Grant boiler pumping over

[king of pipes]

Got a grant oil fired boiler on a large system two heating zones and a hotwater zone each has a honeywell zone valve, the heating is pumping over intermittently a surge of water its as if the boiler is keeping firing when it should be off need to go into it in more depth any ideas guys . cheers kop

 

[Best]

Close coupled vent and feed?
Is it a system boiler, or is the pump somewhere else?
If pump is separate, is it pumping towards a vent?
Is it all wired properly, with boiler and pump off when all zones valves close off?
Is there a bypass valve fitted?

 

[king of pipes]

A Controls issue i am thinking Best meeting the sparks there pm tommorow its a old system but boiler has been replaced within the last 10years i would say to be continued. Kop

 

[Vee]

Inherent bad design?

 

[king of pipes]

Turns out the frost stat was keeping the boiler on and one motorised valve was faulty and closed, the stat was keeping the boiler on with no bypass installed it was overheating and with nowhere to go expanding up the vent into the header tank as Vee said poor design and pipework install needs upgrading . cheers kop

 

[Best]

Perhaps control stat is also faulty

 

[king of pipes]

Will sort the valve out and go from there . cheers kop