Expert assessment for underfloor heating in a single-family house

The fact is that the mixer can never be a disadvantage.
I would not have known that the gas condensing boiler "can" operate at such low temperatures!

The gas boiler does not deliver temperature but power. In this case at least 2.4 kW. If less power is needed due to the outside temperature, it simply cycles (on and off). Above 2.4 kW required power, it hums along. Let's say the required flow temperature is 28 degrees. Then the boiler heats the flow to 28 degrees. The water flows through the pipes and cools down to 23 degrees. Now the boiler heats the water back to 28 degrees. As long as at least 2.4 kW is needed for this, it does so constantly in continuous operation. Therefore, a mixer is completely unnecessary. Much more important is the correct design of the underfloor heating according to the required heating load. The closer the pipes are laid, the lower the flow temperature can generally be. This is especially important for efficiency with a heat pump. If you operate purely underfloor heating without towel radiators or similar, no system separation is needed.

The gas boiler does not deliver temperature but power.

Basically clear, but at 2.4 kW and little flow, it can already get quite "warm" in the heating circuit, even without having calculated it. That must be right!

Yes, the flow must of course be correct. But usually, the heating load is determined first and then the underfloor heating is designed accordingly. This needs to be planned, especially if it is to be future-proofed for [Wärmepumpe].

So from the discussion I gather that I actually don't need a mixer, since the device, with proper design and correct calculation etc., always produces the right temperature (expressed minimally). But does continuous operation also mean more wear? Or is it rather with on/off cycling, where is the consumption better? People also say that the car should be turned off when waiting at a traffic light? By the way, isn't the system separator even mandatory according to a special DIN standard?