DIY solar using Sonoff

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Dirk said:
The chain link I'm think of is galvanized, and that galvanized finish is rough, and even has little spikes and bumps all over it. Is yours like that? I'd be concerned if it was. Perhaps something smooth between the two could work. Like the plastic sheeting used for greenhouses. Or painted corrugated roofing material, maybe? Anyhow, you get the idea, something to think about.

I wouldn't discourage you from tilting the panels to track the sun, can't hurt, but according to the solar installation company that sold me my panels, they claim it's not critical at all for water-heating panels to point at the sun like PV (electrical) panels must do. They just need to be "in the ballpark." In fact, my array is on the north side of my roof, and it works fine. I mounted them there because I reserved the south side for my PV panels.
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The chain link can't be much rougher than shingles. Those are almost designed to be abrasive.
 
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strategy400 said:
I'm thinking about ditching the sonoff for the solar and buying a system. I can still use the sonoff stuff for the rest of the system, pool/spa mode etc. It depends how the solar system interfaces with the pump. I'll have to look into that a bit more. The main reason I don't like using sonoff for the solar is the water temp probe is stainless and touches the water and the unit is powered by 120v. I noticed the pentair temp probes appear to be encased in plastic/pvc.
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That is darn good thinking. Of course, I say that because I had the same thought, for a project of mine a while back. I solved it by encasing a s.s. probe in marine-grade caulk. Even though the probe is 5V, it does connect, round-about, to a device that is powered by a 120V power brick (which does theoretically isolate the pool from the 120). I put a GFCI on that 120 as an additional safeguard, and consider what I did at least as safe as my 120V LED pool light, but hopefully the coroner will some day be able to determine if I was right or not! 💀

I describe it here. And if you make it through this thread, you'll see what I mean about my geekhood!

The Ultimate Thermometer

How ultimate? Hey, it’s me! Since I became a pool owner I’ve been trying to find a good solution for reading both my pool temperature and my outdoor temperature. I’ve been through the obvious ones: floating in the pool, or stuck to a window. But I also had a need for my home automation system...
www.troublefreepool.com www.troublefreepool.com
 
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strategy400 said:
The chain link can't be much rougher than shingles. Those are almost designed to be abrasive.
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Yah, that's what I'm picturing. My Heliocol panels have a system that floats the panels over the roof (concrete tiles, in my case) so that they can't abrade against anything. I'm sure they engineered that in pursuit of maximizing panel life. I believe the two primary failure points are where/how the tubes connect to the manifolds and anything rubbing on the tubes. I don't know how other panel manufacturers deal with that, or if they even bother.
 
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You can kinda make out the spacers in this photo. They run perpendicular to the tubes, about every 12". The spacers are flat on the bottom and have notches on the top, into which each tube clips, so they also align and keep the tubes perfectly parallel. They fit the tubes snuggly, so the tubes also keep the spacers in place. The spacers move with the expansion/contraction, so they do rub on the roof, but they'll outlast the 20 year warranty, and keep the tubes from touching the roof. I'm not sure how you can use this info, but maybe it'll inspire an idea.

heliocol spacers.jpg
 
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I had to pull the panels off to attach the mounts and looking at where the panels sat on the chain link it was barely noticeable. I think they'll last at least a few years. I ended up stacking washers under the mounts to clear the chain link. I have an air temperature sensor near the panels now that can flip relays to control valves and pump. It's not in the water and far from the pool so it could work and if I just have to check the pool water temp periodically and adjust the threshold for the solar to come on on my phone that would be acceptable and limit any high voltage from being near the water. Someone needs to come up with a smart IR thermometer you can point at the water. I think I can make my gas heater and pump come on with the CH4 switch and those are only powered by and switch low voltage and the heater and pump are bonded. I don't think the valve actuators touch the water. Hopefully the coroner will just cremate my waterlogged body.Screenshot_20230407-123047_eWeLink.jpg
 
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I think the algorithm for managing water temp and air temp is more complicated than you realize, but really it's only about maximizing the cost effectiveness of the system. As long as you're OK with somewhat forgoing most heat for least cost, you might not even need to figure out the air temp component. Perhaps just a timer would suffice. Just have the pump and the solar panel engage from 8:00am to 3:00pm (or whatever works for you in your area) and I bet the water will feel great 95% of the days during swim season.

My panels do kick on at various times each morning, but not by much variance. 8ish most of the time. And my system shuts down when the pool reaches 85°, also at various times, but the pool almost never overheats. A few times last summer it got up to 90 or so, but that might have happened with or without the heater. Point being, most days in most areas have the same weather pattern from day to day, with gradual changes throughout the season. The wasted pump runtime during the rare partly cloudy day, or super hot day, might not actually amount to all that much on your electric bill. And who's going to complain if your pool is a little extra warm here and there, right?

I had a pool automation system in place before I added a solar heater, so connecting up the built-in solar controller the system provides was a no-brainer, and the cost wasn't a factor. If I had had to add a dedicated solar controller, would it have paid for itself by now? Who knows. You really don't have anything to lose by trying out your idea. You need the solar valve and actuator either way. You can always add the solar controller later, if your diy doesn't pan out.

Keep us updated on how this works out.
 
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Looks good. In addition to the tilt, you've got a skew, too. That's important and the correct way to mount panels. That not only allows them to drain properly, but to fill and flow properly, too. Where's your vacuum breaker?
 

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So I set my relay to come on at >= 70 and turn off at <= 70. What happens is the temperature tends to rise and fall as it warms up. So it goes 70, 71, 70, 69, 70, 69, 70, 71, 72, 70, 71 etc. and my relay kept going on off on off. I set it to come on at 70 and go off at 68. We'll see..
 
strategy400 said:
So I set my relay to come on at >= 70 and turn off at <= 70. What happens is the temperature tends to rise and fall as it warms up. So it goes 70, 71, 70, 69, 70, 69, 70, 71, 72, 70, 71 etc. and my relay kept going on off on off. I set it to come on at 70 and go off at 68. We'll see..
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Part of the controller's algorithm addresses that, and the threshold for how it does so is user-adjustable, by degrees. That's what I meant by there being more to that algorithm than you might think. It's not like an HVAC thermostat, because there are more variables, including water temp which you're not factoring. And an optimized solar heater can heat a pool even when the air temp is lower than 70, but not always! A controller handles that, too.

I don't mean to discourage your efforts, you might find settings that work. Perhaps have it turn on at some preset air temp, but go off at a specific time of day. That would eliminate the on-off-on-off issue.

Even with a controller my system was turning on and off too often when the air temp was too close to the pool temp. I solved for that by encasing the air temp sensor in a glass jar. I had heard about that trick somewhere, and even though a local solar guy poo-pooed the idea, it does work (for my setup, anyway). The theory being the sensor can monitor the actual air temp without being subjected to cooling breezes.
 
strategy400 said:
Yes they are.
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So I mentioned that tube wear'n'tear and where they join at the manifold are the two failure points. Those connectors are a third. That's the part that usually fails first. Probably because of sun exposure. For your setup, that's not such a problem, because you have such easy access to tighten or replace them if they start leaking. For folks that have them up on a roof they're more of an issue. Not sure there's much you could do about that. I suppose you could try to shade them from the sun. A piece of 3 or 4" ABS pipe, cut in half to make a little shelter might work. I don't know if painting them with some UV-resitant paint would help.
 
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Some paint would probably help. But yes I can replace them and I noticed when I was at home cheapo the other day they have a nice assortment of similar looking items in the plumbing aisle.
Screenshot_20230409-175649_Chrome.jpg
 
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