Solar Heat

[RBHamilton]

Hi there! I've got a SunTouch (Hate that thing!) that controls a valve sending water up to the solar when it feels the urge. The SunTouch has a [FONT=Roboto, Helvetica Neue, Helvetica, Arial, sans-serif]turn-on differential from 3 to 9 degrees and the turn-off differential from to 2 to 5 degrees. I set the Turn on to 3 and the turn off to 2.[/FONT]

Today the air temp was 87F and the pool temp was 90F so the SunTouch turned off the solar.

Problem is the wife likes the pool HOT - around 92F.

The sun is very strong today. Solar is just a black plastic tube sitting on a hot clay tile roof. I thought there had to be a fair bit of heat available.

I manually switched on the Solar and sure enough lots of nice hot water came out of the jets.

I was wondering if there any easy way to disable the Temp Diff setting or any other suggestion?

I guess I could always buy a hot tub

 

[Dirk]

Wet suit for the wife?

The temperature differentials are between the water temperature and the temperature on the panels, not the air temperature. When you write "air temp was 87F and the pool temp was 90F," where are you getting those numbers?

I'm not sure why you're messing with the differentials. Why not just turn the "thermostat" up? What am I missing? If the solar turned off at 90°, and the wife wants it 92°, then just up the thermostat by 2° (regardless of the actual setting).

 

[RBHamilton]

I'm not sure why you're messing with the differentials. Why not just turn the "thermostat" up? What am I missing?

First, thanks for your reply. I'm not sure what you are missing. The pool is set to 92F. The control panel shows the pool water temp as 90F and the air temperature up by the panels as 87. My unit is shutting down the solar valve believing there is no point in running the solar.

Have you ever put a black hose on the sidewalk when it's 72 outside? Take a drink out of that hose and you can burn your mouth. Air temperature can be 87 but the water coming out of the panels could be 100F. Those black panels sitting on a clay tile roof suck up lots of heat. Air doesn't suck up heat the same way. I don't know why they put the sensor beside the panels and think they have an accurate read on the available heat.

Anyway when I manually switch on the solar there is still lots of heat to be had. Turning up the pool temperature won't do anything if the panel refuses to turn on the solar valve.

 

[Dirk]

This from the manual:



OK, I get it now. My solar automation has three temp senders, water, air and solar, that threw me off. The SunTouch has two, and what mine calls "solar" yours calls "air." Mine also allows the calibration of the sensors, so that if it's 87° out, but my temp sensor is reporting 89°, I can adjust the sensor calibration to 87°, to match the actual temp. Which is what you're missing (or haven't found). The manual doesn't mention that adjustment, so I guess that doesn't exist.

So it doesn't matter what temp you want your pool, as long as the SunTouch doesn't think you have the available heat on the roof, it's not going to give it to you. Huh.

(Sorry, just stating for myself what you already know!) So...

Your roof (air) sensor is cheating you because it's giving a temperature that is lower than what is available in the panels. So you need to make the sensor read hotter than it is. I can think of two ways to do that.

One is to move the sensor to a different location. If it's touching the clay tiles, move it off. If it's far away from the roof, move it closer. Or put it on top of a panel. Or put something black under it. I have mine in a glass jar to keep the wind off of it. That idea was universally panned by folks here, as well as my solar installer, but it solved for me the pump going on and off every few minutes on a windy day. Point being, find another spot for your sensor.

If that doesn't work, you could try calibrating the sensor yourself. It is just a variable resistor.

This from my manual:



So, assuming your sensor is the same as mine, you could conceivable recalibrate your sensor by altering its resistance. You'd put a resistor of the proper value in series with it, or in parallel with it. In series, it should add resistance. In parallel it will reduce resistance. I think you want to reduce its resistance. By doing so, you'll probably throw off its accuracy in a non-linear way. By that I mean: the resistor you need to get it to read 90 when it would have read 85 (a difference of 5) will probably make things worse in another temperature range, so maybe it'll be 80 when it's 70 out, or something like that. You'll have to play around with it, to see if this is a solution or not. Check this out:

Resistor Calculator

Now I've never tried anything like that, but I can't imagine any damage resulting in doing it. You're just altering the resistance a little. And it'll either work or it won't.

I'd try moving the sensor or putting something under or over it before I messed around with the resistors idea.

 

[Dirk]

As I continue to contemplate a solution for you (and I've asked a few others here to take a look), I realized I should point out: moving the air sensor on top of the panels might not work. Remember, that panel gets hot when the water isn't flowing, but will cool off when the water runs through it. It's a heat exchanger that works both ways. So putting the sensor too close to the panel itself may or may not work for you.

 

[chiefwej]

I’m using the Pentair SolarTouch panel, which I believe is the cheaper version of the one you have. My panel allows you to adjust the calibration of the sensors on my panel. Check the manual for yours.

 

[Dirk]

Chief, I assumed there'd be a way to adjust the calibration, because I wanted to offer that to the OP, but I couldn't find it in the manual I downloaded from Pentair. Can you give the OP some guidance about where to look, and/or how to adjust that, even it it's for your system and not his? Maybe you can offer a clue on where to look in the menus, and it will be similar.

 

[Dirk]

I just checked. On a Pentair EasyTouch, all three of my temp sensors can be calibrated. It was under "Settings" and then "Calibration."

For reference, around noon today: my air sensor (in the shade) is reading 63°, my water sensor is also reading 63°, and my solar sensor (up on the roof) is reading 104°.

To be accurate, my solar sensor is calibrated to read 104, I have no idea what the actual temperature is up there. I calibrated my water sensor to match the floating thermometer in my pool. And I calibrated my air sensor to match the local Wunderground weather station. I didn't mess with the solar calibration, other than to put the sensor in a glass jar. That is likely both blocking the wind and providing some greenhouse effect. Like your logic, I figure as long as I can feel that the water coming out of the returns is slightly warmer than the surrounding water, then my solar should be pumping!

It is not out of the realm of possibility that you have a bad sensor on the roof. On a sunny day, it should be reading significantly higher than air temperature. If you can bring it down off the roof, you could test it: stick it in the shade and see if it matches your current air temp. Stick it in the pool and see if it matches your current water temp. Etc.

 

[chiefwej]

Dirk,
I downloaded and reviewed the manual for the OPs SunTouch panel. Here is a link to the manual.

https://www.patiopoolsaz.com/wp-content/uploads/2017/09/SunTouch.pdf

Calibration instructions are on page 23.

 

[Dirk]

Ta da! Problem solved. Nice work Chief. I couldn't find that manual on Pentair's SunTouch page. They have two identical links to the quick start guide. Webmaster error, no doubt, I think one was supposed to be the full manual.

RB, just move the calibration setting a few degrees until you get the performance you want.

OR

Here's something else to check on. According to that manual, your SunTouch can accommodate three sensors, just like my ET can. And they refer to the sensors in the same way, too: air, water and solar. The air sensor is used for freeze protection, and is optional for a solar heater system. Be sure your solar sensor, the one on the roof, is wired correctly to your SunTouch, to the terminals for "solar" and not to the terminals for "air."