How do room thermostats work with an FHB?

Good day. I would like to know how the controllers for the underfloor heating, that is the room thermostats, work. I have very simple ones with an LED light that turns on when the underfloor heating is on. On the rotary dial, there are no temperature numbers, only about 15 markings. Currently, I have the rotary dial set to marking 10 out of 15. That means the underfloor heating only starts turning back on when the temperature falls below the marking (how high is this then? There are no temperature numbers on the dial). According to my thermometer, this would be about 22 degrees. So the underfloor heating heats up to just above 22 degrees and then switches off. When the temperature drops below 22 degrees, it switches on again. If I then turn further to the right to marking 11, would the underfloor heating turn on when, for example, 23 degrees is undershot? Can it be understood roughly like this? These simple controllers control the actuators in the distribution box, right? So if the controller is turned further to the right, does the valve open more (allowing more heating water to flow through the pipe), or does the underfloor heating simply run longer (with the same amount of heating water)? And what would happen if I had the controllers replaced with digital ones? You can enter the temperature there, for example 23 degrees. Would the underfloor heating then just run longer at 23 degrees (compared to 22 degrees), or would simply more heating water flow through the underfloor heating pipes? I want to understand this before I talk to the heating engineer regarding a possible conversion. I have already looked for information here, but I did not really understand it. Many thanks.

I currently have the rotary dial set to mark 10 out of 15.
That means the underfloor heating only starts switching on again when the temperature falls below the mark (how high is this then? There is no degree number on the rotary dial).
For me, according to the thermometer, this would be about 22 degrees. So the underfloor heating heats up to just above 22 degrees and then switches off. When the temperature falls below 22 degrees, it switches on again.
If I then turn it further to the right to mark 11, would the underfloor heating switch on if, for example, 23 degrees is fallen below?
Can you roughly understand it that way?

Yes, something like that, but of course it is unknown what kind of controller you have there and which control algorithms it follows. There could be a hysteresis or not.

These simple controllers control the actuating valves in the distribution box, right?
So if the controller is turned further to the right, does the valve open more (letting more heating water through the line), or does the underfloor heating simply run longer (with the same amount of heating water)?

Depends on what kind of valves you have installed. Both variants are possible.

And what if I have the controllers replaced with digital ones?
There you can enter the degree number, e.g. 23 degrees.
Then does the underfloor heating simply run longer (than at 22 degrees), or does more heating water flow through the underfloor heating pipes?

Again, it depends on the internally installed components and also on the software in this case. Because the temperatures can be regulated in different ways. The digital display is basically no more and no less.

Basically, these devices are "emergency brakes." If the heating "runs too fast," these parts brake. As soon as the heating is "slow enough" again, they release again and the cycle starts over. Seen that way, it is a constant uphill and downhill ride and depending on the installed hardware and software, more or less hilly.

Yes, something like that, but of course it is unknown what kind of controllers you have there and which control algorithms they follow. There could be hysteresis or not.

It depends on what kind of valves you have installed. Both variants are possible.

Again, it depends on the internally installed components and also on the software in this case. Because the temperatures can be controlled in various ways. The digital display is basically nothing more and nothing less.

In principle, the devices are "emergency brakes." If the heating "runs too fast," the parts brake. As soon as the heating is "slow enough" again, they release, and the cycle starts over. Seen this way, it is a continuous ride up and down, and depending on the installed hardware and software, sometimes more hilly, sometimes less so.

Good day.
What do you mean by software?
The simple controllers are from Salus RT10. Do such controllers have software??
Unfortunately, I still do not understand that.

No, I meant the controllers with digital displays. These are usually (but not always) microprocessor-controlled, and thus the control algorithm is not implemented with physical components but in one way or another programmed by the manufacturer. In other words, the control happens based on software.

The Salus are still quite simple without so-called software.

Actually, that says it all: In principle, the usual wall controllers (including the current ones from Salus) are "emergency brakes." If the heating "runs too fast," they pull on the valve (block the flow). As soon as the room cools down again, the flow is released.

No, I meant the controllers with digital displays. These are usually (but not always) microprocessor-controlled, so the control algorithm is not implemented with physical components but is programmed by the manufacturer in one way or another. In other words, the regulation happens based on software.

The Salus devices are still quite simple and do not have so-called software.

That basically says it all: In principle, the usual wall controllers (including the current ones from Salus) are "emergency brakes." When the heating "runs too fast," they pull on the valve (blocking the flow). As soon as the room cools down again, the flow is released.

Hello. Ok, understood. So open and close. If the heating water is higher, the underfloor heating simply runs shorter; if the heating water is lower, the underfloor heating simply runs longer until the desired temperature is reached. Running longer, however, does not mean increased heating costs?

Yes, something like that. Very roughly... but you don't need to know more about the function. Unless you want to go deeper.

Running longer doesn't mean higher heating costs?

Um... quite clearly yes and no. Because the heating costs are primarily determined by the comfort temperatures and the heat losses of the heated rooms/houses. The controllers on the wall are just emergency brakes and, in well-regulated systems, are not necessary at all and sometimes even the reason for higher heating costs.