What is a knife switch rated for more than 1200 Amps at 250 Volts or less allowed to be used as?

A knife switch rated for more than 1200 Amps at 250 Volts or less is designed to be used as an isolating switch. This type of switch provides a means to disconnect electrical equipment from its power source for maintenance or safety purposes, ensuring that the system is completely isolated from the electrical supply.

The terminology used in the context of electrical systems is critically important; an isolating switch serves a specific function to safeguard technicians working on electrical systems by disconnecting the load. This application is crucial in environments where safety and compliance with electrical codes are paramount.

While load disconnect switches are also used for disconnecting loads, they must meet specific operational characteristics, such as being capable of interrupting load current in addition to providing isolation. In this instance, the knife switch exceeds a significant amperage capacity which may limit its suitability for frequent load breaking applications and thus makes it primarily an isolating switch rather than a general load disconnect switch.

Using it as a circuit breaker or fuse holder would be inappropriate since those devices have distinct functions, including overcurrent protection and current interruption capabilities, that a knife switch simply does not provide.