Quick Answer
Compliance with NEC 690.12 for off-grid systems involves ensuring rapid shutdown of the electrical system within 30 milliseconds when the system is not in operation, to prevent electrical shock and other hazards.
Understanding the Rapid Shutdown Requirement
NEC 690.12 requires that the electrical system be disconnected from the photovoltaic (PV) system within 30 milliseconds when the system is not in operation. This requirement applies to all off-grid systems, regardless of the system size or configuration. Meeting this requirement can be challenging, particularly for larger systems or systems with complex configurations.
Techniques for Achieving Rapid Shutdown
One approach to achieving rapid shutdown is to use a rapid shutdown panel or a system with built-in rapid shutdown capabilities. These panels typically include a control unit that monitors the system and disconnects the electrical connections within the required 30 milliseconds. Another approach is to use a remote control unit that can be installed at a safe location, such as a building or a fence, to disconnect the electrical connections when the system is not in operation. In some cases, a combination of both approaches may be necessary to meet the rapid shutdown requirement.
Design Considerations for Rapid Shutdown
When designing an off-grid system to meet NEC 690.12 requirements, it is essential to consider the specific needs and configuration of the system. This includes identifying the location of the rapid shutdown disconnect, selecting the correct rapid shutdown device, and ensuring that the system is properly wired to meet the rapid shutdown requirement. In addition, the system designer should also consider the need for communication between the rapid shutdown device and other system components, such as the inverter or charge controller.
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