I have a Biasi Riva boiler. In CH mode, it ignites fine, runs fine, seems to regulate when you turn the CH temp down etc. - as soon as you open a tap and the DHW kicks in, the temperature guage shoots up from about 55 to 90, then it shuts down (without locking out). I have to reset to get the CH back. Effectively, whenever you turn the tap on - you get 10 seconds of increasingly hot water, then the boiler gets switched off by the safety thermostat.
Any ideas?
I've put more water in the system, as it was down to below 0,3. It's now up around 2,0 - which is probably too high (believe it should be
1,0), but didn't seem to make much difference. I thought it might be something to do with the pressure?? ie. not pushing enough water through, so it was heating too quickly and triggering the cutout, but apparently not.
I've taken the housing off of the circuit board, and checked all the connections - nothing seems a miss, but I'm kind of thinking it's maybe the logic - or the DHW potentiometer on the board or something.
I'm presuming it's not the temperature sensor, as the CH works and regulates - and it's clearly nothing to do with the gas - or the supply. Could the DHW element be blocked or something?