In message , John
writes

As a preliminary check (and not to be left beyond a very brief test period)
try turning down the pump speed while listening to the level of noise. If it
is the pump this should be immediately apparent. If its the fan then no
effect will be noticed.
As an aside I installed a Worcester Combi a couple of years ago and it had
been shipped with a noisy fan. Worcesters changed it under warranty but the
second was also noisy :-( The thrd was OK though.

Maybe I should recondition the fan before I install the boiler ... just
a thought
--
geoff