Overcurrent and Overvoltage Protection Changes in the 2008 NEC Code

Dec. 4, 2007
SCCR was not defined in the previous 2005 code. It relied only upon a note referring people to UL 508A Standard for more information. Many questions were raised about the exact type of panels covered by SCCR requirements.

In the 2005 Code for the first time industrial control machinery and panels, air conditioning equipment, refrigeration equipment, meter disconnect switches, and motor controllers had to be marked with their SCCR (Short Circuit Current Rating). This rating has to be equal to or greater than the available fault current at their point of use as outlined in NEC 110.10. If the equipment or device is applied on a circuit where the available fault current exceeded the SCCR, it could become a safety hazard.

Prior editions of the Code considered that the downstream equipment was automatically protected if the overcurrent device feeding it had an adequate interrupting current rating. The 2005 code in harmony with Underwriters Laboratories (UL) required that equipment operate more safely. This included panels supplied by a high interrupting overcurrent device which would permit the downstream equipment to be a hazard due to the high available fault current level. This resulted in a new type of equipment rating, called the Short Circuit Current Rating (SCCR).

Since SCCR was not defined in the 2005 code many questions were raised regarding SCCR panel requirements. One change clarifies which panels need to have SCCR ratings. Another change requires additional voltage information on the nameplate to avoid misapplication.