Bored so spent some time looking for information about fuse size for fans. Note some manufactures state their fans most be protected by a suitable fuse, but not specifically what. Some did, Manrose 3amp for example.
Found this posted by 'rocknroll' on the IET forum in 2012;
'This is likely to happen for a few years to come I am afraid no matter what protective devices you use to protect the fans, I will now enlighten you on the matter, in 2011 whilst at Cambridge this issue was raised and the subject related to fire and forensics.
Firstly some incidental information before I get into the main subject, the fan catching fire.
In an earth fault condition the MCB tripped nine times out of ten compared to the 3 amp fuse.
In a short circuit condition it was around 50/50 MCB and fuse.
Now the fire bit, this normally happens in the stall mode, that is when the blades are impeded either because they are full of fluff, debris from the ceiling void, stuffing them with toilet paper to stop draughts or malicious acts.
During this prolonged stall mode the windings overheat and eventually ignite spreading to the plastic components such as the housing etc; many investigations have found the MCB and fuses intact after a fan fire incident, manufacturers are now required to insert a discrete about the size of a pin head into the windings, a thermal fuse, also the polymers used for the housing have been changed as well, various chloride and nitrogen compounds have been added at the extrusion stage so that the plastic chars rather than burns, but there are still fans being manufactured to the previous standards and with the many thousands of fans out there pre 2011 it is still likely to be a problem for some time to come, although some responsible manufacturers have taken this on board it will be a while before everybody plays ball'.
He gives no link or citation, (and not sure how Class 2 would have earth fault?). It would seem that bathroom extractor fans have caused quite a few fires, but exactly why, is never reported. One suggestion cites poor maintenance, i.e. not being de fluffed. Some report burning fab falling from ceiling onto carpet or plastic bath.
I note that reg 537.3.2.5 states a device used for mechanical maintenance, does not necessarily require interruption of the neutral conductor (TN supplies), so just a double pole FCU would suffice?
And it does seem that some fans have thermistor protection, Xpelair for example.
Anyways, hope you are all now suitably bored.
