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Motor Disconnects, Part 4

Motor Disconnects, Part 4In the NEC, we read “readily accessible” so much where disconnects are concerned that it’s easy to conclude that all disconnects must be readily accessible. This would be a false conclusion.

In a motor circuit, only one of the disconnecting means must be readily accessible [430.107].

However, every disconnecting means in the motor circuit between the point of attachment to the feeder (or branch circuit) and the point of connection to the motor must be one of the seven types named in 430.109(A) unless the application is one of the seven types named in 430.109(B) through (G). If the application is one of those seven types, you’re permitted to, but not required to, use a different type of disconnect than one of the seven named in 430.109(A).

For example, suppose you have a 10hp motor that drives a conveyor. This is considered a “general” application and you can use a listed molded case circuit breaker as the disconnect. Or you can use any of the other six types of disconnects, such as a listed motor-circuit.

If the motor is a 1hp stationary motor, your disconnect can be a general use switch [430.109(C)(1)] if the switch is rated at least twice the full-load current rating of the motor. Similarly, a torque motor can use general use switch [430.109(G)]; there’s no 2X rating requirement. For your 1hp motor, you also have two other disconnect options to choose from.

« Part 3 | Part 5 » | Source: Mark Lamendola | Mindconnection