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  • Adding more panels

    9402829B-1F2D-4B58-98F8-782855F330BF.jpeg Hi all I have a 4215bn controller and currently 2x260w Canadian solar panels what is the absolute max panels the controller can take as I’m struggling to run a 300w water heater for my greenhouse don’t mind disconnecting the extra in summer if need be just need the boost in winter
    thanks all

  • #2
    What is your battery Ah and voltage rating? And what voltage is that 300w water heater?

    With 520 panel wattage you can generate 40amps for a 12volt battery and 20amps for a 24volt battery system.

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    • #3
      It’s a 12v system with 2x120ah batteries the water heater is 300w 12v

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      • #4
        EP max panel power chart.jpg

        While your CC isn't on this list it still gives the max wattage for the 4210 model, which should still apply to your 4215.
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          So that means I can add more panels upto 1560w then?

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          • #6
            Looks that way. The only reason for having such an over paneled system would be where solar insolation is regularly less than optimum. Regardless, your controller will never put out more than it's rated amperage.
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #7
              So would you recommend being able to switch some panels of in the summer months then these are what I’m thinking of getting it what way would you recommend wiring them up please
              Attached Files

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              • #8
                Originally posted by Notty1975 View Post
                It’s a 12v system with 2x120ah batteries the water heater is 300w 12v
                With a 240Ah 12V battery system you really shouldn't exceed 30 amps of charging so with 520w of panel you may see more than that much which could cook your battery system

                Although with a 300w load you will see less "charging" amps going to the battery but you still need to keep an eye on the system so you don't over charge the batteries.

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                • #9
                  Ok getting a little confused now so what would you recommend I do please

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                  • #10
                    Originally posted by Notty1975 View Post
                    Ok getting a little confused now so what would you recommend I do please
                    It depends on how long your water heater is actually drawing a load and how much sun your panels are getting. There is no exact way of saying what will work for you. But IMO you have more than enough panel wattage to charge your batteries and depending on how much sun you get you could over charge them but that is something you need to keep an eye on.

                    Depending on how your water heater works, it may draw down the batteries when the sun is not shining causing you to over discharge your batteries because it will draw 25 amps based on that 300w 12v rating. If the draw is for brief periods it should work but your batteries are only rated for about 2900 watt hours and your water heater could use more than half that in a night if it uses 300watts for more than a few hours.

                    I certainly would use a generator to run the water heater on cloudy days or if you want hot water through the night.
                    Last edited by SunEagle; 02-08-2020, 05:48 PM. Reason: spelling

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                    • #11
                      A generator is not a option what if I were to add another system and add another identical MPPT in parallel

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                      • #12
                        What about a solar hot water system ? Solar thermal collection is more efficient than PV-Electric heater. One PV panel to power the brains and circulation pumps, and a Thermal panel to heat the water.

                        https://www.builditsolar.com/Project...atchHeater.htm
                        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

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                        • #13
                          Originally posted by Notty1975 View Post
                          A generator is not a option what if I were to add another system and add another identical MPPT in parallel
                          Both heating and cooling units are big loads and really do not do well with solar pv. There are solar hot water heaters that Mike mentioned but they aren't cheap although use very little power.

                          I am sure you can build a system dedicated for the hot water heater but you really need to know how many watt hours it will use in a day and then design the solar/battery system to make it work. Just remember the bigger the load the more watt hours it uses and the bigger the battery system needs to be.

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