Hi @Kocta,
Sorry for the latency!
I agree that controlling 40C4 would allow you to reduce the noise (it’s impressive how it can reduce).
However, the first drawback is that this value is not saved in eeprom, therefore after any power outage you have to reapply it.
The second drawback is that the mean to change the value requires using a F3/F4 connection (modulated RS485) on the control layer, I’ve not yet tested the F1/F2 connection (pure RS485) on the set layer. I’m willing to try that, but hadn’t yet had time to.
Also, there is another setting you can change to reduce the pump by default to 70% (which from 100% really kills the noise),
From the wired controller user manual:
FSV #4051=2 : Inverter pump use + Output 70%
And that setting is manageable using the wired controller directly IIRC.
Cheers,