Table 430.22(E) makes no sense to me. Consider the conductors for an intermittent duty passenger elevator.
If the motor is a 5-minute rated motor, meaning it is designed to deliver its rated hp for periods of about 5 minutes, conductors may be sized at 85% of the motor nameplate current rating.
If the motor is a continuous rated motor, the conductors must be sized at 140% of the motor nameplate current rating. [Keep in mind that this is an intermittent duty load, while the conductors for a continuous duty load must only be sized at 125% of the motor nameplate current as per 430.22(A.]
In either case, the motors are doing the same amount of work, for the same length of time, and assuming each motor is the same hp, drawing the same current.
It is the classification of service, and not the time rating of the motor, that determines how long the motor is going to run. Why,then,is the conductor size based on the time rating?
Thanks
Brian Dolan
Palos Park, IL
If the motor is a 5-minute rated motor, meaning it is designed to deliver its rated hp for periods of about 5 minutes, conductors may be sized at 85% of the motor nameplate current rating.
If the motor is a continuous rated motor, the conductors must be sized at 140% of the motor nameplate current rating. [Keep in mind that this is an intermittent duty load, while the conductors for a continuous duty load must only be sized at 125% of the motor nameplate current as per 430.22(A.]
In either case, the motors are doing the same amount of work, for the same length of time, and assuming each motor is the same hp, drawing the same current.
It is the classification of service, and not the time rating of the motor, that determines how long the motor is going to run. Why,then,is the conductor size based on the time rating?
Thanks
Brian Dolan
Palos Park, IL