Quick Answer
Rapid shutdown requirements for commercial rooftop solar systems vary by jurisdiction but generally include disconnecting the DC side of the system from the AC side within 10 seconds of a fault or shutdown signal, and limiting the DC voltage to 30V or less.
Understanding Rapid Shutdown
Rapid shutdown is a critical safety feature for commercial rooftop solar systems. According to the National Electrical Code (NEC) 2017, article 690.12, all PV systems with a DC voltage greater than 80V must have a rapid shutdown system. This system must be able to disconnect the DC side of the system from the AC side within 10 seconds of a fault or shutdown signal.
Rapid Shutdown System Requirements
A rapid shutdown system typically consists of a controller or module that monitors the system and disconnects the DC side when a fault or shutdown signal is detected. The system must be able to limit the DC voltage to 30V or less within the 10-second timeframe. The NEC also requires that the rapid shutdown system be capable of being manually activated by the system operator, such as via a switch or button.
Installation and Testing Considerations
When installing a rapid shutdown system, it’s essential to follow the manufacturer’s instructions and ensure that the system is properly sized for the PV array. The system must also be tested regularly to ensure it’s functioning as intended. This includes testing the rapid shutdown function by simulating a fault or shutdown signal and verifying that the DC voltage drops to 30V or less within the required timeframe.
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