Ariston microgenius 23 MFFI

[ianto-fp]

Hi guys got a fault thats puzzling me, Had call to repair a 9 year old ariston microgenius 23 thats running on LPG, Sorted the initial fault of no ignition by changing the fan, However while watching the boiler fire up, maybe 3 times out of 5 only the right hand side of the burner ignites and then the left hand side follows about a second or two later, sometimes the left hand side does not ignite and the flame detection knocks it off and goes through cycle again. when i stripped out the burner found it to be only about 14 months old and looked like new, no sign of blockages and i stripped out the 12 nozzles and checked them all, also no blockages, inlet pressure was a constant 35 mb on DHW and CH, on burner side, 18mb on CH and 32 mb on DHW, another thing i noticed was what sounded like pulsing on fire up but my u gauge was not moving, Forgot to say i also re set the soft start to check that was not the problem but still no change,

Any help would be greatly appreciated.

 

[diamondgas]

Main hex clear? Fan/flue intact? Possible visciation maybe? Just thoughts

 

[Gary71]

The boiler not cross lighting is a fault in itself, the later models came with a cross lighting strip which helped stabilise the flame picture, it's a strip of metal that screws to the front of the burner bar, if one is already fitted you could try blocking the cut out where the electrodes are as this can have a impact, I would also be looking at the spark electrode for correct position and if a flue restricter is required.