How does my heating system with solar thermal work?

Good morning

A flow meter should be installed in the return line.
When the float rises, the pump operates.


Olli

so, pump is finally running! Upon closer inspection of the pump's connection box, I noticed that the plastic on a component on the circuit board was chipped off, which led to the suspicion that the electronics were not functioning properly and therefore the pump was not running. Unfortunately, Grundfos does not offer service for end customers and I could not find the connection box as a separate part, so I bought a complete new pump... Now I just connected the new connection box to the existing pump and behold, the pump is running! (It is audible and palpable, plus the temperature at the solar collector dropped significantly and quickly, which leads me to conclude that circulation is working.) The control now works too; if the ESR does not send a signal, the pump no longer runs! What I find strange, however, is that the float of the flow meter installed below the pump still does not move! Could it be installed the wrong way around? As wrobel correctly pointed out, the pump must be on the return line. However, I am confused that the line above the pump (i.e., the return from the roof) becomes noticeably warm and the supply line at the Delphis-solarstation has no hand-detectable warmth! So maybe the pump is incorrectly installed in the supply line after all and was possibly damaged by the excessive heat of the water, or the pump is installed backwards and pumps the warm water from the roof toward the storage instead of the cold water from below upward? (which would then correspond to the functioning of a supply line, right?) The installer was apparently quite an expert in his field... -.- Judging by the previous owners, it was probably supposed to be as cheap as possible, I wouldn’t be surprised if the system never worked properly and no one noticed (the owners rented out the house before selling it)... Thanks in advance! Regards

Hi, why don't you make two or three meaningful pictures

Olli

First of all, thank you for taking the time to read my post and respond!

Attached are a few pictures from this afternoon, unfortunately there was not enough sunlight left to keep the temperature on the roof correspondingly high (Image 2, T1 is the sensor on the roof and of course the pump is currently not being operated). I can of course take other/more pictures!

Could air in the system cause such a problem? I have already vented at the solar station (on the supply side), some air came out but the float still does not move even though the pump is running. Also, the pipes do not get noticeably warm... Logically, I should probably vent at the top, at the collector, right? Could the pump be installed backwards? Then the float in the flow meter would be pushed down and of course never float, right?

Thanks again in advance!

Regards

Hi

The pump is obviously installed correctly.
There is an arrow molded on the side of the pump housing, you can check again.
If there is really no flow, flush and vent the system. If there is really a significant amount of air in the solar circuit, that’s the only way.


Olli

If there is air in the system, you will hear it when the system is running. Solar thermal systems are not vented like a radiator. This is done with an external pump. The flow meter can sometimes stick at low flow rates; with the low sun in winter, it definitely won't be dancing.