Hi,
I am running a closed loop hot water system @ 3barg and 80degC. At the moment my expansion vessels are pre-charged to 1.5barg. When we turn off the boilers at the weekend, obviously the water in the loop will cool and contract => system pressure will drop =>Pressurisation pumps turn on in order to maintain 3 barg in the system. Then when the boilers start running after the weekend and the water heats up , the system pressure will shoot up to 4.5bar (relief valve setting)
Question is: What pre-charge should be in the expansion vessels to rid me of this problem? I think 3barg but others disagree.
Anyones input much appreciated
Figs