When are compensators necessary?

As I said, you have to see what happens at the ends. From when does the expansion there become a problem.

finally a statement! But even in your explanation, I can't accept any lengths or similar. I have line lengths up to 14 m and everyone says something different. I'm just uncertain. At the moment it's heating and everything is fine, but what if I come early once and everything is flooded?

I already wrote the same thing a few posts earlier

So at 14 meters you have about 10 mm expansion with a temperature delta of 40k.
From experience, I would install compensators there.

Thank you, I will have some installed just to be safe. It won't make it worse.