Residential solar panel fire attack: Your questions answered

Tackling questions from the FireRescue1 community about how to best prepare for fires involving this increasingly common technology


View the on-demand webinar “Energy exposures: Simple steps for residential solar panel, ESS fire attack,” presented by Captain Richard Birt. 

With increasing frequency, firefighters across the country are finding themselves on the scene of residential structure fires involving solar panels or energy storage systems (ESS) – and unsure of the appropriate tactic to employ based on the fire exposure, location of the panels and other factors. This must change. It is essential that firefighters understand the basic strategies and tactics needed to mitigate such fires, as their numbers are only growing.

Some of the key things to understand:

  • Residential solar and battery storage equipment fundamentals
  • Industry-standard installation procedures
  • Suppression and ventilation tactics
  • How to design an incident action plan to safely respond to these technologies
It is essential that firefighters understand the basic strategies and tactics needed to mitigate fires involving solar panels or energy storage systems (ESS), as their numbers are only growing.
It is essential that firefighters understand the basic strategies and tactics needed to mitigate fires involving solar panels or energy storage systems (ESS), as their numbers are only growing. (Photo/Getty Images)

We covered this in the webinar “Energy exposures: Simple steps for residential solar panel, ESS fire attack.” However, the webinar also prompted several important questions from FireRescue1 community members. We’ll answer those questions here.

Question: Is the ID placard only on codes moving forward or more current, or should it be on any solar panel system?

The placard code has been around for many years. The difference with the new code is that all the shutoffs have to be outside. The identification placard has been around even on legacy systems, but going forward, there should be a placard and all the control shut-offs on the outside.

Do tower lights from the apparatus at night energize the panels?

The UL testing that has been done with panels shows that they have become so efficient that there is voltage at night, and it does come from different sources like apparatus lights. I was teaching initially that there was no voltage at night, but with the newer panels, there is basically a voltage that we have to be aware of and that’s why I’m teaching “do not touch the panels, day or night.”

Do you ever use foam? How about on commercial solar fields?

Foam is not recommended because it’s not really doing anything. Foam is designed to change the surface tension of water, basically making the water wetter, so it can actually penetrate, whereas what we’ve found with solar panels and with the battery cold water is what you need to extinguish the fire and then cool it down with a battery. With a solar panel, you just need to extinguish the fire. So, if you’re just fighting a fire that involves solar panels and nothing else, you’ve got metal, glass and plastic – foam’s not going to help. If you’re fighting a fire on a roof with shingles, wood is involved, I encourage to use foam initially, but when it comes to just fighting a fire with solar panels, you don’t need foam or batteries.

How long after the panels are covered will they be de-energized?

Basically, what I want the fire service to do is this: At any incident involving panels, they should be covered by black, at least 3-mm thick Visqueen. Do not use the blue tarps because they bleed light through them, and do not use your expensive canvas tops because you would want them back. So, the plastic is the cheapest and easiest way to deactivate a panel. And when I say deactivate, as soon as you cover a panel, it turns off; it’s like a light switch. The panels aren’t capacitors, and they don’t store electricity. They turn immediately off.

What if there is no exterior power shutoff? It has been my experience that some residential control systems are inside of an attached garage.

The legacy systems have shutoffs in the garage, whether it’s the inverter or the AC or DC disconnect. What I’m teaching is if you need to make entry to shut those off, make sure you ventilate if you think the battery, if it’s stored in the garage, has been exposed to anything above 200 degrees F. Then be aggressive with ventilation, then make entry to shut everything off. It’s a bit like vent, enter, isolate and search.

Related to the removal of batteries, have you had any experience with a utility company removing the battery?

On the removal of the battery, the utility companies, I’m not going to do it unless they install it. And, my experience is that the utilities do not install the batteries, so it would be the solar contractor or a solar electrician that will remove the battery.

[View the on-demand webinar “Energy exposures: Simple steps for residential solar panel, ESS fire attack,” presented by Captain Richard Birt.]

If used as a backup, how long will batteries maintain during a power outage, like during severe weather?

It depends on the size of the battery system, and it depends on cost. How much does a person want to spend on backup? You can have one battery, which can last, depending on your circuits, up to four to six hours. And you can have a whole residential system backup where you may have two, three, four batteries. So, depending on what you want to spend, you go from partial backup to full backup and everything in between.

Do solar panels increase the fire load on a roof, and how does that affect its structural integrity during a fire?

First, if panels are on the roof and they’re involved in the fire, structurally, is it going to affect the roof? Second, is there a large fire load with the panel itself? Those two questions are together because if you have involvement on a roof with panels and that structure of the roof is involved, then we would use defensive tactics anyway, especially on lightweight construction. So, from that point, the panels don’t really have a load because the actual trusses are involved. The other part of this is this: Can they burn and can they add fuel to a fire? And yes, there are a lot of things on the panel itself that can burn and can add to the load of the fire.

Can you speak to snow load on panels or roofs particularly in the northeast?

The average panel is 4x5 feet – around those dimensions – and we’re averaging around 50-55 pounds, so this isn’t a concentrated load. If you take the weight per square inch, it’s a very distributed load. With the trusses, number one, the building has to be inspected with the trusses and the weight load of the truss before they put solar panels on. Number two, they build into lightweight trusses and new construction; they’re built-in 30-40%, especially areas with heavy snow load. So, we’re finding that it’s not a significant amount, and that the roof is inspected with the trusses before they’re installed. So if there is damage to a roof, the assessment is that it has to be inspected first because these panels are designed to last 30 years.

What is the difference in the number of panels between residential to commercial? I have residential panels that go to the grid and no energy storage on site.

With legacy panels, which are on a home that doesn’t have storage and is directly connected to the grid, when you shut down the grid with no storage, you’re shutting down the panel system as to feeding the home. You’re basically shutting their utility, which shuts down the inverter because it relies on a signal. You haven’t shut the panels off. What you’ve done is you’ve interrupted the flow into the house on a residential system.

Some of these homes are 10,000 square feet, so a 20,000-square-foot home could be considered “small commercial.” The difference that we have to look at in the fire service is how those systems are broken down and accessed. A residential structure, even if it’s 20,000 square feet – a larger home – the way the system is built is different than a commercial system. What the structure is used for dictates how the energy is produced, stored and used.

In the fire service, when we pull up on a building, it’s very important to know what that building is used for because our strategies and tactics change all the time. Size really doesn’t have a lot to do with it most of the time. If we know it’s a residential structure at 3 a.m., but it’s a large structure, perhaps the size of a small, commercial building, then we know that there is life safety involved. But, if we turn up at 3 a.m. on a dry cleaners, we know it’s a dry cleaners. It’s very important that that part of it we know why it’s being used.

Same with solar. What are we doing with a residential? Why is it different from a Walmart? First, a Walmat is not broken down into walls and bedrooms and bathrooms. It’s just a massive space. For the solar panels on the roof, there could be 1,000 of them. With residential, you know the roof is not just one, big flat roof or one large area. It’s going to be broken down into different systems. We must use our knowledge of those two building types and why they are used and how that applies to solar.

Can you talk about solar farms on commercial building roofs over 500 feet, tied to the grid on lightweight trusses?

The key for a commercial building – again, let’s say a Walmart that has 1,000 panels on its roof – is that the ventilation tactics are going to have to change. On a vent operation on a commercial structure that big, it’s usually a trench cut. With panels on a roof, and the amount of voltage from a large commercial system, we don’t have room to cut on the roof. We have to go to horizontal ventilation. We have to use different strategies and tactics. So, with lightweight construction, a commercial building with a large number of panels, we use either a defensive measure or we use horizontal ventilation.

Can fire alarm control panel (FACP) detectors be installed inside the inverter or battery cases for a heads-up on life safety systems to catch it before there’s a problem?

The fire alarm control panel is not really relevant to a battery system. Imagine you go into a Walmart and you go find a panel and see which circuit is being indicated as the alarm set-off. I think the biggest thing that you could educate the fire services on is the new code of the heat detection being mandatory for newer battery installs, and the legacy we should ventilate, ventilate, ventilate.  

Next: View the on-demand webinar “Energy exposures: Simple steps for residential solar panel, ESS fire attack,” presented by Captain Richard Birt. 

Editor’s note: What questions do you still have about mitigating residential structure fires that have ESS or solar panels? Fill out the form below, and we’ll do our best to add your question to the list with an answer from the captain.

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