pumping up to f&e tank

[richard hayden]

I have a standard fully pumped system with hwc ,motorised valves & hwc stat . System has been fine for years but now the hwc is being overheated ,water in hwc is boiling &primary circuit water is pumping up thru the cold feed to the f&e tank . I assume I need to change the hwc stat but am wondering whether the boiler stat is also faulty ...surely if the hwc stat is defective ,the boiler stat should cut in well before the water temperature is high enough to boil the hot water in the hwc.. any views appreciated .

By the way I recently changed the pump & bathroom rad ( which is on the hot water circuit) & also flushed the whole system with cleaner)...poss relevant or just coincidence that probs started after !

 

[Puddle]

as you say,your reasoning correct, replace boiler thrmostsat,should correct siduation 🙂

 

[richard hayden]

thanks for the advice