When it comes to solar, fire safety is a top priority. There are many solar regulations in place to protect against the risk of fire, but constant updates are needed “to reduce hazards for firefighters while performing their duties on or in buildings with PV arrays.” – Underwriters Laboratories (UL).
Many countries have realized the importance of having safety measures in place to ensure that solar operates safely and allows firefighters and other first responders to safely access the roof area.
That’s where rapid shutdown comes into play. Let’s take a closer look at the rapid shutdown requirements and why they’re important for all solar installers and system owners to know about.
Rapid shutdown is an electrical safety requirement that was originally introduced in the United States by the National Electrical Code (NEC). This requirement applies to solar PV systems and requires a way to de-energize, or reduce the voltage, of the solar modules on the roof by adding an “on or off” switch, so to speak.
Rapid shutdown provides a safe way for firefighters or solar installers to stop or reduce the voltage and current from a photovoltaic (PV) array allowing them to perform their jobs safely and efficiently avoiding electrical hazards. Turning off or reducing the voltage on your roof at the module level reduces or eliminates the firefighter’s exposure to shock from the high voltage that may be coming from the solar modules.
Inverters can shut off to prevent the energy generated by the modules from getting past the inverter. However, the solar modules will continue to generate electricity as long as the sun is shining, which creates voltage and current on the wires between the modules and inverter. As a result, most rapid shutdown codes require shutdown to occur at the module level, hence the common use of module-level power electronics (MLPE) or microinverters to meet this function. The US National Electrical Code requires that the inverter communicates with the module-level rapid shutdown device, and these components comprise a system. This “system” is what PVRSS (PV Rapid Shutdown System) refers to.
The National Electrical Code in the United States requires a rapid shutdown system for all new rooftop installations – including residential and commercial buildings. In addition, it is required if any conductors enter a building that is not specifically designed to house the PV system components. So, all new rooftop installations essentially require module-level power electronics or microinverters with the rapid shutdown function in the United States.
There are a few critical components involved in a rapid shutdown system:
First is a Rapid Shutdown Device (RSD). Rapid shutdown devices are a type of module-level power electronic (MLPE) or microinverter that are installed on the backs of solar modules. They are equipped with technology that can turn off and reduce voltage output throughout the solar system to adhere to PV Rapid Shutdown regulations. An example product is the Tigo TS4-A-F or 2F which is our MLPE with Rapid Shutdown compliance only, but Tigo offers multiple MLPE options with Rapid Shutdown compliance.
Another component is an initiator. A rapid shutdown initiator does exactly as the name implies. This device is typically in the form of an emergency stop (e-stop) button that is in an inverter. Typically, Rapid Shutdown can be initiated in two ways, either manually (through an e-stop button) or automatically (loss of power from the grid).
Lastly, you will need an inverter in a rapid shutdown system. An inverter is a device that converts the electricity produced by the solar modules into usable energy for your home (for more information on this process read our previous blog). Many Rapid Shutdown initiators are located inside the inverter.
These three components are referred to as Photovoltaic Rapid Shutdown Equipment (PVRSE). These are equipment used in a rapid shutdown system that reduces the voltage to a safe level. The US National Electrical Code mandates that PVRSE and PVRSS are to be UL Listed for the purposes of rapid shutdown.
As mentioned previously, Tigo offers a variety of rapid shutdown compliant MLPE, ranging from the TS4-A-O that enables optimization, monitoring, and rapid shutdown; to the TS4-A-S that enables monitoring and rapid shutdown; to the TS4-A-F and 2F which are dedicated rapid shutdown devices. Tigo also partnered with numerous industry-leading partners to allow customers the most reliable and flexible solar system building experience. This is because our MLPE are PVRSS certified with many inverter brands that have been vigorously tested to ensure quality and safety.
Through this partnership, Tigo created Tigo Enhanced – plug-and-play rapid shutdown systems with our integrated Tigo technology. When you see the Tigo Enhanced logo on an inverter datasheet, or on the product itself, you can be assured that the devices are integrated with Tigo technology and are UL certified for PVRSS. To find Tigo Enhanced products, visit our site here.
Tigo takes rapid shutdown seriously and is always trying to innovate and improve our technology and devices. In an effort to support rapid shutdown, our team in Brazil collaborated with the 6th military Fire Brigade in Brazil to teach the basics of solar energy. After the training, Lieutenant Colonel BM Danilo Santos Moreira Leite stated, “This training greatly contributed to a better understanding of the operation and possible risks, as an increased number of homes and businesses install solar. With this knowledge, we can avoid submitting our military firefighters to unnecessary danger as we help the community.”
Rapid Shutdown requirements are being adopted globally to protect firefighters while they work around solar PV equipment. The NEC requirement reduces the voltage to a safe level by using a series of devices (PVRSE) that make up a rapid shutdown system (PVRSS). Inverters, initiators, and rapid shutdown devices, such as MLPE or microinverters, are necessary components to comply with NEC regulations. Check out Tigo’s line of MLPE to learn more about rapid shutdown devices and our list of PVRSS certified inverters. For more information on the code itself, check out this past webinar we did or read the webinar transcript here.
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About the timeline of solar: https://www1.eere.energy.gov/solar/pdfs/solar_timeline.pdf
U.S. solar capacity data: https://www.energy.gov/eere/solar/solar-energy-united-states
Environmental benefits of solar: https://www.seia.org/initiatives/climate-change#:~:text=Through%20Q2%202020%2C%20the%20U.S.,tons%20of%20carbon%20dioxide%20emissions
Global solar capacity data: https://www.nsenergybusiness.com/features/solar-power-countries-installed-capacity/
TED-Ed: How do solar panels work? https://ed.ted.com/lessons/how-do-solar-panels-work-richard-komp#watch
How to read your electricity bill: https://www.aurorasolar.com/blog/reading-your-electricity-bill-a-beginners-guide/