Setting the target indoor temperature to 30 degrees likely hasnt changed anything, unless it was frequently hitting the set temperature before and so turning on and off. The target indoor temperature doesn’t affect the target flow temperature at all, this is driven purely from weather compensation.
The thing that likely made a difference was opening more of the circuit. The general consensus is to run heat pumps on a fully open circuit, no zoning & minimal TRV usage. This gives the heatpump more emitter to heat the house with and so can run more efficiently and can reduce cycling. This potential increased cycle time could give more time for the pwm to decrease the pump speed as it can take quite some time to do so after starting up each time.
I’m not super familiar with the intricacies of buffer systems and 2nd pumps, so cannot advise to much on this, but another general concensus is that buffer tanks can also reduce efficiency. You could try piping out the buffer and the 2nd pump and see if the PWM pump can handle the system on its own. But this could potentially lead to increased cycling, going against what I said above.
Thank you. Seems noise started again - even if all circles are still open. I see water flow again ~31lpm and inverter 70%. Why it has changed and not “balanced” anymore? At least it came out this annoying noise disappears when inverter work on ~50% power and water flow ~20lpm.
Heh and now quiet again and inverter below 50%. Most circles open. Outside temp 3.2C. Weird.. does outside temp play so much role here? Auto mode on. Btw at some point display showed 60c in water outlet (Auto mode) when normal is between 28-33c. Not sure if this expected, maybe somehow related to boiler(45C set there)
Good news - Seems issue was related to outdated software that was not respecting inverter pump 70% value (even if user sets 70%, it still used 100%). Software update to latest version seems to fix it, water flow now smaller on 70% and no annoying sound. Will monitor it next few days. To fix the issue with 100% bigger pipes are needed indeed. Thank you everyone.