DIY Solar heater questions

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calivette2003

0
Sep 11, 2010
31
San Diego
Hi all,

I saw a several designs @
http://www.gullsolar.com/index.php?page ... cc41db8ab7
http://ffaat.pointclark.net/blog/index. ... erendipity[csuccess]=moderate

I had a few questions in regards to bulding my solar coil heater and thought I might get some advice here.

Application is on 12'x24'x52'' Intex above gound pool. Plan on everything you discussed in above site with following changes;

1. Coil (250') is to be mounted flush on roof. We are in San Diego CA and the roof is always 90F, even on cloudy days.

2. Given the head pressure of 1/2" tubing going up 20ft to the roof I'm not sure if the main pool pump, 2500gph Intex is the answer. Is that too much strain on the pump? Too much flow? Thinking of buying a hi-pressure, low volume elec. booster pump so as to not blow out the main pump and save on electricity. Check valve between booster pump and roof so when pump shuts off water doesn't fall back towards pool.

3. The booster pump will take a suction off the pump inlet as this is lowest point (4 ft.) below the pool level and should provide constant inlet pressure to the booster pump so priming is never needed.

4. The booster pump to be mounted on a timer, booster pump comes on for 30-45 minutes, push hot water to pool
and refreshes with cold water from pool to coil. Pump comes on every 1.5 hrs. from say 11am to 5pm.

Now questions:

a. Can I tie the heater return line into the main pool pump discharge piping so it doesn't look ugly hanging over the top of pool? Will the small amount of return flow be able to overcome 3ft of 2" piping going from main pump to outlet pool jet (jet is right at pool water level)?

b. What kind of automatic air bleeder valve can I put into the coil on the roof? I know with 20 ' of tubing going to a roof I will have air lock if I don't have a bleeder. Auto store??? Have not sen anything at Home Depot.

Appreciate any ideas or support.

R/
David
[email protected]
 
While DIY solar heaters are very possible to build and do work it's usually better just to buy ready-made panels. They're cheaper and more efficient than anything you can build for the price. I've done the calculations and I can't build them for nearly what I can buy them for.

First lets clear up a few misconceptions you have.
1) When heating the pool your heater needs to run constantly as long as the air temp is higher than the pool temp and the pool water temp is lower than you desire. They're actually more efficient this way than stopping the flow to allow the water to get hotter.

2) You want the panels to drain completely when they're not heating the water.

3) You may not have enough suction flow for both the main pump and the solar pump if they're tied into a common suction. Just something to be aware of here.

Now to answer a few of your questions.

a) You can tie the solar discharge into the main pump discharge but you'll have to be aware and make sure that the main pump discharge pressure must be lower that of the booster pump.

b) You won't really need an automatic bleed valve as the heaters if plumbed correctly will be self filling and will displace the air in the panels to the pool with pool water. You'll get some bubbles in the pool when it starts but that's not an issue. You will need a check valve (or air gap) to allow the panels to fully drain when they're shut off.

I'm not trying to discourage you from trying this just do a lot of research and figuring to see which is the best route for you.
 
Dave, thank you Sir for taking time to reply.
Do you have any pre-made solar panel "favorites" I was thinking of purchasing these to put up on the roof. http://www.aquasuperstore.com/products/ ... ~3664.html
I really like the roof idea even if it requires another pump to get up to the ROOF as my roof temp was 95F, yesterday, air temp was 73F. So even on cold days, the simple conduction of heat from roof shingles to heater, not even including the sun's rays beating down on the heater, will heat the water. You can't get that with a solar heater on the ground by the pool. Plus the earth will cool the tubing laying on the ground.
 
I'm currently also researching this. I have already got a Pentair controller (2nd hand) and have just to design a cheap panel as I feel the 1400€ Heliocol want for 16m2 of plastic excessive. I hadn't thought too deeply about a coil design as the panels I have looked at are standard radiator designs. I managed to get the costs down to about 600€ using 2" pipe with manifold top and bottom and 2 interleaved panels to ensure full coverage of surface area. My design needed a LOT of T pieces and elbows however and the chance for leaks was quite high. I do like the design in either of your designs, using multiple coils so that the 1/2" pipes can be plumbed in parallel to equal the loss of head from a 2" pipe. This way you need many less unions. NICE.
I wouldn't worry too much about glass; from what I can gather from other sources, the heat gain in the panel is so low that the glass causes more loss than the wind. Glass(insulation) is more useful when there is a greater difference between air temp and water temp. I have heard, however, that a low "wall" around the panel can help with windchill, without stopping and solar insolation.
You will need a larger area to use as you lose some surface area in the quadrants that you cannot use to harvest sunlight but the savings where I am would be immense. I personally wouldn't use irrigation pipe but rather, thicker Polypropylene pipe as the cost difference is minimal in dollar terms.
 
Learned alot from this site.. Plumbing and Controlling Solar Swimming Pool Heating Systems: http://www.h2otsun.com/PG5ht.html
-and- The Marriage of a Solar Heater and a Swimming Pool's Mechanical and Plumbing System: http://www.h2otsun.com/pools/index.html

Now I have to say some of it starts to get a little pipe happy by the bottom of the article in the second link I posted, but its a good in depth analisys of solar plumbing by what apears to be a company with real world experiences.
 
After reviewing some pictures/ comments on various websites of roof mounted coils (PE tube) I was thinking about winding the coil directly to the roof WITHOUT the wooden frame. If you look at any of the commercially sold solar heater pads ,they are directly bolted to the roof, no wood or structure underneath them. The wood appears to be an insulator (bad) between the shingle heat and the PE coil.

This idea should:

1. Allow full transfer of roof shingle heat (100%) to the coil through direct conduction. Combined with the heat of the sun on the coils this may be 150% more effective than wood frame models.
2. Limit “wicking” loss of heat due to wind carrying away heat. (wind between roof and the wooden frame/ wind catching heat off coil since the coil is no longer flush with the roof)
3. No time or money spent making the wooden frame.

Guy on one of the pool forums said his heat index increased remarkably by doing this.
One thing would be having to figure out way to hold down coil without having the wooden frame. Maybe some zip ties screwed into the roof or combination of zip ties and PVC hold downs screwed to the roof. Either way pretty easy to do.

Gentleman.....your thoughts???? :cheers:
 
CIVIC TURBO, yeah that's exactly where I got the initial idea. :cheers:
I also thought, instead of just hanging the return line over into the pool how about installing a small PVC eductor, like this one:
http://www.millerplastics.com/eductors.html
Eductor to be tied into your pump's return line going back into the pool. This will greatly enhance the collector's flow (your pool pumps flow thru the eductor creates 15-20" of vacuum in the coil return line).

See explanation:
http://www.primetechrkg.com/images/tme.jpg or at http://www.1877eductors.com/

Even if your collector gets completely air bound the eductor will suck it out automatically aiding in collector flow and less burden (static head) to the pool pump.
We had huge, 500 to 2,000 gpm eductors in the Ship's engineering plants in my Navy days. They will suck up anything, water, air, oil, small people. Even swallow and pulverize 2x4 boards (yes I tried that)....or suck your hand off your arm if your not careful.
 

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The only concern I have before buying the millerjet eductor is total flow
eductors1.jpg

($79.00) .
The water return on Intex pools has these isolation valves
10747.jpg

which have a 90 degree bend and thus some backpressure. If the flow through the eudctor is slowed down or impeded down stream due to these valves then there will not be enough eductor vacuum or worse yet the eductor suction line will become pressurized stopping all solar collector flow. This is why I am going to "attempt" to build my eductor from PVC at first.
If my DIY eductor is sucessfull I will then buy the Millerjet eductor as it is far more efficient than anything you can make(DIY). If the backpressure will not allow a eductor to work then I will revert to the plans Civicturbo sent me and use their "in pool jet pump"
 
Well spent 3+ hrs. up on the roof (105 degrees) and the 1000' of DIG coil turned into one alful notted mess!! Plus it kinked every two inches. At the kinks it ripped open holes as I drug it across the roof. Gave up and returned everything to Home Depot.

Now rethinking whole new project using Sungrabber panels and solid 1/2 or 3/4" PVC lines with a independant pump.

0ca1_35.JPG

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWAX:IT

Replacement panels with no hardware for $72 each. My pool (12'x24') needs up to four units.
Plumb PVC to all four in parrallel using a seperate hi-press. low GPM pump as shown below.

image_21.jpg

http://www.harborfreight.com/1-inch-cle ... -1479.html

Since the system has it's own independant pump no eductor will be needed on the return, just using 2" ABS tee's for both the pre-pump inlet and pool return outlet. Any advise on size of PVC Sch. 40 ??
 
DO NOT USE THAT PUMP!!!
I did that my first year with solar panels. Same exact pump too... it can't take the chlorine (or something in the water).
The thing is a piece of Crud and was frozen in three months as in rusted solid, shaft won't turn even by hand let alone when you plug it in.
I tossed it into the trash and plumbed into my pool pump this year.

Is there a reason that you can't use your pool pump?
 
I was just at Lowe's and saw a above groung pool pump/filter for 33.99 regular white price sticker. It says 1000 gal/hr After my tested of several pumps I would say always test the flow rate yourself. It is the same price I paid for that harbor freight pump on sale. Went to the Lowes website but search dosen't show the pump.
 
civicturbo, you mention testing the flow rate yourself, how do you do that? I have a 2 speed pump and would love to know what my GPM flow rate is with the pump on Low versus High. Do I need a special meter or is there some other way to calculate it? Thank you!
 
I am building some panels like these from Coroplast Panels. I researched this extensively and this has been the best DIY design I have found (at least in my situation) for heating my pool. I ordered the CD to check it out and the instructions are pretty detailed and easy to perform. My Wife was even able to understand the instruction and she has absolutely no technical and or building know how (shh! I didn't say that).


http://www.solarpanelsforpool.com/index.htm
 
An above ground pump will not usually work for panels mounted on the roof. If the roof is lower than normal it might work. If the panels are down near pool level an above ground pump is just fine. Above ground pumps are low "head" pumps, not suitable for pushing water up any significant height (for which you need a high head pump). An eductor will only improve this situation a little. You can't have too much negative pressure or the tubing will collapse, pinching off the water flow.

Also, you do not want to use a low flow rate pump on solar panels. You want a fairly high flow rate. Higher flow rates are much more efficient.

Pipe coil collectors are dramatically less efficient than commercial panels. You want lot and lots of parallel runs of pipe, not one long run of pipe, for peak efficiency. Making all of those connections is time consuming and leak prone. Commercial panels do all of that work for you with very good reliability at attractive prices.
 
m1rabel said:
civicturbo, you mention testing the flow rate yourself, how do you do that? I have a 2 speed pump and would love to know what my GPM flow rate is with the pump on Low versus High. Do I need a special meter or is there some other way to calculate it? Thank you!
Click to expand...
I found the best way was to spring for the GPH gauge. They have them on fleabay for resonable prices.
 
I have a feeling that the instructions you bought from the site would be very similar to this design: http://www.instructables.com/id/Build-your-own-flat-panel-solar-thermal-collector/?ALLSTEPS

My main worry about this design is the potential of leaks. The seal between the panel and the pipe would be a major weak point.


Articfox918 said:
I am building some panels like these from Coroplast Panels. I researched this extensively and this has been the best DIY design I have found (at least in my situation) for heating my pool. I ordered the CD to check it out and the instructions are pretty detailed and easy to perform. My Wife was even able to understand the instruction and she has absolutely no technical and or building know how (shh! I didn't say that).


http://www.solarpanelsforpool.com/index.htm
Click to expand...
 

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