Solar Pool Heater

[muvipix]

Great forum - learned a lot by lurking about the past month or so!

We live up in Maine and, though our weather hasn't yet been the greatest this year (a little on the cool side so far this spring), we're still getting several sunny days in a row and it seems like our solar system isn't as effective as I'd hoped.

We have 6-4x10 panels (all that would fit) on the south roof which receives direct sun from about 10 AM - 5 PM. Water temperature started at about 60 degrees as of Sunday and it's been sunny and in the mid 70s ever since. I turn the system on about 9 AM and let it run until about 5-6 PM and the water temperature has only increased 4, maybe 5 degrees in the past 4 days. Is this normal? It would seem that even if I didn't have the solar panels, the warmth alone would increase the pool temperature at that rate, wouldn't it? I've read other posts that claimed up to 10 degrees in a single day (ie, Indiana, Pennsylvania, Michigan). I even threw the solar cover on yesterday, but it didn't seem to make a difference.

Is it possible that my flow is the problem? When I run the pump/filter by itself, the pressure is normally 8-10 PSI. When I engage total solar panels, the pressure goes up to about 12, but I get air burps out of the returns, so I must close the return ball valve a little (pressure goes up to about 15 PSI) until the air ceases. Is this too much pressure or not enough flow or is it too much flow because of the increase in pressure? Not quite sure how that works.

I've felt the panels on the roof and they are cool to the touch when operating so it seems as if they're working OK. Would love to hear comments, especially those in cool climates with solar heating and your average rates.

I hope I provided enough information to assess.


I think it may be time for a separate Solar forum (IMHO).

 

[dmanb2b]

1-2 degree gain per day seems about right to me, but more importantly...are you using a solar cover along with the panels? I am in the norteast as well and without the cover all that warmth is lost with the overnight temps reaching into the low 50s and even 40's still.

Another sanity check is that around noon, you can put your hand over one of the returns and see if the water coming out is warmer than the pool water around it....given your panels are cool to the touch in direct sun...they seem to be working OK

 

[JohnT]

Like dman says, the cover is a huge help, especially with the relatively cool air temperature. Wind is also an enemy of solar pool heaters.

I wonder about the air in your returns. That could be an indication of some plumbing issue. Do you have a bypass valve or a 3-way valve to control flow through the solar? It seems like you should be able to set that to eliminate any air, without restricting the flow. How high off the ground is the panel outlet?

 

[muvipix]

Thanks for your replies.

I mentioned that I tried the cover (I will continue using it). It was breezy the first few days, good point. Today is not as windy and it's mostly sunny again. Maybe it will make a difference.

The panels are about 40 feet away, up about 15 feet. So, the output is @25 feet. I have it plumbed according to this diagram (nothing automatic and the my vacuum relief is at the top of the panel):[attachment=05l9n19q]plumbing.jpg[/attachment5l9n19q]
And the air is only an issue when I have the [return] ball valve completely open. Do you think that partially closing the valve is reducing the efficiency somewhat?

 

[JohnT]

And the air is only an issue when I have the [return] ball valve completely open. Do you think that partially closing the valve is reducing the efficiency somewhat?

Partially closing the valve is going to reduce flow and increase the pressure in the panels. I'd try to adjust the 3-way valve to send less water to the panels with the valve in the return line fully open to see if you can eliminate the air that way. Are you hearing any hissing on your vacuum relief valve or seeing any water dribbling out of it when the bubbling is occuring?

 

[muvipix]

Partially closing the valve is going to reduce flow and increase the pressure in the panels.

Wouldn't reducing the flow cause the water to warm more as it's flowing slower through the panels? Or do I have that completely wrong?

I'd try to adjust the 3-way valve to send less water to the panels with the valve in the return line fully open to see if you can eliminate the air that way.

I'll try that and see if it works!

Are you hearing any hissing on your vacuum relief valve or seeing any water dribbling out of it when the bubbling is occuring?

Haven't went to the roof to check that. I think that that's what may be happening, though.

 

[JasonLion]

If I am doing my math right, I believe that you have about 50% coverage (the panels cover an area about half as large as the pool surface). With a solar cover on overnight I would expect more heat gain than you report, bit without a solar cover and with cool nights that might be all you can get this time of year in Maine.

 

[JohnT]

Wouldn't reducing the flow cause the water to warm more as it's flowing slower through the panels? Or do I have that completely wrong?

You are right, but closing the return valve reduces the flow through the entire system and increases the pressure in the panels. Moving the 3-way will reduce flow through the panels, but it keeps full flow through the returns and skimmer and maintains a lower pressure in the panels.

 

[haybird]

Hello,

We have the same size pool. My panels are undersized, and I gain 1* per hour.
About 6* on a sunny day. You have to use the cover at night. My net gain is only 3*
because I lose 3* over night. But you are starting 3* warmer the next morning.
If I didn't use the cover I would lose all 6* I gained.
Good Luck

 

[muvipix]

I mentioned twice now that I'm using a solar cover :-D

I reduced the flow with the 3 way and it seems to be doing the trick. No air and the pressure is down to 11 PSI.

The pool temp is about 66 (air temp 77) with a few more hours of sun to go. Hopefully, I get another degree, or 2 if I'm lucky.

Thanks!