Rapid Shutdown¶
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What is Rapid Shutdown?¶
NEC 2014 introduced rapid shutdown requirements for rooftop solar systems. NEC 2017 and 2020 strengthened these requirements significantly.
Goal: Allow firefighters and first responders to reduce voltage in the PV array to safe levels quickly, without waiting for the sun to set.
NEC 2017/2020 requirement: Within 30 seconds of rapid shutdown initiation, conductors outside the array boundary must be de-energized to ≤30V.
How Tigo Implements Rapid Shutdown¶
Tigo's TS4-A-S (Safety) and TS4-A-O (Optimize) units provide panel-level rapid shutdown:
- A Rapid Shutdown Switch (RSS) or transmitter is installed (often at the main disconnect)
- When activated: the RSS signals the Tigo transmitter
- The transmitter broadcasts a shutdown signal to all TS4 units
- Each TS4 unit disconnects its panel from the DC string
- String voltage drops to near zero within seconds
Rapid Shutdown Transmitter Placement¶
The transmitter (Tigo Cloud Connect or dedicated RSS transmitter) must: - Be installed per the manufacturer's specification - Be activated by the main PV disconnect or a clearly labeled button - Cover all TS4 units with adequate RF signal
Field check: Verify the transmitter is powered and that the RSS label at the disconnect is present and visible.
Verifying Rapid Shutdown Function¶
For commissioned systems: 1. Activate rapid shutdown (open main disconnect or press RSS button) 2. Wait 30 seconds 3. Measure voltage at DC string conductors 4. Should be ≤30V
Document the test result in your inspection report.