Hi, the water if failing to heat in my cylinder vial the boiler/coil. When the programmer calls for hot water the boiler fires up and the zone valve (Honeywell V3043H) actuator moves across but water does not seem to get to the coil?. I opened the drain cock at the base of the Cyl, where the water feed should enter ? the coil after the honeywell zone valve but no water comes out?. There is hot water reaching a T junction in the pipes where the feed splits to the zone valve and a rad. The Rad heats up, but the zone vaves does not seem to pass water through?. could the coil be blocked?. The Cyl stat appears to work ok. Any help apreciated...Thanks