An electric power disconnect switch and associated vacuum circuit interrupter with a modular, removable contactor unit housing a modular, removable vacuum bottle unit. The vacuum circuit interrupter may be mounted on a bracket adjacent to the jaws of a disconnect switch, where the blade of the disconnect switch moves the actuator arm of the vacuum circuit interrupter during operation of the disconnect switch. A technician carries a spare contactor unit to the disconnect switch location, where the technician removes and replaces the contactor unit. The vacuum circuit interrupter includes a separable connection between the drive unit housing and a contactor unit housing, which allows the contactor unit to be rotated with respect to the drive unit to unscrew the connecting rod of the contactor unit from the drive shaft of the drive unit. A replacement contactor unit is then installed and the circuit interrupter is returned to service.