Incorrect heating installed — problem and consequences?

Current gas heaters operate in a regulated manner and not just at "full blast." It is also known today that you should not simply turn off radiators somewhere. With a good hydraulic balancing, the oversizing should neither significantly affect the costs nor the lifespan. It’s not a heat pump. Address the topic, agree on a solution (discount or additional service), and stay cheerful.

No worries, I am familiar with the HTD forum. If in doubt, I would also ask there.

I understand that modern boilers modulate — I assume that's what you meant by "running regulated", . But if the installed heating system only goes down to a minimum of 4.4kW, while the house only has a heating load of 7kW, then I do wonder how often it won't be able to modulate low enough and starts to cycle.

I will first seek a discussion with the installer, site manager, and expert to find out how big the problem really is. Of course, I don't want to make a fuss before that. The construction so far and the communication with the construction company have always been extremely pleasant, fair, and solution-oriented, so I expect that we will find a good agreement here as well.

You're right, the minimum performance at startup plays a role.

The previous construction and the communication with the construction company have always been extremely pleasant, fair and solution-oriented, so I also expect that we will find a good agreement here.

That also speaks for you.

So we also have a gas heating system but only 165 sqm. We have a Buderus with 14kw total output and it can regulate down to 14%, which corresponds to about 2kw.

I just checked, because it is running right now. It is 7 degrees outside and the system is making 24-25 degrees flow temperature. It is currently modulating at 15%.

Since your large heating system has twice the output, it would accordingly run shorter and cycle more frequently. I have 2107 operating hours and 1287 burner starts. That averages 1.6 hours per start. At cool temperatures, I get by with 2-3 starts per day.

I would definitely try to get the smaller system.

Approximately 7kw can be suitable in terms of heating load. This is calculated at the standard outside temperature. Depending on the location, probably -10 degrees. Accordingly, you will need even less heating capacity most of the time.

Even if the system is much too large, you will probably have to live with it. No one will pay for a replacement. Also because the originally planned one would already be too large.

With gas, however, it is not that critical. With a heat pump, it is a no-go.

A 20kw boiler in a single-family house still comes from the oil boiler and gas heater era without condensing technology. This indicates an incompetent company.

The coolest thing is of course the statement that 14kw were too little. I would say mission failed.