Yes, 50 m2 is about 538 ft2, but because of the spacing between tubes, it is effective bigger when the sun is at an angle. This tube is very rigid. It will never kink and I have never had a leak. What sort of flow do you have through your panels and how much pressure does that take?EDIT: Those are bigger tubes that I thought on first glance.
So this is similar to what the previous owner put on my house. Same type of tube, but there were only 8 parallel runs of 100 - 250 feet each. I think it was around 200 ft2.
They did not lay them out anywhere close to as nice as your setup, so there was a lot of self-shading. I got tired of dealing with the constant leaks that would start where things got kinked. Tore them out and installed 500 ft2 of panels.
I dunno, the Heliocol manual clearly states a minimum. Admittedly it doesn’t say why so like you say it probably just has to do with efficiency.There is no real minimum. The efficiency just suffers. Some members run them away much lower flow rates than mine. Location of the VRV also is important to how low you can run to keep it from pulling in air.
Honestly right now I think I may have 35GPM at most due to dirty filter.
Panels are still cool too the touch.