Boiler over heating

[HampshireSteve]

Hi All

any ideas on this one. My Grant oil boiler appears to overheat to the point that I get incredible banging through the house then the vent pipe explodes with boiling water (fortunately pouring out of the overflow.)
Other signs that it is about to occur (only occurs maybe 1 in 10 boiler uses) are that the cold water feed gets extremely hot in the 4' of pipe I can feel before it disappears in box work, and there is the telltale boiling noises.

Does this all add up and what is likely to be causing it? I have just added sludge remover and will be flushing out in a week or two but it is still occurring.

Any advice gratefully recieved!!

 

[Agile]

Faulty boiler stat or pump ???

Tony

 

[HampshireSteve]

hi Agile,
ref the stat I am assured it is working correctly by someone far more qualified than i am.

are there any other symptoms of a faulty pump that would prove it?

 

[stardanny]

Does the radiators get hot when heating on?

 

[HampshireSteve]

yes rads do get hot. One upstairs and one downstairs is stone cold but suspect that is stuck valves more than anything else hence the sludge remover. All other radiators are hot. In fact everything is as you would expect and the system appears to be working well.

 

[stardanny]

Pump working. I'm no expert on oil, but sound like faulty thermostat or control board (pcb). Try turn down stat knob on boiler and see if it stop it getting hotter, if it do, faulty stat.

 

[wilhelm]

the limit stat should have operated if it got too hot.

blocked cold feed? . do a search. take a day off and read all the posts..


maybe its overfiring, too big a snozzle/ too high pump press? and flame hitting back of boiler giving local boiling.
apart from that, nothing else springs too mind.