My central heating system is fired by an Ideal Classic 18SE FFboiler.
The system has an intermittent fault. It is programmed to come on twice a day, but on shutdown the circulating water pump sometimes continues to run, also the boiler will fire up whilst the system is switched off. A plumber informed me that the hot water motorised zone valve (Drayton ZA5) was faulty (sticking). This valve actuator was replaced with a new one, but the problem persists. Has anyone had a similar problem And resolved it ?

Allan, December 2009