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Thread: AC Coupled Battery Backup Install Questions

  1. #11
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    Quote Originally Posted by Alex-Sun Energy Solutions View Post
    Ahhh I see what you're saying. This is one of the reasons I wanted to be behind the main breaker, if it's just as simple as switching the breaker manually. Enphase must have something up their sleeve but like you and others have said it is likely a transfer switch which the other battery manufacturers rely on as well.

    I've seen the smart breakers, maybe there will be a SMART main that toggles off when there's no voltage. This wouldn't really help all my other clients who have taps above the main because of the 20% rule (can only backfeed 40 amps of solar on 200 amp service). Now that I think of it this may be an inhibitor for this system as well. We will have a total of 80 amps for the solar circuits. I may have to tap it in above the main breaker.

    Back to the drawing board...
    The NEC would never accept any hybrid system which could produce power with no grid input in which safe operation required manual operation of a main breaker for isolation! Unless maybe there were some automatic interlock which disabled island operation when the main breaker was not known to be open.

  2. #12
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    Quote Originally Posted by Alex-Sun Energy Solutions View Post
    ... This wouldn't really help all my other clients who have taps above the main because of the 20% rule (can only backfeed 40 amps of solar on 200 amp service). Now that I think of it this may be an inhibitor for this system as well. We will have a total of 80 amps for the solar circuits. I may have to tap it in above the main breaker.

    Back to the drawing board...
    One strategy is to move enough loads out of the MSP (to the critical loads panel) to qualify the MSP under 705.12(B)(2)(3)(c).

  3. #13
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    Quote Originally Posted by jaggedben View Post
    One strategy is to move enough loads out of the MSP (to the critical loads panel) to qualify the MSP under 705.12(B)(2)(3)(c).
    Thanks for rolling onwards with this design. So I google searched this and came back across another posting on this forum which discussed this. Some of you are on that thread as well

    https://forums.mikeholt.com/showthread.php?t=188070

    The details of that are getting a bit over my head. I do have some experience with the NEC, code complaince, etc. But my background is Mechanical Engineering, and my electrical work and code knowledge has all been learned in the field and doing research. I worked on commercial solar design for a year before starting my own company, so residential electrical design was never studied or practiced. I converse with my master electrician, but a lot of this design work is above his skill level. I generate all the 1 and 3 lines for my projects. I think this forum is going to be invaluable as well, so I thank you all tremendously for helping me out. I will definitely post pictures and the finished installation when we get to that point.

    I did some research on feed thru lugs, and came across this schematic by Schneider.

    Name:  SF lugs, FT lugs, SF Breaker.jpg
Views: 40
Size:  106.6 KB

    Is this what you would be referring to? The last two options seem like it would be the same scenario as the 120% rule, basically being able to send 200 amps to the bus from the main breaker, and the 60 or 80 amps from the backfeed solar as well. But the first option, the Sub Feed Lug, seems like it may work in that you would still be protected by 200 amps for the main breaker?


    That being said, I am not really following what simply moving enough loads out of the MSP would accomplish? Is the idea to downsize the main breaker to then be able to backfeed? I thought the 120% rule was based off the main breaker size only, not necessarily the ampacity rating of the bus. (If you downsize to 100 amp main breaker you would be limited to 20 amp backfeed). That wouldn't really make sense from a physics standpoint, as the bus can definitely handle 100 amps + 80 amps solar, but I thought the code was simply 120% main breaker rating, which is 40 amp backfeed for 200 amp main breaker, 20 amp backfeed for 100 amp main breaker.

  4. #14
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    Read the section I quoted again. The 120% rule isn't the only rule anymore. I quoted the 2017 reference since you appear to be in MA.

    As far as the subfeed lugs and breakers, those are all options with their own conderations. But what I had in mind was breakers such as the Homeline 2200BB or the Eaton BJ2200.

  5. #15
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    Quote Originally Posted by jaggedben View Post
    Read the section I quoted again. The 120% rule isn't the only rule anymore. I quoted the 2017 reference since you appear to be in MA.

    As far as the subfeed lugs and breakers, those are all options with their own conderations. But what I had in mind was breakers such as the Homeline 2200BB or the Eaton BJ2200.
    Well that explains it, haven't opened my code book since NEC 2014.

    Looked it up more in depth and thank you for the extra nudge. Here's a link I found explaining the section.

    https://www.jadelearning.com/2014-ne...ions/image3-2/

    I think I understand that code change. Basically move enough loads to the subpanel, and keep the OCPD of the subpanel + remaining loads in the MSP below 200 amps and it is in code.

    What exactly do those breakers you referenced accomplish? I looked them up but am not really following.

    They are also referenced in this thread from this forum, which is pretty much exactly what I am trying to do, install a second 200 amp panel. They also mention going up to a 400 amp meter socket with double lugs. This may be a more cost effective route if I were the electrician, but since I am not I have to consider his time on site. It may be more cost effective for my bottom line to use an expensive breaker and keep it simpler than replacing the meter socket and re-pulling feeders.

    https://forums.mikeholt.com/showthread.php?t=134839

    Hopefully I can understand those breakers a bit more tomorrow after some sleep

  6. #16
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    Quote Originally Posted by DeFreitas Enterprises View Post
    At least Enphase isn't as slimy on unveiling then delaying products like TESLA (solar roof, etc).

    Oh no, they're slimy in all kinds of different ways.

    I have PO's open since mid '18 for lots of equipment that haven't been fulfilled. I was forced to move to SolarEdge for all my resi installs because I just couldn't get equipment even on the open market, and there is a very SLIM chance I'll ever go back unless a very narrow set of conditions are met.

    But don't worry, they will offer customers an upgrade program to the same equipment that they can't even fulfill current orders for to fix all the problems they had with M190's.

  7. #17
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    Quote Originally Posted by Whalepod View Post
    Oh no, they're slimy in all kinds of different ways.

    I have PO's open since mid '18 for lots of equipment that haven't been fulfilled. I was forced to move to SolarEdge for all my resi installs because I just couldn't get equipment even on the open market, and there is a very SLIM chance I'll ever go back unless a very narrow set of conditions are met.

    But don't worry, they will offer customers an upgrade program to the same equipment that they can't even fulfill current orders for to fix all the problems they had with M190's.
    Having business problems isn't the same as being slimy. Enphase has been open with distributors about what's going on in a way that Tesla never would be. They've been hit with tariffs like many. Also, how is it slimy to offer past customers below-cost replacement of an inferior product 8 years later? What company in any industry have you ever heard of being that generous?
    SolarEdge has its own problems, you'll find out. But there are reasons these companies are at the top of the market right now.

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