I have a Potterton Prima F boiler and a (new) Honeywell 7 day programmer for water and heating. I have thermostatic radiator valves on all radiators and no room stat. I have a valve for the heating and a second valve on the hot water tank. both seem to be operating, in that the indicators on the outside of the valves move from time to time. As far as can tell, I don't have a frost stat (though am not sure what it would look like if I had one!). I had a new pump overrun switch fitted about 3 months ago.
Intermittently, the pump continues even when the programmer has switched both heating and water off; this happened more often after the evening heating cycle than after the morning heating cycle, though it has happened after both. It can continue all night, and the boiler occasionally ignites - even though everything on the programmer is OFF! When this happens, the only way I can stop the pump is to switch off the mains supply to the whole boiler. The system worked fine for 10 years, but this problem started about a year ago which is why I changed the programmer, but this has not made any difference. I have no idea what to do, nor do the plumbers I have asked. HELP!
Intermittently, the pump continues even when the programmer has switched both heating and water off; this happened more often after the evening heating cycle than after the morning heating cycle, though it has happened after both. It can continue all night, and the boiler occasionally ignites - even though everything on the programmer is OFF! When this happens, the only way I can stop the pump is to switch off the mains supply to the whole boiler. The system worked fine for 10 years, but this problem started about a year ago which is why I changed the programmer, but this has not made any difference. I have no idea what to do, nor do the plumbers I have asked. HELP!