Solar Rapid Shutdown Requirements

Solar Rapid Shutdown Requirements

This page discusses how to meet 2014 and 2017 NEC (National Electrical Code) requirements for rapid shutdown of PV solar arrays. Refer to the NEC Code in Effect and contact the local building department for details about your jurisdiction.

2017 NEC 690.12 Rapid Shutdown

The Section 690.12 update to the 2017 National Electrical Code (NEC) calls for module-level rapid shutdown of solar systems instead of NEC 2014 array-level shutdown requirement. Starting in 2019, when NEC 2017 goes into effect in certain jurisdictions, all conductors within a 1ft boundary of an array has to be reduced to 80 V or less within 30 seconds of rapid shutdown initiation. The boundary for 2014 NEC is 10ft as shown in the diagrams below.

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Module optimizers, microinverters, smart modules, and other module-level power electronics (MLPEs) assist solar systems with module-level rapid shutdown. Here are the products that can bring solar projects to compliance with NEC 2017 module-level rapid shutdown.

Optimizers, smart modules and flexible MLPEs

Whether a panel comes pre-attached with optimizers or other MLPEs as a smart module or installers have to attach them in the field, these DC devices can be module-level rapid shutdown-compliant. When rapid shutdown is required on systems with these DC products, the AC breaker is flipped, and the loss of power causes the module-level electronics to turn off and suspend voltage output. Look for brands like SolarEdge for an integrated system, or brands like Tigo Energy are caompatible to work with most inverters from SMA, Fronius, Sol-Ark, Delta, Outback and many others.

Microinverters and AC modules

Rapid shutdown occurs similarly for microinverters and optimizers: The AC breaker is the only switch to flip for the solar system to shut down. When the main breaker is shut off, all microinverters immediately shut off and all conductors and wiring are de-energized, Put another way, the UL 1741 inverter compliance requires that inverters cease operation whenever the utility parameters fall out range. Shutting off the main breaker places the utility voltage and frequency out of range. Microinverters ship rapid-shutdown-compliant and no additional components are needed. The same can be said about AC modules with microinverters already attached. Look for brands like Enphase, AP Systems, or Chilicon Power.

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