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Thread: Solar panel configuration dilemma

  1. #1
    Senior Member linen's Avatar
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    Solar panel configuration dilemma

    I have run sungrabber agp solar panels for a season on my pool. I had 4 panels and now I am adding 2 more to get my total solar panel area closer to my pool surface area. 6 panels (2'X20') will be 240 sq. ft., and my pool is 346 sq. ft. I have stopped at 6 for now since that is what fits nicely in the space I have.

    First some background on the sungrabber panels. These panels are the ones with the disk in one header that diverts some of the flow to half of the panel with the return flow back on the other half. I have removed these disks. On an older manual it states the ideal flow rate to be 4-8 gallons/panel. The current online manual does not have a flow rate listed. Instead it talks about throttling the flow rate so that the net increase in pressure when the panels are valved in to not exceed 10 psi. In addition, I am assuming because of the disk, that only a portion of the that flow actually goes through the panels and the rest just sneaks through the hole in the disk on the header (about 0.5 inch in diameter if my memory serves right). So I do not have a good number for an optimal flow rate from the manufacturer. The more I am digging into this, the less I like the sungrabber documentation (or lack of).

    Some background on my pool and equipment. I have a 2 speed 1 hp powerflo matrix pump that I was able (marginally, i.e. if my filter was fairly clean) to run the solar on low speed if I primed the panels on high speed first. I would prefer to run on low speed for energy consumption reasons. Last year I was getting about 1.5F bump in water temp through the panels when the sun was strong and the pump was on low. Mark must have just removed his pump graph that had many pump curves on it. My pump ( 1 hp matrix) if I recall at 60 ft head (I am estimating here, I hope to have better numbers after I open), had a flow of about 34 gpm. So for my pump on low speed that would be ~17 gpm. Divided by 3 panels in parallel, that would be ~6 gpm per panel which is why I am thinking doing my panels 3 in series with 3 (I was 2 in series with 2). Again, I do not know have a good number for optimal flow rate for the sungrabbers, but 6 gpm doesn't seem unreasonable to me.


    As mentioned above, previously, I ran my flow out two panels then back with the other two. I am assuming that if I run out three, then back three my pressure loss will be a little bit less since my flow rates through the small tubes will go down?

    Here is my setup last year when I had 4 panels:
    [attachment=2:j8ic7cud]currentsolar.jpg[/attachment:j8ic7cud]

    My first thought was more of the same like this:
    [attachment=1:j8ic7cud]newsolar1.jpg[/attachment:j8ic7cud]

    Another thought was this layout where I avoid possible air entrapment that might exist at upper right portion of the picture above:
    [attachment=0:j8ic7cud]newsolar2.jpg[/attachment:j8ic7cud]

    Sorry about the ugly drawings, but I did them fast over lunch.

    I am interested in leaving the panels on the roof over the winter, so I am motivated to have them at an angle to drain properly.

    Any comments or ideas! Thanks!
    Attached Images Attached Images
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  2. #2
    Senior Member mas985's Avatar
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    Re: Solar panel configuration dilemma

    I think the last one is the only one where it is going to drain properly. I don't know much about sun grabbers but, it seems like since you can add a third panel to each set why can you not just have all 6 panels in one set, all in parallel and have the return in the upper right?
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner, DIY Acid Dosing

  3. #3
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by mas985
    I think the last one is the only one where it is going to drain properly. I don't know much about sun grabbers but, it seems like since you can add a third panel to each set why can you not just have all 6 panels in one set, all in parallel and have the return in the upper right?
    I could, but I was thinking my flow rate to each panel might be too low at ~3 gpm? Also, running 3 out and 3 back reduces how much pvc I need to attach to the roof. I am starting to regret choosing these 2X20 sungrabbers last year (they were cheap of course and so am I) since I would prefer to mount panels vertically and the lack of documentation. With that said, they seemed to work well last year.
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  4. #4
    Administrator JasonLion's Avatar
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    Re: Solar panel configuration dilemma

    Six panels in parallel running water up from the bottom to the top will be noticeably more efficient and only takes 12 ft of additional pipe (give or take). 3 gpm per panel won't be ideal, but it will work well enough.

    Do you really only have 18 rpm going to the roof? 60 ft of head sounds like a really high estimate. Also, with all of the panels in parallel the dynamic head will be noticeably lower, so the total flow rate will be higher.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  5. #5
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by JasonLion
    Six panels in parallel running water up from the bottom to the top will be noticeably more efficient and only takes 12 ft of additional pipe (give or take). 3 gpm per panel won't be ideal, but it will work well enough.

    Do you really only have 18 rpm going to the roof? 60 ft of head sounds like a really high estimate. Also, with all of the panels in parallel the dynamic head will be noticeably lower, so the total flow rate will be higher.
    Yeah, the 60 ft head is just a guess, I was trying to be conservative since I have 1.5" supply piping. The 18 gpm is assuming running the pump on low. It would be around 34 gpm (not 36 due to rounding) on high at 60 ft head loss according to the chart that Mark had in Hydraulics 101 (that chart is now gone ). You have me thinking though, my flow rate might be higher on low speed(i.e. >0.5*34 gpm) since the head loss would be less due to the lower losses in the pipe (due to flow rate) and also less resistance in the panels (assuming all 6 in parallel)?
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  6. #6

    Re: Solar panel configuration dilemma

    I'm going to be installing 4 2'x20' Sungrabbers this weekend. The instructions that came with my panels recommends installing them angled like your third picture. That's what I was planning to do. I don't have the instructions with me but I think it specified an angle where the high side was only 1/4" higher than the low side and no more than that.
    15' x 30' x 52" Oval AGP; 1hp Hayward Powerflo LX Pump; Hayward Sand Filter; 4 2'x20' Sungrabber Solar Panels; Compupool CPSC36 SWG

  7. #7
    Senior Member mas985's Avatar
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    Re: Solar panel configuration dilemma

    Sorry I removed the head curve chart but it was a little cluttered and I didn't think it was getting the point across so I replaced it with another chart.

    But anyway, here is the matrix head table:



    You will note that they don't show flow rates beyond 60' of head so that was an extrapolated part of the curve anyway. But you have made me curious about your setup and I am really surprised you could run your panels on low speed. So if you don't mind I have a few questions:

    Do the panels have a vacuum release valve and if so, where is it (elevation)?

    How high are the panels relative to the pump?

    What is your filter pressure on high speed with solar on vs off?
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner, DIY Acid Dosing

  8. #8

    Re: Solar panel configuration dilemma

    When you say to run them in parallel, do you mean like this:

    15' x 30' x 52" Oval AGP; 1hp Hayward Powerflo LX Pump; Hayward Sand Filter; 4 2'x20' Sungrabber Solar Panels; Compupool CPSC36 SWG

  9. #9
    Senior Member mas985's Avatar
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    Re: Solar panel configuration dilemma

    yes
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner, DIY Acid Dosing

  10. #10
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    Re: Solar panel configuration dilemma

    sturge33, the panels should be slightly tilted so that they drain correctly. In your diagram, the right hand side (the side away from the feed pipes) should be slightly higher than the left hand side.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  11. #11
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by mas985
    Sorry I removed the head curve chart but it was a little cluttered and I didn't think it was getting the point across so I replaced it with another chart.

    But anyway, here is the matrix head table:



    You will note that they don't show flow rates beyond 60' of head so that was an extrapolated part of the curve anyway.
    Thanks Mark! I have been assuming my 2-speed SP15922S high speed is the same as the SP1592?

    Quote Originally Posted by mas985
    But you have made me curious about your setup and I am really surprised you could run your panels on low speed. So if you don't mind I have a few questions:
    First let me say, my memory is not good from last season and I have not opened the pool yet this spring, however this discussion is pushing me to attempt to open this upcoming weekend. When I do, I now have a vacuum gauge ready to be attached to my drain on the pump, so I should be able to get a better idea of how my pump is working. With that said here are answers from my poor memory:

    Quote Originally Posted by mas985
    Do the panels have a vacuum release valve and if so, where is it (elevation)?
    I did not have on last year, and I am hesitant in planning to install one this year due to the desire to run on low. This is a question I have had rolling around in my head...how much risk am I running not having one? If I should add one, should it be near the low panel input?

    Quote Originally Posted by mas985
    How high are the panels relative to the pump?
    Lowest panel corner (lower left on first drawing in the first post) is at about 10.5 feet above the outlet of the pump (I am not at home so this is from memory...I will actually measure).

    Quote Originally Posted by mas985
    What is your filter pressure on high speed with solar on vs off?
    My memory is really really fuzzy here but I seem to remember 13 off 19 on? This is part of my dilemma, I will not be able to get real (new and accurate) numbers for the old panel setup this spring, since I am already heading towards the new setup.

    A couple of other comments.

    Full disclosure here ...I have used non sch40 dwv long sweep 90s sweeps on some of my plumbing with the intent to reduce the loss of the shd40 tight 90s pressure loss (I have not been able to find shc40 long sweep 90s locally). In fact I have 7 in the water path right now, and I have been contemplating using them on the roof with the new setup for a total of 13 in my water path if that is what will make running on low successful

    I have no check valves right now, all my valves are the pvc ball valves. When we ran solar last year on either low or high speed, I diverted all the flow to the panels. We we were not running, the panels were entirely isolated by ball valves from the rest of the system.

    I am suspicious with my original panel layout I had some air entrapment (at the upper right of my first drawing).

    The panels only functioned well (flow high enough not to cause my intex swg to indicate low flow) running on low when the filter pressure was at it's "clean" pressure (and I think the leaf basket and skimmer basket also had to be relatively free of leaves).

    Mark and JasonLion, I appreciate your help on this and I hope to have better numbers available soon. I am leaning toward the recommendation to run them all in parallel.
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  12. #12
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by JasonLion
    sturge33, the panels should be slightly tilted so that they drain correctly. In your diagram, the right hand side (the side away from the feed pipes) should be slightly higher than the left hand side.
    sturge33, mine are tilted at about 1/4" per foot (for at total of about 5 inches) in the direction JasonLion indicated though I am not sure if that is best. I picked that slope, since I didn't know better...so I chose something I knew which is the minimum slope for dwv horizontal drain applications.
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  13. #13

    Re: Solar panel configuration dilemma

    Quote Originally Posted by linen
    Quote Originally Posted by JasonLion
    sturge33, the panels should be slightly tilted so that they drain correctly. In your diagram, the right hand side (the side away from the feed pipes) should be slightly higher than the left hand side.
    sturge33, mine are tilted at about 1/4" per foot (for at total of about 5 inches) in the direction JasonLion indicated though I am not sure if that is best. I picked that slope, since I didn't know better...so I chose something I knew which is the minimum slope for dwv horizontal drain applications.
    Oh OK, that may be what the panel instructions recommended. I know I read 1/4" for the angle and it may have been 1/4" per foot. I'll double check that when I get home but that sounds about right.
    15' x 30' x 52" Oval AGP; 1hp Hayward Powerflo LX Pump; Hayward Sand Filter; 4 2'x20' Sungrabber Solar Panels; Compupool CPSC36 SWG

  14. #14
    Administrator JasonLion's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by linen
    I have used non sch40 dwv long sweep 90s sweeps on some of my plumbing with the intent to reduce the loss of the shd40 tight 90s pressure loss (I have not been able to find shc40 long sweep 90s locally).
    Often electrical supply houses have sweep 90s for use as electrical conduit that happen to be sch40 PVC.
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  15. #15
    Mod Squad Melt In The Sun's Avatar
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    Re: Solar panel configuration dilemma

    Big box stores will have it too; generally up to 2 or 2.5"
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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  16. #16
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    I am so glad you guys brought this up as I used this tubing for electrical but just assumed (doh) that is is not appropriate for plumbing. Is there any reason this gray stuff shouldn't be used? How about the straight tubing with the flair to connect to the next tube? Is sun a problem?
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  17. #17
    Senior Member mas985's Avatar
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    Re: Solar panel configuration dilemma

    Personally, I would skip the sweep 90s. They usually are not worth the extra cost and heartache trying fit them into the plumbing. They have about 1/2 the head loss of an ELL 90 but the 90s in a typical plumbing system are usually a fairly low percentage of total head loss so changing them out does not make a big impact.

    Anyway on to your question about the vacuum release. With strategic placement, you can have the best of both worlds where the system will work on low speed but your panels also drain. I am a little puzzled though that you were worried about priming and draining without the VRV since neither is really an issue without a VRV.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner, DIY Acid Dosing

  18. #18
    Mod Squad Melt In The Sun's Avatar
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    Re: Solar panel configuration dilemma

    Sch 40 is sch 40, so if the conduit says it it meets that spec, I wouldn't worry about using it. I've never used the bell end pipe because I've never needed to plumb a long distance, but I wouldn't hesitate to use it if I had a reason. It may or may not be cheaper or easier than a regular stick of pipe and a coupler. The gray conduit generally says "UV resistant" on it, but I'd still paint it. It will turn nasty brown in a few years.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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  19. #19
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by mas985
    Personally, I would skip the sweep 90s. They usually are not worth the extra cost and heartache trying fit them into the plumbing. They have about 1/2 the head loss of an ELL 90 but the 90s in a typical plumbing system are usually a fairly low percentage of total head loss so changing them out does not make a big impact.
    Makes sense. Here is/was my thought...and I bet I am over thinking this (please let me know), but in this case where I am trying to get my low speed to run the panels reliably, might long sweeps verses short ones be the difference. As we discuss this it becomes even more apparent in my thick head that I should put all six panels in parallel to also reduce loss.

    Quote Originally Posted by mas985
    I am a little puzzled though that you were worried about priming and draining without the VRV since neither is really an issue without a VRV.
    That makes two of us.
    I know I am confused about this. I had been thinking of the vacuum release being at the very top of the system, and thought it might leak if it did not have enough pressure on the water side.

    Quote Originally Posted by mas985
    Anyway on to your question about the vacuum release. With strategic placement, you can have the best of both worlds where the system will work on low speed but your panels also drain.
    Yes, please expound on the where (and what valve)!
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  20. #20
    Senior Member linen's Avatar
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    Re: Solar panel configuration dilemma

    Quote Originally Posted by Melt In The Sun
    Sch 40 is sch 40, so if the conduit says it it meets that spec, I wouldn't worry about using it. I've never used the bell end pipe because I've never needed to plumb a long distance, but I wouldn't hesitate to use it if I had a reason. It may or may not be cheaper or easier than a regular stick of pipe and a coupler. The gray conduit generally says "UV resistant" on it, but I'd still paint it. It will turn nasty brown in a few years.
    Cost may be a good reason not to use it, but seems like one less joint per coupler for long runs might be worth something. The way this layout is heading, I will need at least 1 long run with 3 straight couplers, so 3 glue joints instead of 6 seems like something to at least be considered.

    Any idea how this stuff does underground?

    I have never welded/glued the gray conduit together, is it the same as plumbing pvc?
    TFP Moderator who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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