Ground collectors for smaller areas?

No, not yet. But probably in 3 weeks.

Well, warranty and guarantee ....
Well, it's a matter of opinion.

Ring trench collector brand?
That’s not a brand but rather a system.

Good luck with the installation :)

Ring trench collector brand? That is not a brand but rather a system.

Aren't there different providers, like with thermal paste, ground probes ...? Or where/how do you buy your system?

Oh, I ordered everything - pipe, SBK distributor, and brine mixture - from Muggenhumer in Austria. There are also significantly cheaper suppliers and you can apparently just buy the brine concentrate and mix it yourself with water. But I would recommend you skim through the htd forum once. I have already installed the trench collector ring. I just need to connect the distributor and fill it with brine. There are also several reports from "self-installers" (including mine) in the htd forum.