I have installed new combi Ravenheat March this year. yesterday fan would run but boiler wouldnt fire up, called out engineer as it is still in guarantee, he took of casing and found water coming in round ring plate of vertical flu, having checked flashings etc there was no sign of water coming through , is it possible for rain to be driven under flu terminal plate and down inner flu pipe, i am afraid of it happening again, never happened before. cant put flu horizontal, to near soffit. any ideas??