Thank you very much for the hints.
The attempt to reach the caseworker by phone seems futile.
So the objection will be sent in writing to meet the deadline, with the simultaneous request to provide reasons, since we cannot review the rejection otherwise.
Again regarding the installed devices – I am a bit unsure here:
There are manufacturers who have had every conceivable combination of outdoor and indoor units included in the list (e.g. Daikin) and there are manufacturers who have the outdoor unit only once in the list and then an "example configuration" of the indoor units. This is the case with our Mitsubishi. Actually, it should not really matter, as somewhere in the funding guideline it presumably states that a "comparable" one is also eligible for funding. Unfortunately, I currently cannot find the sources where I read this last year.
In our case, the following was installed:
"Mitsubishi Heavy Ind."
Outdoor unit/heat pump: SCM 80 ZS-W
Indoor units: SRK 25 ZS-W + SRK 25 ZS-W + SRK 35 ZS-W + SRF 35 ZS-W
The following combination is listed in the list of eligible systems:
Mitsubishi Heavy Industries Thermal Systems Ltd. SX series multisplit SCM80ZS-W/SRK35ZSX-W/SRK50ZSX-W
Could this be the crux of the matter?