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Final tire kicking for my new system

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  • Final tire kicking for my new system

    After a couple of rounds of discussion here I think I've nailed down all of the specifics of my new system for a remote cabin. I want to thank all those who contributed because I'd not have gotten this far without you! Now it's time to see if I wound up in the right place

    This is a DC only system (*no* hardwired inverter) powered by three 265W panels wired in series. They feed into a home made 10AGW Y connector that combines two MC4 and an outdoor Anderson plugs. The Y connector feeds the panel power into 6AGW direct burial wire for 100' until it arrives at a 150v/35A charge controller. The charge controller connects to two AGM batteries wired in series with 8AGW and a 40A breaker between the controller and battery bank. From the batteries is a few feet of 10AGW that connects to a junction box which splits power to two different feeds. The first feed is a dedicated line of 14AGW for a high efficiency 24v DC conversion of an old Servel gas refrigerator protected by its own 5A fuse (max rated draw is 3.2A). The second feed is a 10AGW line to a 12v to 24v stepdown protected by its own 30A fuse. The stepdown feeds a single 10AGW daisy chain circuit designed to power all manner of 12v stuff, from lights to USB charging, from about a half dozen points. When I need 110v I have small and medium sized inverters which I can plug into the 12v circuit.

    How does this system look to you all? Have I covered my bases adequately? A previous discussion about VOC reassured me that due to the peculiarities involved I shouldn't have a problem with overcharging the controller.

    Thanks!!

    Steve
    Attached Files

  • #2
    1) I would really suggest you add a DC breaker to be used as a switch, near the Anderson connector for the PV . If you disconnect the Anderson with power on it, you will likely get a damaging arc, and, for troubleshooting, you will want an easy way to turn off the solar to the charge controller.

    2) I see no provision for a battery fuse to protect the + battery and + DC cables. 10ga wire needs 30a limit

    3) is 40A breaker rated for 30V (charging voltage from controller)

    4) Lightning ground and surge protection ?
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Hi Mike,

      1) Ah yes, DC breaker at the panel side. Would a MC4 15A inline fuse between the panel's hot and the Anderson do the trick? I understand a breaker box would be optimal, but those look pricey.

      2) I'm not sure I follow you. There's the 40A breaker between the source and batteries as well as individual fuses between each of the draws and the batteries. Do you mean I should have a 30A fuse/breaker between the two batteries?

      3) Yes, the 40A breaker is rated up to 48v.

      4) I did neglect to put in the grounds. I have a grounding rod which I'll connect to the controller, the batteries, and the junction box (dispensing to the two draws). Does that do it? For surge protection I'm going to rely upon the fuses and breakers. This is on a tiny island so if there's a lightning strike I'm going to have a lot more to worry about than a burned up iPad. Or maybe I won't worry about anything because I'll be dead

      Thanks!

      Steve

      Comment


      • #4
        1) Ah yes, DC breaker at the panel side. Would a MC4 15A inline fuse between the panel's hot and the Anderson do the trick? I understand a breaker box would be optimal, but those look pricey.
        A fuse cannot function as a switch, as in starting the controller :
        Apply battery power first, and after the controller boots up, apply PV power.
        So.... you either have to do all work at night, or learn how to arc weld with copper electrodes.



        2) I'm not sure I follow you. There's the 40A breaker between the source and batteries as well as individual fuses between each of the draws and the batteries. Do you mean I should have a 30A fuse/breaker between the two batteries?
        But there is no breaker or protection for the wires leaving the batteries, going to the loads. Loads seldom fail. Wires short out more often. So the WIRE needs a fuse, not the load. If you split your DC wires to 3 directions, then you need to size the wires to fit the breaker scheme, either 3 breakers, or 1 breaker for max load, and wire sizes to be safe on the breaker. You can add fuses at the loads, but it won't do much for you. Think of a house - the fuse box is at the power source, not a fuse at each outlet.
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          Originally posted by Mike90250 View Post

          So.... you either have to do all work at night, or learn how to arc weld with copper electrodes.
          Sounds like too much fun for me. I'll instead suck it up and invest in a weather proof cutoff.

          Think of a house - the fuse box is at the power source, not a fuse at each outlet.
          Ah, that makes sense now Obviously I was fixed on the potential for damage coming from something shorting out or drawing too much power, not something like me running a sawzall through the wire. Er, something I've never EVER done before. That's my story and I'm sticking to it.

          OK, other than these two issues and making sure I ground in the three places I noted, my homework looks good?

          Steve

          Comment


          • #6
            OK, here's an updated schematic with the above feedback incorporated. Hopefully I've got this nailed down.

            Thanks Mike!

            Steve
            Attached Files

            Comment


            • #7
              OK, more questions.
              The panels, have a sereis of numbers under them, is the Voc per panel. or per array?
              if per panel, that brings your system Voc to 132.6v on a warm morning, on a frosty morning it going to be close to 165 Voc, which will for sure fry a 150v charge controller.

              What is the blue square right about the batteries, with + & - and gnd symbol ?


              Nobody ever intends to run a hedge clipper over it's power cord, but it happens all the time !
              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

              Comment


              • #8
                Originally posted by Mike90250 View Post
                OK, more questions.
                The panels, have a sereis of numbers under them, is the Voc per panel. or per array?
                if per panel, that brings your system Voc to 132.6v on a warm morning, on a frosty morning it going to be close to 165 Voc, which will for sure fry a 150v charge controller.
                Per panel. Yup, there is a danger of VOC exceeding the 150v mark. We had a discussion on that topic in an earlier thread. The conclusion is that since I'm not using this in the winter I should be fine. The math I did suggests even a cold bout in Spring or Fall should not exceed the 150v mark. IIRC I came up with 147.5v based on the coldest morning weather I'm likely to experience while the system is up and running. Worst comes to worst I can use that fancy cut off box to switch off the panels the night before and then switch them on after things warm up.

                What is the blue square right about the batteries, with + & - and gnd symbol ?
                Weather proof junction box so I can split the source down two directions.


                Nobody ever intends to run a hedge clipper over it's power cord, but it happens all the time !
                I still stand by my story that I never put a sawzall through a 110 line. And if you speak with the three so-called "witnesses", know that my position is that they are liars and conspiring to tarnish my reputation. Plus, if it did happen, then why didn't one of the "witnesses" (aka homeowner) tell me there was a wire behind where he asked me to cut? Just saying...

                Thanks Mike!!

                Steve

                Comment


                • #9
                  Originally posted by SolarSteve View Post

                  Per panel. Yup, there is a danger of VOC exceeding the 150v mark. We had a discussion on that topic in an earlier thread. The conclusion is that since I'm not using this in the winter I should be fine. The math I did suggests even a cold bout in Spring or Fall should not exceed the 150v mark. IIRC I came up with 147.5v based on the coldest morning weather I'm likely to experience while the system is up and running. Worst comes to worst I can use that fancy cut off box to switch off the panels the night before and then switch them on after things warm up.

                  Steve
                  You do know that in the cold dark of predawn and for a time after the sun comes up, a panel's temperature can be lower than the air temp. and, depending on atmospheric conditions including dew point, wind and a few other things, and stay that way for some time, right ?
                  Last edited by J.P.M.; 07-05-2018, 01:09 PM.

                  Comment


                  • #10
                    Originally posted by J.P.M. View Post

                    You do know that in the cold dark of predawn and for a time after the sun comes up, a panel's temperature can be lower than the air temp. and, depending on atmospheric conditions including dew point, wind and a few other things, and stay that way for some time, right ?
                    Yup, but we have a huge margin of error because of when it will and won't be hooked up.

                    Using the MidNite Solar system calculator I figured the VOC danger level is somewhere under 10F, more approaching 5F. In our neck of the woods that doesn't even come close to being a risk until December and never after March. We open up late May and close late October, so we'll never get close to the VOC problem no matter what variables are added to the equation. Plus, the panels are shaded to the east, which gives even more margin for error as it will take several hours of light before the panels get hit directly.

                    The MidNite Solar calculator is quite handy...

                    http://www.midnitesolar.com/sizingTo...playSizing.php

                    I can't say this enough... I know this system would fail as a year round system in our climate. This year we had nearly 2 weeks of below zero weather with one daytime high of something like -12F even with full sun IIRC. This system would be toasted first year, for sure, if it was a year round system. But it's not and that makes all the difference. At least according to the math!

                    Steve
                    Last edited by SolarSteve; 07-05-2018, 06:41 PM.

                    Comment


                    • #11
                      Originally posted by SolarSteve View Post
                      Worst comes to worst I can use that fancy cut off box to switch off the panels the night before and then switch them on after things warm up.
                      Never, EVER depend on the actions of a user to protect a system from damage.

                      There are chargers out there that will survive (not operate, but survive) during significant overvoltages. Midnite Solar has something called hyperVOC, for example, that will protect their controller under cold/high voltage conditions.

                      Comment


                      • #12
                        Originally posted by SolarSteve View Post

                        Yup, but we have a huge margin of error because of when it will and won't be hooked up.

                        Using the MidNite Solar system calculator I figured the VOC danger level is somewhere under 10F, more approaching 5F. In our neck of the woods that doesn't even come close to being a risk until December and never after March. We open up late May and close late October, so we'll never get close to the VOC problem no matter what variables are added to the equation. Plus, the panels are shaded to the east, which gives even more margin for error as it will take several hours of light before the panels get hit directly.

                        The MidNite Solar calculator is quite handy...

                        http://www.midnitesolar.com/sizingTo...playSizing.php

                        I can't say this enough... I know this system would fail as a year round system in our climate. This year we had nearly 2 weeks of below zero weather with one daytime high of something like -12F even with full sun IIRC. This system would be toasted first year, for sure, if it was a year round system. But it's not and that makes all the difference. At least according to the math!

                        Steve
                        I was simply asking if you knew that panel temps. can be significantly lower than air temps. under a lot of common conditions. How you run the system is immaterial to me. Forget I brought it up.

                        Comment


                        • #13
                          Originally posted by jflorey2 View Post
                          Never, EVER depend on the actions of a user to protect a system from damage.
                          Generally that's fantastic advice that I follow. I included the unhook possibility just to be complete. If the science isn't lying to me, I'll never, ever, ever have to worry about going over 150v unless we start to get a new ice age. Given how things are going I doubt that's a serious risk.

                          There are chargers out there that will survive (not operate, but survive) during significant overvoltages. Midnite Solar has something called hyperVOC, for example, that will protect their controller under cold/high voltage conditions.
                          I read about that feature when researching VOC factors. The MidNite Solar calculator I noted above takes that into consideration, which is cool to see when casing out various scenarios. However, while HyperVOC does protect the controller from turning into a "ball of flames", it isn't doing any charging while in HyperVOC mode. If I were to try and use this system in the winter that wouldn't work for me. Over the course of the winter I'd have several days straight where I'd never get any charge (i.e. the temp is too low all day), about two weeks solid of no charge in the morning hours, and a dozen hours scattered throughout the winter that would be wasted. Maybe more. So I'd have a perfectly good charge controller and empty batteries. Not ideal Therefore, if I were to use this system in the winter I'd need a charge controller that could handle 200v straight up.


                          OK, so it seems like I've got the system I need for my peculiar circumstances. Thanks to everybody who's contributed to this and the previous advice threads. It's been a massive help and I'll start assembling it this weekend. The big unknown now is whether I've sized it correctly for my purposes. I should know that by early August after the big wave of family hits our shores. If you saw how they use a fridge you'd know what I'm talking about. Feels like they exceed 100 door openings/closings to make a flipp'n sandwich!

                          Steve

                          Comment


                          • #14
                            Originally posted by J.P.M. View Post

                            I was simply asking if you knew that panel temps. can be significantly lower than air temps. under a lot of common conditions. How you run the system is immaterial to me. Forget I brought it up.
                            I asked for opinions, you provided. Thank you for that. The way I work is if someone takes the time to offer up advice, I feel an obligation to take the time to demonstrate that I've read and understood it. Sometimes unexpected turns come from discussion, so it's time well spent IMHO. For someone who is planning to use a system through the winter, which someday might be me, the comments here could make the difference between a system that works and one that burns up. So no, I will not forget you brought it up because it's good info

                            Steve

                            Comment


                            • #15
                              Originally posted by SolarSteve View Post
                              Generally that's fantastic advice that I follow. I included the unhook possibility just to be complete. If the science isn't lying to me, I'll never, ever, ever have to worry about going over 150v unless we start to get a new ice age.
                              OK. I thought you said that at lowest possible temperature you were overvoltage. If that's not the case then no problem.
                              However, while HyperVOC does protect the controller from turning into a "ball of flames", it isn't doing any charging while in HyperVOC mode. If I were to try and use this system in the winter that wouldn't work for me. Over the course of the winter I'd have several days straight where I'd never get any charge (i.e. the temp is too low all day)
                              Once the sun is up the panels get much warmer. If you have that problem even with warm panels then you absolutely have to go with a 200V controller - or a different panel arrangement.



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