On 16/11/2012 09:11, Phil K wrote:
Phil K wrote in
:


PS... Correction!: The boiler DOES sound noisy at its location in the
coat cupboard. (I just checked again, during a period when the rest of
the house is quiet). In fact, its location in the cupboard, is the
place where the noise is loudest, as you'd expect. I've noticed that
the noise doesn't stop as soon as the "burner on" LED goes out. And if
I switch the boiler's front knob to off (i.e., from 'central heating'
to completely 'off', the noise continues for approximately 4 minutes
afterwards. The noise starts again instantly, as soon as I switch the
boiler back on to "C" mode or "C+D" (ie., c/h + dhw). The noise sounds
to me like the sound of a main burner - hence my earlier reference to
a jet engine.


PPS... Since the noise seems to be constant, while the c/h is turned on,
and continues 4 minutes after it is turned off, and dos not disappear when
the burner LED goes out, does this suggest that it is the flue fan that is
making all the noise? Is this normal?


To me that sounds like a pump and water noise. If there is circulating
air signified by a sound of small tacks in the heating system then it
would be prudent to remove this air if at all possible. The pump is
generally powered through the boiler and will run for an extra few
minutes to remove heat from the heat exchangers after the flame is out.

The pump is in the boiler and I'm not sure if you can alter the pump
speed. If you can it might be worth reducing it by one notch.