Solar Pool heater

   / Solar Pool heater #41  
A steam fitter at work was telling me that he set up a pool heater for a buddy years ago; basicly a big volume of pool water was left in the PVC run on the roof, heated all day, and just before they got in they'd run the pump and empty the loop, refilling it with cold pool water to be heated the next day. Some figuring would be need to calculate the amount of water needed... but something to consider. You could play with doing this vrs running all day.
 
   / Solar Pool heater #42  
the biggest issue is being able to time it right turning the pump on during day and off before sun goes down. I did a simalar thing by using a smaller submersible pump that connects to garden hose and I put all the hoses I got on the house roof leading to south side and back. I put the pump on a timer and it only rose water 2-5 degrees higher then it was, but not enough to be higher then air temps during the cooler days . So I abandoned this concept.

Use a photocell with a relay or SCR wired reverse acting, no sun photocell turns on but wire so your pump turns off (contacts open).
 
   / Solar Pool heater #43  
sparc,

The better way to do this is to use a differential solar controller. Very well proven technology and better than simply looking at the sun. It measures stored temperature and compares it to available solar as determined by the temperature of the solar sensor. It has a few settings like differential and high limit.
 
   / Solar Pool heater #44  
sparc,

The better way to do this is to use a differential solar controller. Very well proven technology and better than simply looking at the sun. It measures stored temperature and compares it to available solar as determined by the temperature of the solar sensor. It has a few settings like differential and high limit.
 
   / Solar Pool heater #45  
Blankets have lots of problems but I'm a fan of them nevertheless.

However, I have a theory that blankets do nothing to heat the water during the day and possibly have a negative effect because they 'shade' the water. All they do is heat the top few inches due to the physical contact between the blanket and surface water.

Their real advantage is stopping heat loss during the night. (i.e they are retaining the warmth that the pool would gain anyway during the day, with or without a blanket.)

My theory is that without the blanket the suns rays will penetrate deeper and warm more of the water overall. So, my theory goes, that for best heating, the blanket should be put on at night, but taken OFF during the day.

Arguments against my theory would be the cooling effect of the additional evaporation of an uncovered pool during the day and the cooling effect of the extra water required to top up the pool.

But if I'm right and the solar cover really could be left off during the day this would solve a number of the reasons people give for hating covers. (Not least that they get sun damaged and disintegrate after a few years).

I've tried to google an answer to this idea, and read numerous blurbs from solar blanket companies, but no-one specifically addresses it. The listed advantages of keeping the cover on during the day seem more concerned with evaporation, chemical use, reduced cleaning etc.

One small thing in support of my idea was a test I found regarding solar camping shower bags. They definately work better with the clear side up, rather than the black side up. In other words, letting the rays penetrate into the water is more efficient than trying to 'absorb' it into the plastic.

I'm 'sans pool' nowadays so I cant test this idea but I'm thinking of experimenting in summer with 3 tubs of water. One with a cover 24 hours a day. One with a cover at night only. And one with no cover at all.

Any comments?

You are half correct...
They really do heat up the pool on sunny days. I've had 10 degree rises in one day with ours, when we had it. The water in the top 6-10" under the cover could easily hit well over 100 degrees. Too hot to touch. I'd circulate the water severa times per day to mix it up. If the water got too hot, I'd pull the cover and run the filter at night. I could drop the pool temp 10 degrees overnight.

But you are correct about it holding heat in at night.
 
   / Solar Pool heater #46  
Looking at 2 parallel runs of 1", so just need to finesse the manifold aspect (I think)

David Sent from my iPad Air using TractorByNet

Do the math first.... area of a circle is pii x radius squared.
For example:
1" hose has an area of 3.14 x .5 squared or, 3.14 x 0.25, which equals 0.785 square inches.
Two of those 1" runs will have an area = to 1.57 square inches.
A 2" hose has an area of 3.14 x 1 squared, or 3.14 x 1, which equals 3.14 square inches.
You'd need FOUR 1" hoses to equal the surface area of ONE 2" hose.
Now if you are using only a 1.5" hose from the pool...
Area of a 1.5" hose = 3.14 x .75 squared, or, 3.14 x 0.5625, which equals 1.766.
In that case, you'll be closer, but still constricting if you use only two 1" hoses. You'd need three to lower the pressure below the pressure of the 1.5" hoses....

Hope that makes sense. :D
 
   / Solar Pool heater
  • Thread Starter
#47  
Thanks for that, MR. I think I'm 11/2 in, but will check. It wouldn't be particularly difficult to split my array. Something else to consider.

David Sent from my iPad Air using TractorByNet
 
   / Solar Pool heater #48  
You are half correct...
They really do heat up the pool on sunny days. I've had 10 degree rises in one day with ours, when we had it. The water in the top 6-10" under the cover could easily hit well over 100 degrees. Too hot to touch. I'd circulate the water severa times per day to mix it up. If the water got too hot, I'd pull the cover and run the filter at night. I could drop the pool temp 10 degrees overnight.

But you are correct about it holding heat in at night.

See my post #39. Reliable sources say that solar blankets reduce solar penetration by 5% to 40%. You can get more heating if you remove the blanket during the day. (It won't be as hot at the surface but the heating will go much deeper. BUT (and its a big BUT) the cooling effect of evaporation can negate the extra warmth you gain by leaving the blanket off.

Its pretty line ball really. If you want your blanket to last longer you can certainly leave it off during the day with little to lose, and possibly a lot to gain, heat wise.
 
   / Solar Pool heater #49  
See my post #39. Reliable sources say that solar blankets reduce solar penetration by 5% to 40%. You can get more heating if you remove the blanket during the day. (It won't be as hot at the surface but the heating will go much deeper. BUT (and its a big BUT) the cooling effect of evaporation can negate the extra warmth you gain by leaving the blanket off.

Its pretty line ball really. If you want your blanket to last longer you can certainly leave it off during the day with little to lose, and possibly a lot to gain, heat wise.

Just speaking from my personal experience, the pool water gets hotter faster with the solar cover on than with the solar cover off on sunny days.
 
   / Solar Pool heater #50  
And don't forget that if the filter is running with the solar cover on, it will mix up the water and provide circulation, which will move the warmer water at the top throughout the pool. ;)
 

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