Installing ERMS Switches in Switchgear to Reduce Arc Flash Incidents
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Installing ERMS Switches in Switchgear to Reduce Arc Flash Incidents


How NEC Section 240.87 Impacts Your Gear

As National Electrical Code (NEC) Section 240.87 continues to evolve, contractors must adapt.

When the section was first introduced in 2011, electricians were required to reduce clearing time when circuit breakers without instantaneous trip devices were used. A 2014 update shifted the focus from these devices to the actual problem that NEC is attempting to resolve: reducing arc flash incidents (AFI) across electrical workspaces.
Rather than looking for the presence of certain trip functions, the latest update focuses on the ampere rating of circuit breaker frames—and their relationship with AFI. It states that any circuit breaker that can be set to 1200A or more is required to install safety components, such as an energy-reducing switch.
This change impacts a wide variety of gear from commercial strip malls to large medical installations.

One method for reducing AFI is to install an Energy-Reducing Maintenance Setting (ERMS) switch.

An ERMS switch, when activated, can set circuit breaker trip units to "maintenance mode” reducing the overall clearing time and lessening the chance of AFI. When the switch is turned off, the settings return to their previous values and circuit breakers continue with normal function.
In new projects, ERMS switches are now included as factory-assembled items and allow an operator to easily switch the breaker between “normal” and “maintenance” modes.
For existing installations, inspectors may require the equipment be brought up to 2014 standards. Installing an ERMS switch in the field can cost twice as much as a factory installation not including the amount of downtime involved.

When gear representatives understand local standards and national codes, they can help contractors save time and money.

As of January 2019, the AFI reduction standards determined by Section 240.87 are in effect in 43 states. (New codes have not been adopted in Illinois, Indiana, Kansas or Nevada, and Arizona, Mississippi and Missouri remain outside NEC standards altogether.) With more and more states moving towards 2014 standards, Graybar recommends installing components like the ERMS switch which can improve safety and reduce cost.
Graybar’s sales representatives are up-to-date on local code and can assist you by asking the right questions about your next installation.?