NC AMENDMENT 430.99

The North Carolina amendments did not change NEC 110.9 or 110.10 which are still enforced. Even though the AFC at the MCC is not required to be documented in North Carolina, it must still be calculated in order to ensure compliance with Sections 110.3(B), 110.9, 110.10 and the MCC installation instructions.
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The North Carolina amendments did not change NEC 110.9 or 110.10 which are still enforced. Even though the AFC at the MCC is not required to be documented in North Carolina, it must still be calculated in order to ensure compliance with Sections 110.3(B), 110.9, 110.10 and the MCC installation instructions.

Amend NEC® 2017, page 313:

430.99 Available Fault Current. Deleted.

ELR commentary: This section is all about motor control centers (MCC) and making sure that they are properly rated for the available fault current (AFC) at their location which goes hand in hand with the requirements in Sections 110.9, 110.10 and the manufacturers installation instructions.

In the 2017 NEC®, 430.99 requires the following:

430.99 Available Fault Current. The available short circuit current at the motor control center and the date the short circuit current calculation was performed shall be documented and made available to those authorized to inspect the installation.

The only way to ensure that an MCC is not installed at a location where the AFC is higher than the MCC’s SCCR in compliance with NEC® 110.9, 110.10 and the manufacturers installation instructions is to perform a calculation to determine the AFC at the MCC.

Knowing the amount of AFC at the MCC is the first step in selecting the right MCC. For example, if a calculation is performed and it is found that the amount of AFC at an MCC is 60,340 amps, then installing an MCC with a short-circuit current rating of 65,000 amps is code compliant with NEC® 110.10.

Special note:

The North Carolina amendments did not change NEC® 110.9 or 110.10 which are still enforced. Even though the AFC at the MCC is not required to be documented in North Carolina, it must still be calculated in order to ensure compliance with Sections 110.3(B), 110.9, 110.10 and the MCC installation instructions.

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NC AMENDMENT 430.99

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true regarding available fault current and motor control centers in North Carolina?

A: The available short circuit current at the motor control center shall be documented and made available to those authorized to inspect the installation.
B: There is no requirement to document the available short circuit current at the motor control center.
C: The available fault current must be greater than the short-circuit current rating of the MCC.
D: The short-circuit current rating of the MCC must be less than the available fault current.
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