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Thread: Auto Cover & Solar Heat Gain

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    Join Date
    Jul 2011
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    Auto Cover & Solar Heat Gain

    I am having an auto cover installed this summer. The cover will be navy blue.

    Has anyone experimented with how much water temperature rises having the cover open during the day vs. having it closed? Obviously, its better to have it closed at night, but I'm not sure about during the day.

    On a sunny day, my pool will heat up 3-4 degrees from morning to evening uncovered. I have a dark blue liner. It doesn't seem like I'd be able to get that much temperature rise with the cover on.

    I know there are other factors to consider when deciding to leave the pool covered or uncovered during the day (chlorine consumption, water loss, debris in pool), but want to focus this discussion only on heat gain.
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    mas985's Avatar
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    Re: Auto Cover & Solar Heat Gain

    Predicting these things is difficult at best. Why not try it and see. My guess is there won't be as much heat gain with the cover on and probably worse than having a solar cover. However it might be better to leave it closed on windy days.
    Mark
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    harleysilo's Avatar
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    Re: Auto Cover & Solar Heat Gain

    The good thing is you have some baseline data to make comparisons to. We built are pool last summer with an autocover so I have no reference for heat gain without it, or with a solar cover. I always close my cover when not swimming, so Iíve never attempted to see what type of gain I get without it on during the day, mainly for safety reasons but also because I donít want to skim or vacuum. Incidentally I donít vacuum or skim because of the cover.

    What happens during the day with the cover is that if you leave the circulation off, a thermo layer of super heated water develops directly under the cover. For me, on a windy day at 80 degrees this layer is 100 degrees and 12Ē deep. If the pump is on all day, no layer develops but water gets heated. Iím sorry I canít tell you how much heat gain I get on a given day.

    Iíve had this same discussion several times here, there are simply not enough auto cover users to draw hard and fast conclusions. Those without them swear the pool will heat faster and hotter with cover off during full sunlight conditions. Iím not convinced that is true, yet. Which gets hotter, a open glass of water, or a unopened dark colored can of beverage? Which gets hotter, a hose full of water laying on the ground, or a dog bowl full of water?

    I keep meaning to fill up to 5 gallon buckets of water, placing a piece of blue tarp on the surface of one, and then measuring temps at the end of the day, just never get around to it.

    Be interesting to see what you experience since you have that baseline of data.
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    Re: Auto Cover & Solar Heat Gain

    Thanks for the replies. Once the cover is installed I'll do some experimenting.

    Good to know about the super heated layer. I'll probably adjust my pump run time so that it is always running during the afternoons to help draw hot water away from the cover.
    20'x40' Oval 27,000 gallon Vinyl IG, Coverstar Auto Cover
    Hayward MaxFlo SP2303VSP, Sta-Rite PLD50 30 sq. ft. DE filter
    Rheem 266,000 btu natural gas heater
    Dolphin Nautilus Plus with Clever Clean
    TF-100 testkit w/ Speed Stir

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