potterton prima 100 short cycling when off

[martindavie]

Hi i have a long running problem with a potterton prima f 100e , after the boiler has been used and programmer is not calling for any heat or hot water it should be OFF but it continues to short cycle (burner fires for 10/20 secs then turns off) every 20 mins for ever ,unless i disconect supply to boiler via a timer plug.
I have changed thermostats ,overrun +boiler + tank , the motorised valves appear to be working as they should , i have reduced flow through the systems to increase efficency ,
i suspect the initial wiring of boiler to heating controls , any similar problems experienced by any one else with possibly a logical fix? . martin

 

[Puddle]

Would point maybe to one of the micro switches on one of the motorised valves being broken/stuck in the on position even when valve is in closed position

imho

 

[martindavie]

thanks microswitch giving a signal all the time , have new actuator on order, should be sorted now ..