How to Heat your
Pool With the Sun

While looking on the internet for plans to build a solar heater for my pool I found that there just wasn't any decent plans available so armed only with a desire to swim in warm water and the knowledge gained by reading Popular Mechanics magazine for 30 years I set out to build my own system.

I knew I wanted a standalone system with it's own pump and if possible I wanted to make the pump run automatically with a thermostat. One of the things I've learned from my research is that a solar panel will also work as a radiator when the box is cooler than the pool water. Also I didn't want to have black pipe all over my roof.  I think that looks so tacky,  So I decided to make a wooden box that would sit in my back yard and be of sufficient size to handle the job.

I decided on a one sided pup tent style design made out of 2 X 8's.  This way if I needed to turn the unit to get the right orientation to the sun I would be able to move it wherever I needed. Fig 1.  First thing was to build the bottom of the box. 6 - 2x4's laying flat with mitered corners and a cross brace with a half lap joint in the middle.  Fig 2. After I got the frame done  I laid 2 sheets of 3/8 plywood over the base and squared everything up and screwed the plywood to the 2 X 4's. Next step was to wrap the 2 X 8's around the outside of the base and fasten them to the 2 X 4's. I left the outside 2 X 8's - 24 inches longer so that when it's up I'll be able to get the lawnmower under it. Fig 3.
This picture shows the back side of the box laying against my chimney.

It's tough working on a summer project in the carport when your surrounded by 6 ft. snow banks.

And your pool looks like this

With the box almost all set I started on the window frames.  I built them out of 1 X 4 strapping & constructed  two 4 X 8 ft. frames. Building them on a plywood table it made it easy to get them square.

This is the end of day two, Feb 16 2004.
Both window frames are built and the box is almost done.
 

Day 3 Feb 17.
Well it's 5:30 AM. and way too early to be outside using power tools so I thought I would draw up a schematic of my backyard to give everyone an idea of what the project will look like after it's done.

Day three saw the doors sanded and the rabbits cut to accept the glass.
Time for a week off.

Feb. 22/04
I just got home from Vernon where I picked up 500 ft. of 1 inch poly drip tube, My original plan was to use 1 1/2 black poly but after talking to my plumbing buddy, we decided the 1 inch would work better account I would get more surface area touching the inside of the pipe, a big plus is now that I'm using a smaller and softer pipe I'll be able to get my coil down to a smaller diameter.

Feb 24/04
I see I'm getting hits on my page but no comments so I thought I would ask some questions.
This is the box I'm building the blue is the cold water coming in at the top and spiraling to the middle, and the red is the heated water spiraling back out to the edge, I will have one coil sitting on top of the other. My first question is, Should I have the cold water enter the top coil or the bottom?
Or will this matter.

Feb 26/04

Well today started out great, I had 3 replies to my E-Mail that I sent out in my search for glass, a friend of mine called and said he had an old window I could have, so off I go with an other friend to have a look at it, it was perfect 4’X6’ double pain. I figured I would be able to get twelve pieces out of this window, that was till the three of us picked it up and as we were carrying it to the truck the damn thing broke. Oh well I should be able to salvage three maybe four pieces out of what’s left.

So off I went looking for my second window, seems it was sitting in the garage for 7 years, but when we went to look for it was nowhere to be found, so much for that.
Here’s what I was left with.

Feb. 28/04

I started my day trying to salvage what was left of the broken pane. After cutting the two panes apart and only breaking it one more time I was left with 3 sheets of glass large enough to cut down to size. By my calculations I should have been able to get 5 lights for my frame. Unfortunately my glass cutting skills were never any good but still I tried cutting the first piece on my own. The first two cuts went great but the third cut to square off the top was a disaster. Oh well, one sheet down and two to go. I decided to call a friend who had cut glass for a living. He dropped by and we got to work. We got two lights cut from the second piece. The third sheet was a different story. On our second cut the line strayed and ruined the sheet. Well I guess that’s the chance you take cutting your own glass. In closing, I started out with 48 sq. ft.  of glass and ended up with two pieces 19 ¼” X 19 ¼ “. Maybe I’ll have better luck with my next window.

Feb. 29/04

Well today was kind of a slack day. It started out with grand ambitions of finding a couple of windows that I could tear apart and cut up. As it turned out I spent most of my morning playing out in the carport practicing my glass cutting. That’s not a bad thing with all the scrap glass I had in the back of my truck. I was able to make 35 to 40 cuts and 75% to 80% of them worked. With any luck I won’t have to sacrifice too many more windows to my cutter. In my opinion any day you learn a new skill it’s not a wasted day.

March 14/04
Well I have half the glass I need.  I would have it all but I've broke more glass than I've cut so I'm still on the hunt for old windows to sacrifice to my cutter.  There's also very little I can do till I get the inside of the box painted black and for that I need better weather so with any luck I'll be able to paint within a week or so.
 

April 6/04

It's been a very busy couple of weeks. Between getting the yard work caught up after a long winter and working like a dog I've been able to get quite a bit done with my collector. I have collected all my glass and cut it down to size & I have the window frames painted and ready for the glass. The box is painted and I'm almost ready to lay the pipe in the box.
Here's a couple of pix to catch everyone up on what I've been up to.

 I was also able to get my spacers painted and cut down to size

I had a couple of friends drop over for beers yesterday and just by chance one of them is an Mechanical engineer. We started talking about my project and he helped me out by setting up an Excel program to show me the time the water will be in the box at different flow rates. I'm shooting for 600 GPH.
I just hope 1.7 min. in the box will be enough time to pick up some heat.

With any luck I'll be ready to lay the pipe in the box on Friday

April 10/04

 Well it’s Saturday and I finally got time to work on my project.
With the poly being in such a tight roll, I thought it would be easy to just lay the pipe in the center of the box and then start to fasten the pipe to the outside edge and work my way inside.



 

I spent 3 hours getting eleven wraps laid down and tied into the box and then the pipe stated to kink. I decided after 3 hours and 6 beers it was time to call it a day.







 

Monday April 12/04

Well, with the help of a friend I was able to get the rest of the pipe installed in the box. By reducing the radius in the corners the kinking problem seemed to take care of itself. I was able to get the pipe down to a 24 inch diameter and then I started to work back out to the edge. Contrary to just about everyone I’ve talked to all 500ft. fit into the box. She may not look pretty but it’s all in there. Next up is getting the frame work on the box and a brace in the center to hold the windows in place.

April 13/04

I started out Monday cutting the face frame for the box. I missed one calculation while designing this system & the windows were too small for the frame.  I used 2 sheets of 4X8 plywood with 2X8's wrapped around them & then I built the window frames to be 4X8. While painting the windows I realized that they would slip inside the frame. To correct this problem I cut a face frame out of 1X'4s.

With this problem out of the way  I turned my attention to supporting the window frame in the center of the box. I think a simple box built out of 1X4's should do the trick.

So all I have left to do on the collector is get everything primed, painted and the center support assembled. Then I should be ready to get it moved out to the back yard.
All I have to do is bribe three of my friends with beer to give me a hand moving it.
This is just an estimate but I'm guessing this unit will weigh around 300 lbs. dry.

April 26/04

Over the last two weeks I was able to get the rest of the painting done, and the final assembly of the collector completed. Today was moving day what a wonderful feeling to get this behemoth out of my parking space. So far I think it turned out pretty well, I still have to trim out the windows and run the plumbing, the plumbing should only take me a couple of hours, and the trim I'll worry about next week.

I should mention I've made a design change, I'm not going to run a separate pump, I'm going to plumb the collector right into the main pump. I'm going to cut off the pipe to my old oil fired boiler and reduce the line to one inch, with the ball valves I should be able to control the flow through the collector, when I'm able too I'll pick up a couple of zone valves and figure out how I'm going to make this system automated.

We finally got everything set up at 16:45 it was a very nice day with temperatures reaching 23 degrees C. (73 F.) the thermostat inside the box reached 48 degrees C. (119 F.) this is with no foam tape sealing the windows, and I also have to cut a center strip to go up the center between the two windows to seal that area, It'll be interesting to see what the temps are with water running through the pipe .

I would like to thank my friends for giving me a hand today
Larry, Nick and Duncan.

                                                                              Comments or Info

Fig 1

Fig 2

Fig 3

Here's a basic parts list along with the prices

Lumber
2-2X8 12ft.
2 2X6 12ft.
6 2X4 8ft.
2 3/8 plywood
12 1X4 strapping
1 3/4 plywood
for table

Total cost $168

PVC Pipe
 500 ft. PVC Pipe
$164

Glass
Freebie

Pump
Still to come
 

Extras
Paint $30
Hardware $8

Time

GPH Imp.

Outside Temp

Box Temp

Intake Temp

Outtake

13:30

240 F.

64 F.

72 F.

48 F.

56 F.

1355

"

66 F.

"

"

"

14:30

"

66 F.

71 F.

"

"

16:00

"

64 F.

68 F.

"

"

17:20

"

64 F.

65 F.

"

53 F.

17:40

"

57 F.

62 F.

"

51 F.

11:00

480

59 F.

65F.

48 F.

49F.

11:30

"

63 F.

66 F.

"

50 F.

12:15

140

66 F.

70 F.

"

60 F.

13:00

480

70 F.

77 F.

"

52 F.

15:00

"

71 F.

77 F.

"

52 F.

Time & weather

Outside Temp

Box Temp

Pool Temp

Outtake Temp

10:00 Part sunny

60 F.

76 F.

65 F.

63 F.

11:00 Part sunny

64

87

65

65

13:00 Part sunny

65

88

65.5

65.5

15:00 Cloudy

63

74

65.5

65

16:30 Cloudy

62

62

66

64.5