HI, JUST WONDERED IF ANYONE COULD SHED ANY LIGHT ON MY PROBLEM WITH 30CXI. I DRAINED THE WATER FROM THE HEATING SYSTEM AND WHEN I WENT TO REFILL A COUPLE OF HOURS LATER, THE WATER WOULD NOT FLOW WHEN THE FILLING TAP WAS OPENED. THE HOT WATER FLOWED THROUGH (COLD) BUT THE HEATING SIDE DOES NOT...