I have had problems with this boiler on and off for a year now. Pressure relief valve drips, boiler fails on low pressure showing .6 bar. I'd repeatedly looked at forums where this seems a very common problem. I had replaced the fill valve after suggestions it was letting by, replaced the pressure relief valve due to suggested weak spring, drained and flushed the boiler, all to no avail. I added an external pressure gauge which showed the pressure was climbing to over 3 bar when the heating was on. This showed that the internal pressure gauge was not following the actual pressure. It turned out that the pressure sensor was clogged up with rust and scale. A careful clean with a cocktail stick and descaler fixed that problem with the sensor. The 30CI has an air filled pressure vessel fitted at the back of the boiler and is fed via a flexi braid covered pipe from just behind the pump. Turns out this was full of water and would not drain when the boiler was drained. Though fiddley it is possible to undo the 18mm connection and drain the whole thing. If water comes from the tank and the pipe you know there's no blockage. Leave to drain, reconnect and refill. The pressure change on my boiler is now about .2 bar from cold to hot and the boiler runs fine. Hope this helps someone out there. Brian.
