Hi, I've brought a house with a 24CDI RSF installed that untill
recently had seen less than 2 months intermitant use since it was
installed approximatly 3-4 years ago.

The previous owners tell me that just proir to leaving the house they
had the boiler serviced (which invovled the engineer taking the unit
off the wall) Since then it has been "noisy".

It is working well, nice and warm and good flow rate etc but - whenever
the fan is running there is a anoying rumble that can be heard allmost
throughout the house. It not a "metal on metal" noise but more of a
resonation or perhaps a combination of the fan+pump vibrating the whole
unit. The fan is not noisy just it sets up a reverberation when
running.

Any hints or clues as to what could be the cause?

Thanks.