Solar – Line side tap

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    • #7364 Report Abuse
      msturtz
      Member

      I have a 10kw solar, which is too large to backfeed a 200 amp main breaker (NEC code says only 20%, 10kw could be about 45.5 amps which is more than that).  The utility lines come from the meter into my panel to the main breaker, but before the main breaker are taps, which are then connected to a fused disconnect, and separate panel, and then on to the inverters (and nothing else).  It’s standard residential split-phase.

      The 200A CT’s are on the main lines, after the taps, before the main breaker (with the arrows pointing towards the breaker, away from the utility).  They will measure only the load, NOT production.  I have one 50A CT on the solar (arrow pointing toward the main line, away from the inverters), which will measure only the production, none of the load.

      How do I configure this setup in the app?  During the guided installation, I was assuming it would give me some choices, but it didn’t.  My goal is for the app to show me both usage and production, as well as the net.

    • #7367 Report Abuse
      Emporia Support
      Emporia Staff

      Hey @msturtz,

      Just a couple points of clarification:

      Related to the position of the 200A CT, you can have the CT placed between the tap and the main breaker, but this will measure any solar generation as a consumption reading as part of your NET. If you’re monitoring your solar separately (which it sounds like that’s the plan), you’ll be able to collect those numbers, but the App still needs some functionality to be added for these numbers to aggregate correctly. We’re actively working on features that allow for more customization of circuit monitoring, as well as better clarification/separation of generation vs. consumption numbers.

      So, currently, the best way for your use case to display accurately within the App would be to relocate your 200A CT’s above the tap. This will provide the NET (generation and consumption) as well as a specific reading from your 50A CT (on the solar) to get your exact generation. Again, the development team is working on App features to aggregate these numbers on the user interface and to separate consumption and generation.

      One additional note, if you want the full measurement of your solar generation, you’d need one 50A CT on each line. If you need the extra CT sensor to monitor another circuit, make sure to add a circuit multiplier of ~2.0 to your solar monitor (within the App).

      When installing your Vue for solar, make sure your solar generation is turned off while setting it up. Its also probably a good idea to have a decent consumption load running, that way the Vue has a baseline on setup that helps it recognize the solar generation when its running.

      If you have any questions or ideas, definitely reach out to the support team.

    • #7374 Report Abuse
      msturtz
      Member

      Following up here.  Chatted with support.  The recommendation was to move the main CT’s to be “upstream” of the taps, so that they measure the Net.  Then I still have one 50A CT measuring just production.  So at this point, it looks exactly like it would with solar backfeed.  Of course, everything looks correct now — in the app, where it says “Main”, that’s the NET, but under that it shows production, and then below that you can see Total Usage.

      What’s annoying is the Graph page only shows the Net — with blue for net-use, and green for net-produce.  It doesn’t show them separately.

    • #7390 Report Abuse
      Emporia Support
      Emporia Staff

      What’s annoying is the Graph page only shows the Net — with blue for net-use, and green for net-produce. It doesn’t show them separately.

      This should be fixed with the future update that will clarify these numbers. Keep a look out early this summer for a much better look to the graph (I’ll post some previews if/when I can).

    • #7712 Report Abuse
      dr_zerocool
      Member

      @emporiainfo Is the new app version still planned to be released this summer?

      My 11kW solar system is going in this week and I need to understand if I need to reconfigure the CTs to get proper readings in the app.

      My Emp 2 has been running great for months (since Dec I believe) and I don’t feel like rocking the boat. My solar install will have line side taps. The utility will go into an ATS. There will be no solar breaker in the main breaker panel just a generator breaker as an extra backup source to backfeed home when the grid goes down and solar is not generating enough juice. I was planning to move one of my 50A CTs to this generator breaker to measure that production when turned on. Will this work?

      The solar inverter is going to drive the main breaker panel as its load. It’s a hybrid inverter so grid, solar, and generator all connects to the inverter unit.

      I am thinking to leave setup as-is and simply use the inverter app to monitor solar, grid, and battery levels. The 200A CTs on the main panel will monitor the overall home consumption with the 50A CTs providing the individualized breakout as normal. Does that sound right?

    • #7713 Report Abuse
      dr_zerocool
      Member

      One correction…the main breaker panel is a load to the inverter only when the ATS senses no grid power and switches over to the other ATS input leg that is driven by the hybrid inverter load out. The default ATS input leg is the normal grid up operation and power is fed back and forth to utility over the tapped line.

      • This reply was modified 5 months ago by dr_zerocool. Reason: fix you
    • #7715 Report Abuse
      msturtz
      Member

      It would help a bit if you provided some sort of one-line drawing…

      The Emporia Vue2’s main CT’s have to measure the net.  If you have a line-side tap, you need those CT’s on the upstream (utility) side of the taps.  If you have an Auto Transfer Switch (ATS) for a home standby generator in front of the main panel, your line-side taps are most likely upstream of the ATS:  Utility -> Meter -> (taps here) -> ATS -> main panel  …  In this case, the ATS basically is your main panel, and your main panel becomes a sub-panel.  The Vue’s main CT’s need to be between the Meter and the Taps.  Then you can add one of the smaller CT’s on the solar side of the taps if you want to monitor your solar separately, along with whatever other loads you want to monitor — you’re exactly right.  If you have a contractor adding all this for you, they should be able to move the CT’s if you aren’t comfortable doing it yourself.  If you prefer, you can do as you suggested — let the Vue just monitor the house, and not measure the solar at all, and let the inverter’s monitoring give you the solar production as well as the Net.  I’d imagine that’s fine too.

      I’m confused though…  You mentioned an ATS, and you also mentioned backfeeding a generator, on the main panel.  It is absolutely imperative that you NOT backfeed a generator.  You MUST connect a generator the right way, or somebody will get hurt or killed.  Check this out:  https://www.youtube.com/watch?v=XlLkD1ir2t8  ….  If you have an actual Auto Transfer Switch, then you’re good — utility power drops, which will also knock out the solar, the ATS will start the generator and switch the house over, and reverse all that once utility power is back.  If you have a solar battery (Power Wall) providing backup power, your contractor will do this the right way as well.  If you want both, your solar should be upstream of the ATS, so that the ATS will only see the utility power if/when the solar battery is depleted.  It is critical that you understand this though — Do.Not.Ever.Backfeed.A.Generator.

       

      • This reply was modified 5 months ago by msturtz.
      • This reply was modified 5 months ago by msturtz.
    • #7718 Report Abuse
      scrambler
      Member

      A line drawing would definitely be a good idea.

      Just keep in mind that right now only the 200A CTs report bidirectional data.

      The 50A CT for now do not (EE said they will at one point in the future), so if they are on anything that has power flowing in both direction depending on the situation, you wont be able to know that from the reported values.

    • #7721 Report Abuse
      dr_zerocool
      Member

      Thank you @msturtz and @scrambler for the inputs. I really appreciate it. Sorry for my earlier ramble. Re-reading it I see how it may be somewhat confusing. You both are also correct that I should have posted a diagram. See attached.

      I went over the drawing with the inverter tech support and with the solar company who will be bringing in a master electrician for the install. I did the Vue 2 install myself and my main panel is recessed in the garage wall so running lines between that box and others for the Vue may be problematic.

      My main goal is to keep the visibility I have into the 16 50A CT loads. As noted in the diagram, the generator will be connected to a NEMA plug which will be connected to the inverter. I need to confirm with the solar company that they will add an interlock to avoid backfeeding the utility line when the generator breaker is manually turned on. They will need to do something to pass inspection.

      Sorry again for the confusion. Solar Setup Connection

      • This reply was modified 5 months ago by dr_zerocool. Reason: Typos
    • #7723 Report Abuse
      dr_zerocool
      Member

       I need to confirm with the solar company that they will add an interlock to avoid backfeeding the utility line when the generator breaker is manually turned on.

      I forgot backfeed won’t be a problem since the generator plug will be connected to the inverter which will be unidirectional. I believe the isolation is handled within the inverter itself. So ignore the above line.

      If you all think I can just leave the Vue 2 as-is, I’ll ask the electrician not to mess with my setup in the main panel if possible.

    • #7773 Report Abuse
      dr_zerocool
      Member

      Hi again and thanks for the prior inputs. My solar install was completed and we were able to leave the Vue 2 as-is per earlier discussions. One follow-up question that I have is can I use the 50A CT to see how much solar energy I am offsetting my household load with? See diagram of current setup and potential 50A CT placement. The inverter app shows me solar generation, the emporia app shows my total household load, but I can’t see how much of that load is being addressed by the Utility vs. my solar system because of the line side tap. So far, I have been waiting a day and using the Utility website to see what usage they are reporting for the prior day and simply doing the math (Vue 2 daily use – Utility reported use = Solar energy consumed). Please let me know if you have additional suggestions for my use case. Thanks again!

      • This reply was modified 4 months, 2 weeks ago by dr_zerocool. Reason: Typos
    • #7775 Report Abuse
      msturtz
      Member

      The 50A CT’s only measure in one direction, not both, so if the indicated location is both “buying” and “selling” power, then the data will be incorrect.  If you’re only “selling”, then I’m pretty sure that will work just fine.

    • #7776 Report Abuse
      dr_zerocool
      Member

      Thank you @msturtz for the reply. I can’t remember is that a HW limitation or currently SW? The line will mostly be “selling” but will seldomly bi-directional as well, i.e. if I use grid pwr to charge batteries on a cloudy day.

    • #7777 Report Abuse
      msturtz
      Member

      I guess the Emporia folks will need to weigh in if that can or will be changed in software, as I’m not sure what the hardware looks like.  I’m telling you what I’ve read elsewhere.

      My system, as I described earlier in this post, I had to move the “main” 200A CT’s out beyond the line-side taps, this way they are seeing the NET usage, both buy and sell.  The downside is they don’t show the usage, only the net of use/produce.  Just like you, I added a smaller CT around just the solar (one of the two legs, but its balanced so correction factor 2 in the app works perfectly) — but my solar is just inverters, no battery, no generator.  That CT measures only production, which is also included in the “net” as I described.  This SHOULD mean the app can calculate usage by subtracting production from Net, but they don’t have that functionality.  In other threads they’ve said it’s coming, but they’re a small team, yada yada.  🙂  But that doesn’t help you in your situation.

      You almost need two separate devices, one measuring the various production, and one for your usage.  I’m not sure how that would work out though.

      Good luck!

    • #7778 Report Abuse
      scrambler
      Member

      The 50A CT has been said by emporia to be capable of measuring bidirectionally, but the SW right now is not doing it.

      They mentioned before that they do plan to support bidirectional reading on the 50A CT in the future, and all the solar homeowners hope it will be in the big summer update 🙂

    • #7783 Report Abuse
      dr_zerocool
      Member

      Roger that. Thanks to you two once again. I think all my current questions are answered. I will hold until that new SW update is eventually released.


      @emporiainfo
      , How is that summer SW update going?

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