This article explains the basics of a Tigo Fire Safety system and how it works.
- Rapid Shutdown - How it Works
- Required Equipment
- Tigo Energy RSS Transmitter Power Specification
- Frequently Asked Questions (FAQ)
Rapid Shutdown - How it Works
Rapid Shutdown (RSD) is an NEC requirement for any structure-mounted system (ground-mount systems are not subject to RSD compliance).
Tigo's Fire Safety products come with an RSS Transmitter. When this transmitter is powered on, the RSS core will transduce a PLC signal onto the string wiring. This is sometimes referred to as a "keep-alive signal," as the MLPE units will only respond if the signal is active.
When the PLC transmitter is powered off, this keep-alive signal is no longer present and the entire DC-side of the system goes into a RSD response: The Tigo TS4-F MLPEs disconnect their PV-Modules from the string and the accumulated string voltage is reduced to: under 80V within 30 seconds (as per NEC requirements).
Important: Tigo's TS4 Fire Safety and Monitoring products both offer RSD compliance, but they use different technologies to deliver the signal. For this reason, they are not inter-mixable within single systems or arrays. (must be installed, independently).
Designing a system to meet rapid shutdown with TS4-A-F and -2F (Fire Safety Group) is simple, but in order for it to be compliant with RSD requirements, it must have a TS4-A-F (or TS4-A-2F) attached to each PV-module in the system, and TS4 (certified) PLC Transmitter supplying a keep-alive signal.
The TS4 MLPEs come in two models:
Integrates with a single PV-Module (one MLPE, per Module):
Integrates with two PV-Modules (one MLPE, per two Modules):
The keep alive signal for the MLPEs can be supplied by either Tigo's original RSS Transmitter, the new Pure Signal RSS Transmitter, or even from a Tigo UL PVRSS Certified Inverter (these come pre-equipped with an internal Tigo (certified) integrated compatible PLC Transmitter).
To see a full list of Tigo Certified Inverters, see: UL PVRSS certified inverters with Tigo
Once on the page, select Tigo Integration > RSS transmitter, under Filter list by feature and brand
Important: As with all Tigo MLPEs, make sure to connect all MLPEs to their PV Modules BEFORE connecting them to each other. For complete details, refer to the manuals in our Technical Downloads section.
Tigo Energy RSS Transmitter Power Specification
Each Tigo Energy RSS transmitter is powered via 12V DC input. This power supply is included in the purchase of the RSS Transmitter and can be ordered with either:
- 120/240V AC-to-DC power supply
- 277/480V AC-to-DC power supply
Frequently Asked Questions (FAQ)
Is there a class on how to design and assemble these systems?
Yes, all of the necessary TS4 Fire Safety Group design topics are covered in Lesson 1.2 of the Tigo TS4 Design & Installation Certification Course. We highly recommended that every Tigo installer and designer complete this course.
How long can my String wiring be, per string?
The entire DC loop (measured from ends of home runs, or + to - terminal on inverter) for each string, can be up to 1000 feet (300 meters).
How many Tigo add-on RSS transmitters do I need for Commercial & Industrial Systems?
The maximum strings that can be attributed to a single transducer core is 10 strings. A Transmitter can have up to 2 Transducer Cores. However, you may want to have more or less transmitters, based on the design needs for the system.
Why can't I measure Open Circuit Voltage?
RSS Transmitters require DC string-loop continuity (ie., closed circuit), to enable the transducer signal to propagate over the string wire (and reach the TS4-F units). This means the home run leads must be connected to the inverter. The inverter may also need to be powered on for proper signal propagation throughout the loop (the MPPT must be active).
What is Crosstalk?
Crosstalk happens when the conductors of 2 separate signal transmitters are in close proximity to each other. When installing a system with 2 or more RSS transmitters, it is mandatory to meet the string wiring separation requirements for each transmitter to avoid Crosstalk. For more information, see: Crosstalk and How to Mitigate it
What do I do, if I have TS4-A-2F MLPEs and an odd number of PV-Modules on a string?
If you have an odd number of PV-Modules on a string (and are using the TS4-A-2F MLPE), you can either; install a single TS4-A-F at the end of the string, or short-circuit the input #2 leads of the last TS4-A-2F MLPE, by connecting them together. Do not leave the #2 inputs unconnected, as it prevents the MLPE from sending voltage (from input #1) to the string.
Where can I find Technical Documentation?
All technical documentation can be found on Tigo's Downloads page.
Special note for SMA -41 model inverters: The "-41" inverters have a built-in PLC Transmitter, designed and manufactured by SMA. This transmitter is powered from the DC side (PV-String Voltage) and requires 4.2V in order to start.
Without a keep alive signal, the standby/resting voltage per MLPE is .6 V. For this reason, it is required to have a minimum of 7 TS4-A-F Fire Safety MLPEs per MPPT, to meet the inverter's minimum 4.2 VDC input. Otherwise, the integrated SMA PLC transmitter will not operate.
If the array has less than 7 TS4-A-F Fire Safety MLPEs per MPPT, the addition of an external Tigo RSS Transmitter will be required and the SMA internal PLC Transmitter MUST be disabled.
For more information, see: Application Notes: Tigo SMA RSS