Alpha CB50 only coming on for few seconds for both DHW and CH

[Arniep]

Got an alpha CB50 which has suddenly stopped working. Both hot water and central heating only come on for a few seconds before cutting out only to restart trying again a minute later for the same result.
Did have issue that builders removed flue but that is back in place so shouldn't be an issue. Any ideas.
I would like to resolve myself before calling an engineer in.
Thanks in advance

 

[king of pipes]

Builders removed the flue? they have broken the gas regulations pal do not use this appliance untill a gas registered engineer has looked at it you cannot resolve this yourself croppie this ones for you bud .

 

[Arniep]

Only top part removed (bit through the roof) not too near the boiler.

 

[Dotty]

Doesn't matter. They have broken the law and placed you and your family in real danger.

Turn it off and call in a gsr.