General solar info

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OK, sounds like not.

I spent a while interviewing local pool solar installers and trying to understand their systems. It was very difficult to find good, unbiased info either in person or online, so I’ll share what I learned for others like me who are starting from zero pool solar knowledge. Hopefully people who know more will correct anything that’s wrong here and add more info.
  • There are a bunch of panel variations—header sizes, welded vs. separated tubes, etc. Although they have their own agenda, I found one installer’s blog helpful to learn about panels and be more informed when talking to local installers: Blog - Florida Solar Design Group
  • Pool solar systems are comprised of the controller/actuator that direct water up to the panels based on a thermostat, the plumbing to get from the pool equipment up to the panels and back from the panels to the equipment, and the panels themselves. The panels have large header tubes along the top that water flows into, smaller capillaries the water flows through to heat up (panel manufacturers call these riser tubes), and identical headers along the bottom the water flows into from the riser tubes. The internet can provide a graphical view, e.g.
    https://www.pinterest.com/pin/136093219959198454/
    .
  • Supposedly, some very cut-rate installers may install near-end return systems to save on return plumbing labor. Figure 21 at The Flow Imbalance Myth Debunked graphically explains near-end vs. far-end returns (“unbalanced flow” and “balanced flow” respectively in the figure). Near-end return would be insanely inefficient and I don’t know if any installers really do it, but it ties into a deception I was given by an installer, the bullet below.
  • One installer spoke highly of the tiny openings in FAFCO panels where the water flows from the top header to the riser tubes. These are smaller in FAFCO panels vs. other brands, and so went the logic that if riser tube openings were too big, the water would only go through the first few panels of the system. I don’t know why FAFCO decided to make their riser tube openings small, but the installer’s explanation only makes sense in the context of near-end return, which should be avoided anyway.
  • The same installer suggested that water would heat up more in panels with slower flow because it stayed in them longer. While that’s true, less flow has a net negative effect on heating because less hot water is getting back to the pool from the panels. All else equal, the higher the flow, the more new water gets through the panel, the more total heat the water can extract from the panel.
  • In my area, Heliocol (one of the most established pool solar panel brands) has exclusivity contracts with a couple installers, meaning other installers can’t sell them. One of the excluded installers pushed SunUp panels, saying they were made in the same factory as Heliocol and physically identical, but renamed and given a lower warranty (10 vs. 12 years) for market segmentation.
    • The SunUp website itself contradicts this. SunUp panels have hexagonal, 2” headers, as opposed to Heliocol’s round, 1.5” headers.
    • The local SunUp distributor told me the panels are not physically identical to Heliocol, but similar in form and quality.
    • Heliocol West in Phoenix confirmed their factory makes both panel models, but said the hexagonal header panels (sold under a few names) are lower quality and made for pool builders who want to include affordable solar with the pool. The Heliocol branded panels have been in production over 30 years, and the hexagonal header panels about 3 years.
  • I’ve held samples of FAFCO and Heliocol panels. Heliocols feel significantly more substantial, both in the header and the tubes. I didn’t get to see a sample of the hexagonal header panels.
  • There’s a lot of talk by installers of panels with 2” headers about how much more water 2” headers can carry vs. 1.5”. This makes sense to me toward the goal of increasing flow (for a given pump RPM), especially since all the installers I talked to use 2” plumbing.
    • FAFCO headers are 2”, and Heliocol are 1.5” (internal diameter). I’ve read in forums that other pool owners have 2” Heliocol headers, but the dimensions I provided are from measurements I took from the panel samples myself, and searching online I can’t find other models of Heliocol panels with larger headers. If anyone knows of a Heliocol model with 2" headers, please let me know. Maybe others were referring to outer diameter. In any case, FAFCO are 2” internally and Heliocol are 1.5” internally.
    • Heliocol West didn’t have any engineering explanation for why their headers are 1.5”, except that they didn’t feel they needed to be larger. I’m electrical rather than civil so I think about this stuff in terms of circuits, and any increased series resistance (smaller headers) will reduce current (flow) for a given voltage (pump RPM). A friend I asked who runs flow simulations agrees, so I can’t understand why they wouldn’t just use 2” headers.
  • Heliocol panels come in 3 lengths: 10.5’, 12.5’ and 14.5’. Everyone else’s panels come in 10’, 12’ or 14’, as far as I've seen. So if you need to replace a Heliocol panel, you’re replacing it with another Heliocol panel.
  • When my pool was built, the builder included a wifi pump controller that does not support solar. Some solar installers said they can work the solar controller in with it to retain the wifi capability for basic on/off and RPM control, some said they could not. The solar controller also needs control over RPM to turn it up when directing water to the panels. If you are getting a new pool built and plan to install solar, and the pool company is installing a wifi pump controller, get one that natively supports solar. Otherwise you'll end up with this Frankenstein two controller system.
In the end, I’m planning to go with the Heliocol installer for better panel build quality, unless anyone has feedback to the contrary. There are obviously other major panel models, but these are the ones used by the main local installers in my area.
 
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M,

Sorry you didn't get many replies. I live on the opposite side of the country so I can't really help you with a dealer. I only bid two installers that both had good references and I didn't experience any of the false sales hype you did. I do think both exaggerated the performance prediction somewhat but I went in with my eyes open and did my own calculations. I did not expect better than 5 year payout and that's about what I have seen. I can't recommend a professional installer but I can provide you with information about my solar panels system and I hope that helps. Based on the research I did I agree your Heliocoil panels are one of the best. My installer used Aquatherm panels. They are now 5 years old and holding up well. They've also withstood sustained 85 mph winds during two different storms. My pool was 2 years old when I installed the solar. I had at that time a 2-speed Jandy pump. The solar was controlled using a Hayward Goldline controller. At low speed my pump would not provide sufficient head to take water to the roof so I just ran it on high speed during the hot part of the day. The Goldline controller only opened and closed the solar bypass valve. Not the best world but it worked reliably right up to the time I added Intellicenter that has a solar control feature. At that time I removed the Goldline. I've since also upgraded the pump to a V-Green VS motor and I use the solar control signal to trigger low speed on one of the motor's digital inputs. This works great and any time there is a cloud that obstructs the sun or we get an afternoon shower the bypass opens and pump switches to 1700 rpm. In order to use the VS motor's higher capacity more effectively I increased the impeller size to the next size up. High speed is set to about 2900 rpm and provides plenty of flow. If you don't have automation I think you could achieve the same automatic control by using the valve bypass signal from a Goldline solar controller to trigger switching from high to low speed so long as your pump motor has digital input capability.

Lately in Florida my pool cools to about 84 deg F at night. The temp rises to 89-91 deg F by late afternoon and it's only March. Later in the summer the bypass is opened by automation mid afternoon to keep the pool below 92 deg.

I hope this helps.

Chris
 
Last edited:
  • One installer spoke highly of the tiny openings in FAFCO panels where the water flows from the top header to the riser tubes. These are smaller in FAFCO panels vs. other brands, and so went the logic that if riser tube openings were too big, the water would only go through the first few panels of the system. I don’t know why FAFCO decided to make their riser tube openings small, but the installer’s explanation only makes sense in the context of near-end return, which should be avoided anyway.
  • The same installer suggested that water would heat up more in panels with slower flow because it stayed in them longer. While that’s true, less flow has a net negative effect on heating because less hot water is getting back to the pool from the panels. All else equal, the higher the flow, the more new water gets through the panel, the more total heat the water can extract from the panel.
[/QUOTE]

Wouldn't a smaller flow of hotter water or a higher flow of cooler water, work out even, considering that the volume of the pool is the same.
 
setsailsoon said:
M,

Sorry you didn't get many replies. I live on the opposite side of the country so I can't really help you with a dealer. I only bid two installers that both had good references and I didn't experience any of the false sales hype you did. I do think both exaggerated the performance prediction somewhat but I went in with my eyes open and did my own calculations. I did not expect better than 5 year payout and that's about what I have seen. I can't recommend a professional installer but I can provide you with information about my solar panels system and I hope that helps. Based on the research I did I agree your Heliocoil panels are one of the best. My installer used Aquatherm panels. They are now 5 years old and holding up well. They've also withstood sustained 85 mph winds during two different storms. My pool was 2 years old when I installed the solar. I had at that time a 2-speed Jandy pump. The solar was controlled using a Hayward Goldline controller. At low speed my pump would not provide sufficient head to take water to the roof so I just ran it on high speed during the hot part of the day. The Goldline controller only opened and closed the solar bypass valve. Not the best world but it worked reliably right up to the time I added Intellicenter that has a solar control feature. At that time I removed the Goldline. I've since also upgraded the pump to a V-Green VS motor and I use the solar control signal to trigger low speed on one of the motor's digital inputs. This works great and any time there is a cloud that obstructs the sun or we get an afternoon shower the bypass opens and pump switches to 1700 rpm. In order to use the VS motor's higher capacity more effectively I increased the impeller size to the next size up. High speed is set to about 2900 rpm and provides plenty of flow. If you don't have automation I think you could achieve the same automatic control by using the valve bypass signal from a Goldline solar controller to trigger switching from high to low speed so long as your pump motor has digital input capability.

Lately in Florida my pool cools to about 84 deg F at night. The temp rises to 89-91 deg F by late afternoon and it's only March. Later in the summer the bypass is opened by automation mid afternoon to keep the pool below 92 deg.

I hope this helps.

Chris
Click to expand...

Hi Chris,

Thanks for all the info on your upgrades. That's awesome your pool's in the 90s in March, but Florida's another world. I guess I'll find out what kind of other system upgrades are needed after I have the panels in for a while. What do you mean by not getting better than 5-year payout?

Matt
 
[/QUOTE]

Wouldn't a smaller flow of hotter water or a higher flow of cooler water, work out even, considering that the volume of the pool is the same.
[/QUOTE]

Been decades since I did heat exchanger design. But here's what I recall. That's not what happens because of several factors including temperature approach and on the tube side liquid flow must be at turbulent flow rates to maximize overall U ( which is heat overall transfer coefficient U BTU/Ft2*deg F).

Chris
 
Wouldn't a smaller flow of hotter water or a higher flow of cooler water, work out even, considering that the volume of the pool is the same.
Click to expand...

That all depends on the numbers: how much hotter and how much more flow? Consider the panel to be an engine we want to keep cool. We'd want greater coolant flow so the coolant wasn't heating up as much in the engine. The cooler we keep the panels with water flowing through them, the more heat we've extracted from the panels, and all that heat has been transferred to the water.

Analogies and engines remind me of something else I thought was funny through this learning process. Every installer and every panel distributor I talked to used car analogies--this panel's a Honda Civic, that panel's a Cadillac...I can't say their analogies helped any in my decision. Maybe mine above is similarly useless.

Matt
 
m100psi said:
Hi Chris,

Thanks for all the info on your upgrades. That's awesome your pool's in the 90s in March, but Florida's another world. I guess I'll find out what kind of other system upgrades are needed after I have the panels in for a while. What do you mean by not getting better than 5-year payout?

Matt
Click to expand...

Matt,

Glad that the info is helpful. We've have had a long string of partly cloudy skies with air temp low 80's during the day and high 60's at night. We swim almost every night and hit the spa couple times per week. When we do that we're adding some heat from the gas heater on 800 gallons so I'm sure that's helping a little. But still getting fabulous output for March.

By payout period I mean the initial cost ($5000) divided by the annual gas bill savings. So it showed I'd break even in 5 years. But I did this calculation with my old 2-speed pump. This meant I was running at the higher speed all afternoon. Now I have a more efficient pump (PM pump motor vs induction motor) plus I only incur the high speed operating cost when the panels generate sufficient heat to offset the cost of pumping. So I'm sure the payout is better but I haven't checked to see how often. I might take an attempt at is since I now have the data with my Intellicenter historical data.

I hope this helps.

Chris
 

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m100psi said:
That all depends on the numbers: how much hotter and how much more flow? Consider the panel to be an engine we want to keep cool. We'd want greater coolant flow so the coolant wasn't heating up as much in the engine. The cooler we keep the panels with water flowing through them, the more heat we've extracted from the panels, and all that heat has been transferred to the water.

Analogies and engines remind me of something else I thought was funny through this learning process. Every installer and every panel distributor I talked to used car analogies--this panel's a Honda Civic, that panel's a Cadillac...I can't say their analogies helped any in my decision. Maybe mine above is similarly useless.

Matt
Click to expand...
I think there are more factors then just temperature differential versus flow. For example the size of the panel array versus the size of the pool, what percentage of time and degree, the pool is shaded. How much heat you lose over night. A Solar heater would benefit my pool., while the roof is in full sun, the pool is shaded a lot of the day, due to some big trees.... This would also reduce the solar exposure of the roof deck under the panel, yeah you spend an extra $2/day running the pump, and save $10 on less A/C use....

This panel is a Honda Civic it costs $X, and will probably run trouble free for 15 years; this panel is a Cadillac, it will cost $3X, and need constant, expensive futzing with....
 
I agree, all those factors are important as well. Just trying to sort through which features on panels do and don't make sense, since panels vary in their implementation. All else being equal, more flow is better. If more flow came at the expense of greater surface area or sunlight, that tradeoff would have to be evaluated.
 
wogster said:
Wouldn't a smaller flow of hotter water or a higher flow of cooler water, work out even, considering that the volume of the pool is the same.
Click to expand...
Math wise yes, totally.

The problem is, the hotter the water gets in the collectors, the more heat is lost to the air. Therefore, more flow for cooler water temps in the collectors means more heat in the pool.
 
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So just a few questions as I am considering solar panels as well. I have a very large southern facing roof line that would be ideal.

So are there any issues in mid summer when I am not going to running water through the panels on them overheating?
Chris, you mentioned that they survived 85 mile an hour winds how high are they rated? Would they survive 130mph?
Also they fill up and drain out several times a week or day does that shifting weight do any damage to the roof?
 
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