boiler fault - Anti Frost in function burner in operation
 

I've got a Britony Combi SE installed.

The past two weeks I started seeing this error message displayed by the
boiler "Anti Frost in function burner in operation". this happens
intermittently for no obvious reason.

Anyone has got an idea what is wrong with the boiler. if so do you know
which part i might replace to fix it.

thanks for all the help
Gisele