Hi all,
I have installed a Vaillant arotherm plus VWL75 A/6 heatpump for my parents and they have used it for a little bit less than a year and it has worked fine so far. Since about 2 weeks the heatpump does not turn itself on anymore after a DHW run. After doing some investigations into the issue I noticed that when the flow temperature of the unit reaches about 55 degrees the unit turns off and the compressor is blocked for about ~63700 minutes.
When I reset the unit the heatpump turns on again as the blocking time is reset/cleared. Only to block the compressor again during the next DHW run when the flow temperature reaches about 55 degrees.
So far I have checked the circulation pump, the diverter valve, the magnetic filter and the control module (VWZ AI). The diverter valve operates normally as expected and can be operated trough the VWZ AI module. The circulation pump reaches about 1700 liters per hour when set to full power. The magnetic filter was also relatively clean, so there does not seem to be blockage of the hot water/heating circuit.
I also tried swapping the VWZ AI module with my own to see if the problem was in the VWZ AI module but that also did not change the issue. So therefore it seems to me that this either a configuration issue with the thermostat or a hardware issue with the heat pump itself
A factory reset also did also not offer any permanent relieve (this was actually the first thing I tried) it initially did make the issue dissapear for about 2 weeks but then it returned.
I am not really sure what to do next. Therefore I would greatly appreciate any suggestion, advice or ideas from you.