The Self-draining System
This particular solar system works differently from other systems. If there is no sun or if the balloon no longer needs heat, the circulation of the fluid stops and all the water contained in the solar collector is emptied into the balloon. The addition of antifreeze products is not necessary because, when the installation is not in service, the sensor does not contain water - an additional point in terms of the environment! This also means that there is no pressure in the circuit, therefore no expansion tank, therefore less risk of leaks!
Unlike other systems, there is no longer a risk of overheating of the fluid containing antifreeze in summer, which can withstand high temperatures very poorly!
Limestone has no chance.
During the first start-up, the accumulator tank is filled only once with running water, without using additives. This water serves as a medium for heat accumulation and will not be changed during operation. On the accumulation water side, there can therefore only be a single deposit of the limestone contained in the volume of water.
Constraint: contact a specialist for this system to be sure of the mandatory slopes for self-draining!
Origin of the text: http://www.neowatt.fr/Chauffage-Solaire.htm