I understand that Elektra runs at 9 bar (Scace), so, it's fair to lower the OPV at Bezzera to 9 bar too;
at my Magica, this was not possible without the 9 bar OPV kit, but on BZ10 several people I know, did it with the existing OPV;
then, if you had an imposed grind and a too high flow, you could increase the dose if the headspace would allow;
anyway, 3 bar is much too lower, I had it only via severe channeling (you are using the bottomless filter)...

IMO, you do not have to add brewing pressure to already a lot of the other parameters
brewing pressure is kept constant to, say, 9 bar, via the OPV for a vibration pump; for an 1 ml/sec extraction flow (single), at 9 bar, some of the Ulka EX5 flow (260 ml/min avg) should be dumped somewhere, otherwise the pressure would increase; it's impossible to have a 9 bar pressure for a single, without a kind of dumping/recirculating the excess flow of the vibratory pump, outside the puck;
on my Magica, I do not even consider the possibility of brewing at a pressure controlled by me, via dose/grind! that would make anyway a highly variable flow, or as I saw - by recording the temp profiles - a highly variable flow would compromise any flat and consistent profile, after the HX hump (not discussing the flow profiling);

Hi Radu, just spotted your post on the BZ10 OPV adjustment. At the risk of diverting from the initial topic: The OPV on my BZ10 is set at 12.5 bar (checked by the retailer with a manometer PF). I tried to lower the setting but that resulted in a high pitch squealing sound. When I readjusted it back above 12 bar, the squeal stopped again. Anyone out there with similar issues?
The machine is relatively new (10 months) and I am fairly zealous about keeping things clean. I am quite happy with the shots I get already, but I would like to adjust the OPV to the 11 bar mark (which appears to be the sweet spot for vibe pumps) at no flow and see where that brings me tastewise. However for now the squeal keeps me from fiddling further.
If I put the Bezzera 9 bar OPV kit in as a replacement, would that still allow readjusting to a slightly higher pressure?

well, honestly, I didn't went too high with the 9 bar kit OPV, but I kept it a while at 10 bar indicated with blind filter;
now, the gauge shows 9.5 bar, both during extraction and with blind (which is normal, since the gauge is connected after the pump);
that squealing sound have been met by several people with the old 12 bar OPV (some resonance due to the 12 bar OPV calibrated spring assy. in marginal conditions); I had it also;
since the new accessories parts catalog does not include the 9 bar OPV kit, I suppose there is something changed on the new OPV's for a larger adjustment range; in which eventuality, you can get the new 12 bar OPV to have covered comfortably the 11 bar spot;
however, either with the new 12 bar OPV, or with the 9 bar kit, I would recommend you to settle around 9 bar working pressure, instead of 11 bar, and work at the OPV regulated pressure; I cannot see a technically motivated reason for 11-12 bar brewing pressure (they say, standard for non-commercial Bezzera's), another than the vibratory pump better regime (perhaps?), some water savings and... coffe bags compatibility;
I was not able to identify any differences in cup, between 12 and 9 bar pump pressure, but that's me;
however, there is a noticeable difference in the shot quality at the bottomless PF level: lower pressure makes the machine more tolerant and this could be important especially for BZ10 which relies for pre-infusion on the vibratory pump starting pressure ramp;

Hi Radu, thanks a lot for the advise. I will consider the replacement OPV at lower pressure, perhaps it will reduce tendency for channeling.
Cheers,

In the meantime I almost solved my problems.
Or at least I'm on the way to do it.
I had mainly some grinder issues and a couple of false friends that organised a joke with ground coffee.
Anyway I discovered that one of my two Demokas needs replacing of the burrs and the strange thing is that it seems that BZ10 is the only machine to notice it.
In fact I have my two HXs in different houses (the semi is used by my father) and to compare them I carried a grinder from one to other. With the first grinder (bought used about 6 months ago) I obtained good results with semi and no crema with BZ10. When I tried to carry the other one (bought 6 months ago too, but this was a demo unit) I noticed that results were very good with both machines.
So I'm guessing that the Semi is more tolerant towards grinding issues.
Again I don't understand why.
Alberto