Clicking sounds in the circulatory system during thermal stagnation

Dear house construction forum members,

I operate a heat pump system (Buderus WPS-10, geothermal) with a storage tank as well as solar thermal support (2 x Braas TK8) in our single-family house.

When the sun shines very strongly in summer and the system goes into thermal stagnation, meaning the circulation pump switches off, there are persistent ticking noises in the attic, somewhere around where the connection of the hoses of the solar collector modules with those leading to the basement to the storage tank is located, as if someone had hidden an alarm clock behind the drywall of the roof.

I reported this as a defect to the heating engineer and expressed my suspicion that cavitation was occurring there and my concern that this could lead to material wear in the long term.

After the service technician was finally able to witness the effect live (the sun has to be shining), he adjusted the setpoint or limit/alarm values of the system. As a result, there was a daily alarm value exceedance at the heat pump whenever the sun shone, and it beeped in the basement every day and the alarm had to be acknowledged.

For a time, I then dissipated the heat through the collectors again at night by manually switching the controller to manual in the evening and turning on the pump. However, this is very inconvenient, so I reset the limit values, after which the ticking noises returned.

A — repeated — call to the heat pump manufacturer (Buderus) and an email were completely useless—I might as well have asked my grandma. These people appear to be there only to take phone calls—without any technical expertise.

I actually maintain a not-so-bad relationship with the heating engineer, but I fear this also exceeds his competence. At any rate, he is very reserved on this issue and anything but proactive.

Therefore, my question here in the forum to you: Has anyone ever experienced this phenomenon themselves or heard of it and perhaps knows what can be done about it?

The system is at about 2.5 bar in the basement, thermal stagnation sets in at about 150 °C, then the pressure rises to about 4.5 bar, the temperature up to max. 190 °C.

Thank you very much and best regards Thorsten

That is a very specific and technical question, for that I would definitely drop by the "Rosa" Fo... There are, among others, the heating engineers around.

Dear house-building forum members,

I operate a heat pump system (Buderus WPS-10, geothermal) with a storage tank as well as solar thermal support (2 x Braas TK8) in our single-family house.

When the sun shines very intensely in summer and the system goes into thermal stagnation, meaning the circulation pump switches off, there are persistent ticking noises in the attic, somewhere near where the fittings of the solar collector module hoses connect with those that lead down to the storage tank in the basement, as if someone had hidden an alarm clock behind the drywall of the roof.

I reported this to the heating engineer as a defect and expressed my suspicion that cavitation occurs there and concern that this could lead to material erosion in the long term.

After the service technician was finally able to experience the effect live (sun has to shine), he adjusted the target and limit/alarm values of the system. As a result, there was a daily alarm value exceedance at the heat pump on sunny days, and the basement alarm beeped daily and had to be acknowledged.

For a time, I then drained the heat away through the collectors at night by switching the controller to manual in the evening and turning on the pump. But this is very annoying, so I reset the limit values, after which the ticking returned.

Repeated calls to the heat pump manufacturer (Buderus) and an email were completely useless—I might as well have asked my grandma. These people seem to be there just to take phone calls—without any technical expertise.

I actually have not a bad relationship with the heating engineer, but I fear that this also exceeds his competence. In any case, he is very reserved on this topic and anything but proactive.

Therefore, my question here in the forum to you: Has anyone ever experienced this phenomenon themselves or heard of it and possibly knows what can be done about it?

The system is at about 2.5 bar in the basement, thermal stagnation begins at about 150 °C, then the pressure rises to about 4.5 bar, with the temperature reaching a maximum of 190 °C.

Many thanks and best regards
Thorsten

We had something similar: the supply and return lines to the heat storage tank coming from the heat pump were swapped.

This is a very special and technical question, for that I would definitely show up at the "Rosa" forum.
Among others, the heating engineers are active there.

Hello KingJulien,
thanks for the tip!
Best regards
Thorsten

We had something similar, the supply and return lines to the wgt coming from the heat pump were reversed.

Hello Offtopic, thank you very much for your post. That’s exciting! I will definitely look into it further! Such things can indeed easily happen to the professional craftsman. In our case, hot water was also connected to the toilet, resulting in warm flushing and condensate dripping from the water tank. Took off the tile and swapped the connection, and just like that, it was fixed! If it were that easy here, much would already be achieved! One question though: What does "wgt" mean? Best regards Thorsten

Hello Offtopic, thank you very much for your contribution. That is exciting! I will follow up on that! Something like that can indeed easily happen to the professional craftsman. In our case, hot water was also connected to the toilet, resulting in a nice warm flush every time and condensation dripping from the water tank. Chipped off the tile and replaced the connection, and presto, it was fixed! If it were that easy here, much would already be achieved! One question: What does "wgt" mean? Best regards Thorsten

Wgt is the controlled residential ventilation; it has a heat exchanger to preheat the fresh air after heat recovery so that no drafts occur.