Review of Solar Pool Heating for a Season

[piku]

Hey all,

Earlier in the season I got solar pool heating. I have 8 2x20 panels on my garage roof facing South-Southeast and one tree that blocked them in the earliest morning hours (before like 8am). The panels are sungrabber panels from ebay which are an economy fafco brand panel. They are cheaper and a bit harder to work with than a standard fafco panel I'd say. I got them mainly because their design and sizing meant I could fill my ENTIRE roof area with them.

First, the panels are installed horizontally and not allowed to be installed vertically (and if you make a warranty claim they will want a pic of your install). This causes the panels to get a little bit of sagging or rippling here and there and though it's not an incredible eyesore it's annoyed me all year and I'll be trying to put a small strap on the edges to tighten them a bit to stop it. Their support said I can strap the headers back on one side to try to flatten them. I've not had any problems with wind. We've had some very strong wind storms and even the one panel that is rippled good isn't going anywhere.

After install I found one panel with a hole in it facing down (so the leak was hard to pinpoint). Their support asked a couple questions and promptly sent me a new panel. They didn't really care if I sent the one with a hole back so I guess I have a spare or something, not that I'd have enough roof area to add it on. If I did, you better believe I would! Later in the season the very lowest panel developed a pinhole leak that shoots a tiny stream of water about 1 foot into the air. I'll probably ask for another panel from them as my warranty is like 10 years I think.

The panels are heating a near 30,000 gallon 18x40 free form pool. The pool has a solar cover that was used whenever additional heat was desired. During august the pool stayed around 88 to 90 but never really got bathwater hot like I wanted to (to have a nice night party). Now that it's been cold (75-80F max days but usually more like 70F) the pool has managed to stay around 78F-80F max and it is still swimmable.

The whole problem with my entire theory is that my desire to swim in this cold weather just isn't there. I'm already not that warm to begin with and though a friend just closed his pool because it hit like 65F and mine is near 80F it's still not that tempting to swim. And so I fear I may have wasted $1000 on these panels because I think for me the most valueable setup would be solar panels to boost the incoming temp to a propane heater but then a propane heater to do the rest of the work when it gets cold like this. I just can't spend the money on a propane heater right now as the pool has 25 year old plaster and the house needs siding and windows.

I don't know really. It's been a cold year and I'm really disappointed in general that I've gone to this amount of work and used the pool so little due to the weather. Hopefully the impact is more dramatic next year.

As a "cheap" economy product though, despite whatever issues I've had, I'm overall satisfied. One thing is for sure that I've gotten a LOT of heat out of these panels overall without paying a dime in fuel costs and I get to feel "green". The goldline controller it comes with is a very boring product that simply works flawlessly without any drama, as a pool controller should. I plan to build the solar control into my main system for next year. I'll be developing and testing once I'm sure my swimming days are over. I also have the main house roof top. I could definitely extend and add additional panels to the main house roof if I felt daring. It would certainly help because I am at minimum spec panel area for my enormous pool.

 

[kjcole]

Two leaks so far! What's with that? Quality control issues or something else?

Considering the size of your pool, I'd say you've been getting pretty good performance out of those panels, considering the less-than-ideal solar conditions we've had this summer.

 

[lborne]

You said you have 2x10 panels, but those are allowed to be hung vertical. Maybe you have the 2x20 that are only allowed horizontal?

If they are only 2x10, then I think you have far too few sq. ft. for a 30k gal pool. Most recomendations are for 80% - 100% area coverage. Even if they are 2x20's, you still seem to be on the low side.

I agree, installation was more of a pain than I expected and now they are wavy and I can't get them straight. I have the return pipe running down the side of one header and it is secured, so this weekend I'm going to use cable ties to pull the header to the return pipe to see if I can straighten it. I also have had them slide down a bit and pinch some of the lower tubes. I'm surprised I have not had a leak there. I fear the constant movement of the panels on the asphault shingles will result in leaks.

BTW, the 10 year warranty is pro rated - 10% less each year.

 

[piku]

Oops sorry I meant that I Have 2x20. And yes when I originally purchased them I was under the impression that my pool was 18000 gallon 16x32 and that I was dramatically oversizing them. After ordering I remeasured because then I was worried about fitting the solar cover to my nice $25 craigslist solar reel and that's when I realized the awful? truth.

Next time I buy a house I will specifically look for one with a smaller pool. It's nice having a huge pool but seriously. I'm only so big People don't believe me when I tell them I can swim laps in it though. Yeah it's not olympic but 40ft is pretty far.

But really that's the joy of solar. I can order 4 more panels and for the price of some pvc and some design considerations I have more heat.

 

[AV8TOR]

So the 2x20 are they supposed to be installed horizontally or vertically and what is the reason?

Where did you tie the system to your filter? What is the required flow rate for this?

 

[piku]

The 2x20 per the manufacturer must be installed horizontally. I believe their worry is that the weight of the panel supported by only or mostly only by the top header will cause damage to the panel in the long run and would encourage you to not strap down the panel properly too

A good flow rate is 3-4GPM per panel. I don't believe that is maximum flow rate either. I have 8 panels so 32GPM. My filter can flow maybe 50GPM max so considering the head loss with 200ft of piping, I just send all water to the panels - no problem that I see from that. You want to flow as much water as you can through them without building up much if any additional pressure or stressing the panels. More heat gets transferred overall that way.

The solar is tied into the plumbing after the multiport valve (exiting the filter). You wouldn't want to send unfiltered water into the panels. If you had a chlorinator though you would tie it in before that unless there is some kind of flow requirement for the salt chlorinators which could be a different story.

 

[pooladdict]

I have 3 Fafco 4 X 20 Panels for 240 Sq Feet.

I am in Canada and have a 14 X 28 Pool, and I easily would strongly suggest solar to anyone. As long as the sun comes out, we have heat, and our way of looking at it, no sun, we do not want to swim.

I think your solar set up is undersized for your pool. Also you must pay attention to where you have them in terms of sun strength and angle on the roof, believe it or not, that makes a huge difference.

I had my pool up to 80 degree's two days after opening up in April, even went swimming. As the sun moves during the summer, my heating ability drops easily by 40%, but still warm enough to swim.

I ran my pool around 90 for 3 weeks this august, and next year I will not do it again. I guess up here in Cooler climes, when it does get really hot, a pool around 90 has no cooling effect at all, We will attempt to keep our pool around 84 next summer.

 

[AV8TOR]

Would someone please share how the Fafco type panels are fastened to the roof.

 

[piku]

The sungrabber 2x20 panels I have are strapped to the roof using a polypropylene (I think) coated stainless steel strap. You drill a pilot hole into the roof through the shingle, inject some roofing cement into the hole and then screw down the strap using lag bolts. I then took the additional step of covering the lag bolts an the strap sides and front with roofing cement to try to divert any water away from the hole. But yeah you make holes in your roof and that's somewhat scary.

 

[lborne]

For my 2x20 FAFCO panels, I found the straps don't really do much. Since the panels are 20' long and must be mounted horizontally, they tend to sag in the middle and cause them to buckle at the ends so it looks like potato chips. When they sag, they then get caught on the lipe of the shingles and are not easy to straighten.

I too was worried about putting so many holes in my roof. By the time I got the panels flat, I ended up with 3x as many holes as I had wanted. But as long as you use liberal roofing cement, you should be fine.

I ended up securing one side of the panel headers at the connecting pipes with metal conduit clamps, then securing the pvc pipe on the other end with metal conduit clamps and using cable ties to secure the opposite panel header to the pvc - thus pulling the panels tight so they stayed flat. I did this when it was cold and so when they heat up and lengthen, the cable ties will allow movement. At first I used plastic conduit clamps to avoid corrosion issues, but they start to soften in the heat and bend too much. I'll try and get photos up within a week.

 

[lborne]

Here is my setup...

The first photo shows the check valves and 3 way valve setup. The small line and valve T'd off the 2" pvc is for connecting a hose for filling the pool.

In the second photo you can just make out the pipe clamps holding the pipe to the roof and the cable ties used to hold the panel header tight.

 

[piku]

Yeah yours is nicer than mine, at least in part because I had to run all the way around to the front of the house, my pool equipment pad was a preexisting disaster (it actually has DWV fittings on it!) Your roof angle is also lower. My roof is a tiny bit under 45 degree angle. This makes working on the roof ALMOST impossible (and I probably damaged my shingles nicely) but worse, it makes the panels want to sag and fall much more so they press hard on the straps where the bottom of hte panels are. The setup would be much better if they included a load distribution plastic piece that had a u channel that held hte panel over a wide area (say 5-6 inches) and then tapered to a channel the width of the strap. I have a feeling I'm going to be doing some engineering next spring.

I see your stretch system. I was planning to use (and already purchased) a special screw down mount and polypropylene straps. I got them from solar direct. The mount has a base that you lag bolt into the roof and then it has a top piece that holds the strap that you screw down onto the strap. You can unscrew and tighten the straps if necessary, etc so I can adjust the tension seasonally. I have to fix my upper panel though. I mounted the bolt too high so it causes the top panel to really sit on it. Need to move the bolt and tighten the strap down better but like I said, it's really really hard to work up there.

 

[lborne]

The photos are a bit deceptive. My roof is not as flat as it seems. If you lay a tool down, even a heavy cordless drill, it slides right off. It was a royal pain getting the panels up and I reworked them 4 times and went through two tubes of roof tar (half ended up on me).

I like your idea of some sort of u-channel for load distribution. Depending on how mine do over the winter and next summer, I might add something like that. 1" PVC cut lengthwise to for a C and then clamped at the bottom. Or some small aluminum angle or T extrusions would do fine too.

As for the function, now that I've got the flow adjusted correctly, my 160 sq. ft. (50% coverage) is bringing the water temp from about 83 to 87 degrees each day with about 4 hrs of good sun. On a sunny day, I seem to gain about 4 degrees and loose about 3.5 at night. Today it started at 83.5. My panels are already getting considerable shade at about 3:30. They are on the West side and that is really my only option as the South side gets even more shade. Looking at sun charts, I can see that I won't be able to heat the pool Dec - Feb, but I hope I can get the spa high enough during the day so the electric heater does not have to run so much.

 

[lborne]

UPDATE: The cable ties are not holding. I am using the black heavy duty ones, but because they get so hot, they are expanding and slipping. I'm now going to use nylon packaging strap with metal clips.