Suntouch Solar Controller Question

[trader4]

Hello, all. Occasional visitor here where I've found lots of good and useful info. Now I have a question that hopefully someone with some experience with the Pentair SunTouch Solar controller can answer. I'm looking at using one of these to add solar heat to a pool. The problem is, I've read the manual front to back and IMO, a lot of the solar mode operation explanation is either wrong or makes no sense. The unit comes with 2 sensors, one for location in the pool water line to measure pool temp and the other that goes near the solar collector to measure the temp available at the panels.

Here is how I would expect this should work. There are two factors. First, is the pool below the desired set temp? If so, then we would like solar heat. Next, is the temp at the solar sensor high enough above the pool water sensor temp to make it worthwhile to turn on solar heat and if it is, then it activates the valve and turns on the pump. Further in the solar mode in this contoller, there is the ability to set the turn-on differntial from 3 to 9 degrees and the turn-off differential from to 2 to 5 degrees. To me this would logically be the temp differential BETWEEN THE POOL WATER SENSOR AND THE SOLAR SENSOR temps. Meaning, if I set the turn on diff to 6 and turn off diff to 3, the solar sensor would have to be 6 degrees higher than the water sensor to start heating. And then it would stay on until the solar sensor is 3 degrees or LESS above the water temp, at which point it would shut off. All this assumes of course that the pool water temp is below the set temp, ie the pool needs heat.

Here's the problem. The manual makes a whole bunch of statements that to me seem either totally wrong or at least make no sense. Some examples:

1 - Solar heat is available when the set point water temp is higher than the solar temp and the solar temp is higher than the actual water temp.

2 - Solar heat is not available when the set point water temp is lower than the solar temp and the solar temp is lower than the actual water temp.

3 - If "start" differential is set to 3deg, this ensures that the solar collector water temp has to deviate by at least 3deg to the specified set point temp before it switches on.

4 - Stop differential sets how close to the target set point temperature to switch off solar heat.

I was on the phone with tech support today and couldn't get past #1 above. We read it together from the manual and he insisted it's absolutely correct and that's how it works. Maybe he's right and someone here can enlighten me. Curiously, according to the LX220 manual, which I believe was the previous Pentair product, that works like I think it should work, but it has a fixed turn on differential of 5 deg between the pool water sensor and the solar sensor. So, does anybody here have one of these and/or really know how it works in solar mode? This really looks like the right product for what I want to do and I'd like to buy it, but only if it works like I think it should. I'm particularly interested in what the differential settings actually relate to.

Here's the link to the manual if you want to take a look. The relevant stuff starts on page 4 of the manual.

http://www.pentairpool.com/pdfs/suntouchUG.pdf

TIA for any help.

[Pool Clown]

I think you are confusing solar sensor temp with solar set point temp (thermostat). The solar sensor measures weather there is sufficient temperature to get heat out of the panels, i.e. sun or no sun. The solar air temp sensor is in the sun, so you can imagine how hot it gets. So it isn't very likely that there would be a differential of <10 degreees between pool and sensor on the roof,(not including cloudy days). So the differential Pentair is referring to is the diff between actual water temp, and what you set the desired temp to.

Does this make sense?

The manuals don't always get the proof reading they require.

[trader4]

"I think you are confusing solar sensor temp with solar set point temp (thermostat). "

I don't see how there can be a "solar set point temp". There is only a pool set point temp, ie the temp I want the pool at.

"The solar sensor measures weather there is sufficient temperature to get heat out of the panels, i.e. sun or no sun. The solar air temp sensor is in the sun, so you can imagine how hot it gets."

There isn't an air temp sensor unless you order the optional air temp sensor, which is used, as far as I can tell, only for freeze protection and to put it up on the display so you can see it if you like. All of the Suntouch solar kit configurations to support this type of application include the controller, 3 way valve, etc and only include 2 sensors. One for the pool water temp and the other for the solar temp. The solar temp one gets mounted on a flat surface similar to the water panels, so it's trying to be close to the temp at the collectors, not the air temp. That seems logical and how it should work, no? Whether you have solar heat available only depends on whether the temp at the collectors is high enough above the actual pool water temp.

Let;s take two examples of how I believe it should work. The solar panels are at 100, the pool is at 80, the set temp is 85. First, the pool needs heat. Next the solar temp is 20 deg ABOVE the WATER TEMP so there is enough differential to make turning it on worth it, so the controller turns on the pump.

Another example, solar panels at 83, pool is at 80, the set temp is 85. Pool needs heat. But the solar temp is only 3 deg above the water temp, so it's not worth turning on the pump and the controller doesn't. And here is where it would make sense to have control of the differential, being able to set it from 3 to 9 deg, no? The previous Pentair controller that Suntouch replaced, LX220 operated exactly like described above with a fixed differential of 5 deg, which is curiously in the middle of the range of the Suntouch programmable differential of 3-9. The only problem is that isn't what the manual says and from reading it, it's not clear what Suntouch actually does.

"So it isn't very likely that there would be a differential of <10 degreees between pool and sensor on the roof,(not including cloudy days). So the differential Pentair is referring to is the diff between actual water temp, and what you set the desired temp to.

Does this make sense? "

In trying to decipher the manual, I thought of that possibility too, that they are giving you the option of setting a differential between the actual pool temp and the desired pool temp that has to be achieved to avoid turning heat on and off repeatedly over a small fluctutation. Similar to what you have in a home thermostat, where the temp has to vary by typically 1 deg or more. But it doesn't make sense here for a number of reasons. The main one being, the ability to set this differential in the Suntouch only applies to SOLAR MODE. If it were the differential between actual pool water temp and desired pool water temp then it would apply to all heat, eg heat pump, gas, etc no? And also, why a range of 3 to 9 deg? No one would want their pool to vary by over 9deg before calling for solar heat and most would want the pool temp regulated closer than 3 deg, but that is the SMALLEST differential setting allowed. My existing Jandy gas heater keeps it spot on. If it were the differential between actual pool water and set pool water that is programmable, I would expect a range of 1 deg to maybe 4 deg, no?

"The manuals don't always get the proof reading they require."

That's for sure in this case.

[Pool Clown]

In trying to decipher the manual, I thought of that possibility too, that they are giving you the option of setting a differential between the actual pool temp and the desired pool temp that has to be achieved to avoid turning heat on and off repeatedly over a small fluctutation. Similar to what you have in a home thermostat, where the temp has to vary by typically 1 deg or more. But it doesn't make sense here for a number of reasons. The main one being, the ability to set this differential in the Suntouch only applies to SOLAR MODE. If it were the differential between actual pool water temp and desired pool water temp then it would apply to all heat, eg heat pump, gas, etc no? And also, why a range of 3 to 9 deg? No one would want their pool to vary by over 9deg before calling for solar heat and most would want the pool temp regulated closer than 3 deg, but that is the SMALLEST differential setting allowed. My existing Jandy gas heater keeps it spot on. If it were the differential between actual pool water and set pool water that is programmable, I would expect a range of 1 deg to maybe 4 deg, no?

"The manuals don't always get the proof reading they require."

That's for sure in this case.

All good points/questions. Fortunate for me,I don't work for Pentair.

Hey, i didn't see if you posted earlier but, does this Suntouch work OK?

[trader4]

In trying to decipher the manual, I thought of that possibility too, that they are giving you the option of setting a differential between the actual pool temp and the desired pool temp that has to be achieved to avoid turning heat on and off repeatedly over a small fluctutation. Similar to what you have in a home thermostat, where the temp has to vary by typically 1 deg or more. But it doesn't make sense here for a number of reasons. The main one being, the ability to set this differential in the Suntouch only applies to SOLAR MODE. If it were the differential between actual pool water temp and desired pool water temp then it would apply to all heat, eg heat pump, gas, etc no? And also, why a range of 3 to 9 deg? No one would want their pool to vary by over 9deg before calling for solar heat and most would want the pool temp regulated closer than 3 deg, but that is the SMALLEST differential setting allowed. My existing Jandy gas heater keeps it spot on. If it were the differential between actual pool water and set pool water that is programmable, I would expect a range of 1 deg to maybe 4 deg, no?

"The manuals don't always get the proof reading they require."

That's for sure in this case.

All good points/questions. Fortunate for me,I don't work for Pentair.

Hey, i didn't see if you posted earlier but, does this Suntouch work OK?

I don't know if it works OK or not. I am looking at buying it for adding solar heat to an existing pool and that's why I wanted to know how it works. It looks like it's been out for about 2 years and lots of places online are selling them. However, it can also be used as a general pool/spa controller, so no way of knowing how many are used for solar installations. I can tell you one thing. While this could be perfect for adding solar to an existing pool, there is no way I would use this for general control of the pool pumps, spa, lights, waterfalls, etc that it can also do. It has a very basic small LCD display and a half dozen or so buttons with vague lables. IMO, it would be like trying to run a nuclear reactor from a digital watch.