DIY solar using Sonoff

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strategy400

Well-known member
Jun 6, 2013
158
Southern California
Pool Size
40
Surface
Plaster
Chlorine
Liquid Chlorine
I'm trying to build my own pool automation using sonoff devices. for solar control I have the device/probe for water temp but I'm trying to implement the solar sensor part of the system (see image). Is there a device/sensor available to determine readiness of the panels to heat the water? How can the switching of the valve(s) be implemented. Trying to avoid any equipment that makes reference to fruit or berries.

Solar_Heater_plumbing.jpg
 
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The "solar sensor" component of a pool solar heater is just an air temperature sensor. It doesn't "signal" anything but the ambient air temperature near the panels. You'll need a computing device to analyze and/or control: (1) water temp, (2) water flow (the pump), (3) air temp at the panels, (4) desired temp and (5) the solar valve actuator. Since I have no idea how all that is done, I can't advise further. Except to say, based on what I consider my time to be worth, I wouldn't undergo such a project myself. There are pool solar heater controllers cheap enough to make building one not a particularly good ROI (if you consider the parts and your time as the investment).

Here's an example of one for a couple bills. What is your time worth?


There are other models and brands that come bundled with the solar three-way valve and/or the actuator and/or the temp sensors, making the package an even better deal.
 
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Here's an example of a bundle. Note the hole in the diverter of the three-way valve. That valve is specifically designed for use in a solar heating system, it's called a "solar drain down valve." The hole is there to allow water to drain out of the panels and back into the pool each day at the end of your heating cycle. Depending on your setup, you should have one of these valves if you don't already. It's possible to convert a normal three-way valve to a drain down valve.


If you have, or plan to someday have, a pool automation controller that controls your pump and other pool and yard electrical devices, know that pretty much all of them include solar heater controllers built in.

BTW, you'll get more comprehensive answers to your questions if you complete your signature. Something like mine is helpful to the folks that answer your questions.

 
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Rancho Cost-a-Lotta said:
Are you asking how to operate/control the valve actuators?
Click to expand...
Hi Rancho, I think I can control the valves. I just have to do some switching with my sonoff 4CH units and use some 24AC. My question was regarding the solar sensor at the panels. I have 2 sonoff TH switches. I have the temp probe for the water but the temp probe for the solar panels... I thought maybe it was supposed to detect sunlight? I guess I can just use temperature according to Dirk. Can I also use a "DS18B20 Waterproof Temperature Sensor" to detect ambient air temperature? The air and humidity temperature probe sonoff offers looks like it is for indoor use.
Also it appears that you can do some conditional "things" in the ewelink app using "scenes". There is some "if that then" type of functionality. If air temp is greater than water temp, switch on the pump and/or valve.... not sure if I can get that to work.
 
Dirk said:
Here's an example of a bundle. Note the hole in the diverter of the three-way valve. That valve is specifically designed for use in a solar heating system, it's called a "solar drain down valve." The hole is there to allow water to drain out of the panels and back into the pool each day at the end of your heating cycle. Depending on your setup, you should have one of these valves if you don't already. It's possible to convert a normal three-way valve to a drain down valve.


If you have, or plan to someday have, a pool automation controller that controls your pump and other pool and yard electrical devices, know that pretty much all of them include solar heater controllers built in.

BTW, you'll get more comprehensive answers to your questions if you complete your signature. Something like mine is helpful to the folks that answer your questions.

Click to expand...
Dirk, I am still contemplating buying a solar controller. Unfortunately I am stuck with a hayward pump :poop:
 
If your solar panel array is lower than the pool surface, you wouldn't need a solar drain down valve, the panels would stay full of water 24/7.

Keep in mind that solar panels, especially the little tubes, expand and contract with the air and water temperature they encounter. Keep an eye on that, as you would not want them to contract such that the tube connections to the two manifolds get stressed. Those connections are a failure point for solar panels.

My panels are fixed to the roof at one end, but are sort of "free floating at the other end. They can expand and contract freely, quite a bit. That's in the direction parallel to the little tubes. They can also freely expand and contract in the direction parallel to the manifolds, because the manifolds are not actually fixed to their brackets, they can slide within them.

The tubes of my system don't sit on the roof, they are attached to spacer-brackets that elevate them off the surface of the roof an inch or so. These spacers keep the tubes from dragging across the roof tiles as they expand and contract throughout the day and night. Keep that in mind. Your tubes will move slightly across whatever you have supporting them. Be sure whatever you're using for supports minimize abrasion. That's another failure point for solar panels. That may sound unlikely, but realize those panels will be rubbing on whatever they touch, every hour of the day and night for the next 20 years or so.

I eventually replaced all the zip ties I first used to hold various components of my system in place. Even the UV-rated ones don't last long in the sun. For all things yard, I now use stainless steel wire.

 
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strategy400 said:
Dirk, I am still contemplating buying a solar controller. Unfortunately I am stuck with a hayward pump :poop:
Click to expand...
Hayward makes a solar controller. Perhaps it can interface with your existing pump. They have bundles, too.

www.poolsupply4less.com

Hayward Goldline Solar Controller GLC-2P-A - PoolSupply4Less

Simply set the controls for the Hayward GLC-2P-A desired pool temperature and the unit will heat your pool whenever there is enough solar heat available. Buy now and save on sale. Frees shipping on all items.
www.poolsupply4less.com
 
Dirk said:
Hayward makes a solar controller. Perhaps it can interface with your existing pump. They have bundles, too.

www.poolsupply4less.com

Hayward Goldline Solar Controller GLC-2P-A - PoolSupply4Less

Simply set the controls for the Hayward GLC-2P-A desired pool temperature and the unit will heat your pool whenever there is enough solar heat available. Buy now and save on sale. Frees shipping on all items.
www.poolsupply4less.com
Click to expand...
Notice how much more expensive that one is than the pentair. The smart temperature switches I bought were ~$20. Hoping I can make it work. I'll have to drop a little cash for the valve.
 

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Dirk said:
If your solar panel array is lower than the pool surface, you wouldn't need a solar drain down valve, the panels would stay full of water 24/7.

Keep in mind that solar panels, especially the little tubes, expand and contract with the air and water temperature they encounter. Keep an eye on that, as you would not want them to contract such that the tube connections to the two manifolds get stressed. Those connections are a failure point for solar panels.

My panels are fixed to the roof at one end, but are sort of "free floating at the other end. They can expand and contract freely, quite a bit. That's in the direction parallel to the little tubes. They can also freely expand and contract in the direction parallel to the manifolds, because the manifolds are not actually fixed to their brackets, they can slide within them.

The tubes of my system don't sit on the roof, they are attached to spacer-brackets that elevate them off the surface of the roof an inch or so. These spacers keep the tubes from dragging across the roof tiles as they expand and contract throughout the day and night. Keep that in mind. Your tubes will move slightly across whatever you have supporting them. Be sure whatever you're using for supports minimize abrasion. That's another failure point for solar panels. That may sound unlikely, but realize those panels will be rubbing on whatever they touch, every hour of the day and night for the next 20 years or so.

I eventually replaced all the zip ties I first used to hold various components of my system in place. Even the UV-rated ones don't last long in the sun. For all things yard, I now use stainless steel wire.

Click to expand...
The panels are in place temporarily so I can mark the mounting points. I'll have to remove them to install the mounts/screws. The zip ties are also temporarily installed just to keep them from blowing into the neighbors yard. Mine are laying across chain link I stretched across the frame. I hope they don't rub on there too badly but they seem like they'll hold up for a while. I also welded the mounting rails at a ~2 degree angle so the panels will drain to one side. The array will tilt to 15, 30 and 45 for summer, fall, winter, spring. This first one is for proof of concept. hopefully it will at least heat my spa water a bit so I don't have to buy stock in natural gas. The whole thing is about 12 inches above the pool water.
 
strategy400 said:
Notice how much more expensive that one is than the pentair. The smart temperature switches I bought were ~$20. Hoping I can make it work. I'll have to drop a little cash for the valve.
Click to expand...
You may be comparing the wrong apples to oranges. The Pentair stand-alone controller is about $200. The Hayward bundle, which includes the valve and actuator, is more, but cheaper than the Pentair bundle (which offers the same components).
 
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strategy400 said:
The panels are in place temporarily so I can mark the mounting points. I'll have to remove them to install the mounts/screws. The zip ties are also temporarily installed just to keep them from blowing into the neighbors yard. Mine are laying across chain link I stretched across the frame. I hope they don't rub on there too badly but they seem like they'll hold up for a while. I also welded the mounting rails at a ~2 degree angle so the panels will drain to one side. The array will tilt to 15, 30 and 45 for summer, fall, winter, spring. This first one is for proof of concept. hopefully it will at least heat my spa water a bit so I don't have to buy stock in natural gas. The whole thing is about 12 inches above the pool water.
Click to expand...
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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strategy400 said:
In order to drain down the panels, the pump must be off, is this correct? Because I usually run the pump 24/7....
Click to expand...
Correct. When the pump first starts up, the empty panels stay empty until the solar valve is first engaged. Then the panels fill with water and start heating your pool. If the pool reaches temp, or the sun ducks behind a cloud, and the solar valve shuts down flow through the panels, they still stay filled with water. They stayed filled thoughout the pump's cycle, no matter how many times the solar valve turns one way or the other. When the pump finally shuts down for the day, and the entire pool plumbing circuit depressurizes, that's when the panels will drain down through the solar valve.

If you never turn off your pump, the solar panels won't drain.
 
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You could use one of these. It is compatible with Sonoff and lots of other sensors and switches with many control programs built-in. The only problem is that once you go down this rabbit hole you may never come back.

hubitat.com

Hubitat Elevation® Model C-8 North America Version

Automate smart devices with a local processing solution that is more reliable, faster, and private than cloud-based hubs. Works with Alexa, Google Home, Lutron, Zigbee, Z-Wave, and more.
hubitat.com hubitat.com
 
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Hal3 said:
You could use one of these. It is compatible with Sonoff and lots of other sensors and switches
Click to expand...
The cost of that device and one switch, which I'm gunna guess doesn't come with pool solar heater control algorithms pre-programmed in, is only about 30 bucks less than a dedicated pool solar heater controller, that does what it needs to do right out of the box (and is made to be used outside). What am I missing?

To be fair, @Hal3 actually answered @strategy400's question better than I did, which was how to get Sonoff devices to heat a pool. And if you've ever stumbled on any of my various threads, you'd know nobody geeks out on home automation and diy more than I do. But I'm of the school of thought that there is a place for home-baked, and a place for store-bought. The trick is to know when to go with which.
 
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Dirk said:
The cost of that device and one switch, which I'm gunna guess doesn't come with pool solar heater control algorithms pre-programmed in, is only about 30 bucks less than a dedicated pool solar heater controller, that does what it needs to do right out of the box (and is made to be used outside). What am I missing?

To be fair, @Hal3 actually answered @strategy400's question better than I did, which was how to get Sonoff devices to heat a pool. And if you've ever stumbled on any of my various threads, you'd know nobody geeks out on home automation and diy more than I do. But I'm of the school of thought that there is a place for home-baked, and a place for store-bought. The trick is to know when to go with which.
Click to expand...
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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