Off-Grid Solar Systems and NEC 690.12: What’s the Relationship?

Understanding NEC 690.12 Requirements

NEC 690.12 specifies that solar PV systems must be capable of reducing the voltage at the module level to 30 volts or less within 30 seconds of a rapid shutdown event. This requirement is designed to prevent electrical shock or fires in the event of a system fault or isolation. In off-grid solar systems, rapid shutdown is typically achieved through a combination of circuit breakers, contactors, and relays that are designed to disconnect the DC voltage supply to the system.

Implementing Rapid Shutdown in Off-Grid Solar Systems

To comply with NEC 690.12, off-grid solar systems should be designed with a rapid shutdown system that can disconnect the DC voltage supply quickly and safely. This can be achieved by using a dedicated rapid shutdown controller that is specifically designed for off-grid solar systems. The controller should be capable of disconnecting the DC voltage supply within 30 seconds of a shutdown event, and should also provide a disconnect signal to the system’s inverter and other equipment to prevent electrical shock or fires.

Design Considerations for Off-Grid Rapid Shutdown Systems

When designing an off-grid rapid shutdown system, it’s essential to consider the specific requirements of the system, including the number of modules, the type of inverter, and the system’s operating voltage. The system should also be designed to meet the requirements of NEC 690.12, including the ability to rapidly disconnect the DC voltage supply and provide a disconnect signal to the system’s inverter and other equipment. Additionally, the system should be designed with safety features such as overcurrent protection and arc fault protection to prevent electrical shock or fires.