I have a small room with an IT rack which gets quite warm, I do have internal cabinet fans and a room ceiling extract fan, but I wanted to pull cooler air from outside into the space to create a crude forced ventilation system.
I already had a 4″ duct to the outside and didn’t want to start making the hole bigger, so I wanted to get a fan of this size.
Struggling to find a 4″ reversible extraction fan, I decided the cheapest option would be to modify a traditional extractor fan to blow rather than suck.
The model of Manrose fan modified is 17122-0001 and was bought from Screwfix.
Motor Reversal Process
The motor in these fans is a shaded pole induction type with a fixed direction of rotation which cannot be altered electrically, the only way is to dissemble to motor and rotate the internals by 180o degrees and reassemble.
First job is to remove the spring clip from the fan blade and slide off the motor shaft.
Turning the fan over, remove the black wires from the connections, then pop out the two screw covers and remove the Philips screws to release the motor.
The motor will now come away from the fan body.
The motor will need to be physically altered in order for it to rotate in the opposite direction, enabling air to be be drawn in rather than exhausted.
This involves drilling out the end plate rivets at both ends and swopping the bearing plates around, effectively the motor shaft will end up on the right rather than that shown in the unmodified picture above.
Securing the motor body in the vice and using a 6mm drill bit, drill the rivet lip off at both ends, this allows both bearing plates to come off, I needed to gently pry these off the rivets using a small screwdriver.
The longer fan shaft has indentations, so will not slide out of the bearing plate.
Change the ends where the bearing plates were and using 2 x M3 machine screws and nuts, reattach them to the body of the motor.
Once done, reassemble the motor into the body, connect and test.
Conclusion
The task was fairly simply to do and took no more than 10 minutes with the end result of a working intake fan.
Obviously this will invalidate any warranty, so undertake at your own risk 🙂
