I have had a problem in the last few days with my central heating system. I keep my hot water and central heating on at all times, all year round and worked the heating with the room thermostat. That has worked well for 17 years. But, at the weekend my central heating radiators became so hot that they were impossible to touch and the house was like a sauna. I checked the room thermostat and it was still showing set at 15 degrees. I checked the room temperature using this thermostat and it clicked at 30 degrees. I turned the central heating off at the boiler (Potterton Prima F) panel control (Potterton EP2001). But, that made no difference. The radiators remained so hot that they could not be touched. So, I had to turn off the hot water at the control panel as well. I also turned off each of the radiators individually, except 2 which would not turn off due to the valves just going round and round. When I switched on just the hot water today, the 2 remaining radiators that I could not switch off turned back on and again became incredibly hot. But, there was no hot water available at the tap. It seemed that the radiators had used it all up. Just prior to this fault occurring one of the non-faulty radiators was leaking a lot of water from both its valves. I do not know if that is connected in any way to this fault. Can anyone help with a diagnosis. The 3 port valve on the tank is a Honeywell motorised valve.