Glow Worm 23c Combi - Pressure Varying

[POJ190]

My son has a Glow Worm 23c Combi Boiler fitted in his flat, over the past couple of days the pressure has been playing up.
Basically, about 5 minutes after the heating switched on the pressure dropped and the heating switched off. He refilled the system to increase the pressure and heating came back on, then about 15 mins later the pressure went very high and heating switched off. Some of the pressure was bled off and all was OK again.

Next day same thing happened, heating came on and 5 mins later pressure dropped and heating went off. Refilled the system, pressure at 1.5 bar, heating came on. A short time later pressure went high and heating switched off. Again bled off some of the pressure and heating all OK.

This morning the same process is happening again.

There are no blatantly obvious leaks anywhere.

Does anyone have any idea what the problem could be?

Many thanks for any help you can give.

POJ

 

[jtsplumbing]

Check out side , look at the safety discharge pipe, could be a simple fix or one requiring a couple of new parts, cant go into to much detail about boiler repairs, Forum Rules , You will need to call a Gas safe registered guy to have a look