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Thread: Getting the most heat gain. Solar cover on or off?

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    Getting the most heat gain. Solar cover on or off?

    My water temperature is currently about 54 degrees and it looks like it might hit 80 degrees out tomorrow during the day. I was just wondering if I will gain more heat during the day taking the solar cover off and allowing the sun to fully penetrate or to leave the solar cover on and hope that it will heat up as well or better?

    I am thinking that the evaporation that will occur will offset any heat gain I will get with the cover off but I am not certain.

    Obviously this does not matter much but I am trying to get the water as warm as quickly as possible to try to extend my season since this is our first year with the pool and my 3 year old daughter really wants to swim!

    Natural gas heater is in the works for next year, just not in the finances this year!
    16 x 32 Vinyl IGP ~22000 G

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    Administrator Leebo's Avatar
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    Re: Getting the most heat gain. Solar cover on or off?

    Cover off during the day, cover on at night. You may not notice a huge difference this early in the year however.

    Just toss them in..... she won't mind

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    JasonLion's Avatar
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    Re: Getting the most heat gain. Solar cover on or off?

    I believe that you want the cover off when there is sunlight shining directly on the pool from reasonably high in the sky (ie not at dawn) and it is not too windy. The rest of the time it should be covered. The cover reduces heat absorption from sunlight, but there needs to be enough sunlight to make it worth a little evaporation, which is only when it is sunny and not too windy (which increases evaporation).
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    Re: Getting the most heat gain. Solar cover on or off?

    A lot depends on the weather like Jason states. Right now in So Cal, our temps are hitting about 70 for a high and if I remove the cover during the day it doesn't heat the pool as much as leaving it on. The kids were out of school last week so the pool was used every day, and our pool temp only got up to 86. Normally it will be 88, that's our solar setting, so having the cover on during the day does help to heat our pool more at this time of year. We usually have a lot of evaporation if the cover is off and that keeps the pool temp down also.
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    Mod Squad JohnT's Avatar
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    Re: Getting the most heat gain. Solar cover on or off?

    Like Jason said, wind is a big factor.
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    Re: Getting the most heat gain. Solar cover on or off?

    Solar Cover on day and nite. If it is a solar cover it actually helps to warm the pool with it on during the day and cuts down on evaperation. Hence the name "Solar Cover". If you leave it on during the day you can actually feel the upper portion of the pool is alot warmer than deeper down. If it is just a "pool cover" than it would shield the light and heat from being absorbed in the water and should be removed during the day.

    skeeter
    47 yr old(1977) 18,000gal Kidney shaped 38ft long plaster Pool with built-in Spa, Pentair Intelliflo VS3050 Pump, Pentair 48sf DE filter, Raypack RP2100 gas heater. HTH 5-way test kit

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    Mod Squad jblizzle's Avatar
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    Re: Getting the most heat gain. Solar cover on or off?

    While the solar cover does help mainly by preventing loss to evaporation. The blue bubbles do not in fact help heat the water. The top few inches will feel warmer due to the cover getting hot and conducting heat, but you will in fact better heat the bulk of the water without the "solar" cover on.

    There are some detailed discussions about this in the forums if you want to search for them ... regarding blue vs clear vs opaque covers.
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    Re: Getting the most heat gain. Solar cover on or off?

    Quote Originally Posted by skeeter_ca
    Solar Cover on day and nite. If it is a solar cover it actually helps to warm the pool with it on during the day and cuts down on evaperation. Hence the name "Solar Cover". If you leave it on during the day you can actually feel the upper portion of the pool is alot warmer than deeper down.
    You are right about feeling the warmth by the cover, but this in not a good thing if you are trying to most efficiently heat the bulk of the pool water. Even the more transparent pool covers filter out a good amount of energy going to the pool. If your ambient temperature is decent and there is not much wind, leaving the pool cover off will heat the water faster (and not just heat the cover and the water near it).

    And, yeah...they shouldn't really call them solar covers...it just confuses everyone.
    TFP Expert 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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    Re: Getting the most heat gain. Solar cover on or off?

    No pool cover allows 100% of the light/heat into the pool so there is always some reduction of heat gain due to the cover. However, this can easily be offset by the reduction of evaporation and the resulting heat loss. But it really depends on the local conditions. Dry winding climates would benefit most from a cover while humid climates with little wind (i.e. low evaporation conditions) would probably benefit more with the cover off.
    Mark
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    Re: Getting the most heat gain. Solar cover on or off?

    Well maybe it's just antidotal but with a cover on my pool heats up alot quicker. i also have my pump on and it helps to circulate the water around some. When i don't use the cover i only get about 2 months of swim time and maybe 4 with it.

    Just my 2cents,
    skeeter
    47 yr old(1977) 18,000gal Kidney shaped 38ft long plaster Pool with built-in Spa, Pentair Intelliflo VS3050 Pump, Pentair 48sf DE filter, Raypack RP2100 gas heater. HTH 5-way test kit

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    linen's Avatar
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    Re: Getting the most heat gain. Solar cover on or off?

    Quote Originally Posted by skeeter_ca
    Well maybe it's just antidotal but with a cover on my pool heats up alot quicker.
    If you have any amount of sustained wind, if your ambient temperatures are low, and/or if you live in a very dry climate, then I would think you might warm faster with the cover. But with no wind and ambient temps around the pool temp or higher, cover off is better for warming in my experience.
    TFP Expert 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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    Re: Getting the most heat gain. Solar cover on or off?

    Reviving this thread back from the dead. The thread has risen!

    Quote Originally Posted by linen View Post
    If you have any amount of sustained wind, if your ambient temperatures are low, and/or if you live in a very dry climate, then I would think you might warm faster with the cover. But with no wind and ambient temps around the pool temp or higher, cover off is better for warming in my experience.
    I just want to confirm what Linen has said. I live in the Phoenix area, and right now, despite the sun being pretty strong (and it's still February), I can't get my pool warm enough nor have it sustain the temperature for very long. I have a pool heat pump, and it still cannot keep up with my demands. Yesterday was windy and dry, with a humidity level of 12%. Again, despite the sun beating into 2/3's of the pool, the heat pump still wanted to kick on to maintain the temperature. This confirms Linen's statement.

    Here in Phoenix, the problem also is this: 30-34 degree day vs. night temperature swings. This past Sunday was 84 during the day, but only 50 at night (actually right before dawn of the next day). Those are according to Weather Underground's history function. I think I observed about 55 degrees actual. None the less, how can any pool deal with that?!?

    The solution is a solar cover. It's juggling act to decide to put it on during the day, but it's almost a requirement at night. Until night temperatures are in the 80's 90's 100's, and they will be eventually, the solar cover should remain on.

    However, I have one and I dislike using it. It's cumbersome even with a roller, it gets dirty due to the dust, and it caused my pool to get into a partial algae bloom. The latter was my own fault as I didn't check chemistry as often as I should have nor could I see the "green".

    I'm thinking about cutting it into manageable pieces, either squares or circles. Still on the fence with that though...
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    Mod Squad pooldv's Avatar
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    Re: Getting the most heat gain. Solar cover on or off?

    Good info, it is about time to start warming the pools for spring. My first ever solar cover is in transit. Clear, 8 mil.
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