Anybody out there familiar with this boiler as i'm not . It has seperate time control for dhw for some reason, if constant is selected in dhw boiler seems to run all the time even if dhw is not called for (how long does it take to heat the pre-heat storage tank?). Also if you fire it up in ch mode then select dhw it will not switch back, no div valve to stick as it has two pumps on it. could it be that a sensor on dhw side is not recognising that pre heat has been satisfied this would account for the pump being full of steam when I got there. Any help would be appreciated as instructions are hopless and I cant get hold of technical