Fighting Fires with Solar Safety

Solar PV systems give firefighters special challenges

With the spread of rooftop solar energy nationwide, there is growing concern about the safety of firefighters when facing a fire in a structure equipped with a photovoltaic ( PV) system. They may be unfamiliar with how a PV system works, what equipment is involved and how to shut it down. While PV panels themselves are not considered a fire hazard, they can only be safely dealt with if the fire service understands the particular hazards they do present, according to Fire Captain Matthew Paiss, a fifteen-year member of the San Jose Fire Department.

Paiss is on a mission to educate firefighters, building code officials and solar contractors about solar electric fire safety by offering seminars and writing articles. In June, CCSE hosted Paiss for two workshops, one at the Energy Resource Center and the other at the City of Chula Vista Police Department, both locations topped with PV systems for attending firefighters to examine.

In his seminar, Captain Paiss focuses on how to recognize the presence of a PV system, identify system components and operate safely around a PV system. He emphasizes the various switches involved in successfully disconnecting systems and how systems are wired.

When firefighters arrive at a burning building, one of the first tasks is to disconnect the utilities to the structure, however doing so does not power down solar PV systems. The PV system inverter, which transforms solar-produced DC ( direct current) power into standard AC (alternating current), can hold a charge and send electricity back up to the solar panels, and the panels themselves will continue to produce power as long as the sun is shining – and even at night when bright lights are present. While utility companies will help firefighters disconnect the service line, they will not assist with solar systems, which are considered an owner-side appliance, Paiss said.

Thankfully, most PV systems are installed with both AC and DC disconnect switches that isolate the inverter from all wires and conduit lines, and many systems have rooftop disconnects as well. Still, Paiss recommends that if it is a daytime fire, firefighters should cover the entire array with a totally opaque material, such as black plastic or a dark canvas tarp. The #1 rule for firefighters: Don’t assume PV system power is off until verified by a qualified person.

Because rooftop PV may not be visible from the ground, one of the best safeguards is labeling, Paiss said. Labels warning that a solar system is present and giving guidance for isolating the system need to be on display at the main electrical service panel and at any disconnect switches. Warning labels also need to be applied at ten-foot intervals along conduits and cables, at junction boxes and above and below places where wires penetrate walls and ceilings.

Most often, firefighting requires working on the roof and cutting vertical ventilation holes for clearing smoke and gasses from inside and for accessing the attic to curtail the fire from spreading. On the roof, PV systems present two main hazards: tripping and electrical shock. Obviously, firefighters need to stay clear of PV panels and conduit lines, which may be obscured by smoke, to avoid tripping. But they also need to be forewarned about standing on PV panels that can be extremely slick when wet and that still may be energized, even if damaged. As for ventilation, the key is to cut based on fire and building conditions, but to penetrate as shallow as possible to avoid cutting into PV conduit that may run along the rafters. A conscientious installer will put conduit along the bottom of a framing piece, but it’s also likely wires will be suspended between spaces.

“As always, the fire service must stay on top of new technology and adapt to new developments in building and vehicle materials while maintaining safety and effectiveness,” Paiss said. “Determining the presence of a PV system is the key to understanding these systems and not getting hurt. There is a much greater risk to firefighters from the line voltages that come into every structure than from PV systems.”

Further Reading:
Solar Photovoltaic Installation Guideline, established by the California Department of Forestry and Fire Protection, fire departments and the solar photovoltaic industry in 2008.
Solar Electric Systems and Firefighter Safety, an article by Paiss at the FDIC Fire Engineering website.

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