Ferolli F30 combi hot water problems

[Adam0987]

HI

I have a ferolli F30 combi. The problem is that when running hot water the boiler flame turns off after about 30 secs, the water goes cold and then the boiler fires again for about 10 -20 secs the water goes hot and then it cuts out again. And so on until you stop running hot water.

I have had the temperature sensor changed as though it was the cause but no joy.

Any help or things to check anyone can provide would be great

 

[cross thread]

uses two thermistors on hot water to control the boiler in conjunction with several adjustments on the pcb and gas valve so get a experienced ferolli eng and it will be a easy repair