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Thread: optimal solar flow

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    optimal solar flow

    What is the best way to know that you have the optimal water flow through your solar panels? I know the panels should be cool and the water should be approx 4 deg warmer, can you have too much flow?
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    Mod Squad Bama Rambler's Avatar
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    Re: optimal solar flow

    While it's possible to have to much flow. It's much easier to have to little flow. There's a recommendation by the mfg of your panels and you should follow that.

    The easiest way to tell if you have the right amount of flow is to install a flow meter, but Mark might be willing to give you a hint if you'll post all your equipment and plumbing info.
    Dave J. TFP Moderator
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    mas985's Avatar
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    Re: optimal solar flow

    As Bama pointed out, in most cases it is pretty hard to have too much flow. The real issue is with pressure but most panels can handle quite a bit of pressure. With a VS, you have a lot of flexibility in setting the flow rate. What is the height of your panels plus the filter pressure and RPM when is solar mode?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: optimal solar flow

    The panels are approx 6' above the pump at the low end and 13' above at the high end. right now my rpm's are set at 2500 for solar and the filter pressure is 20 psi. At 1900 rpm, solar off, the pressure is 12 psi. Today the pool went from 80 deg to 84 deg so I think that is pretty good but I would like to adjust if it could help.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    mas985's Avatar
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    Re: optimal solar flow

    With 288 sqft of panels, you really don't need more than 30 GPM for the panels and you are more than likely well exceeding that flow rate. But one concern I have is that your filter pressure is way too high for those RPM settings. So I would like to get some more information about your plumbing setup.

    Pump elevation relative to the water level
    Filter type/size
    Suction side plumbing diameter, length of runs, and number of runs from pool to pad
    # Suction side valves if any

    Also, when you shut off the pump does the pressure gauge go to zero?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: optimal solar flow

    Quote Originally Posted by mas985
    With 288 sqft of panels, you really don't need more than 30 GPM for the panels and you are more than likely well exceeding that flow rate. But one concern I have is that your filter pressure is way too high for those RPM settings. So I would like to get some more information about your plumbing setup.

    Pump elevation relative to the water level
    Filter type/size
    Suction side plumbing diameter, length of runs, and number of runs from pool to pad
    # Suction side valves if any

    Also, when you shut off the pump does the pressure gauge go to zero?
    The pump is approx 2' / 3' below the water level.

    The filter is the Pentair 420. I do notice that the cartridges seem to get dirty fast, even when the psi has only risen 4 psi from clean the flow is reduced allot.

    It's all 2" pipe, I'll post a pic.

    There is a valve that controls suction from either the main drain or the skimmer.

    Gauge goes to zero.

    I'll verify the pressure reading's tomorrow to be sure I remembered correctly.
    Attached Images Attached Images
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    Re: optimal solar flow

    To correct the rpm / pressure readings: At 1800 rpm, no solar the psi is 10. At 2600 rpm, solar on, poolcleaner & booster pump on, pressure is 21 psi.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    Re: optimal solar flow

    Quote Originally Posted by mas985
    With 288 sqft of panels, you really don't need more than 30 GPM for the panels and you are more than likely well exceeding that flow rate. But one concern I have is that your filter pressure is way too high for those RPM settings. So I would like to get some more information about your plumbing setup.
    At 30 gpm it would take 18+ hrs to circulate the pool once, I'm only running 10 hrs right now, would'nt that decrease the rate that the pool is heated? What I mean is if the flow was 50 gpm it would turn over in 11 hrs, so would'nt this heat faster?
    I think the flow gauge would be a good idea, just havn't got around to buying one.
    At the current flow the water from the panels seems like it is 5 / 10 deg hotter than the pool, I'll get an actual measurment to see if I'm right. All I'm judging by is it feels warm when you swim up to it.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    mas985's Avatar
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    Re: optimal solar flow

    Quote Originally Posted by bobby1017
    At 30 gpm it would take 18+ hrs to circulate the pool once, I'm only running 10 hrs right now, would'nt that decrease the rate that the pool is heated? What I mean is if the flow was 50 gpm it would turn over in 11 hrs, so would'nt this heat faster?
    Short answer is no.

    The time it takes to turnover a pool is not that important in heating with solar. However, heat transfer efficiency is related to the flow rate through the panels. The higher the flow rate the more efficient the panels will be. However, most solar panels will peak out in efficiency around 0.1 GPM/sqft. After that there is little to gain with higher flow rates and is generally not worth the extra energy required for the higher flow rate. But again, it doesn't hurt anything to run higher flow rates, it just may not add much more heat and it may cost more for the pump electricity.

    At 2600 rpm, solar on, poolcleaner & booster pump on, pressure is 21 psi.
    Your plumbing setup has the highest head loss I have ever seen on a pool. I still think there is either something wrong with the filter gauge or the return plumbing has an issue somewhere. But assuming it is an issue with the plumbing and the filter pressure is correct, then here are the estimates that I came up with:

    Without solar, your flow rate should be about 28 GPM and will follow the line: Flow rate (GPM) = RPM / 63.5

    With solar, your flow rate should be about 40 GPM and will follow the line: Flow rate (GPM) = RPM / 65.2
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: optimal solar flow

    Quote Originally Posted by mas985
    Your plumbing setup has the highest head loss I have ever seen on a pool. I still think there is either something wrong with the filter gauge or the return plumbing has an issue somewhere.
    The gauge goes to 0 when the pump is off. The pool is approx 60' away from the equipment pad. When you say return plumbing what is that exactly? I assume the water returning from the filter to the pool. I have been increasing the rpm's lately, it has been about 4 months since I cleaned the cartriges, and I can tell the flow from my waterfalls has decreased to the point of not hitting the pool. I think I may have been better off with a sand filter as this one seems to have to be cleaned often. The pressure may only rise 4 psi but the flow is reduced alot.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    mas985's Avatar
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    Re: optimal solar flow

    By return plumbing, I mean anything post pump.

    So it could be the filter or something after the filter. If the filter is reducing flow rate that much with only 4 PSI pressure rise, it could be that cartridges are calcified or plugged. Have you ever soaked the cartridges in TSP or acid? It might be worthwhile to try this but first soak the cartridges overnight in water with TSP, rise and then soak again in a water/acid solution.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: optimal solar flow

    I did the tsp cleaning last time but not the acid, I'm going to buy 4 new cartriges then I can swap and clean these better. Thanks for the input.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    Re: optimal solar flow

    new ones on the way.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    Re: optimal solar flow

    Old cartriges were pretty dirty, with the new ones at 2600 rpm, solar on, the pressure is 14 psi, it was 21 psi before. I adjusted the rpm down to 2250. I'm going to do the tsp soak then the acid soak on the old cartriges. Also bought one of the correct nozzles to clean with.
    At 1900 rpm, no solar, is 5 psi. I guess the pressure rise from clean was more than 4 psi, but since I was messing with the rpm I lost track.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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    Re: optimal solar flow

    Everything is working good again. The flow is increased dramatically. Cleaned the filters overnight in tsp, rinsed, then soaked in the 1-20 acid solution, they didn't bubble much. We'll see how they do compared to the new one's when it's time to change.
    DONE, 20 x 40, inground gunite, 30" raised bond beam with 3 12" sheer descents, 8' diving board, pentair 420 cartridge filter, vs-3050 pump, intellechlor ic-40, auto cvr, Tahoe blue pebble tech, 6ea 4' x 12.5' & 2ea 1' x 12.5' helicol solar panels, legend robotic cleaner.

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