My father in law has a 115 volt 6 amp attic fan motor hooked up to a 2 pole (low & high speed) toggle switch. The electrician who installed it 25 years ago advised him that he had to turn the fan on high first and then low. If you turn the switch on low first it will trip the breaker. Why would that be since the motor draws more amperage on high speed?
Start up amps.
Not true. you can easily demonstrate this by holding a motor shaft. When it is running free it will draw less current than when you hold the armature stationary. Much depends upon how the low speed is achieved with the motor.
Why would a 6 amp motor blow a 20 amp circuit when start up is approximately 175%?
That’s why most fan rotary speed controls go from Off->High->Med->Low.
It’s gotten old.