Trying to keep up w/ Chem Geek

[CarlD]

Ok,
But let's add this: If you have 3 panels hooked as in your diagram, ShellyAnn, (in series) you will only be getting 8 gpm AT MOST, and probably less, but the water will be hotter.

Actually, I think your max will be LESS than 8gpm, due to tripled resistance. If it was electricity I'd estimate it at 1/3 (less than 3gpm) but this is water and I don't know it as well. But the pressure WILL give you less flow---let's ball-park it at 6gpm.

As Chem_Geek says, hooked in parallel, the panels will give you 24gpm -- or 4 times what I guess-timate the series flow rate to be. Each gallon you flow from the series must be FOUR TIMES HOTTER than each gallon from the parallel to get the same effect.

But what does 4 times hotter mean? Well, that depends on the difference between the pool water temperature and the panel water discharge temperature. If the parallel panels' water is 1 degree warmer than the pool, then the series must be 4 degrees warmer. If the parallels are 10 degrees warmer, the series must be FORTY DEGREES warmer to have the same effect.

Why? Because a BTU is the amount of heat energy needed to raise 1 pound of water 1 degree. So 4 pounds of water 1 degree warmer than the pool is the same as 1 pound of water 4 degrees warmer. Converting pounds to gallons doesn't change anything but the raw amount of BTUs, but not the ratio. (I can't remember if a gallon of water weighs 8.3 lbs or 9 lbs--).

Oh, it's SO much easier to figure in metric and calories...1 liter of water weighs 1 kilo...
24 liters/minute that is 1 degree (Celsius) warmer than the pool adds 24 calories /min. 6 liters/ min 4 deg warmer adds the same 24 calories/min... so if the difference in temp is 10 degrees for the 24-lpm, then it's adding 240 cal/min. The series must be 40 deg warmer at 6-lpm to add the same 240 cal/min.

For reference, 40 degrees celsius is the difference between freezing (0 in Celsius, 32 in Farenheit) and 105 degrees farenheit--a dangerously high fever!

Sorry, you can't bet on gettin' that from solar panels! Not even in Farenheit!

No, it's far more efficient to run them in parallel.

BTW, Richard, I continue to be dubious of manuf calculations: For Fafco to run at their efficiency levels of even 80%, the panels will still be easy to touch even on a blistering day. But you won't get that if you plumb them in series. I STILL go by the rule-of-thumb that if the panel is hot to the touch, or too hot to touch, your flow rate is far too low.

When the panel is hot to the touch, all that good heat is being radiated back into the air. Unless the pool water is already hot, you are nowhere near your maximum transfer efficiency, either your theoretical maximum or your effective maximum.

On a more positive note, manufacturers like Fafco grossly overestimate the number of panels you need to warm your pool. THEORETICALLY, my panels on my deck are far too small in surface area, being only 1/3 the area of my pool. HAH!

My parents had a 13,000 gallon 18x33 oval AG that only got 6 hours of direct sun per day (525 square feet). Even with a solar cover they were lucky on a GOOD day to get 80 degree water--it was usually 78. As they aged that became more and more uncomfortable for them.

I added a 4x20 and a 4x10 panel plumbed in serial--120 square feet with 6 hours of sun per day. All summer the pool ran at 84 degrees, far, FAR more comfortable for them. I had them run the panels whenever the water from them was warmer to the touch than the pool. They lay on the ground and the ground got warm (actually, baked), and after the sun passed would continue to transfer heat BACK to the panels. And this was north of New York City, where swim season is only June thru August.

So, given that, even in series you are likely to get very nice results!