A module-level rapid shutdown device is a small unit fitted to each PV module. It brings module voltage down to a safe level so firefighters face less shock hazard. The inverter has a power line communication transmitter that sends a keep-alive or permission-to-operate signal over the DC string conductors. The devices let string voltage build only while they receive that signal. Opening the AC disconnect or breaker, losing the grid, or pressing the inverter's rapid shutdown switch stops the signal, and every device then switches into shutdown mode. Relevant requirements are NEC 690.12 and CSA C22.2 No. 330. Signalling may follow the SunSpec specification, and inverters are listed as PV rapid shutdown equipment under UL 1741. Always attach the device to its module before the module is wired into a string. Attaching it to a module that is already in a string can permanently damage the device through overvoltage. Selecting the wrong rapid shutdown mode is a common setup fault. For example, TS4-R-F devices need SunSpec Shutdown, and this setting should only be chosen after the strings are connected. With SunSpec shutdown, every module on the inverter must have a compliant device or the inverter cannot start feeding in. If rapid shutdown is enabled with no devices installed, the inverter can be damaged. Devices are matched to specific transmitters, so check the inverter maker's compatibility listing and follow the device maker's installation instructions.
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output_limitConditions: Module output when rapid shutdown receivers stop getting the keep-alive signal and go into shutdown mode (Yaskawa Solectria PVI RSD wire box systems)
sec=h32 h=1f1fbca75b2averified by: review-workflowverified on: 2026-10-24
c2 drafted · lead nominal 0.6 V
Conditions: Voltage measured across one PV panel with a Tigo TS4-R-F attached, before string connection and with no SunSpec permission-to-operate signal present
The source expects a string of 10 such assemblies to read about 6 Vdc before commissioning.
sec=h1 h=32d44e3827b9review note: support check: partial - The 0.6 Vdc per assembly and ~6 Vdc for 10 assemblies are stated, but the passage doesn't say 'no SunSpec permission-to-operate signal present' and it is a nominal reading, not a limit.; review: partial - The SMA passage gives 0.6 Vdc (nominal) per panel/TS4 assembly before stringing and about 6 Vdc for 10 assemblies, but it never mentions the absence of a SunSpec permission-to-operate signal, and it presents 0.6 V as an expected nominal reading…
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