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Posts: 3
Reply with quote  #1 

Hi there,

After reading a lot on this forum i started my own project a few weeks ago.
I used a "sandwich" panel as my back plate and some pex tubing to pump the water trough.
I have made a box of some old wood and insulated it with rockwool.
To seal it off i will use a double layerd polycarbon plate.
To measure the temperatures in the collector i will use a raspberry pi with the code of the website below. https://temperature-machine.com/

We will place the collector on the roof and the tank on ground level so it can drain back. I am not sure with pump to use and how to control it.

I am thinking of a snap-switch but i am not sure how that will go if there will be any condens in my collector. The other idea is to use a pv-solar panel directly to the pump. Can anyone advice on this?

Some pictures:

First we where thinking about a spiral collector, but after reading here we decided it was not good for the winter weather.


pex2.jpeg pex1.jpeg 

pex3.jpeg  pex5.jpeg 

Kind regards,



Posts: 149
Reply with quote  #2 
Welcome to the Forum! 

I am not sure there is an easy answer to your question of which pump to use.  You will have to take into account a few factors...like head (height to the top of the collector) and flow requirements....I see you have all 1/2 inch pipe which will require more pressure and flow in the headers feeding your 4 "loops". I know I made the mistake of buying a Taco pump that did not have enough head to lift the water to the top of the collector.  It was a nice differential controlled pump, but too small for the task. I read a little more specs on various pumps and ended up with a Grundfos 3 speed coupled with a Senca controller for about the same cost.  I over built (standard procedure in my family) and run my pump at low speed and have plenty of head and flow. 

I suggest you provide a little more info to us, like maybe design pics (we love pics and drawings, no matter how crude) and someone with more technical skills will respond, sooner or later.  It is the slow time of the year for projects and I am not sure how many people are visiting the Forum regularly now.  Good luck!

Posts: 3
Reply with quote  #3 

This weekend I tested the electronics and finished up the collector.

I used a 24v power supply, a 24v/220v relay and a Bi-metallic thermostat.

solar2.jpg  solar3.jpg  solar1.jpg 

It is working as supposed and I decided to the finish up the collector.

Next weekend (if there is any sun) i will test the collector with a submersible pump. I think later i will go for the Laing/swiftech pump.


On the website above it says: "Speed signal: With 3-Pin Molex connector as speed signal output (for Mainboard or fan controller connection)". Does anyone have experience with hooking up such a pump?

This pump has a head of 5,7 meter which is 1,5 meter more then i need. But this is for 8mm tube, i am using 16mm pex. Is there way to calculate if this pump will work?

Kind regards,


Posts: 3
Reply with quote  #4 

A little update on my project.
I left the project for a few months, because i was busy with other things. This weekend i wanted to use it for the first time to heat the pool.

It turned out that the pex tube just melted. The tube was totally blocked.

It is the end of this project.

WhatsApp Image 2020-06-22 at 18.59.57.jpeg  WhatsApp Image 2020-06-22 at 18.59.55.jpeg 


However i have seen a project of someone using solar panels directly connected to a heating element. Someone has experience with that? 


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Posts: 3,063
Reply with quote  #5 
So sorry to hear you abandoned the project. One of the problems with solar thermal collectors is that without continuous "cooling" they WILL overheat if not covered.

As far as directly connecting PV panels directly to a heating element is concerned, I'm sure a lot of us have thought of it and personally I think it would work. COST would be a factor, though panels ARE getting less and less expensive. Matching the heating element and the output of the panels might be a problem, but at least the panels won't melt.

Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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