All electrical devices that are designed to interrupt a circuit when there is a fault must have an interrupting rating that is equal to or greater than the available short-circuit current at the point of installation. Fuses and circuit breakers must have an adequate interrupting rating to be able to safely clear a short circuit.
The interrupting rating of these devices is determined by standard test conditions to make sure they meet the needs of the installation. It is important to note that the interrupting rating is different from the short-circuit current rating.
NEC Article 110.9 Interrupting Rating
This section of the Canadian Electrical Code (CEC) describes the interrupting rating of an electrical device. It states that devices must be rated to open and interrupt the circuit they are protecting at their full-load current rating.
The interrupting rating must be at least equal to the maximum short-circuit current available at the point of installation. The section also states that the interrupting rating for a device must be equal to or greater than the available short-circuit current at the point of installation.
What is Minimum interrupting rating?
what is minimum interupting rating? The minimum interrupting rating for an electrical device is the maximum short-circuit current available at the point of installation. This rating must be equal to or greater than the available short-circuit current.
Equipment intended to interrupt current at fault levels
Equipment intended to interrupt current at fault levels must have an interrupting rating equal to or greater than the maximum available short-circuit current.
Fault current rating
Fault current rating must not be confused with short-circuit current rating. The short-circuit current rating explains the amount of current a device can safely handle without damaging its components.
Minimum short-circuit current rating
Minimum short-circuit current rating is the amount of current that can flow through a device without causing it to overheat and become damaged. This rating should be greater than the available short-circuit current.
Arc fault damage
Arc fault damage is closely related to the value of the available short-circuit current, and the equipment’s interrupting rating must be higher than the available short-circuit current in order to protect against this type of damage.
NEC fuse requirements must be followed to ensure that the system is properly protected.
Short-Circuit Current Ratings (SCCR) Requirements as per NEC
The National Electrical Code (NEC) has specific requirements for Short-Circuit Current Ratings (SCCR). These requirements are outlined in Section 110.9 of the NEC. This section states that any electrical device that is intended to interrupt a circuit at fault levels must have an interrupting rating that is equal to or greater than the maximum available short-circuit current at the point of installation. It also states that the equipment must have a minimum short-circuit current rating that is greater than the available short-circuit current. Furthermore, the equipment must have an arc fault rating that is higher than the available short-circuit current. These requirements are necessary in order to ensure that the system is properly protected against electrical faults and arc flash hazards.