I only put the pic up as it contains the type of ball I meant, it isn't like our system, we have no boiler.Nope.
We have an expansion "ball" on the solar (closed system). But the hot water tank outlet comes from the top, but not at the top so allows for expansion of the water due to heat. Just like the "ball" I.E has an air space closed system.
But your pic shows a closed system tank so that 250L(?) tank needs expansion into the "ball"
Our 500L buffer tank (heated by solar but separate water) is ATM (open vented to tank)
J
I'll have to see if I ever took any pics of our system, because I am not sure where the water comes out of the solar tank, I think it is straight out of the top but I could well be wrong. But like you we do have one of those balls connected with a serious, flexible, metal hose. Don't think it is very flexible now!