Solar Fire Safety
At HelioPower we apply the fire safety guidelines provided by the California Department of Forestry and Fire Protection. The guideline was developed with safety as the principle objective. The solar industry as been presented with certain limitations in roof installations due to firefighting suppression techniques. The intent of this guideline is to provide information that will aid in the designing, building and installation of solar PV systems that should meet the objectives of both the solar industry and the Fire Service.
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Basic Solar Fire Safety Checklist
1. Is there a single shutdown point for the PV System?
(Yes) Ask for the number of disconnects, AC and DC, required to minimize the total current on the roof.
2. What is the maximum DC Volts___(<50Vdc) and maximum DC Current___(<15A) on the roof during shutdown?
PV Module level shutdown either through DC controls or the use of AC Micro Inverters minimizes the available DC Voltage and Current. These levels can be as low as 1 Vdc and 10 Adc. Without PV Module disconnects, available DC voltages can be as high as 1000Vdc and Current as much as 1,200 Adc.
3. Does the system comply with Cal Fire Rooftop Guidelines or equivalent?
(Yes) Does your local jurisdiction have a set of guidelines for arranging PV Modules on the roof? If so, have your contractor provide an assessment of their layout against the Cal Fire standards. If not, demand a PV Module layout that conforms to that standard. The system size may be reduced but the ability to minimize fire damage will be greatly enhanced.
4. Obtain a sample emergency shutdown instruction placard for the PV system
Execute your due diligence and examine an existing PV installation by your contractor. Examine the point of interconnection look for emergency shutdown labeling. Could you shut down the PV system safely?
Solar Safety Risks Solutions from SolarEdge
PV modules typically have an output voltage of 30-60V. Connecting several of these modules serially in a string creates a high voltage which can be dangerous to installers during system installation. Traditional string inverters cannot reduce this DC voltage even if they are turned off.
Maintenance and Fire Safety
Once modules are connected in a string, the voltage can reach up to 600Vdc (residential and commercial systems) or up to 1000Vdc (commercial systems). Several safety measures can be employed in these cases, but none of them remove the high voltages:
- Shutdown functions in traditional inverters merely interrupt current flow while voltages remain dangerously high.
- Automatic DC breakers located on the inverter cannot disconnect the voltage at the modules (only at the inverter), adding cost without decreasing the risk.
- PV module covering (during firefighting):
- Spray Foam - this approach has proven to be ineffective because the foam evaporates or slides off the modules before the fire is extinguished.
- Covering the module with an opaque material - this approach requires the firefighters to climb onto the burning roof, risking electrocution.
Firefighter Safety and Photovoltaic Installations Research Project
As a result of increased use of PV systems in residential and commercial applications, firefighters and fire safety officials have voiced concerns about the potential risks when PV systems may be part of the fire hazard or the impact on fire department operations. To learn more please visit here.