Post the correct name, for starters.
I believe you have a FERROLI boiler. Not sure about the exact model, tjhough, since you didn't mention it.
Have you checked the manual? (should be easy enough to find online, once you search for the right model and make)
The best advice and by far the safest is: Get a Gas Safe certified engineer to look at it.
If its a FERROLI F30b, I understand the most common related faults on these are
• Fan stiffening up.
• A wrong flue restrictor - On a ferroli this can suddenly cause a problem even if its worked great for a couple of years.
• Fan relay on the PCB.
There's other stuff it could be of course but there's where I look first on these.
Read more: http://www.diynot.com/diy/threads/ferroli-f30-b-f5-issue-fixed.389870/#ixzz4TEwt17in
On the Ferroli Optimax the F5 error code is:
Fan problem
• Tachometer signal
interrupted, fan connection
• Fan damaged, debris in fan
Possible Solution
• Check the wiring and fan
• Check the fan, clean debris
Hope this helps you to get started. Good Luck.
Get a Gas Safe certified engineer to look at it., December 2016
