pressure loss

[frontslide]

I have a Worcester 28i RSF, fitted about four years ago
it recently started loosing pressure that i traced to the pressure relief valve
(overflow pipe). Since discovering the cause of the loss ive been reading the manual and in particular the section "pressure relief valve" where it states that if the pressure indicated on the gauge is greater than 2.65 bar when operating at max temp an extra expansion vessel must be fitted.
The temp is exceeding this figure which suggests to me that damage has occured as a result.
A, If this problem has occured since the boiler was fitted what could be the cause?
B, Could this problem have been there since the boiler was fitted, if so why hasn't it damaged anything before now?
Hope this makes sense and any help would be greatly recieved
Thank you

 

[cowley]

Hi the water expands as it is heated, and this expansion is taken up by the expansion vessel fitted to your boiler, an extra vessel is only required when the system is large, your problem is more likely to be that the charge pressure in your vessel has been lost and the only way the water can expand has been lost so the pressure rises to a point where the safety valve lifts and discharges through the safety pipe.
You will need someone to check out/recharge or replace your pressure vessel.