Other heating system changed after the heating load calculation was created

Hello, we are building a turnkey house with a developer, and the heating system was precisely defined in the offer. During construction, it turned out that it was oversized. We insisted on a heat load calculation, which was also included in the construction specification; however, the heating engineer wanted to build based on experience. After the heat load calculation, a significantly smaller system was installed, with fewer heating circuits and fewer pipes. Can we demand a credit? The heating engineer only wants to credit us €60 per saved manifold. The saved material costs alone amount to around €2000 gross. Maybe someone knows something, thanks

I cannot/would not like to say anything about contractual matters.

But do you really want to do without heating circuits and tight installation?
What does the current planning look like?

The house is finished. The heating is already well designed, but also in a way that it can be regulated. This has been independently tested twice. ☺️

If everything is well designed and well built, why do you want to claim compensation then?

The heating engineer paid significantly less for the system. I think it's legitimate that we also get a share of that? After all, we have to bear all additional costs too? I don't want to receive any compensation‍♀️

fewer heating circuits, fewer pipes.

Really? As a rule, after a proper sizing of the heating system, these things increase.