Central Heating that sometimes won't switch off

[PilotGP]

Hi all,

I've been searching through the forum but can't find a previous mention of my particular problem.
I have a system comprising combi boiler, HW tank, and plumbing including both a two-port and three-port valve. The system feeds rads, underfloor heating and hot water, and I leave all three on "continuous" in order that the various stats can call for heat as required. The problem is that the rads sometimes remain hot despite being commanded off by the thermostat. I can't figure out what drives whether they go off or don't, but am assuming that it's unlikely a wiring problem, and therefore most likely a three-port valve issue?
Any help would be very much appreciated.

 

[ianmcd]

are your radiators fed from the three port valve ? and the two port for the underfloor ?

 

[PilotGP]

Hi Ian - yes, that's correct.

 

[ianmcd]

I would suspect the threeway valve actuator is faulty if the system did indeed work at one time and this is a new fault,but like a lot of faults on here without seeing the system I cant be sure, another problem you have is that unless the system is faulting when an engineer is onsite its just best guess Im afraid