[Outwest34au]

In that case
a) as Gaz suggested
b) read the amps off the back of the fan then allow extra for the inertia draw, if it is in watts use the formula I=P/V where I is Amps, P is Watts and V is Volts

The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts

For example 12 watts/12 volts = 1 amp
120 watts/12 volts = 10 amps etc

Circuit breakers can be good but they can also be good at damaging equipment that is half faulty as they keep kicking back in as they cool down.

If you have serious doubts about the fans integrity get a cheapo Amp gauge and hook it in line and view the actual current draw. Many a mechanics electrical box has a common round amp gauge in it for such purpose.