solar heater

[jmb120]

I am looking to get a solar heater for my AGP. I live in upstate NY and my pool temp never gets over 80. The pool is about 1/2 shaded in the afternoons. I have been looking at these on ebay since that seems to be the cheapest place to get them. Here's the link http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWAX:IT

In case the link doesn't work it is for 4-2'x20' Solarheat Super System II manufactured by Fafco. The price is $390. Are these ones you would recommend? Does the price seem reasonable?

 

[greif]

look on craigslist 1st..

you will need a couple depending on the size of your pool

 

[dmanb2b]

Hey neighbor...welcome to TFP, you will want 2-3 solar bear/fafco 4x20 panels. Our pool was at 84 deg today with solar cover on at night...was 50 last night. I have 2 panels on a 13,500 gal pool

These are the ones I got

http://cgi.ebay.com/4x20-Pool-Solar-Hea ... ltDomain_0

 

[jmb120]

Thanks for the info, I think I am going to hold off and get them next year. I do have one other question about the ones recommended, it mentions extra large 2" headers. Will this work with my currently pump/filter in which everything is 1-1/2"?

I really want them now, the pool is currently just under 70 degrees, way to cold to swim. We have had cold nights and several cool and rainy days. I can't justify spending the money now when we only have a few more weeks of swimming weather here.

 

[chem geek]

Thanks for the info, I think I am going to hold off and get them next year. I do have one other question about the ones recommended, it mentions extra large 2" headers. Will this work with my currently pump/filter in which everything is 1-1/2"?

Yes, you can mix piping sizes with no problem and in fact having 2" headers will be better since it won't add as much resistance to the water flow. You are already less efficient than you could be with everything at 1-1/2" so adding more piping to your system that's 2" is better than adding more that's 1-1/2".

 

[KPenn]

Hello all,
I have a couple of questions concerning solar heater panels. I converted my old solar water heating panels to heat the pool, they work, but not as well as I would like. My question concerns dwell time (the amount of time water spent in the panel to be heated), currently I have a small secondary pump drawing water from the pump/filter assembly that feeds the panels. I have a check valve on the inlet side of the panels, to prevent drainback. Right now, the panels get direct sunlight from about 10 a.m. to 3-4 p.m., so I have the secondary pump set to run at these times, but the return water is not as warm as it could/should be. In some intial tests, the panels produced STEAM after 15 - 20 minutes, so I know the potential is there. I need a thermally operated timer to control the pump, so far I have determined that the pump needs to be on a 20 minute off/5 minute on cycle. I'm trying to extend the usable pool time into the fall. Anyone have any experience with this?

Thanks

 

[danbutter]

KPenn... I'm sure others more familiar with this will chime in, but from what I have learned about this type of stuff is that the water heater panels are not suited for heating the pool.
A small amount of really hot water...what you can make with your panels, won't do what a large amount of warmer water will do for your pool.
I have been searching this site for more info on solar heating, but there doesn't seem to be a FAQ about them or anything...you have to read threads one by one.
Maybe if we ask nice we can get them to add one to pool school!

 

[chem geek]

As Dan noted, it is far more cost effective for pool heating to use panels designed for that purpose. The key is a large surface area since the volume of water that needs to be heated is far higher. The fact that your hot water heater panels make the water very hot isn't very relevant -- the pool water circulating through such panels won't get that hot and will take a long time to heat the pool. Such panels won't be any more efficient than pool water panels (i.e. flat mat plastic panels). If it's all you've got, then fine, but the flat black plastic panels are the least expensive and let you buy more to get more surface area which is key. Basically, you can't get more heating than what the sun provides and that's a certain amount of energy per area of panel. So getting more panel area is key. There is a technical comparison of different solar panel technologies in this thread.

 

[KPenn]

Yes, I knew that these weren't the best panels to use, but they were already installed, and the cost to repair the domestic water heating system was not cost efficient, but the panels were already here, so I said why not try.

When I manually cycle the pump, I can increase the overall pool temp about 5 degrees over a 4-5 hour period, but since the pool holds over 12,000 gallons, I don't get enough sun exposure to do much better, and I'm not really too happy about moving the panels to a different part of the roof, even though it would nearly double the exposure.

On top of that my "Higher Power" (pronounced "WIFE"), has given me a strict budget to work with!

I have created solar heating systems before, which worked nicely for heat/hot water, so I know the theories behind it, but I've never tried to heat such a large amount of water over such a (relatively) short timespan.

I will check out the links you all have provided, but I'm sure that I will have more questions.

Thank you all for your help :-D

 

[Renron]

KPenn,
What no one has mentioned (on this thread) is that your system IS working well and as expected. If you can heat the pool by ~5 degrees per day and perhaps only loose 3 degrees at night then you have a 2 degree gain per day. That's 14 degrees per week! Pretty darn good for free!
Its not a gas heater that will heat the pool in 5 hours, but it won't cost you anything either.

The most relevant fact you posted is that the water temperature after the solar collector is warmer than the input water. You DO want to heat the pool water gradually with solar, which is what you have now. The steam which the unit is capable of producing is not as efficient at heating the pool as is a few degrees per day. Reason is Water temperature delta. The hotter the water the more energy that WILL be lost. Efficient solar panels (for pools) will be cool to temped to the touch. Remember it is a different scenario than heating your domestic Hot water for showers and dishes. Patience will pay off here.

Ron

 

[KPenn]

Renron,
I have been doing some research and more "Testing" (my wife calls it tinkering...). Anyway, I have what appears to be older Gobi style panels, the house was built in the early 70's and I think they were installed then, as a "Added feature".

I have installed a few things, one is a temp operated valve on the inlet of the panels, with the thermocouple at the outlet of the top panel, along with a temp operated timer for the pump. The valve serves two purposes, 1. control the length of time the water stays in the panels, and 2. to prevent gravity fed drainback keeping the water in the panel.

With the thermocouple at the highest point, it reads the highest temp, and when it gets to 190 - 200 degrees, in opens the valve and starts the pump. The pump timer runs the pump for about 5 minutes, OR when the water temp drops to below 100 degrees at the thermocouple, then it shuts off, as well as closing the valve.

After doing this, I have been able to increase the overall water temp by almost 10 degrees a day, I haven't been monitoring the temp loss over night, but I figure it's about 6-8 degrees. Over the past week, the overall water temp has gone from 75 to just over 80. Not bad for a total investment of about $200 ( I just wish I had ONE MORE PANEL!)

And as far as the steam is concerned, I know that isn't the most effecient way to heat the pool, I just stated that as a matter of fact that the panels were getting enough sun, and are working (relatively) well.

Thanks for the input, I think I have a few more things to try . . . :idea:

KPenn
"Grumpy Old Man" :grrrr:

 

[JohnT]

You don't want high temperature rises in your panels. Although glazed panels deal with it better than open panels, high temperature rises are less efficient than raising a large volume of water by a very small amount.

It takes about 830 BTU to raise 100 gallons of water 1 degree F.

830 BTU will also raise 1 gallon of water 100 degrees F.

That water will increase your pool temperature exactly the same amount when it goes back to the pool.

But the hotter water will lose more energy through the plumbing as it goes back to the pool, and the panel will operate less efficiently at the higher temperature. Both effects mean that the best operation of your panels will be to run them at their maximum flow rate to minimize the temperature rise of the water flowing through them.

 

[KPenn]

JohnT,
I see what you're saying, the greater the temp difference between the heated water, and the air temp around it will cause it to lose heat faster that a lower temp difference.

Infact, before I had the timers/valves, the pump ran continously (during the day), and the water seemed to be a few degrees warmer than the pool water.
I ran 3/4" pipe to/from the panels, and then put a ball valve at the end of the line, where it was returned to the pool water, I used the valve to restrict water flow back, to ensure that I had constant pressure in the system, and to increase dwell time in the panels.

After much trial and error, I found that I could get the hottest water for the longest time by having the pump cycle on/off about every 20 minutes or so, and run for about 5.

Are you suggesting that I should lower the hi/lo temp settings on the valves by say, 50 degrees, or remove the valve and run the pump continously?

Thanks for the input

KPenn

 

[JohnT]

Are you suggesting that I should lower the hi/lo temp settings on the valves by say, 50 degrees, or remove the valve and run the pump continously?

Yes. If the panels get warm, some of that heat is being radiated to the air. Heat transfer is proportional to temperature difference. That means cool panels gain more heat from the sun, and hot water loses more heat while it flows back to the pool. Cool panels mean you are extracting all the heat you can from them.

 

[KPenn]

Makes sense, just like in HVAC, the greater the temp difference between the condensor and the outside air, the more heat is dissipated, thus the unit cools better (i.e. car A.C. blows colder drivng than at a stoplight)

Since I have the valves installed, I'll try backing the temps back to something like 150 for hi, 70 for low. Then I'll try bypassing the valves and letting the pump run cont. see which one works the best.

Thanks again

 

[Renron]

Perhaps I was not clear enough with my earlier post? Sometimes I am too verbose. The delta I was referring to was the difference between water temps In and out of the solar collector.
A few things to consider;
Thermal cycling is very hard on plumbing parts, expanding and contracting will shorten their life cycle considerably.
A glazed collector works more efficiently because there isn't any heat loss due to wind chill factors. Short wave radiation (sunlight) passes through the glass and becomes long wave radiation, which does not pass back through the glass this is known as the Green House effect. Long waves are absorbed as heat and transferred to medium which is pool water.
The hotter the water the more energy it has stored, which in turn has a higher factor of energy loss. (delta)

Remember the "Tortoise and Hare" parable?

Ron