Tech Q & A: Rapid Shutdown When the Grid is Down

Q: With a DC-coupled system, how do you meet rapid shutdown requirements when the grid is down? Are there any rapid shutdown options for off-grid that don’t require an AC input?

A: The biggest difference here is of course that you don’t want the Rapid Shutdown (RSD) device to activate when the grid power is interrupted. So that means you must use a manually only triggered RSD device, like an emergency OFF button. Both OutBack Power and MidNite Solar make RSD systems for DC-coupled PV systems with emergency power OFF buttons. The MidNite will work without AC power but it is recommended. At this time the MidNite LSOB does not yet work with charge controllers, equipment for that is being developed. The OutBack ICS+ system does not use any AC power.

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