How the Automatic Shut Off Switch Works

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Solar Inverter's Automatic Shut Off Switch

When people think of installing solar, they envision complete independence from the grid. However, this is usually the exception of solar installation,s not the rule.

Since solar arrays themselves aren’t able to store energy, other options need exploring. Battery backup would be ideal, but for many, whole-home energy storage isn’t a financial option.  This is why most individuals that get solar are still connected to the grid.

Staying connected to the grid allows customers to send excess energy back on to the grid and extract it from the grid when solar panels can’t cover all the necessary production of electricity themselves. However, when the power grid is down everything connected to it doesn’t stay turned on.

Solar Power During an Outage

It would make sense for a solar array to continue running during a daytime power outage. However, this isn’t what happens, and for good reason. It is against metropolitan and municipal fire code for solar systems connected to the grid to stay turned on when the grid is down, which demands the need for a rapid shut down mechanism in solar panels.

Rapid Shutdown Requirements

This requirement is called a rapid shutdown. It shuts down the solar array as soon as it detects that the grid in the area is down.

Rapid shut down stops power from going onto the grid. This helps prevent linemen from getting hurt while trying to fix power-line issues. The problem is that rapid shutdown also shuts off power to the house.

Rapid Shutdown Solutions

The rapid shutdown switch is normally on the inverter. Go Solar Group has used the SolarEdge inverter and SMA Sunnyboy inverter.

Rapid Shutdown: SolarEdge

The SolarEdge is a commonly used solar inverter. It will also disconnect from the solar modules if it detects that the grid is down.

However, if it needs to be manually turned off for any reason, there is a mechanism to allow that. Start off by turning the inverter on/off switch at the bottom to the off position.

Once the voltage has gone down below 50 volts of direct current (DC) turn off the DC safety switch. Once this is completed the alternating current (AC) can be turned off.

SMA Rapid Shutdown

The SMA has an easy-to-use rapid shutdown switch. However, it is for fire department use. If it is accidentally turned off, it can be turned back on with the key that comes with the inverter.

If the power goes down, the rapid shutdown will disconnect the home and grid from the solar panels. If the SMA’s Secure Power Supply (SPS) is also installed, it will allow solar to power some essentials during an outage.

The SPS is an outlet connected directly to solar panels. It allows individuals to use solar power during an outage without any of the power leaking onto the grid. If a visual is helpful, Go Solar Group also has a tutorial on how to use the SMA inverter.

Rapid Shutdown Requirements Effective January 2019

As of January 2019, the requirements for rapid shutdown received an update. It is now a requirement to adhere to NEC 2017 instead of NEC 2014. This new regulation requires a module-level shutdown.

All conductors within a foot of an array now have to reduce to 80 volts in fewer than 30 seconds. This is to increase the safety of firefighters should they have to enter a home through the roof.

New Requirements’ Effect on Future Inverter Shut Off Switch

Before this change was put into effect, inverters could cut off power at the inverter. The solar panels, however, were still creating a current.

Inverter companies, such as SolarEdge, are updating their products to decrease potential risk. This, however, makes it more difficult to power a home during an outage.

Future Power in an Emergency

Home backup batteries can avert this crisis. They allow individuals to store power for later. This means that although the power may be out in the neighborhood, it doesn’t have to be out in the home with solar.

Go Solar Group has several affordable backup solutions.  These batteries and other backup solutions give individuals the ability to choose how much backup they can afford.

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