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Important Notice: Behavior of TS4-X and TS4-A (725W) with Third-Party Inverters Using Integrated RSS Transmitters

  • Updated

Summary

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Installers using the TS4-X and the new TS4-A (725W) with third-party inverters that have integrated Tigo RSS Transmitters (or third-party RSD transmitters) need to be aware of an important safety consideration.


Even if the Cloud Connect Advanced (CCA) is powered down, full array voltage may still be present. This can create a shock hazard if installers assume the system is de-energized when it is not.

Also, all TS4-X and TS4-A (725W) products are shipping in the ON position. This means full module voltage will pass as soon as these TS4s are connected to the module. 

Always exercise proper electrical safety practices and wear appropriate PPE when installing or servicing these units.

Relevant TS4 Units

MLPE_Device_TS4-X-O-102024_1.jpg

TS4-X-O
MLPE_Device_102024_1.png

TS4-X-S
MLPE_Device_TS4-X-F_102024_1.jpg

TS4-X-F
TS4-A-O 725W front.png

TS4-A-O (725W)
TS4-A-S - 725W - front.png

TS4-A-S (725W)
TS4-A-F - 725W - front.png

TS4-A-F (725W)
Non-725W TS4-A units will only have 4 cable glands on the bottom of the unit, except for the TS4-A-2F which also has 6.
TS4-A-O outlined Hi Res_cropped.png

Non-725W TS4-A

Background

The TS4-X line, and now the TS4-A (725W), includes a multifactor rapid shutdown (RSD) feature:

  • They respond to both PLC signals from an RSS Transmitter and wireless commands from the CCA and TAP.
  • If a third-party inverter with an integrated RSS Transmitter is present, the TS4 devices will continue to see the PLC keep-alive signal.
  • This means that even with the external CCA turned off, the TS4s remain active, and the PV array stays energized.

This behavior is intentional—it allows the TS4 to remain compatible with multiple rapid shutdown methods. However, it changes how the system behaves in the field, so installers should not rely on CCA shutdown alone to de-energize the array.

Schematic - X-O - MFRS 2.png

Safety Guidance

  1. Do not rely solely on turning off the CCA to de-energize a system when using third-party inverters with integrated RSS.
  2. Always verify voltage at the array conductors with a properly rated meter before touching or servicing.
  3. If working on the DC side, isolate PV circuits at the combiner, disconnects, or breakers before handling conductors.
  4. Train all crew members that CCA OFF ≠ Array OFF in this configuration.

How to Fully De-Energize the Array in These Configurations

To ensure rapid shutdown is triggered and the array is de-energized:

  1. Turn OFF both the CCA and the inverter.

    • This disables both the wireless keep-alive and the inverter’s integrated RSS Transmitter.

  2. Follow the inverter manufacturer’s instructions to deactivate its internal RSS Transmitter (if applicable).

    • Some inverters allow disabling the transmitter through commissioning software or dip-switch settings.

  3. Use a compliant initiator (external rapid shutdown switch) designed to simultaneously shut down both the inverter’s RSS Transmitter and the CCA.

  4. After shutdown, test for absence of voltage on array conductors before servicing.

If the inverter’s internal RSS Transmitter remains active, the TS4-X and TS4-A (725W) will keep the array energized regardless of CCA status.

MFRS shutdown graphic.png

Key Takeaway

When paired with inverters that include their own RSS Transmitters, the TS4-X and TS4-A (725W) will remain active as long as they detect the PLC signal—even if the CCA is turned off. Installers must take this into account during design, commissioning, and service to avoid shock hazards.

Questions

Contact Tigo Customer Success with questions.

Additional Information

Multi Factor Rapid Shutdown Overview

 

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