over flow problem

[Fixitphill]

Pumping over problem has justed started after years of smooth running! Fed and expansion tank is overflowing on a regular basis, but we it's not a ball valve fault. What is the likely cause, although we can rectify it short term.? Regards
Fixitphill

 

[seco services]

is it pumping over the vent pipe ?

 

[Fixitphill]

Thanks for your quick reply! Yes it is!

 

[seco services]

can be a faulty boiler stat, blockage in pipework etc.

is it constant pump over ?
whats the boiler stat on and pump speed ?

does the boiler shut down if you turn the boiler stat down ?

 

[steved101]

as seco services says - if you turn the boiler stat on the boiler down to 0 (off) and the boiler stays on (as long as the programmer is on for h/w or htg) then this will prove that the boiler stat is faulty (STUCK SHUT) and thus the temperature getting up to about 100 degrees C and pumping over (you will have an older boiler with no overheat stat).

the pump speed - try turning it down to setting 1 and if the pumpni gover stops then it will be a sludged up system causing the pumping over to happen (the cold feed pipe from the header tank where it joins the system, usually just before the pump will probably be the point of blockage) - use a magnet around that point and see if it sticks.....