darren bastin
Gas Engineer
Have been to look at the above boiler with an intermittant fault (It is an Ariston microgenus 2 badged up for city plumbing ). The boiler does not go into fault mode on central heating. On hot water especially at lower flow rates after the hot water tap is turned off, the pump runs over , after a few minutes the boiler clunks and goes into overheat lockout.
The boiler should deliver 9.7 lit a min at 35 degree rise , it actually delivers a lot more. (hence dont think there to be a blockage in the p hex) .
I did not have access to any tech data but noted the max burner pressure was 11.25 mb, since i have found it should be 10.3 mb. I will go back and adjust the bp so it is not overgassed and this may sort it.
I would have thought the overgassing would have shut the boiler down when there was demand during low flow rates, as would if the gas valve was failing to modulate down. The boiler never trips to overheat until the tap is closed.
Any other possible causes ?
The boiler should deliver 9.7 lit a min at 35 degree rise , it actually delivers a lot more. (hence dont think there to be a blockage in the p hex) .
I did not have access to any tech data but noted the max burner pressure was 11.25 mb, since i have found it should be 10.3 mb. I will go back and adjust the bp so it is not overgassed and this may sort it.
I would have thought the overgassing would have shut the boiler down when there was demand during low flow rates, as would if the gas valve was failing to modulate down. The boiler never trips to overheat until the tap is closed.
Any other possible causes ?
