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  • Grid-Tied Solar Panels & Backup Generator Electrical Hookup

    Hi Everyone. Brand new to the forum ... first post. I am building a new home/garage, and am putting about 30 365w panels on my roof. I am getting a "kit" containing the panels and Enphase IQ7A Microinverters on each panel. There will be no battery backup/storage. Here's my challenge:

    My utility company (located in San Diego, CA) is running the underground line on my ranch about 800' from the existing Hi Voltage Transformer to a smaller transformer to be located 100' from my 200-amp Main Breaker Panel, where they will mount their meter on the exterior wall next to my Panel. I intend to install a 22kW Generac Generator with a whole-house transfer switch (i.e. it covers everything in the breaker panel). I'm having a hard time figuring out how to diagram this system/hookup so it works correctly and with maximum efficiency. From what I've been told, and the research I've done, I would like to install the solar as a line side tap so I don't have to de-rate the main breaker. The proposed solar system will require a 60-amp breaker, so if I don't get this installed on the line side, I will have to de-rate my 200-amp breaker down to a 175 amp (if I can find it) or worse, a 150-amp main breaker. I know that the solar system must "shut down" if/when I lose grid power - not an issue.

    I'm looking for a "box" that will be mounted on my outside wall downstream from the utility company meter, and upstream of the generator transfer switch & main breaker panel. I can't seem to find such a device. I would think this would be easy ... utility meter to "connection box" where the solar will connect, then out to the Generac Whole-House transfer switch, and finally to the 200-amp Main Breaker Panel.

    I'm hoping that some of you that are much smarter with more experience than me can guide me on exactly what to do, in what sequence, and what product (if any) I could use to connect on the line side of my main panel (assuming of course the utility company will agree and approve). I've heard I can use some type of "alligator clamp" or something like that, but since everything is brand new, I'd LIKE this to look good and look like it was planned, with everything hidden neatly inside boxes!!! Thanks in advance for any/all help this forum can provide! Airborne!

  • #2
    Originally posted by Airborne View Post
    ........

    I'm looking for a "box" that will be mounted on my outside wall downstream from the utility company meter, and upstream of the generator transfer switch & main breaker panel. I can't seem to find such a device. I would think this would be easy ... utility meter to "connection box" where the solar will connect, then out to the Generac Whole-House transfer switch, and finally to the 200-amp Main Breaker Panel.
    ..........
    Is this issue complicated by your desire to not derate your panel? I would think the simplest thing would be connect the solar to the main panel. Just put two breakers there, one for solar and another for the sub panel. Then install a 150 Amp sub panel that would contain your loads and be controlled by the transfer switch. That way the solar is isolated from the generator when the generator is powering your sub panel. Am I missing something on the physical layout that makes that difficult? I don't know what you are planning to do with that "box" but that would be a good place for the transfer switch if I understand what you are trying to do.
    There are also solar ready panels that may not need that much derating. What kind of loads are you expecting that 150 Amps would not be sufficient especially when your solar is pumping out 60 Amps. Your generator will only put out less than 100 Amps. What does a typical Generac line drawing look like. I would be surprised if Generac does not have a solution?

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    • #3
      Thanks for the reply Ampster. Yes, I am looking to not have to de-rate my panel. Hence the desire to tie the solar in upstream from my panel, but downstream from the transfer switch. As I understand it, the solar setup has a way to know when grid power is lost, and it automatically shuts itself down, preventing a utility tech from frying himself. So if I've got the solar tied in downstream from the meter, then have the backup generator transfer switch downstream from the solar hookup, everything will work fine. If the grid goes down (1), then the solar shuts down (2), then the transfer switch kicks in (3) and tells the generator to crank up (4) and feed the 200-amp main breaker panel (5). And life is good. You are right - I MAY never need 200 amps for my main panel, but if I'm doing all this from scratch, why limit myself and have to reduce my main breaker to 150-amps? That's why I'm looking for this forum to help me figure out how to do what I've outlined, in terms of a box or boxes I can use to connect the solar immediately downstream from the utility meter. Hope that makes sense. To me it's like this: I buy a brand new Mercedes that can top out at 150 mph, but then the dealer puts on a governor that allows it to only go 120. Maybe I'll never GO 150mph, but I don't want to limit myself in case I ever want to.

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      • #4
        Okay, I understand your thinking. The issue I have observed with some of the 200 Amp panels I have looked at is there is not much room between the meter and the buss bars for a load side tap. Perhaps your electrician or supply house has a better selection of panels. I know when my solar was installed, I got a 200 Amp service but the panel was "solar ready" and did not have to be derated. However my solar was only 20 Amps. The solar breaker did have to go at the top of the buss bars because they were fed from the middle. That was where the 200 Amp breaker was and that may have been what made it "solar ready".

        I don't know the derating rules that well but it seems to me I have seen some discussions here or on another forum where there is some inconsistency with the derating rules when calculated at the sub panel level and that may be a question you can ask the electrician who will be installing this equipment. A friend has an old screw in fuse panel and the load side tap they did for him went to a box six inches from the meter in that panel that was a fused disconnect which served both purposes of a viable disconnect and protection of the solar circuit wiring of the load side tap. Good luck, it sounds like a nice project.
        Last edited by Ampster; 08-13-2020, 04:09 PM.

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        • #5
          Thanks Ampster. Yes, my system will require a 60-amp breaker, so my panel would definitely have to be de-rated if I put the breaker in the 200-amp Main Breaker Panel with everything else. What I am hoping someone is going to tell me is: "Hey Airborne! Take a look at the XYZ box; it's a panel that your meter feeds into, and the solar connects with a breaker, and then it feeds out to your transfer box/main breaker." It seems simple to me. I looked at the Eaton "Solar Ready" boxes and all of them are just regular main breakers with a spot for the solar!

          Comment


          • #6
            Originally posted by Airborne View Post
            ,,,,,,,,,,, What I am hoping someone is going to tell me is: "Hey Airborne! Take a look at the XYZ box;..........!

            Hey, Airborne, that is what I have been alluding to with a solar ready panel. I knew the concept but don't have the tools to do the calculation without spending a lot of time.

            Acording to this link
            https://www.eaton.com/us/en-us/catal...r-centers.html
            Their Solar Ready panel is designed to do that without derating. "Up to 225A rated copper bussing maximizes solar source up to 70A for standard units. "
            I tend to trust reputable manufacturers specs more than sales people but I would verify with an electrician or anyone who understands the NEC calculations better than I do. I could look it up and spend some time understanding more than the concept but those are details that I don't store very well so I will leave that up to you.

            I still think you would be wise to use a sub panel in conjunction with the transfer switch for loads that you know can be supported by the generator and to isolate it from the GT solar. That may also be a recommendation of Generac anyway. As a personal preference I like my breakers on an interior wall so I can lock my main panel for security and can get to my load breakers in the middle of the night if there is an outage that I need to check. That is also where my hybrid inverter is located..
            Last edited by Ampster; 08-13-2020, 05:42 PM.

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            • #7
              Originally posted by Ampster View Post

              Hey, Airborne, that is what I have been alluding to with a solar ready panel. I knew the concept but don't have the tools to do the calculation without spending a lot of time.

              Acording to this link
              https://www.eaton.com/us/en-us/catal...r-centers.html
              Their Solar Ready panel is designed to do that without derating. "Up to 225A rated copper bussing maximizes solar source up to 70A for standard units. "
              I tend to trust reputable manufacturers specs more than sales people but I would verify with an electrician or anyone who understands the NEC calculations better than I do. I could look it up and spend some time understanding more than the concept but those are details that I don't store very well so I will leave that up to you.

              I still think you would be wise to use a sub panel in conjunction with the transfer switch for loads that you know can be supported by the generator and to isolate it from the GT solar. That may also be a recommendation of Generac anyway. As a personal preference I like my breakers on an interior wall so I can lock my main panel for security and can get to my load breakers in the middle of the night if there is an outage that I need to check. That is also where my hybrid inverter is located..
              I don't think of the above answers are correct He's installing a whole house ATS ahead of the main panel Just do a fused disconnect supply side connection on the line side of the ATS.

              Andy

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              • #8
                Originally posted by PVAndy View Post

                I don't think of the above answers are correct He's installing a whole house ATS ahead of the main panel Just do a fused disconnect supply side connection on the line side of the ATS.
                Rereading his post I see that the meter may be separate from the Main panel and an ATS was going between the meter and his main panel. If I understand you correctly the fused disconnect for the solar would be on the supply (line side) of the ATS so when the grid is down the inverters are isolated from the generator.
                The 200 Amp ATS is $700 versus $300 for a 100 Amp switch but it is much simpler than a subpanel.
                Last edited by Ampster; 08-13-2020, 07:19 PM.

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                • #9
                  Yep. PVAndy has it right. Ampster, by the way - I actually saw that information on Eaton and called their tech support department. They acted like what I was doing was new news to them, and said they hadn't built a panel that would work! Go figure! This is a brand new installation, so I'm free to do what I want in terms of panels, connection boxes, where I hang them on the wall, etc. So essentially I'm an artist with a blank canvas, and I get to paint what I want, within guidelines handed down by the NEC and local government here in California.

                  So I think PVAndy has it right ... I do a fused disconnect supply side connection on the line side of the ATS in some type of a connection box, and then I'm good, and I don't have to de-rate my Main Breaker Panel. Thanks for the feedback to both of you. I've gotten a LOT smarter on this in the past 48 hours, and appreciate both of you taking the time to respond. If anyone else has thoughts, jump in!

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                  • #10
                    I rarely see an installation in California with a meter separate from the service panel so I could not go outside the box in my thinking. Andy also has had experience with Generac.,

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                    • #11
                      I am preparing for my solar install and upgraded to the Eaton BRP42BC225 panel I bought at Home Depot. It came with a 225 amp breaker, but brand new on eBay from another person’s derate got me a 200 amp main breaker for another $35.

                      Now, it’s a 42-space, 84-circuit panel, so you can see if they have a smaller one for your needs. Btw, it also has copper bus bars vs. aluminum. My install just completed a few hours ago and is await a rough-in inspection.

                      Would this panel work as your main and make feed the ATS, which then feeds the subpanel that is the “main” for the house?

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                      • #12
                        I think that would work great CycloneFW ... I just need to get the outdoor-rated version. Thanks for the tip!

                        Comment


                        • #13
                          Originally posted by Airborne View Post
                          I think that would work great CycloneFW ... I just need to get the outdoor-rated version. Thanks for the tip!
                          No problem. Gotta thank Ampster and others as their prodding in my thread led me to searching for “solar ready panels”, which I found to be more than I wanted to spend. However, by chance, I searched for 225 amp without the “solar ready” keyword and voila, that’s the panel I found.

                          FYI, even though I bought it from Home Depot, it was shipped directly from Eaton to me via FedEx Ground.

                          Comment


                          • #14
                            Originally posted by Airborne View Post
                            Yep. PVAndy has it right. Ampster, by the way - I actually saw that information on Eaton and called their tech support department. They acted like what I was doing was new news to them, and said they hadn't built a panel that would work! Go figure! This is a brand new installation, so I'm free to do what I want in terms of panels, connection boxes, where I hang them on the wall, etc. So essentially I'm an artist with a blank canvas, and I get to paint what I want, within guidelines handed down by the NEC and local government here in California.

                            So I think PVAndy has it right ... I do a fused disconnect supply side connection on the line side of the ATS in some type of a connection box, and then I'm good, and I don't have to de-rate my Main Breaker Panel. Thanks for the feedback to both of you. I've gotten a LOT smarter on this in the past 48 hours, and appreciate both of you taking the time to respond. If anyone else has thoughts, jump in!
                            Thanks, you don't need a separate box, just od the connection either on the lugs or with insulation piercing lugs on the supply wires. We do this all the time

                            Andy

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                            • #15
                              PVAndy - I'll show my ignorance ... what is "OD the connection" and can you explain a little more about how you do this, and with what "lugs" or other items you use? It sounds like that is the way to go.

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