solar heater

[rmeden]

As I mentioned before, I try to keep my rise close to (but not over 10). The reason? I like feeling warm water dropping into the pool! (I have a vacuum hose leaving the panels on the deck and dropping into the pool.. I pull it out when I want to feel. )

I agree I lose some efficiency, but nothing beats feeling the warm water going into the pool. I bet the efficency loss is negligable.

Robert

[JohnT]

I agree I lose some efficiency, but nothing beats feeling the warm water going into the pool. I bet the efficency loss is negligable.

Robert

I would guess the efficiency loss to be in excess of 50%

[rmeden]

I would guess the efficiency loss to be in excess of 50%

*WOW* that much? I was thinking less than 10%... we're talking about a 77->87 degree rise... you're saying a 77->80 degree would put twice as many BTUs in the water?

Granted, I never had thermo in college, but that seems a bit much...

Robert

[Poconos]

Been a long time since I had Thermo (40 years?) but what you have to know is that the temperature differential is what governs heat transfer. You are trying to get maximum heat transfer from the surface that is heated by the sun to the flowing water. In the case of a solar heater the differential would be the temp of the heater surface with 'normal' water flow compared to the temp without water flow. Pretty close, not exact. Without flow probably pretty hot...120F+. In tphaggertys post, a couple above, you can think of a term like 'GPM x degree rise'. What it means is you have some constant heat input to a panel therefore higher flow yields less temp difference input to output of the heater and visa versa. 'GPM x degree rise' is a constant...almost. If you are trying to squeak every last BTU (British Thermal Unit...a measure of heat) from the system then you want max flow. Do what is best for the equipment, circulating, and sanitizing and enjoy the warm water flow. Whatever that implies.
Al

[tphaggerty]

I agree with Poconos. If you want to get the most heat, it really is a matter of temp rise x flow rate.

But, this thread has me thinking I might add a diverter valve to my system so that once the pool reaches the temp we like, I can set it up to "trickle" water through my panels to get that LEGAL, non-biological return line rush.

[harryk]

Flow rates intrigue me. I'm about to spring for a mat, and I'll be putting it on my roof the OTHER side of the pool from my pump. This means I can't easily use my pump system. I'm planning on using a submersible pump (kind of like a cover pump) on a timer to run it during the day. These aren't good for terribly good flow, but then again, they are cheaper than the pool pump (I don't use the pool much, and it's mostly covered, so I get by very nicely running the pump and filter about 90 minutes in the morning and 90 minutes in the evening).

So, the question is, will I be killing my efficiency with this lower flow? And, I am a degreed and licensed mechanical engineer, so I fully understand and agree with the statements that the lower the temperature rise, the higher the effectiveness.

Thanks,

Harry

[tphaggerty]

CarlD is right on for this one. The most efficient panel setup may see less than a 2 degree rise from the panels, but if you're turning over 40gpm vs 10 degrees at 5gpm, that's almost twice as much HEAT going into the pool. Thats why many permanent installations push for as many panels as possible, not only do you get a larger surface area, but you can put through a lot more water. I just saw JohnT's post, I would have to agree that it is probably that or more.

But, if your pool is at or close to where you want it to be, I like the idea of slowing it down and getting a warm rush from the returns!

[CarlD]

But, if your pool is at or close to where you want it to be, I like the idea of slowing it down and getting a warm rush from the returns!

There's ANOTHER way to get that