Still waiting for the second quote, but in the mean time I have found options for controlling, or at least read the De Dietrich heat pump with a RS485 interface. A lot of the info is in French, and unfortunately registering to the before mentioned site did not result in the ability to download the mentioned files. But I found a github repository with a python based solution, which gives the needed information.
Are you sure it's a good idea to get something which isn't very well documented? Going by what you've said, that company could be a pain to deal with.
I'm not afraid of a bit of research. If needed reverse engineering is a way to go. The whole thing will become a big experiment to reach a solid and economical solution.
I think the only big issue you finally have is how successfully the pump is positioned.
But how big is big is questionable, obviously after the pump itself is generally fine.
Maybe you add a battery backed circulation pump no matter what.
Maybe you must later add some acoustic insulators, but so be it then, even if you must dig under the foundation, it's actually not very big qube.
(how high can engine hoist lift)
What comes to generic heating service persons around here, more experienced ones are many times very aware of many kind of specialities.
Since these things are generally pretty fine over longer periods of times these service fellas must have a wide customer base.
Around here it can include stores, dairy farms, meat packing places and so on, plus considerably old water circulations around different generations of machines.
BTW,
that earlier mentioned cold water is actually not very cold.
It's from pipes that are around a room temperature and a tap lever is usually lifted straight up, so somewhere around the middle.
Winter stream water is cold, even as cold as tap can give is not really cold, winter times it's probably close to 6C.
People who swim in ice hole would probably argue against the whole concept of cold water.
BTW2,
I had to drop HVAC target temp, the area was closing to 23C and ask was 19C.
The machine has been a bit eager from the beginning.
It's Panasonic E12 series scroll and my educated guess is that it's internal curves are too low for our temp ranges.
Maybe it's because of missing liquid, but if outdoor temps are skyrocketing or dropping equally it sometimes goes bonkers.
Then removing mains for a moment will do the trick, luckily it's indoor unit fed wall plug thing that actually has that plug.