Ariston combi boiler going out and relighting frequently

[alexogilvie]

Hi,
When the central heating is on the boiler keeps going out and relighting itself quite frequently. It also looses pressure every day but we can see no sign of a leak anywhere. The boiler is due for a service but does any one know what could be the cause of these things?
Many thanks

 

[BingoBongo]

it wont work if the pressure is low

prv could be passing

expansion vessel could be flat

or both

 

[alexogilvie]

Hi Thanks for replying - I dont know what that means though - could you elaborate?
Cheers!

 

[kevplumb]

pressure relief valve could be leaking outside

expansion vessel pressure may be low

if the boiler is on 1 bar cold what is it hot

 

[BingoBongo]

if the pressure is low..........it wont work


there is a safety device called the prv which activates usually at 3bar (pressure).it is basically a rubber on a spring,if there is dirt on the rubber or its worn water will drip out the copper pipe sticking out the wall.

there is a part called the expansion vessel,think of it as a baloon.If there is no air int,when the heating is on the pressure will rise to 3bar and the prv (see above) will activate.Then when the heating has cooled the pressure will have dropped.

see faq on how to repressurise exp vess.

also the prv can be opened and shut a few times if its passing as sometimes this can re-seat the rubber.Although it can also make it worse.

hope this helps