2017 National Electrical Code®: Changes in Overcurrent & Surge Protection

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2017 National Electrical Code®: Changes in Overcurrent & Surge Protection

Mersen recently released a guide to understanding its changes in overcurrent and surge protection in the 2017 National Electrical Code®. These changes are to increase worker safety and help prevent arc flashes.

Arc flashes are the result of a massive release of energy due to an arcing fault between two phase bus bars, neutral or a ground.  This energy discharge burns the bus bars, vaporizing the copper and thus causing an explosion, which destroys everything in its vicinity and creates deadly shrapnel as it dissipates. Short-circuit current ratings (SCCR) indicate what fault current a system can handle without unacceptable damage in the case of a fault. Proper documentation is essential to ensure the available short-circuit current does not exceed the SCCR and that suitable precautions are in place.

We offer Mersen safety solutions to help you comply with the updated code and increase your workplace safety. Mersen’s guide covers nine key changes to the 2017 National Electrical Code®:

  1. Arc energy reduction

    Any fuses rated 1200 A or higher must have their location documented and available. The fuses must also have a method to reduce clearing time if their clearing time is not already 0.07 seconds or less.

  1. Field marking of available fault current

    Industrial control panels, industrial machinery and motor controllers of multimotor and combination-load equipment must have the date the current short-circuit calculation was performed and available short-circuit current rating (SCCR) documented.  If the available short-circuit current exceeds its short-circuit current rating, they shall not be installed. Elevators must also have the maximum short-circuit current clearly marked.

  1. Branch circuit and ground fault protection for single motor power conversion equipment

    Semiconductor fuses and instantaneous trip circuit breakers must now be installed as a single unit if instantaneous trip circuit breakers are permitted.

  1. Short-circuit current rating for elevator control panels

    Elevator control panels must be marked with their SCCR. If the available short circuit current exceeds its short-circuit rating, elevator control panels shall not be installed.

  1. Surge protection for emergency elevator, dumbwaiter, escalator, moving walk, platform lift, or stairway chairlift

    Surge protection shall be provided if the elevator has been designated as supplying an emergency system load.

  1. Surge protection for critical operations data systems

    A cascading protection scheme should be used throughout the entire operations data system.

  1. Surge protection for industrial machinery

    Industrial machinery with safety interlocks are required to have surge protection.

  1. Surge protection for fire pump controllers

    Surge protection was required previously for emergency systems at distribution level, but are now also required in or on the fire pump controller.

  1. Short-circuit current rating documentation and field marking

    Transfer switches can often have several different SCCR, so the rating based on the protective device and settings shall be externally marked.

Want to learn more about the changes in the 2017 National Electrical Code® or how best to implement them in your workplace? Contact your French Gerleman Account Manager or e-mail info@frenchgerleman.com to learn about Mersen safety solutions.