Got a 9yr old kettling GW Micron 50FF boiler which's had the reset light come on and the boiler stop working of late, caused by a "non-volatile lock out" according to manual(!). Turn the boiler off/on, comes back to life.
If I turn the boiler temp down to 3/4 it stops the boiler locking out. I dosed the system last week with fernox boiler silencer for the 2nd time which had stopped the kettling for a time and the boiler ran ok on max temp until yesterday. The kettling has come back but not as bad as it was.
I was thinking the boiler is locking out due to overtemp cutout due to air pockets in the heat exchanger or is this a red herring?
I also have an Alpha+ pump which lowers the speed of the pump according to pressure (got TRV's fitted to all rads but one). Could the pumps (sometimes) low speed be exacerbating the problem?