically bring your service entrance conductors into a gutter/tap box, make your connections there, and then come out of the gutter separately to the three phase disconnect/meter and to the single phase disconnect/meter.

          Yeah, that doesn't make sense, so don't do that. You're making this much more complicated than it needs to be. If you want to meter the consumption and the production separately, just arrange your meters so that one measures only production, and the other measures only consumption. That should fly with the POCO, assuming they are on board with this meter them separately idea.
          Not sure if "before" is the right word there- isn't connecting the 2 accounts "side-by-side" the only right way to do it?

          So...
          Imagine the bolded T is actually upside down here, with the vertical connected to main switch- the left side of the horizontal goes to PV account, the right side goes to non-PV.
          The .... .... ... is nothing- that just makes the ^ be in the right place.

          Service
          |
          Main shut off box w/manual switch
          |
          T----> non-PV meter --- non-PV load panel
          |
          |<----> PV account meter (bidirectional) <----> load panel for PV account
          . ........ ..... ..... ...... ...... ...... ...... ....... ...^<---- PV disconnect/PV meter/PV inverter


          If the whole thing is a big T, with the service wires going into the main service switch at the bottom of the vertical leg of the T, you can't put any meter or combo of meters on the vertical- the meters have to go on the 2 lines that the top of the T makes to left and right- that's what I mean by side-to-side.
          Any meter on the vertical would measure a load twice.

          Comment


            #80
            Originally posted by PVfarmer View Post
            Service
            |
            Main shut off box w/manual switch
            |
            T----> non-PV meter --- non-PV load panel
            |
            |<----> PV account meter (bidirectional) <----> load panel for PV account
            Sure, that will work. You don't need to have a "main shut off box", you could have individual disconnects after the "T" point but before each meter (since your POCO requires cold sequence meters). Which is what my diagram showed.

            Cheers, Wayne

            Comment


              #81
              Originally posted by wwhitney View Post
              You don't need to have a "main shut off box",
              Well...are you sure?
              The main switch is what makes the meters cold.
              So with a 480/277V 3 phase account AND a 277/480 1 phase account, no main switch would really mean TWO main switches- I don't think POCO wants that.
              They want a main switch, then a load panel for each customer- that way it's one service xfmr-wise, with two totally separate accounts bill-wise...and that set-up messes up the line-side (hot meter side) PV connection idea.

              If the PV has to be load side, it has to be on the 3 phase customer load side- so you need that upside down T to accomplish the "load panel for each customer" idea.

              Comment


                #82
                Originally posted by PVfarmer View Post
                Well...are you sure?
                The main switch is what makes the meters cold.
                For cold sequencing, each meter needs a disconnect before it, but there doesn't need to be a single disconnect for both meters. Each meter could have its own disconnect before it.

                Originally posted by PVfarmer View Post
                So with a 480/277V 3 phase account AND a 277/480 1 phase account, no main switch would really mean TWO main switches- I don't think POCO wants that.
                I haven't read your National Grid book to see if they allow that, but from what I've read here on other threads, that would be a pretty standard arrangement in most parts of the country.

                Originally posted by PVfarmer View Post
                They want a main switch, then a load panel for each customer- that way it's one service xfmr-wise
                The arrangements of meters/disconnects has nothing to do with transformers.

                Cheers, Wayne

                Comment


                  #83
                  Originally posted by wwhitney View Post
                  For cold sequencing, each meter needs a disconnect before it, but there doesn't need to be a single disconnect for both meters. Each meter could have its own disconnect before it.
                  The arrangements of meters/disconnects has nothing to do with transformers.
                  I can't see how two main service disconnects would work visually.
                  Right now the service is this, there is no PV-
                  Two POCO wires coming from the 4 POCO wires running along the road- that's a line and a neutral, so they run 200+ feet from the road overhead to a pole (across one support pole) to a 7200 L-N to 120/240 xfmr, 25kVA.
                  The 3 wires for the 120/240 run from the pole to a building, overhead, through the meter (it's hot) to the main switch. The main switch is 400A and there are 3 or more load panels from that going to various buildings (one is the residence that isn't supposed to use PV according to the weird rule.)

                  With the PV (480/277 wye Sunny Tripowers), the service will be changed to 480/277 wye, hopefully 100A and not the standard 200A, because 90kVA of xfmrs for 83kVA of "service" is plenty for 72A max PV output and less than 25kVA max load. (I think)

                  So that service would be all 4 wires from the road, to the same pole where the 25kVA xfmr is now, running down to the ground with say 3 30kVA xfmrs on a pad, 12.47kV delta on the grid side and 480/277 wye on the service side- from there (the base of the pole), the 4 wires would go underground to the same building (actually a 6x8 foot shed outside the building) where currently the meter is on the outside and the main switch is inside.

                  The meter can stay where it is, the new meter will go right near it (but not in the same socket or enclosure).
                  The 480/277 wires will go to the switch first, and then those meters will be cold, but they can't be on the same line because they'd be double measuring something.
                  So you have to split it there- technically, both meters would still be "hot" after you threw the main switch until you threw the PV disconnect switch.

                  Comment


                    #84
                    Originally posted by PVfarmer View Post
                    I can't see how two main service disconnects would work visually.
                    I described one possibility earlier: "In practice, I think you'd typically bring your service entrance conductors into a gutter/tap box, make your connections there, and then come out of the gutter separately to the three phase disconnect/meter and to the single phase disconnect/meter."

                    Originally posted by PVfarmer View Post
                    So that service would be all 4 wires from the road,
                    I think the POCO transformers typically are delta on the grid side, so they'd only need to bring 3 wires from the road to their transfromer. [Edit: or do they need to bring the HV neutral for bonding?]

                    Originally posted by PVfarmer View Post
                    So you have to split it there- technically, both meters would still be "hot" after you threw the main switch until you threw the PV disconnect switch.
                    If the inverters are grid tie inverters, then throwing the main disconnect should cause them to stop producing power for anti-islanding.

                    Cheers, Wayne

                    Comment


                      #85
                      Originally posted by wwhitney View Post
                      1. I described one possibility earlier: "In practice, I think you'd typically bring your service entrance conductors into a gutter/tap box, make your connections there, and then come out of the gutter separately to the three phase disconnect/meter and to the single phase disconnect/meter."

                      2. I think the POCO transformers typically are delta on the grid side, so they'd only need to bring 3 wires from the road to their transfromer. [Edit: or do they need to bring the HV neutral for bonding?]

                      3. If the inverters are grid tie inverters, then throwing the main disconnect should cause them to stop producing power for anti-islanding.
                      1. Well, golly, I just found this in italics below. So you *can* have either/or. Hmm. I'm assuming OR dual secondary xfmrs means in that case there's a single primary.

                      2. I think you are right there- I tried looking it up just now- seems to be the case as far as I can see.

                      3. Also a good point, thamks.

                      4. I just sent the POCO guy an email, so hopefully I'll have some answers Monday.

                      12. Multiple service facilities may be supplied to the customer from the Company’s Distribution
                      EPS. These service installations may be either dual primary switchgear or dual secondary
                      transformers. To assure that the reliability and proper protection are maintained in these
                      multiple service facilities, the Customer-Generator is not permitted to:
                      • Parallel secondary services from a common facility.
                      • Parallel secondary facilities supplied from separate locations.
                      • Exceed the ampacity rating of any service facility.
                      • Create an unbalanced loading condition in excess of 2% voltage unbalance between
                      phases of a service

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