Can anybody tell me what is wrong with my alpha ocean 240e boiler, please?

Hello!

My alpha ocean 240e boiler has trouble starting in CH mode. There is not problem whatsoever whit hot water but when the CH has to start the boiler kicks off, then goes immediately off, then on again and off, and on, and off. It usually takes between 7 to 10 minutes for the boiler to get working. I have also noticed that there are tiny little ‘explosion’ when it goes on as obviously the gas seems to build up inside the boiler.

I have had several plumbers in who don’t seem to know what it is wrong but they all charge me for the call out. One of the plumbers said that is the computer inside the boiler needed replacing, got the call out money and I have never seen or heard from him ever since. I have by now paid different plumbers enough money to have a new one put in place but this boiler is only about 7 years old and apart from this it works beautifully.

I have to say to this that the CH is on a timer and the boiler never fails to start at the programmed time, only that it takes a long while for it to get working. Can anybody please help me giving me a clue of what it is wrong with it?

Many thanks.

Mavamos