Water flow through a solar heater

[80sDweeb]

I plan to build a 4 x 8 or 4 x 16 solar collector (as seen on YouTube) and I see the volume of water that can flow through the 1/2 inch tube isn't much. My idea is, if I don't want to put too much strain on the pump, it seems like it will be better to "double up" or "triple up" the lines in the heater, to reduce back pressure. I mean, split the inflow into two different heating circuits, or three circuits, so the pump can push against much less restriction (vs. pushing the water through a very long 1/2 inch circuit, it would be pushing it through 2 circuits 1/2 as long, for example.)

I saw one YouTuber who was trying to restrict flow in the heater to increase the temp, and I know that's wrong. If anything, the faster you can get the heat out of the collector, the better (sun heats a cool collector better than a hot one,) as long as you're not using extra electricity to increase the speed.

Will I run into any unforeseen issues with this approach? How do I evenly split the flow between "circuits"?

Thanks,
Scott in Snowflake, AZ

 

[chiefwej]

Do your self a favor and just look for some solar panels. It has been proven time and again that homemade panels end up costing much more for the amount of heat produced. Panels are relatively cheap. You may even score some used on Craigslist. Save your DIY talents for the plumbing and install of the system.

The goal of a solar system is to raise the temp of a lot of water by a small amount. You don't want hot water coming out. Large volume, small temperature differential. With higher temps, there is much more loss of heat in the system.

 

[domct203]

Do your self a favor and just look for some solar panels. It has been proven time and again that homemade panels end up costing much more for the amount of heat produced. Panels are relatively cheap. You may even score some used on Craigslist. Save your DIY talents for the plumbing and install of the system.

The goal of a solar system is to raise the temp of a lot of water by a small amount. You don't want hot water coming out. Large volume, small temperature differential. With higher temps, there is much more loss of heat in the system.

Agreed.

I've seen pictues of DIY solar heaters comprised of nothing but 500+ ft of poly tube, passing water that is scolding hot, but maybe only 20-30 gallons of it daily. What is that going to do in a 10,000 gallon pool? With the flowrates of commercial panels you could easily pass hundreds of gallons (even in the thousands depending on size of system) of 3-5F warmer water to your pool every sunny day.

I bought my Fafco panels on eBay, I think it was $260 + shipping for 72 square feet of panels, gives me a solid 3-4F in my 6700 gallon pool every 'mostly sunny' day, and the pool is shaded after 3pm, the panels are shaded after 5pm. The more square footage of surface area of the panels, the more heat transferred to the pool.

The best efficiency is with a solar controller, and a solar cover to retain the heat you put in. The controller will ensure that the panels do not run when it get cloudy and/or the air temp falls below the pool temp, and the cover will help retain the added heat overnight. Some controller can even be set to cool the pool by running the system at night to use the panels to radiate heat into the colder air temps.

If you're really determined to do this DIY, put many waterlines in parallel (which is what you are describing when you say to run two or three together) to increase efficiency. A solar panel is just that, many small tubes that are joined at headers at each end. You are correct in thinking that parallel plumbing will move more water with less resistance, and that is something you want with solar, to heat a large amount of water a few degrees.

Something like this (random pic I found):


I can't imagine that after all those barbed fittings, poly tube, PVC pipe & fittings, and your time, that you could DIY for less money and get the same BTU output & reliability as the same size (sq.ft.) commercial panel.

 

[CJadamec]

The other two hit the nail on the head. If you are looking to DIY something there is still plenty to do even if you buy the panels. You can easily find a 2x20 (40sqft) panel from a number of online retailers for around $100. I put in 3 panels and they work way better than I ever would have thought they would.

DIY the installation not the panels.

 

[80sDweeb]

Thanks, everyone. I've ordered a kit with (2) 2x20 FAFCO panels ($200 shipped), and as you all say, I'll have plenty of DIY with the mounting and setup, as well as figuring out the cheapest/best/simplest controller so I don't have to remember to shut the valve on and off whenever it rains or every night. I'll also have the option of adding a third panel, like Chuck has, but we'll see if it's necessary.

I have a big 6 x 16 ramp I built to unload a semi trailer, which I thought I could cover with the DIY tubes. I'll have to re-configure the lumber from the ramp to fit the 4x20 solar.

I just left Rochester, NY (elevation 500 ft,) and now we're here in Snowflake, AZ, elevation 5600 ft. Wow, is the sun BRIGHT here. I look out my house windows at 7AM and wonder if I should give them some limo tint. It does get cool here at night, but today it got to 100 degrees, yet nobody here has a pool. I haven't found a single person, other than a Walmart Intex-type 12-footer that I saw in a real estate listing when I was house hunting. There are some rich folks who have their pools indoors, but no outdoor pools at all. I've ordered a solar cover, and I'm going to have to figure out the best way to deal with it, so that we'll use it every night, otherwise the solar heater will be hopeless (cold, clear nights here in the desert.) Plenty of info about that on TFP.

Not having a pool isn't an option for my wife. We didn't have one back in NY, but we had a YMCA membership, and the Y was just a few minutes away. Here there's no YMCA, no public pool, just an "aquatic club" you can join in a neighboring town, about a half hour away. We ask people why no pools, and they tell us it just isn't warm enough(!) for it. 100 degrees today, and 99 degrees yesterday, 100 last week, and it isn't warm enough for a pool?

The cool nights are one of the big differences between here and NY. But NY had far fewer days of sun, all year round, than here, so with a solar heater, I hope to get at least a 4 month season. We ordered a 15x30 above ground (not a single pool store within 75 miles, as far as I can find.) The challenge is finding someone to set up the pool. Since I just moved in, I couldn't tell you where a single screwdriver is, and I just don't want to be responsible for a poor pool installation. I will be reading up on TFP so that I'll know enough to check the installers' work, but I'll leave it to them (they may have to come from Flagstaff or Phoenix.) We'll see.

 

[domct203]

The best advise I can give you is to buy a recommended test kit a few weeks before you plan to install the pool. The test kit may look a bit intimidating at first, but it is many different tesst, and you don't do them all, every day.

Accurate and reliable testing, the pool owner's knowledge of what his/her own pool needs, as well as only adding to the pool what it absolutely needs is the basis of what we teach here.

The two test kits we recommend are the TF Testkits TF-100 & the Taylor K2006C. Both kits use industry standard Taylor reagents. The TF-100 is really the best value as it contains more of the testing reagents for the tests you will be doing frequently. If you can find it in the budget, I highly recommend the Speed Stir magnetic stirrer. Not only does it increase accuracy and repeatability, it will bring out the mad scientist in anyone LOL!

The TF-100 can be found here:
http://tftestkits.net/TF-100-Test-Kit-p4.html

Have you discovered Pool Math & Pool School here at TFP yet?

Pool Calculator Instructions

Pool School

ABC's of Pool Water Chemistry

Chlorine CYA Chart

Good luck with the install, we will be here if you have any questions along the way!

 

[CJadamec]

The Pentair Solar Touch is about as cheap as you can get for a solar controller with a automated diverter valve and actuator.

If you do ad a third panel try and make sure its the same exact brand as the two you already have. You can't really see it but that top panel is about 5 inches shorter in length than the bottom two. That made keeping the plumbing looking clean a bit harder than it should have been.

 

[chiefwej]

I agree on the Pentair Solar Touch, shop around, you can find them for $200-$225. That is a real bargain. It comes with two temperature sensors (one for panel, one for water), a three-way solar control valve, a valve actuator, and the controller. The cost of the valve and actuator alone would justify the price.

I've been using one for several years now, it even controls my variable speed pump. Monitors the water temp, panel temp. When heat is called for and available at the panel it opens the valve, activates the pump. When finished it closes the valve and returns control to the pump timer. Although I doubt you will ever need it, there is also a pool cooling feature that will run it at night to cool water.

 

[80sDweeb]

I just ordered a Pentair SolarTouch for $205 delivered. Trying to have everything here before I need it, if I delay "pool day" my wife won't be happy!

 

[chiefwej]

Well that leaves a solar cover and reel. For a cover, most people find that there is little difference in the performance. Mostly they work by preventing evaporative cooling at night, which in a desert is a real issue. You are going to want to keep the pool covered anytime it is not in use. Recommendations for the cover, thinner and lighter is better. None last more than a season or two. Buy cheap and light, it makes it much easier to handle and more likely that you will keep it on. I'm not familiar with above ground reels, so I'll stay out of that one. But you can have a cover ready and decide on a reel once the pool is in place.

And while you are waiting, I suggest you spend some time studying in Pool School (it's the button at the upper right of this page). You will find everything you need here on this website. There are experts on anything related to pools and pool care, and they are ready and willing to share all that information.

You are also going to need a good test kit. There are two that are commonly recommended, of those the best value by far is the TF-100 from TFTestkits.net. It contains more of the reagents you will be using the most. The Speedstir may look like a gimmick that you don't need, but everyone who has one couldn't do without. It makes testing much quicker and much more accurate.

 

[chiefwej]

Since there are no pool stores in your area, at least you have no worry about being "pool stored". All those magic potions that are sold at ridiculous prices can be easily replaced by a few that you can purchase at local grocery and hardware stores, for much less. That is the prime purpose of this website, to show pool owners how, with a few simple grocery/hardware store chemicals you can have a safe, sparkling pool. It is based on pure science, accurate testing, and only adding to a pool exactly what is required. Instead of magic combination chemicals, we use liquid chlorine (AKA bleach) for chlorination, in place of other pool store expensive powders, we use things like muriatic acid, borax, baking soda, occasionally even some ice melt (calcium chloride). It is using basic chemistry to properly manage a pool. Not all those will be required. They are just examples. The only thing I've had to add to my pool in months is just a bit of acid.

We will have you educated and equipped to start out your new pool right.
Welcome to the world of Trouble Free Pools!

 

[80sDweeb]

I have ordered a TF-100 test kit, with the stirrer - for $35, it pushed me into the "free shipping" range, which saved $20, so a $15 dollar expense. I also have a solar cover on the way, and will probably cut it in half and use the floating ABS DWV foam-based pipe attached directly to the centerline of the cover halves to allow rolling and (somewhat) unrolling of the cover. May have to involve some straps or cords to allow for cover deployment without entering the water. This site has given me some good ideas about that, too.

Wow, talk about "Pool School", my brain is too old for all this cramming!

 

[chiefwej]

Take it slow, there is so much information on this site it's a bit like trying to take a sip out of a fire hose. I know it seems overwhelming at first, but with a bit of study it all begins to fit together and make sense. Once you have your test kit, you can test your water supply, to learn how it works and find out what kind of fill water we will be dealing with. Are you on city water or an individual well?

BTW: I'm pretty sure your brain is much younger than the one I'm using, and if I can do it.......

You could have gotten a discount on the test kit for donating to helping support this website. I don't think you can do it retroactively but if and when you do want to help keep the lights on and servers running.....

CLICK HERE to Become a TroubleFreePool.com Supporter!!