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Protective device ratings

The proper application of overcurrent protective devices according to their ratings is critical to device performance.  The three main device ratings addressed here are: voltage rating, ampere rating and interrupting rating.  Each of these ratings plays a significant role in system reliability and safety.  Below are articles discussing the main device ratings and how they vary for different types of overcurrent protective devices.

Interrupting Rating

Interrupting Rating is a very important device rating that relates to a device's ability to handle potential short-circuit currents.  This article also notes the difference between Interrupting Rating and Interrupting Capacity.

Single-Pole Interrupting Capability

Some overcurrent protective devices will have single-pole interrupting ratings significantly lower than their rated IR.  This can result in misapplications unless proper attention is paid to this single-pole rating.

Voltage Rating

An overcurrent protective device voltage rating plays an important role in its ability to interrupt a fault.

Slash Voltage Ratings

Slash voltage rated devices can only be installed on specific systems, using them on circuits they are not designed for is a misapplication.  Here you will find information on these ratings and the types of devices that carry these ratings.

Amp Rating

Selecting the amp rating of an overcurrent device requires consideration of the type of device, Code requirements and load type.