Need some pump advice

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Wolfmarsh

0
Jun 18, 2007
151
Charleston, SC
Hi everyone,

I installed my solar heating panels last summer, and based on everything I read, I am not getting enough flow through them. Everything I have read says that I should only feel a few degree difference between the pool water and the water coming in the pool after running through the heater. It feels like it is at least like 20 degrees warmer (very scientific, i know). I can measure it this summer to be 100% positive, but I was very disappointed in the performance of my panels this past summer and I am thinking the lower flow might be to blame.

The other thing I am thinking about is that since it is a AG pool and if the panels are off, there is literally like 5-10 feet of piping from the skimmer to the return, that 1hp is grossly overpowered for that small run.

I was thinking about upgrading to a 2 speed so when the solar was off, it would run on low, and when the solar cut on, the pump would switch to high, but I wasnt sure what the top end of the pump should be (1.5hp?), or if i should be using a more powerful IG pump instead of the AG pump.

I can take pics and measure the travel of my pipes to the solar system if necessary, but I imagine its about 40 feet level, 10 feet up, 10 feet down, and 40 feet level back to the pool.

Thoughts? If you need any photos or more info, just let me know.

Thanks!
 
A two speed pump is a great idea.

For guessing at the pump size you need, it would help to know the diameter of the pipes, the number of panels, and how the panels are plumbed (in parallel, in series, some mixture of the two).
 
It is all 1.5" piping, four 2x20 panels, plumbed in parallel.

Here are some pics of the installation for reference:

IMG_2944.JPG


IMG_2946.JPG
 
For 160 sq-ft of panels, you should only need 16 GPM to maintain a temperature difference of less than 5 degrees. Is the flow rate significantly different with and without the panels? What is the difference in filter PSI?
 
An above ground 1 HP pump ought to be able to handle that setup just fine. In fact, I would expect that you would need to set the valve to allow some of the water to bypass the panels or you would get too much flow through the panels.

That suggests that there is a problem somewhere else in the system.
 
I misspoke in my post above, and my math was wrong :) They are 2x10 panels, there is 80 sq ft total. When I saw mas mention 160 sq ft i realized my error.

80 sq ft should be enough for my size pool though, correct?

Edit: And since there doesnt seem to really be anything obvious wrong, I will probably just revisit this come summer time. I can do temp measurements easily, is there any easy way to measure flow rates?
 
Seems to me the panels are mounted sideways. They should be fed from the bottom of the panels to push the water up to the top. A self closing bleeder at the top lets the air out till the panels are full and then shuts under the pressure of water flow. When the system turns off, the water drains back.

Typical right sized systems, as I understand them should be 1/2 to 3/4 the area of the pool surface with additional dependencies of wind, # of sunny days vs. cloudy days, angle and direction of the panels, # of hours the sun hits them, etc...

Scott
 
PoolGuyNJ said:
Seems to me the panels are mounted sideways.
Click to expand...
While not ideal, this would not normally cause any serious problems, let alone the problems that have been described. Mounting the panels sideways is very common in seasonal installs. The main thing that can go wrong is that the panels don't always drain completely, which can be an issue in the winter if they are not removed for the winter. They are also a bit less efficient mounted sideways, but that difference is relatively small.

PoolGuyNJ said:
Typical right sized systems, as I understand them should be 1/2 to 3/4 the area of the pool surface with additional dependencies of wind, # of sunny days vs. cloudy days, angle and direction of the panels, # of hours the sun hits them, etc...
Click to expand...
There is no "correct" size for a solar system. Just one panel will help noticeably, while some people who like to swim nearly year round in Canada have systems with three times the area of the pool or more. The more panels you have, the warmer you can get the pool. So it is really a question of how far you want to extend the swimming season and how much space and money you have.
 

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You cant tell from the picture, but it is actually slightly tilted as well, so the lowest point is the front pipe. When it switches the panels off, the vacumn release valve gurgles and the panels do drain.

It never really freezes here in Charleston, so draining them before winter and leaving the pipes open to dry any remaining water should be good enough to prevent freeze damage, no? If you look closely at the bottom picture, you can see I have drain plugs in both pipes to and from the panels, so before the winter, I completely opened them up and let the panels completely drain out, and all the piping too.

I was able to get the temperature up to like 85 by running the panel all day. Overnight though, it would drop like I had never had a panel (I assume a solar cover would help with that). There were days though that you could feel the very hot water coming from the return, but it never seemed to make a difference to the pool water except for 2-3 degrees.

I know this is a wierd problem to solve, so I am just going to collect more data when I get the pool open, and Ill ask for more assitance then :)
 
The best case you can assume in June-July is about 2000 BTU/Day/sq-ft with an 80% efficient panel (2500 * 0.8) so that is about 160,000 BTU/day. For 8000 gallons of water, that will add only about 2.5 degrees per day. You will easily lose that overnight in a AG pool so net gain is probably 0. So my guess is you don't have enough panels.

I have 480 sq-ft for a 20k pool or about 41 gallons of pool per square foot of panel and maintain 86-90 degrees throughout most of the summer with daily heat gains of up to 10 degrees in June-July (with pool gain). To get the same performance, you would need close to 195 sq-ft.
 
I was worried that might be the answer. I have used all of the available space on the little patio roof i built, so I may have to get creative at this point....

I might try the cheap way out and try a solar cover during the week (since we only swim on the weekends) and see how much that helps.
 
Wolfmarsh said:
I was worried that might be the answer. I have used all of the available space on the little patio roof i built, so I may have to get creative at this point....

I might try the cheap way out and try a solar cover during the week (since we only swim on the weekends) and see how much that helps.
Click to expand...

That will definitely help! Don't forget to peek under the cover once in a while to make sure the algae has not moved in.
 
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