Pressure on worcester 28i junior keeps going up and down!?

[annavtaylor]

Hi
I got back from holiday yesterday to find the pressure on my boiler at 0. I looked in the manual and used the key at the bottom to increase this to 1.5. I did this by turning the key clockwise to open and then the nut to the left to inc pressure then turned both off. However whenever i turn the heating on the pressure starts to creep up! It hit almost 3 last night and I switched it off quick. When its not on the pressure falls again- back to the 2 range. help???
Someone has suggested that the expansion vessel needs pressurising to 0.5??? However I don't know what this means and how to do it?
best wishes from shivering in suburbia!

[heathfield]

For what an expansion vessel does, scroll down for a description here.
I've used a car foot-pump in the past to raise the pressure in the vessel. This is done with the system cold, and using the foor-pump pressure gauge to get 0.5 bar, not the gauge on the front of the boiler.
If this doesn't fix it, it may be that the diaphragm is holed, and you'll then need a new pressure vessel.

[gucciman]

Call out a heating engineer you tight wad !

as already answered the problem is down to the expansion vessel, and as i'm getting really fed up now of everyone trying to do their own repairs i'm not gonna tell you how to re-pressurise it or how to identify if you need a new expansion vesel or not but i can tell you heathfields method is incorrect.

[heathfield]

Oops! Quite right, Gucci. Thank you. I totally forgot to say that the system pressure should be bled off before the expansion vessel is re-pressurised.