Just wondering if anyone has even seen an issue with the pressure gradually increasing on a closed loop system where there is no fill loop attached. I'm seeing this issue on a gshp and whats more unusual is its on the cooling side. If it was on the heating side you could put it down to expansion but this water/glycol is gradually cooling but the pressure steadily increases over over a couple of hours from 1 bar to 3 bar before it eventually triggers the safety valve. I've never seen a system gradually increase like this. Has anyone ever had a similar experience?