Hi Solveweb, you asked about my Thermal Store experience. I eventually ripped it out and all my problems were solved by fitting an unvented tank. However, my system is vastly different to yours. I now believe that I was missold the heap of junk as I was specific with my demands and needs, this tank was never going to work, all I have is a single source gas condensing boiler, I was told by many people that thermal store is not suitable for single source input, despite this thermal store being designed in this way. I have no experience of muti heat source inputs.