# How to heat pool?

wrote:

They use heat pumps, not toaster wire heat. It is actually pretty efficient but the upfront cost is higher than a burner.
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I wonder where you live in Texas... 940 Btu/ft^2 of sun falls on the ground on an average 48.8 F January day in Austin with an outdoor humidity ratio wo = 0.0052 pounds of water per pound of dry air, so 1 ft^2 of 80 F unshaded pool with an R1 cover would gain 0.9x940 = 846 Btu and lose 21.5h(80-48.8)1ft^2/R1 = 671 Btu/day of sensible heat and 1.5hx100(Pw-Pa) Btu/day of latent heat, where Pw = 1.05 "Hg at 80 F and 100% RH and Pa = 29.921/(1+0.62198/wo) = 0.248 "Hg. The total loss would be 791, less than 846, so you might make it more than 80 F with solarcover.com's \$75 14'x28' 411428 clear cover, and make it warmer still with 2 of them, or use their \$99 16'x32' 411632 cover with water under 2' of dark coping during the day.
Darkening the pool sides and bottom would also help.
Nick
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Nick,
You are not accounting for the loss on the other 5 sides ( the ground )
My pool in Florida, it takes 300 sf of solar thermal panels ( thermoplastic type of pool heating ) to keep the water ~80
Texas is a bit cooler in Jan than my location so it would require even more heat input
SG
wrote:

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This is a ball park calc... 90% of the heat loss is from the top. Here's a more detailed calc: say it's above-ground... 696 ft^2 of R10 sides and bottom would lose 24h(80-48.8)69.6 = 52.1K Btu/day. The cover would gain 12x28x846 = 284.3K Btu/day and lose 12x28x791 = 265.8K Btu/day. At 80 F, the 12% shortfall is 284.3K-265.8K-52.1K = 33.6K Btu/day, not much, but...
If 1 ft^2 of R1 cover with 90% solar transmission collects 846 Btu and loses 6h(80-48.8)1ft^2/R1 = 187 Btu/day, the net gain is 659, so another 33.6K/659 = 51 ft^2 of cover over a dark coping could provide the extra 33.6K Btu... solarcover.com's \$99 16'x32' 411632 cover could provide an extra 116K Btu.

You seem to have left out a few details :-) How big is it? In ground? Shaded? Covered? With a clear solar cover or a blue one? Nick
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Why do you say 90% is from the top? , the other 5 sides will have ~25 degree delta to the ground, area wise wouldn't this double the losses
http://www.solar-guppy.com/solar_pool.htm
My pool is 7500 gallon in ground, about 28x14x5 , but its not a rectangle , more hour glass shaped. no cover .. the panels can keep up with the losses except for those rare weeks of sub 70 degree weather
Point was your not accounting for over 65% of the surface area from a BTU loss stand point
wrote:

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That's how it usually works out, esp with no cover.

But the OP's new pool might have R10 sides, and some people soil has a built-in R10 thermal resistance to downward heatflow, and the deep ground temp in Austin is 68.6 F, vs the average 48.8 January temp, and the pool warms the ground under it.

"No cover" makes a big difference, esp in a dry climate.
Nick
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Nick,
Austin's ground temp is not 68.6F from 0 to 10' below surface. Austin's ground temp asymptotically approaches 55+-/4 degF annually > 10' below surface.
Regards, JT
wrote:

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Au contraire, NREL says the annual average air temp, ie the deep ground temp is 68.6 F, and that may be unimportant for this pool.

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On Tue, 17 Oct 2006 15:46:36 GMT, "Solar Guppy"

The OP's main problem with solar is he wants to use the pool in the morning. That is when a solar heated pool is coolest.
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By about 0.7 degrees F :-)
Nick
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On Oct 17, 2:58 pm, snipped-for-privacy@aol.com wrote:

Cheapest solutions -- wear a wetsuit...
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On 17 Oct 2006 20:09:09 -0700, snipped-for-privacy@gmail.com wrote:

Helps ya float, too. <G>
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