By Kate Collardson and Aaron Bingham
On January 1, 2020, California, Maryland, South Carolina, and Wisconsin, will all adopt the 2017 NEC. As that date approaches, we wanted to provide a refresher on the 2017 NEC rapid shutdown requirements and share the ways that BayWa r.e. Solar Systems can help you stay code-compliant.
The two most prevalent residential inverter solutions in the United States comply with NEC 2017 Module Level Rapid Shutdown requirements (PVRSS) by their MLPE based design:
- Module-level monitoring
- Module-level inverter, each module is independent
- AC circuit-integrated communications
- Integrated PVRSS functionality
- Module-level monitoring
- Module-level DC string optimization (required)
- Integrated PVRSS functionality
- String inverter integrated communications
- Commercial and residential options
- Note: While all SolarEdge Optimizers are UL listed to satisfy NEC 2017, some commercial optimizer options require two modules wired in series. Depending on the module choice, the voltage in the resulting small circuit may exceed 80V. Where this issue is encountered, the P860 or the P505 should be considered.
Over the last five years, the module-level solutions above have become near ubiquitous. But you may be surprised to find that manufacturers like SMA and Fronius also have NEC 2017-compliant residential and commercial PVRSS options.
Both SMA and Fronius can be paired with TS4-R series MLPE units to bring rooftop arrays into compliance with NEC 2017. While there are a variety of TS4-R options, matching those options with the appropriate inverter can be challenging.
We’ve summarized the differences below:
| TS4-R-S | TS4-R-O | SMA-TS4-R-F | |
|---|---|---|---|
| SMA | √ | √ | √ |
| Fronius | √ | √ |
- Inverter-agnostic module-level PVRSS
- Module-level monitoring
- Rapid shutdown functionality (PVRSS)
- Requires Rooftop Communication box when paired with an SMA -40 or -41 SunnyBoy inverter
- Requires Cloud Connect Advanced Outdoor Kit when paired with non SMA or SMA commercial inverter (STP or Core1)
- Inverter-agnostic module-level PVRSS
- Module-level monitoring
- Shade mitigation via module optimization
- Rapid shutdown functionality (PVRSS)
- Requires Rooftop Communication box when paired with an SMA -40 or -41 SunnyBoy inverter.
- Requires Cloud Connect Advanced Outdoor Kit when paired with non SMA or SMA commercial inverter (STP or Core1)
- SunSpec based module level rapid shutdown*
- No external communications needed, no additional accessories to buy when paired with a compatible Sunspec enabled inverter
- No module-level monitoring
- Works with most SunSpec enabled inverters**
* Applies to SMA Brand units only. Tigo Branded -F units are not SunSpec enabled at this time.
**Fronius Symo Advanced SunSpec enabled inverters are not compatible with the SMA-TS4-R-F.
Questions about code-compliance? Leave a comment or email us at solar.review@baywa-re.com.
