Solartouch roof sensor questions

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L

Lena12

0
Jun 14, 2018
12
New york
Hi everyone,

New to the forum. Recently had heliocol panels installed with the pentair solartouch control system. It is set up by the manufacturer to turn on when there is a 6 degree difference with the pool water. For example the roof sensor was showing 84 and the water was 78, obviously it wouldn’t turn on. Reached out to pentair to see if we can override the difference. The only way to do so is overriding the system but that in turn could make the panels generate cold water. The rep suggested placing tin foil behind the sensor and using zip ties or another method to keep it in place. That would reflect more heat to the sensor triggering the degrees to be higher.

It’s a bit frustrating since we want the water to be just a bit higher, when it’s a nice day out to swim.

Has anyone had a similar experience? Has anyone done anything similar or have any other ideas?


thank you!
 
Welcome to TFP!

Are you sure the roof sensor is not being shaded by anything? It should be in full sun and out of any shadows generated as the sun changes angle during the day.

It is mounted up on the roof and not on the solar panels themselves? I should be on the roofing material and not suspended in the air.

Is the sensor shiny silver or is a dark color? I painted mine black.
 
Hi! Thanks for the reply! I should have been more clear. I am referring to when we (NYC) have weather of about 74-76 degrees outside. Right now it is 81 in nyc and the sensor is showing 95, we have no issues when it’s above 81-82 outside. It is working well! There is no shade, no trees around to block it. It is in a perfect location. It’s just when the weather allows for swimming as we had the previous week, the pool was rather cold for us and the kids. So we’d like to try and fool the roof sensor.

The sensor is not on the panels, it is on the return pipe but it is not drilled into the pipe. should we have it moved?I asked the same question to the pentair rep and he said it’s not an issue. But is it?

It looks like it’s black with a black tip. I am uploading the best quality picture I can get. I will try to get a ladder and take a closer up. I traced a circle around the sensor location.
 

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CJadamec said:
The sensor should be on the shingles of the roof. Not on the pipe. At least that's what works for me.
Click to expand...

Same. Ours came with a black sensor. Pentair switched to a black sensor a while back. But, i think mounted to the pipe is probably ok.

You can lower the temperature differential, i think 3 or 4 is the minimum diff. You can also put it into manual mode and open the valve and change the pump speed. But, you definitely need to remember to put it back. Running solar at night will cool your pool which is handy for us in July and August.
 
pooldv said:
Same. Ours came with a black sensor. Pentair switched to a black sensor a while back. But, i think mounted to the pipe is probably ok.

You can lower the temperature differential, i think 3 or 4 is the minimum diff. You can also put it into manual mode and open the valve and change the pump speed. But, you definitely need to remember to put it back. Running solar at night will cool your pool which is handy for us in July and August.
Click to expand...


according to the PB and pentair it doesn’t make a difference if the sensor is on the pipe but I will speak with another rep again.


had to edit my post. Just reached out to pentair again and changed the diff to 4 degrees start. That’s the lowest we can go. The second rep said the same thing as the first in terms of the sensor placement. If it’s getting direct sunlight, it doesn’t make a difference. Kind of lost at this point.
 
Lena12 said:
according to the PB and pentair it doesn’t make a difference if the sensor is on the pipe but I will speak with another rep again.


had to edit my post. Just reached out to pentair again and changed the diff to 4 degrees start. That’s the lowest we can go. The second rep said the same thing as the first in terms of the sensor placement. If it’s getting direct sunlight, it doesn’t make a difference. Kind of lost at this point.
Click to expand...

I tend to agree with that. You just want to make sure it is in full sun.
 
I'm still of the camp that the surface of the roof will be a measurably different, and warmer, than the surface of that pipe in the full sun especially on a windy day. I could be wrong and often times I am but I know if I was on that roof I would rather kneel or put my bare hands on that pipe than the shingles.
 
OK, this from my last pool guy, who was an idiot. I checked with the solar panel supplier, and he thought the pool guy was an idiot too. So I resisted. But my controller was turning the actuator back and forth so often, like every few minutes, I figured I'd give it a try. Get a small glass jar, with a lid. Like a small pickle relish jar. Cut a 3/4" slot in the lid, right through the edge of the lid. Run the sensor wire through the slot. Wrap some electrical tape around the wire, right where it goes through the lid, to protect the wire from the sharp edge. Affix the lid to the roof (roof goop, or silicon). Screw the jar onto the lid.

The theory is: the jar allows the heat of the sun, and blocks the wind. My solar now runs non-stop when the sun is out. It doesn't flip on and off as it did. It comes on a bit earlier in the day. I suppose I've messed with the temperature differential, but it seems to be working better than it did. I did this not too long ago, and haven't tested it completely. I think all I have to do to confirm is put my hand in front of the return. If the sun dips behind some clouds, or it's first thing in the morning, or a cool day, and the controller doesn't bypass the panels, then I just feel the return water. If it's warmer than the pool, even by a little bit, then jar = no harm.
 
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Dirk said:
OK, this from my last pool guy, who was an idiot. I checked with the solar panel supplier, and he thought the pool guy was an idiot too. So I resisted. Buyt my controller was turning the actuator back and forth so often, like every few minutes, I figured I'd give it a try. Get a small glass jar, with a lid. Like a small pickle relish jar. Cut a 3/4" slot in the lid, right through the edge of the lid. Run the sensor wire through the slot. Wrap some electrical tape around the wire, right where it goes through the lid, to protect the wire from the sharp edge. Affix the lid to the roof (roof goop, or silicon). Screw the jar onto the lid.

The theory is: the jar allows the heat of the sun, and blocks the wind. My solar now runs non-stop when the sun is out. It doesn't flip on and off as it did. It comes on a bit earlier in the day. I suppose I've messed with the temperature differential, but it seems to be working better than it did. I did this not too long ago, and haven't tested it completely. I think all I have to do to confirm is put my hand in front of the return. If the sun dips behind some clouds, or it's first thing in the morning, or a cool day, and the controller doesn't bypass the panels, then I just feel the return water. If it's warmer than the pool, even by a little bit, then jar = no harm.
Click to expand...

This is a little more drastic of an approach but the idea is the same. The jar is creating a greenhouse which is making the probe read higher than it should but solves the issues or rapid temperature swings in what the probe is reading.

The temperature difference when air is allowed to circulate around the thermal probe is quite a bit different then when the air is still. The reason you put the panels flat on the roof and not up on racks is to prevent the air from circulating under the panels which will greatly reduce their convective heat loss to the air and put more heat into the water. Right against the shingles a boundary layer of air forms that is fairly still and much warmer. Also the shingles and roof itself have much higher thermal mass than that small contact area on the pipe which will do the same as the jar and greatly slow down the probes response to temperature changes.

An easier and less noticeable solution to the glass jar would be to glue the probe to a shingle with a small spot of roofing tar. The spot of tar is a far more accurate representation of the energy hitting the panels than the probe just out there in the breeze.
 

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CJadamec said:
I'm still of the camp that the surface of the roof will be a measurably different, and warmer, than the surface of that pipe in the full sun especially on a windy day. I could be wrong and often times I am but I know if I was on that roof I would rather kneel or put my bare hands on that pipe than the shingles.
Click to expand...


Thanks! I think I am going to get that ladder and get on that roof to feel the pipe and shingles later on in the day. It should be close to 75 here today with some wind. Seems like a good day to try.
 
CJadamec said:
This is a little more drastic of an approach but the idea is the same. The jar is creating a greenhouse which is making the probe read higher than it should but solves the issues or rapid temperature swings in what the probe is reading.

The temperature difference when air is allowed to circulate around the thermal probe is quite a bit different then when the air is still. The reason you put the panels flat on the roof and not up on racks is to prevent the air from circulating under the panels which will greatly reduce their convective heat loss to the air and put more heat into the water. Right against the shingles a boundary layer of air forms that is fairly still and much warmer. Also the shingles and roof itself have much higher thermal mass than that small contact area on the pipe which will do the same as the jar and greatly slow down the probes response to temperature changes.

An easier and less noticeable solution to the glass jar would be to glue the probe to a shingle with a small spot of roofing tar. The spot of tar is a far more accurate representation of the energy hitting the panels than the probe just out there in the breeze.
Click to expand...


thank you for the response! I think your explanation makes a lot of sense! We will talk with the installer and have it moved.
Is the sensor supposed to be sticking up in the air or lying flat on the shingles?
 
Mine sticks up. I'll yield to Chuck on moving the sensor to the roof. It certainly won't make it worse and could well make it better. Would try moving the sensor to the roof to see how that works before doing the pickle jar thing. :) but, hey, if it fixes a problem and doesn't create another one then that is great!
 
Gluing it flat to the shingles makes sense to me. If the solar is tuned well, the panels, and the pipes, should all run cool. So affixing the sender to either doesn't seem like it would best measure heat on the roof.
 
Good point. I would expect the thermistor to be at the top of the sensor. But, 80 degree water moving through that pipe could reduce the temp on that sensor could reduce the temp enough to make difference from a 140ish degree shingle.
 

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