the condensate trap underneath the main heat exchanger [MHX]is blocked, resulting in condensate water building up in MHX, the flue gases cant escape, effectively choking the boiler, which results in the boiler shutting itself down
you need to ensure the condensate pipe from the boiler to the drain is not blocked[with ice] by pouring hot water on it, if your 100% sure this pipe is clear of blockage and you still get an LF fault accompanied with a loud growling noise from boiler, then the condensate inside the boiler needs removing and cleaning
WARNING! make sure you electrically isolate the boiler before you do this, remove the pcb and cover all electrical connectors with a towel to prevent them getting water soaked when you do manage to remove condensate trap
its not an easy job, ive had to do dozens of them over the last month
manwithnoname, January 2010
