Most states have adopted the 2017 update of the National Electrical Code, and some have even graduated to the 2020 version. In both, module-level rapid shutdown is required for any solar project on a building. In the past year, many manufacturers have introduced their own rapid shutdown devices with different features and price points.
“Having multiple different manufacturers or technologies in the market for that allows flexibility and actually allows a lot of forward compatibility,” said Michael Mills-Price, head of inverter and energy storage business at PVEL.
Along with longtime RSD manufacturer Tigo Energy, installers can now choose among a number of brands, from APsystems to Generac, that are now offering their proprietary rapid shutdown tools.
Some devices on the market are compatible with any brand of string inverter. For example, APsystems produces the rapid shutdown package called APsmart, a small device that can either be buckled to the module frame or applied to the backsheet using adhesive. The company says its device works well for bifacial applications due to its compact size and tucked-away installation option.
ZERUN makes a similar product called the ZERUN Rapid Shutdown Solution. The devices are duration-tested before shipment to ensure longevity and can also be mounted on the module frame or backsheet.
IMO Automation makes the FireRaptor, a device that comes with a 20-year warranty and doesn’t require powerline communications. The FireRaptor can automatically shut down if the temperature sensor detects a rise above the programmed trigger level.
Other rapid shutdown devices only work with one brand of inverter. Generac’s PWRzone system comes with an optimizer and small rapid shutdown switch, but it only works with the company’s PWRcell inverters. Similarly, SolarEdge offers a power optimizer with built-in rapid shutdown functionality, but only works with SolarEdge inverters.
As a final option, installers can choose to use microinverters to satisfy rapid shutdown requirements without having to install both a string inverter and RSD. Microinverters are often seen as inherently compliant with rapid shutdown rules because they convert high-voltage DC power to lower-voltage, safer AC power that can drop down to 80 V within 30 seconds. However, the 2017 NEC does not specifically identify microinverters as a way to satisfy the rapid shutdown requirement.
Module-level rapid shutdown has added cost and time to installations, but also brings important protection to first responders in case of a fire. Although rapid shutdown devices can vary widely, installers should review test reports like those from PVEL to ensure rapid shutdown functionality before choosing which of these important devices to use.
Yi Kang says
That’s good point, those products which is using PLC signals to initiate rapid shutdown function had that challenges you mentioned, like not be able to perform IV analysis before commissioned.
But it had been conquered after APsmart developed a simple handy tool: RSD-Start Kit. This tool can turn on all SunSpec RSD PLC communication protocol devices(receivers) independently, including Tigo’s systems, temperately switching RSD system on isolated just like FireRaptor does. Then installers could measure string dc open air voltages, perform IV tracing, or do self-checking string inverters without Grid. The most important: field engineers could do troubleshooting easily now, especially on string inverter side.
For MLPE, I would suggest customers to pay attention on services quality rather than how many years manufactures promised warranty, and that’s why we believe following SunSpec Alliance as multi-vendors solutions would be benefit for whole industry. After all, the NEC RSD codes will bring more surprises than people imaged…..
“Module-level rapid shutdown has added cost and time to installations, but also brings important protection to first responders in case of a fire. Although rapid shutdown devices can vary widely, installers should review test reports like those from PVEL to ensure rapid shutdown functionality before choosing which of these important devices to use.”
This is what I see as the major problem, no consistency, more costs to the homeowner and no real “way” to verify a system works when commissioned. Yeah, you can trip the protection and look at end voltage, but this does not necessarily prove the power out allowed is really safe or effective. The mentioned FireRaptor device that needs no power line communications and has a 20 year warranty sounds more reliable than some of the other products on the market now. Over just the past five years, manufacturers have brought out simplified roof mounting systems that do less intrusion into the roof structure and make it easier to install a roof mount array. The old Engineering adage KISS still applies. Although solar PV has a better ROI than it did just 15 years ago, the installation of solar PV and now more often smart ESS is still a marathon not a sprint.