Incorrect heating installed — problem and consequences?

Hello everyone,

I need your advice: We contractually agreed with our general contractor that the Wolf Gas-Solar-Central CSZ-2-14/300R would be installed in our house. This week, I accidentally discovered that instead the next larger device, the CSZ-2-20/300R, was installed. (House is not finished yet, acceptance is expected in March)

As the name suggests, the devices have 14 or 20 kW maximum capacity. If I read our energy saving certificate correctly, our house (Energy Saving Ordinance, 225 sqm) has an annual heat demand of 14,987 kWh (11,681 kWh heating, 3,306 hot water). Due to lack of expertise, I found in my initial research that I can calculate the heating load of our house by applying the annual heating time (2100h?). With my layman’s knowledge, I come to a heating load of about 7.1 kW. Is that correct so far, and am I right in assuming that the 20 kW version is totally oversized?

The next problem is that the lower modulation limit of the larger boiler is significantly higher: 4.4 kW compared to 2.1 kW. Here I fear that especially in the transitional period the boiler will cycle more often, causing faster wear and tear and overall less efficient performance.

I have not been able to speak directly to the installer yet. The general contractor’s site manager gave me the installer’s explanation after consultation, that the device was "sized larger due to the size of the property."

I will speak with our construction supervising expert next week.

Therefore, the following questions:

Is my assumption correct that the 20 kW version is completely oversized?

Is my assumption correct that the worse lower modulation limit is a disadvantage for us?

How would you proceed, i.e. how critical do you see the problem and what options do I have?

Thank you for your help

I only know that an oversized heat pump is not good because in the worst case it can break down. Is there a heating load calculation?

With heat pumps, a problem, with gas, actually no problem.

Uff

Always these witty posts that don't bring anyone anything, except that the poster has one more pointless post..... If it were spoken, one would say: The main thing is that the air made a bang..... I would first talk to your energy consultant. You normally also have a corresponding one for gas, to see if it really is a problem. But yes, I also think it is seriously oversized....

Oops, I overlooked that it is about gas. My comment was only about heat pumps, I am not familiar with gas...

Secondary school ☝ If at all