A Short Circuit Current Rating (SCCR’s) is different than an interrupting rating which is a term used for defensive devices that protect against an overcurrent condition. The SCCR is a term reserved for passive components that cannot protect themselves against an overcurrent condition.

A lighting contactor is an example of a passive component that requires an overcurrent device ahead of it to protect it against a fault condition that can occur somewhere in the lighting circuit that it controls. Passive devices will have a SCCR which is basically a rating that represents the maximum amount of fault current to which the device can be connected without sustaining major damage.

A lighting contactor might be rated to interrupt 20 amperes of inductive lighting load every time the coil receives a completed circuit from a timer or photocell, but it is also common to have a Short-Circuit Current Rating of 5,000 amperes which means that it can be connected to up to 5,000 amperes of electric current without exploding.

Many passive components such as timers, contactors, molded case switches and relays are used in industrial control panels and will not have a SCCR value physically marked on the device so it can be confusing to determine the actual SCCR of each individual component. UL 508A, is the Standard for Industrial Control Panels and contains a table which provides default SCCR values for unmarked components.

The SCCR of a component is used by the electrician in order to determine compliance with NEC^® 110.10 which has been in the NEC^® since 1965.

See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2014-2017 Code Language:

Article 100 Definition:

Short-Circuit Current Rating. The prospective symmetrical fault current at a nominal voltage to which an apparatus or system is able to be connected without sustaining damage exceeding defined acceptance criteria.