... to eastern Europe a few times with friends who have relatives there (BiH).[/QUOTE]
Any truth to Europe "had variable drive water pumps like WILO in the early 90's ?
Making a transition from small pump + larger pump and then both pumps (or not) for 3 staging, to variables in the past 4 years only ('cause I saw less advantage at a public library installed 1997 on 27 ton GeoT and 19 boreholes that used a single variable drive rack) - and used for so long FlowCentrProcucts com pumps (to 60 hp racks) with the 3 staging or 2 staging method, sacrificing a very small energy difference/ in annual utilization tracking;
with the dual compressor (sm+larger+then both for 3rd staging water source Hydro-Temp com of AR (that is not hydro delta hydro heat which does not do heat reclaim 100% in the A/C mode like H-T patented in 1981...).
Also versus variable, a loop pump of only two different models in an entire 20- 500 ton school GEO-T and GT+ Conventional Hi Eff hybrids and back up systems… has demonstrated a couple of things:
The Primary loop IS the entire loop; not needing cv flow devices and those $500. t&M installations to units; no mechanical room with electric boxes and starters and any pumps for even the largest systems --- can be so for any tonnage, all things designed for that.
(Kinda like instead of having one big blower on 10 units in a duct (plumbing of air- fluid dynamics, same variable flow result , individual blowers)
I suppose variable costs would be down at building maintenance, etc if every unit consoles, splits, unitary packages, all had a variable ... but those jobs are already way past 23 to 25 tons per loop pump horsepower since the 90's. (See schools in AR, and KY tracked and discussed at ASHRAE boldly since 2008 (NY School goals surpassed by 30% + HVAC and Hot Water AND Make up air with heat reclaim all inclusive).
Variable Iq eff on the way for me only for a short time now seeing so many great installs surviving the counter balanced controller's "footprint" to net savings comparisons.