Solar Pool Heater Sensor.

[PeterG]

Hi All, what temperature sensors are used in solar pool heating systems?

They seem to use two sensors, one for the roof water temp and another for the pool water temp.

Regards

[ttp]

What brand?

[PeterG]

Is there a general type of sensor device they use ?

It looks like i will need to replace a pump control unit on a solar pool heater system. A replacement controller is well over $400AUD.
Given the cost of an off the shelf unit, i am thinking it will be cheeper to put one together out of my bits box.

Regards

[Ed.Kloonk]

What's wrong with the controller? Just wondering if the solar sensor has had the Richard and that's your problem..

[PeterG]

The controller is a MS3D. It was DOA when i received it. It had a bad power lead which i replaced and also had blown its bridge rec. It ended up being brain dead with a corrupt mcu and i have no firmware to reflash to it,assuming the mcu is not damaged.

These things seem to fairly straight forward and should not be hard to put together.

Regards

[Ed.Kloonk]

The controller is a MS3D. It was DOA when i received it. It had a bad power lead which i replaced and also had blown its bridge rec. It ended up being brain dead with a corrupt mcu and i have no firmware to reflash to it,assuming the mcu is not damaged.

These things seem to fairly straight forward and should not be hard to put together.

Regards

Yeah. If you can decipher a temp-dependant voltage out of both sensors you'll be right. Don't know why you'd need a micro just to heat the pool.

[PeterG]

From what i have been told, you set the desired pool temp and the controller works off that.
The temp sensors are connected with figure 8 cable at least 4 meters long so i have discounted any type of thermo couple. Maybe some sort of  resistive device?

Regards

[Ed.Kloonk]

From what i have been told, you set the desired pool temp and the controller works off that.
The temp sensors are connected with figure 8 cable at least 4 meters long so i have discounted any type of thermo couple. Maybe some sort of  resistive device?

Regards

Be interesting to see how this all goes.

[SeanB]

2  Thermistors. One reads the temperature of the panel and when it is above the setpoint for pool temp it turns on the pump to circulate water through the panel. If it then drops below it turns the pump off. The pool one senses when the pool is warm enough and then disables the pump until it is cool enough again.

[T4P]

The temp sensors are connected with figure 8 cable at least 4 meters long so i have discounted any type of thermo couple. Maybe some sort of  resistive device?

I have seen 10meters thermocouples for sale 

[SeanB]

I used to buy thermocouple extension wire in kilometer reels....... But all the solar sensors I have seen use a NTC or PTC thermistor that typically is 10k at 25C. Thermocouples are really not a good thing when you want to sense within 100C of ambient, the cost to get an accurate reading is way too high for the associated electronics and they need calibration to match the sensor to the input. RTD and thermistor are easier, as they have both a larger signal and are easier to interface, you have signals in the range of 100mV to 5V, as opposed to measuring a signal of 100microvolts or less. You can also have then with a 1% or less initial error and a no calibration install is possible.

[PeterG]

SeanB, thanks for the info. I will let you know how this progresses.

Regards

[GJN]

I know this is an old topic but I'm interested to know if anyone knows what sort of sensor these things are? My controller died and I am building my own with a Raspberry Pi and a couple of Python scripts. My best guess is these are a type of thermistor so I have searched and I am going to try and interface these to the Pi via voltage divider into a MCP3002 ADC. That sounds like I know what I am talking about but I don't really!

The thing is that in this thread and in others people have said that thermistors normally are in the k-ohm range but when I have measured mine with a multimeter I am getting readings from 340k up to 15MOhm depending on temp. This is across a run of about 20m of cable. So could this be right?

Edit: I can see they are different sensors from their website as the pool sensor is rated 1-50deg and the roof sensor 1-100?

[CJN]

Resurrecting and old old thread

@GJN did you make any progress ?