PV Solar Safety for Firefighters
What Did You Learn?

You are dispatched to a scene for report of an unknown odor of smoke. You arrive and find an energy storage system with a lithium ion battery burning.

1. What is your agent of choice for extinguishment?

  1. ABC or CO2 extinguisher
  2. Copious amounts of water
  3. Class D extinguisher
  4. Foam

Lithium-ion batteries get intensely hot. Per NFPA and the National Highway Traffic Safety Administration “if the fire involves a lithium-ion battery, it will require large, sustained volumes of water for extinguishment.”

2. All visible fire has been extinguished. What is your next step to leave the scene safe?

  1. Use thermal imaging camera to monitor
  2. Turn the scene over to homeowner
  3. Open the battery to allow air to ventilate
  4. Remove the battery from the wall to cool

In a thermal runaway event, the heat from a failing cell can move to another cell, causing damage before moving to the next cell. This can happen in a few seconds or a few hours. A thermal imaging camera can reveal a slow moving thermal runaway event that would not be discernible otherwise.

It’s 11:00 a.m., and you are dispatched to a partial roof fire at a residence. After you arrive at the scene, you do a 360 walk around and find on the exterior of the home:  an electrical meter and a PV DC disconnect. In the garage you find the main electrical panel and a PV inverter.

3. IC instructs you to secure utilities, including the PV system. Given the information provided, of the choices below, what is the most effective and quickest way to proceed?

  1. Shut off the main breaker in the electrical panel AND any visible disconnects
  2. Shut off just the AC disconnect
  3. Shut off just the DC disconnect
  4. Tarp the array

It is a good rule of thumb to shut off any visible disconnects that can be safely accessed. Doing so decreases the length of the segment of conductor that would otherwise remain energized. This is true for both the AC and DC side of the circuit.

4. The fire is out, and the PV system and utilities have been successfully secured. You are assigned overhaul. Which of the following conditions is most likely?

  1. The system will be energized for at least two hours after shutdown
  2. The system is safe and completely de-energized
  3. Conductors coming from the array into the house could still be energized
  4. AC power is still on in the house

Since this is a string/central inverter system, if there is no rapid disconnecting means installed, there is the potential the conductors from the array could still be energized during daylight hours.

5. The fire is out. The PV system is damaged. How do you leave the scene as safe as possible?

  1. Tarp the solar array to prevent light from reaching it
  2. Contact a PV-qualified person to secure the system and post a fire watch
  3. Remove the modules to ensure overhaul
  4. Wait until night to leave the scene

This is a best practice for any structure fire where a PV system is damaged.

You arrive at the scene of a 2nd floor fire. Walking in and around the house, you see the electrical meter and a disconnect marked with red “AC disconnect”, but you have not found an inverter.

6. Based on your initial 360 walk around, which statement(s) could be true?

1. The house has a string inverter system with DC optimizers
2. The house has a microinverter system
3. The house has a string/central inverter
4. Any of the above could be true

If you have not yet seen a string or central inverter system, it could either mean there is not one (and there is a microinverter or DC optimizer system) or you just haven’t found the string inverter yet!

7. The Homeowner confirms this is a microinverter system. What happens when you secure all utilities?

1. No effect. The array will always be energized in the daytime
2. Conductors are energized from the array down to the main panel
3. The array is de-energized to the module level

This is one of the attributes that makes a microinverter somewhat safer to operate around.

You are dispatched to a reported rooftop fire on a large supermarket. On arrival you witness a black smoke column visible on the A-side coming from the roof area. The 360 is unremarkable and interior crews report negative fire and smoke conditions. Your crew is advised to stretch a line to the roof for extinguishment. You find an active fire involving some of the solar modules on the roof.

8. Using a smooth bore nozzle, what is the closest distance you can attack the fire from?

  1. 5’
  2. 10’
  3. 15’
  4. 20’

Per the UL study reviewed. You can find the study on the course resource page: www.irecusa.org/stepff

9. If you had a combination nozzle, what is the closest distance you can attack the fire from?

  1. 5’, with a minimum 10 degree fog stream
  2. 10’, with a minimum 10 degree fog stream
  3. 15’, with a minimum 10 degree fog stream
  4. 20’, with a minimum 10 degree fog stream

Per the UL study reviewed. You can find the study on the course resource page: www.irecusa.org/stepff

10. The fire is quickly extinguished and contained to the array of origin. There is no interior extension and limited damage to the building is found. Allowing power to remain on in the building would keep the refrigerators running. How could this be accomplished?

  1. Shut off one of the DC disconnects
  2. Secure by shutting off the main breaker in the main electrical panel
  3. Have the utility company cut the power at the street
  4. Isolate the PV system by shutting off the PV AC disconnect

Doing so will disconnect only the PV system without shutting off the main power.