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240.87 Arc Energy Reduction

A general overview of section 240.87.  we can talk about the focus of this section.  why it exists.  what is its purpose.  an overview of when it was introduced and by who.  This is for the electrical worker.

NEC 2011 Changes
This is the first cycle that includes 240.87 titled “Noninstantaneous Trip”.  This is a historic moment for the National Electrical Code as the only previous change that included a technology required to be installed to try to address incident energy is found in 230.95 back in 1971.

NEC 2014 Changes
NEC 2014 changed the title of this section to focus on arc energy reduction and not on a circuit breaker without instantaneous.   This section introduced the 1200A requirement and an additional method to reduce incident energy. It also left the door open to other solutions that may be available that will also meet the requirements of 240.87.

NEC 2017 Changes
This change introduces an instantaneous trip that operates based upon the arcing current.  The new term arcing current is introduced as part of this change into the NEC but it is not defined.  A new reference to IEEE 1584 helps the user of the NEC understand the reference used to calculate arcing current.  IEEE has limitations though and the important one for this discussion is that arcing current cannot be calculated for bolted fault currents greater than 106kA.  The video I prepared can help you address this limitation while trying to enforce the NEC.

NEC 2020 Changes
Arcing current is getting more of a focus and field adjusting instantaneous is specifically addressed not permitting this as a means to meet the requirements of 240.87.  Introduction of performance testing upon installation as well during this cycle.

Solutions to meet these requirements

Enclosed Circuit Breaker

Arc Reduction Maintenance

Enclosed Breaker

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Check out Eaton’s Arc Reduction Maintenance System.  This is the fastest and most economical solution that can be leveraged to meet the requirements of 240.87.

This is a video from the facility that makes these devices.  

The Quencher

Quencher Video

240.87 Live Event

The Arc Quencher from Eaton is a solution that would fall under the envelope of the active arc flash mitigation system as permitted by the NEC 240.87.  This solution is amazing in its response time providing protection for the electrical worker and for the investment of the owner.

Watch Adams Baker explain how the quencher functions.

This is a live session with David Smith looking at the requirements found in Section 240.87.  This deep dive into this topic will help in the complete understanding of this section of the NEC based on the 2020 version of the National Electrical Code..

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