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  • Parents bought a house with solar panels, a few questions.

    Hello, I apologize for posting on the forum as I am very new to this, but my parents have recently purchased a house near Manassas VA with 5 solar panels and we need your help. The former owner told them that he had them hooked up to x6 12V car batteries and was using them to power his swimming pool pump. The former owner took everything with him when he moved out, but left the panels. The only other information that the former owner told us is that the panels were making 2kW/day, but we will have to pull the panels off and look at the backside of them for the exact specs. Judging by the condition that the former owner left the house in, I don't know if I trust anything he says.

    I was able to find out that the former charge controller that he was using was an ebay style controller, PWM 30A Solar Charge Controller, pretty inexpensive.

    The pool pump is a Zodiac brand, but the motor is a Jandy VS-FHP2.0. According to those specs it's 230V and 2400W at it's highest setting, which runs for about 2 hours a day, then goes to a lower setting for the rest of the day. 2400W seems like a lot for only the 5 panels, even if it's for only a couple of hours.



    My questions for you are what information can I use to get us started in figuring this out? Will a 12V or 24V system be better for us, how many batteries are needed, will I then need a 3000W inverter and a switch that will put the pump back on the house if the batteries get low? Is this even worth it at all or should I use the panels for something less critical? Any help is appreciated, thank you.

  • #2
    off grid systems are not worth much and not likely to save you any money.

    Further those modules do NOT look to be mounted at all correctly, safely, or to code.
    I would pull them all off, check them out and see if they are worth anything. If so you could then get them properly mounted with some rails like from ironridge etc.
    get a permit, interconnect and some micros to handle them.
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

    Comment


    • #3
      5 panels is a tiny 'system'. We have 10 panels. When we did our install calculations showed that it can only produce about 60% of our monthly consumption. So you have some decisions to make, beginning with what do you want your solar power to do for you?

      Would you be happy with it powering your swimming pool?

      We live in an area with frequent grid outages, we wanted power even through the grid outages.

      We learned a lot by talking with off-grid neighbors and looking at their systems. A 12vdc system is extremely simple and reliable [and cheap]. One of our neighbors wired his entire home to run on 12vdc back in the 1980s, and it still works for him.
      4400w, Midnite Classic 150 charge-controller.

      Comment


      • #4
        The former owner of this house jerry-rigged just about everything in there, so I have no doubt that they aren't mounted properly and need to be re-set. Do the panels need permitted if I'm not planning on doing anything with the grid? And outages are very infrequent in their area, so they don't have a lot to worry about. Since a 2hp pool pump can cost $50-100/month or more, they would be more than happy to run the pump off of the panels. The panels have all been daisy chained together and a pair of wires dropped to the basement where the former owner had his set-up installed. I'm guessing by micros, you are referring to micro-inverters, which is fine, but I have no clue as to how to figure out what is needed or what the panels are capable of. Could I bounce some basic maths off of you to see if I am headed in the right direction? Google is only so helpful, and experience is much more valuable. If I'm jumping steps here, let me know.

        Solar Panels: My dad needs to check the specs on the back of one of them to get the exact numbers, but let's say for now that the former owner is correct and the total panels produce 2kW/day and use a worst case scenario for the rest of the equipment.

        Pool Pump: 2HP 2400W 230VAC variable speed. Let's say under worst case scenario it runs at full speed for 10hrs/day.

        Inverter: The current pump is 2400W at full power, so the inverter that he would need would have to be 3000W 12VDC-230VAC.

        Charge Controller: Use the same 30A controller that the former owner was using.

        Batteries: Since the pump is 2400W @ 230V, the amperage is 10.5A. Assuming the batteries are 40Ah, each battery could run the pump for 3.8hrs. Of course we don't want to discharge the batteries down this low, so let's say we want 40% of the battery discharged, so that means that each battery could run the pump for 1.5hrs. I would need at least 7 batteries in parallel to run the pump for 10hrs/day. I guess the former owner having 6 batteries wasn't that far off, perhaps he depleted them to 50%.

        Switch? Is a switch needed to put the pump back on house power if the batteries get below the 60% discharge? Can this even be done? Or is it easier to just unplug it from the inverter and plug it back into the wall if the batteries are depleted?

        Extra: I'm not sure if diodes and fuses are needed, but they are inexpensive, so why not.

        Am I doing this right?

        Comment


        • #5
          Originally posted by ssjneko1 View Post
          The former owner of this house jerry-rigged just about everything in there, so I have no doubt that they aren't mounted properly and need to be re-set. Do the panels need permitted if I'm not planning on doing anything with the grid?
          In most places yes. and most likely in Manassas. If they are attached to an occupied home yes.

          Originally posted by ssjneko1 View Post
          And outages are very infrequent in their area, so they don't have a lot to worry about. Since a 2hp pool pump can cost $50-100/month or more, they would be more than happy to run the pump off of the panels. The panels have all been daisy chained together and a pair of wires dropped to the basement where the former owner had his set-up installed. I'm guessing by micros, you are referring to micro-inverters, which is fine, but I have no clue as to how to figure out what is needed or what the panels are capable of. Could I bounce some basic maths off of you to see if I am headed in the right direction? Google is only so helpful, and experience is much more valuable. If I'm jumping steps here, let me know.
          just take a photo of the spec sticker on the back of one of the modules.



          Originally posted by ssjneko1 View Post
          Solar Panels: My dad needs to check the specs on the back of one of them to get the exact numbers, but let's say for now that the former owner is correct and the total panels produce 2kW/day and use a worst case scenario for the rest of the equipment.

          Pool Pump: 2HP 2400W 230VAC variable speed. Let's say under worst case scenario it runs at full speed for 10hrs/day.

          Inverter: The current pump is 2400W at full power, so the inverter that he would need would have to be 3000W 12VDC-230VAC.

          Charge Controller: Use the same 30A controller that the former owner was using.

          Batteries: Since the pump is 2400W @ 230V, the amperage is 10.5A. Assuming the batteries are 40Ah, each battery could run the pump for 3.8hrs. Of course we don't want to discharge the batteries down this low, so let's say we want 40% of the battery discharged, so that means that each battery could run the pump for 1.5hrs. I would need at least 7 batteries in parallel to run the pump for 10hrs/day. I guess the former owner having 6 batteries wasn't that far off, perhaps he depleted them to 50%.

          Switch? Is a switch needed to put the pump back on house power if the batteries get below the 60% discharge? Can this even be done? Or is it easier to just unplug it from the inverter and plug it back into the wall if the batteries are depleted?

          Extra: I'm not sure if diodes and fuses are needed, but they are inexpensive, so why not.

          Am I doing this right?
          you are really bouncing way down the wrong path. Go grid tie and get far better efficiency from them, you can still offset the pool pump as well as anything else.
          less equipment, no batteries, no complicated calculations. It just isn't going to work very well off grid.
          AND no Diodes are needed but YES fuses are definitely needed.

          OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

          Comment


          • #6
            Originally posted by ssjneko1 View Post
            Am I doing this right?
            Not really. Regardless of the battery size, you need to look at your ability to replenish it. You need to distinguish power from energy. 8 panels at 250 W DC rating would be a PV array rated for 2 kW. I don't know where you are located, but a 2 kW system ideally mounted in San Diego would produce something like 12 kWh on a good day in the summer. Your system will produce less... you can tinker with PVWatts for your specific location and the mounting orientation of your panels, but you may also have to take some loss for shade.

            For your pump, the inverter needs to be sized to handle the starting surge, which could a few times greater than the running load. A 3 kW inverter with 6 kW surge capability *might* work, but you probably need to go even larger.

            You are mixing up output amperage (10.5 A @ 230 V) with the input condition. To deliver 2400 W from a 12 V is 200 A of current. That won't work. If you want to keep discharge less than 50%, to run the pump for just *one* hour you'd need something approaching 6 kWh of storage, once you account for the inverter efficiency and other losses. 6 kWh of storage at 24 V is 250 Ah.

            You could build a 24 V, 225 Ah battery by putting 4 T-105 in series, at a cost of around $600 or more. I think you'll find that if you do the math, you are much better off just leaving the pump attached to the grid.

            Your best chance to get some value from those panels would be to get a permit, properly install them, and make it a grid-tied system (assuming you have some kind of net metering where you are at).
            Last edited by sensij; 07-31-2017, 12:26 PM.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

            Comment


            • #7
              Originally posted by sensij View Post
              I don't know where you are located, but a 2 kW system ideally mounted in San Diego would produce something like 12 kWh on a good day in the summer. Your system will produce less...

              Your best chance to get some value from those panels would be to get a permit, properly install them, and make it a grid-tied system (assuming you have some kind of net metering where you are at).
              He is in Manassas VA outside of Washington DC.

              VA has net metering. https://www.dominionenergy.com/home-...s/net-metering
              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

              Comment


              • #8
                Originally posted by ssjneko1 View Post
                The former owner of this house jerry-rigged just about everything in there, so I have no doubt that they aren't mounted properly and need to be re-set. Do the panels need permitted if I'm not planning on doing anything with the grid? And outages are very infrequent in their area, so they don't have a lot to worry about. Since a 2hp pool pump can cost $50-100/month or more, they would be more than happy to run the pump off of the panels. The panels have all been daisy chained together and a pair of wires dropped to the basement where the former owner had his set-up installed. I'm guessing by micros, you are referring to micro-inverters, which is fine, but I have no clue as to how to figure out what is needed or what the panels are capable of. Could I bounce some basic maths off of you to see if I am headed in the right direction? Google is only so helpful, and experience is much more valuable. If I'm jumping steps here, let me know.

                Solar Panels: My dad needs to check the specs on the back of one of them to get the exact numbers, but let's say for now that the former owner is correct and the total panels produce 2kW/day and use a worst case scenario for the rest of the equipment.

                Pool Pump: 2HP 2400W 230VAC variable speed. Let's say under worst case scenario it runs at full speed for 10hrs/day.

                Inverter: The current pump is 2400W at full power, so the inverter that he would need would have to be 3000W 12VDC-230VAC.

                Charge Controller: Use the same 30A controller that the former owner was using.

                Batteries: Since the pump is 2400W @ 230V, the amperage is 10.5A. Assuming the batteries are 40Ah, each battery could run the pump for 3.8hrs. Of course we don't want to discharge the batteries down this low, so let's say we want 40% of the battery discharged, so that means that each battery could run the pump for 1.5hrs. I would need at least 7 batteries in parallel to run the pump for 10hrs/day. I guess the former owner having 6 batteries wasn't that far off, perhaps he depleted them to 50%.

                Switch? Is a switch needed to put the pump back on house power if the batteries get below the 60% discharge? Can this even be done? Or is it easier to just unplug it from the inverter and plug it back into the wall if the batteries are depleted?

                Extra: I'm not sure if diodes and fuses are needed, but they are inexpensive, so why not.

                Am I doing this right?
                2Kw/day is a strange number, most likely he meant 2kWh / day, meaning how much energy they produce. Sounds like 150-200W panels to me. It also means they won't be able to run your pull pump at full speed even for 1 hr as it would require 2.4 kWh. Start your design from energy then go into voltages/amps/etc. If there's not enough energy produced by panels no other equipment will be able to 'compensate'.

                If I were you I'd scrap those panels off the roof as they don't do anything useful and may be plain dangerous- they may simply fly off the roof in a strong wind. Then I'd step back and start this process from the beginning- analyze loads, electric bills, check if their utility has net metering program in place, etc and we can certainly help with all that. At the end of this you might find you don't actually need solar. As many ppl said before this is anti- solar forum . In any event you need to plan this from beginning to end before buying even single screw.

                Comment


                • #9
                  Thank you all very much. Yes I did mean 2kWh/day, but that was just a number the former owner told us. I had a feeling that it would go in the "not worth it" sort of way since that pool pump is much beefier than most of the ones I've seen online. I will more than likely tell them to scrap it or if they want to use it for something small like outdoor lighting than that's up to them. But I know he's not trying to spend thousands of dollars to get this setup to work if it's only going to save him a trivial amount of money. I think even a with a grid tied system, the amount it would cost to get them permitted and working, it would still not be worth it in the long run with these current panels. I would just hate to scrap $1000 worth of panels.

                  Comment


                  • #10
                    Originally posted by ssjneko1 View Post
                    I think even a with a grid tied system, the amount it would cost to get them permitted and working, it would still not be worth it in the long run with these current panels. I would just hate to scrap $1000 worth of panels.
                    Grid tie shouldn't cost that much at all. Especially if you DIY most of as it sounds like what you are planning.
                    get ironridge rails and flashfeet for 5 modules, get 5 M250 enphase micro inverters, some wire, disconnect, fuse.

                    if the modules are 250w then you would have a 1.25kw system that likely could generate maybe 6kWh a day.
                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                    Comment


                    • #11
                      Originally posted by ButchDeal View Post

                      Grid tie shouldn't cost that much at all. Especially if you DIY most of as it sounds like what you are planning.
                      get ironridge rails and flashfeet for 5 modules, get 5 M250 enphase micro inverters, some wire, disconnect, fuse.

                      if the modules are 250w then you would have a 1.25kw system that likely could generate maybe 6kWh a day.
                      I'd still approach it in more orderly fashion- remove panels off the roof if they are not tied to it in some custom but sure way so they won't end up flying around in some storm, assess what I have, understand what I want, figure out costs involved to get me there and only then start actually doing anything. This process will spare you a lot of efforts / money even if at the end you find out you're better off without this system altogether. It's much easier to move things on paper than on the roof.

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