Heating defective due to ammonia from the channel

Have you already asked an expert for advice? Maybe another heating engineer can also tell you if that is okay.

Sometimes it already smelled like urine, but then it went away again without us refilling anything. But we almost always have the window open in the HAR. A ventilation system is also installed in our house. The HAR is an exhaust room from which air is extracted, like in our bathrooms, the hallway, and the kitchen.

I also can't say how professional the statement from the technician from Tecalor is, or whether it was just an initial assumption on which all further arguments are now based.

At the moment, the costs are holding me back from consulting an expert. They amount to about 3600 net, including metallurgical examination of the copper corrosion.

You will need the [Gutachten] as soon as it comes to a legal dispute. Before that, you can ask another installer for advice. It should be considerably cheaper.

Didn't you receive any instruction from Tecalor directly?
Take a look at Tecalor's homepage, there should be a detailed installation manual. Maybe you'll recognize something there.
You probably won't get around getting an expert opinion.
Or you pretend to be clueless and call the next plumbing and heating company that services such systems. Of course, there is a risk of making things worse.

There was no instruction directly from Tecalor. An employee from Fehl und Sohn briefly explained the menu of the system's control panel to me, and that was it. I only learned from the maintenance technician in April 2019 that Tecalor usually commissions these systems and that you would then have an extended 5-year warranty. In my case, the installation company did this without informing me.

The technician from Tecalor said: I don’t know this system at all. Actually, we are the ones who commission the systems.

This technician also noticed the absence of the siphon at the condensate drain.

The company Stiebel Eltron has an installation video of an identical system in which all three of these drains and overflow pipes merge into a funnel siphon.

I would first have an expert come to independently assess the whole thing again, for more like 360 than 3600€. If I do not misunderstand the explanation of the [TecalorMA], it does not make any sense.