Article 240.87 Arc Energy Reduction and the Implication to Docking Stations
As new states adopt the 2020 NEC, it is important to stay current on how these changes may affect your next Trystar project. Here we provide a brief overview of new developments in Article 240.87 and some of the potential implications when designing your docking station requirements.
Notable Revisions in 240.87(B):
240.87(B) Method to Reduce Clearing Time – One of the following shall be provided and shall be set to operate at less than the available arcing current.
1. Zone-selective interlocking
2. Differential relaying
3. Energy-reducing maintenance switching with local status indicator
4. Energy-reducing arc flash mitigation system
5. An Instantaneous trip setting. Temporary adjustment of the instantaneous trip setting to achieve arc energy reduction shall not be permitted.
6. An instantaneous override
7. An approved equivalent means
Designers and installers can choose one of the seven methods above (found in NEC 240.87(B)) as an acceptable means to reduce clearing time.
One clarification provided in 2020 does not permit the use of a temporary adjustment to the instantaneous trip setting. Meaning a field update to the breaker’s instantaneous trip dial is not acceptable. This is a key change for projects that previously relied on this practice, going forward the use of another method to reduce clearing time must be considered.
Trystar’s Code Compliant Solution:
Trystar breaker products are available with an optional Energy Reductive Maintenance Switch** with local status indicator as an approved Method to Reduce Clearing Time per NEC 240.87(B) no. 3. This feature allows the worker to set a circuit breaker trip unit to “no intentional delay” to reduce the clearing time during maintenance or repair. This feature is available on all breaker units above 1200 Amps or higher. The photo shows the use of the ERMS adder in action.