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NOTE: This is an unformatted excerpt from our online fire protection training library.

General Requirements in the NEC

Short-Circuit Current Ratings

Short-Circuit Current Ratings

Section 110.10

Section 110.10 addresses the requirement for short-circuit current ratings, which are essentially a measurement of the amount of current that can flow through equipment without causing extensive damage. Short-circuit current rating is defined in Article 100.

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.

When a short circuit occurs, a particular piece of equipment might be damaged, or parts of it might have to be repaired or replaced, but the damage would not extend significantly beyond the equipment. The short-circuit current rating indicates that the equipment will allow that much current to flow without a catastrophic failure. This requirement applies to equipment like motor controllers, some types of switches and the busing of a panelboard or a switchboard.

Some types of equipment are really only intended to interrupt normal levels of current, such as some controllers or a toggle switch or contactor for controlling lighting. That type of equipment is not required to have an interrupting rating but is usually required to have a short-circuit current rating.

NOTE: This is an unformatted excerpt from our online fire protection training library.

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