6-34 Solar photovoltaic systems
A photovoltaic (PV) installation typically includes:
- arrays of solar panels: since a single PV panel can only produce a limited amount of power, a typical PV system installation contains several panels connected together to form an array
- one or more inverters, which convert power from direct current generated by the array to alternating current
- interconnecting wiring
PV systems are used for either on or off grid applications.
In the event of a fire, shutting down the electricity in a building with a PV system is more complicated than in a building without one because the system is energized from two sources – the utility and the PV system.
Actions for employers
- make workers aware of the hazards of a PV system
- develop procedures for working safely with PV systems
Disconnecting the photovoltaic system
Employers should consider the following information when developing procedures for working safely with PV systems:
The PV system can be isolated from the rest of the building’s wiring system by shutting down the “Utility Disconnect” of the PV system in addition to the main electrical switch. These system disconnections are usually located near the meter, main electrical panel, PV system inverter and/or on the rooftop.
The Ontario Electrical Safety Code requires the clear marking and labelling of the electrical system equipment, indicating the system is fed from more than one source.
This is an example of the information that may be found on a label:
Photovoltaic System Utility Disconnect Switch
Warning – Electrical shock hazard – do not touch terminals – terminals in both the line and the load sides may be energized in the off position.
Hazard of electric shock, explosion or arc flash.
The solar PV system cannot simply be switched off. Shutting down the PV’s “Utility Disconnect” switch, inverter and the main electrical switch will disconnect the array from the building and/or the grid. However, the PV panels and other apparatus connected from the solar panels to the inverter will always remain energized as long as they are exposed to a source of light. They should be treated as live electrical equipment.
Employers should consider these unique safety concerns when developing procedures for working safely with PV installations.
Electric shock is the primary hazard for firefighters. An array of multiple panels can produce direct current and voltages above 600 volts. Firefighters may come in contact with damaged panels or energized exposed wiring during firefighting or ventilation operations.
Battery storage areas are another potential source of electric shock.
A PV system generates direct current. An arcing fault from direct current is more intense and sustained than that from alternating current. An arcing fault is a high power discharge that could result from the unexpected contact of electrical components. In addition, the value of arcing fault current may be too low for the required circuit protective devices to operate. This creates additional fire hazards unique to these systems.
Solar PV systems add additional weight to the roof of a building, which may pose a structural concern. This may require alternative ventilation tactics, particularly where roof joists have been compromised by fire.
Power cables and PV panels pose trip and slip hazards for roof operations.
PV panels exposed to fire can produce toxic and carcinogenic combustion products. Battery storage areas can generate corrosive/explosive gases when exposed to fire.
Fire fighting safety precautions
When developing procedures for dealing with fires in buildings with solar PV systems, employers should consider the following:
- assume the solar PV array is energized at all times
- inform the incident commander immediately upon identifying the presence of a solar PV system
- remember that securing the main electrical panel, inverter and PV’s “Utility Disconnect” switch will not shut down the solar PV system—when exposed to sufficient light, electricity will continue to be generated by the PV system
- stay away from the panels and conduit
- do not cut into, remove, or walk on the solar PV system
- wear appropriate personal protective equipment including self-contained breathing apparatus
- contact the local utility provider to assist with cutting power sources
- fight the fire based on flow, pattern and distances as recommended in the Electrical safety handbook for emergency responders – Best Practices for Coping With Electrical Hazards in Rescue and Fire Situations, revised 5th edition, 2013
Note: At night, moonlight or apparatus-mounted scene lighting may still produce enough light to generate electricity from the arrays. Lightning strikes can also be bright enough to create an electrical surge in the system.
Applicable regulations and acts
- Occupational Health and Safety Act
- clause 25(2)(a) for providing information and instruction to a worker
- clause 25(2)(d) for making workers aware of hazards
- clause 25(2)(h) for taking every precaution reasonable in the circumstances to protect workers
Read the Electrical safety handbook for emergency responders – Best practices for coping with electrical hazards in rescue and fire situations, Hydro One Networks Inc., Electrical Safety Authority, Office of the Fire Marshal, and Public Services Health and Safety Association, revised 5th Edition, 2013.
For requirements for electrical work in Ontario, read the Ontario Electrical Safety Code
Read firefighter guidance note 6-20 Electrical hazards in rescue and fire situations