Worcester Greenstar

[MGG]

Hi!
We have recently moved into a house fitted with a Worcester Greestar 40 CDI boiler. Now and again the boiler shudders and makes a loud howling noise. It only lasts for a few seconds but it's quite scary when it happens! The previous owners said that they had had it looked at and were told that it was due to the outside wind direction and that it is a known problem with this boiler.
Does this sound right or should we be more worried?

 

[Andygasman2010]

Get an RGI's opinion. He will probably check the high and low combustion settings with a flue gas analyser.