Code Change Summary: A new code section requires arc-energy reduction for certain fuses.

Placing electrical equipment into a safe working condition (de-energizing) is by far the best way to avoid electrical related injuries but there are instances where hot work is unavoidable.

The movement to reduce arc energy and protect workers servicing energized equipment is on. The 2014 NEC^® began raising awareness by the changes made in 240.87 pertaining to large frame circuit breakers. Now in the 2017 NEC^®, language has been introduced that provides additional rules for large fuses.

Arc energy occurs during an arc-flash event. Arc-flash events only occur with energized equipment. Often, equipment is serviced or maintained while energized and the worker follows guidelines in NFPA 70E for proper work practices and ratings of required PPE in order to provide a level of safety while working on the live equipment.

The amount of potential arc energy is based on several factors, one of which is the fault duration or time the fault persists before an overcurrent device ahead of the faulted circuit opens to clear the fault condition. This new code section was put in place to ensure an extra measure of safety for the worker. Using one of the new methods to reduce potential arc energy ensures additional worker safety should a mishap occur triggering an arc flash event.

Notice that the effective date of the code change is January 1, 2020. This should give manufacturers ample time to bring equipment up to speed.

Below is a preview of Article 240. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC^® edition of NFPA 70.