Fire Risk Assessment and Emergency Planning for PV Systems

Fire risk assessment

It is recommended that a fire risk assessment is completed for all PV installations on historic buildings. The assessment should be completed during the initial survey or early design phases of a PV project to identify the following:

• Potential fire hazards
• People and property at risk
• Existing fire safety measures
• Appropriate mitigation measures
• Firefighting strategy
• Main isolation switch to cut off the supply from the system and local isolation where required

The joint RICS Authority and Fire Protection Association (FPA) document RC62: Recommendations for fire safety with PV panel installations provides a useful checklist. 

Mitigation measures

There is limited information about fires from PVs, but most come from DC arcs caused by faulty or poorly connected DC switches. Water ingress into external enclosures is also a known cause. It is essential to include mitigation measures to ensure good fire safety.

The Institution of Engineering Technology IET Code of Practice Grid-Connected Solar Photovoltaic Systems identifies some key measures to mitigate the risk of fires with PV systems:

• Ensure the use and correct selection and sizing of DC overcurrent protection, isolators and switches. In some installations inverters can be fitted with arc fault detection devices to reduce the voltage and current to a safe level
• Wall mounted inverters should be fixed to non-flammable surfaces
• Cable management and routing should ensure that minimal stress and risk of damage is placed on the cabling. Cables that are directly exposed to wind and thermal effects should be avoided and placed in cable containment that will resist the spread of fire
• Avoid burying cables in walls or hidden in fabric elements where cable faults that could lead to a fire are far harder to detect
• All cable connections should be torque tested and verified to prevent arcs from developing. Over time as part of the routine maintenance, these should be checked to ensure they have not become loose
• Use of thermal imaging can be used as part of routine maintenance. This will capture the excessive heat generated by electrical faults before they become a problem. More information can be found on our Thermal Imaging page
• Installation of suitable fire detection equipment to British Standard BS 5839 - 1-6:2019, where a system is installed in a remote or rarely visited location. The type of detector to use is likely to be a smoke, heat or multi-sensor detector. Where the location is infrequently visited, the detector(s) should be interlinked with others located in occupied parts of the building so that any audible or visual alarm is acted upon. Our Fire Alarms for Historic Buildings web page provides general information when installing or upgrading a fire alarm system in a historic building
• Some types of battery, such as lithium-ion, can be subject to something called thermal runaway, which in extreme cases can lead to cell rupture, explosion and fire. However, battery packs have control circuitry that protects against such hazards. Other battery types also have this potential, and care must be taken to ensure that the manufacturer’s installation guidance is followed, and that control circuitry is not damaged or modified. Care must be taken to ensure that the batteries are not damaged, that they are connected correctly, and that they are only connected to approved charge/discharge units
• Many serious fires in historic buildings have been caused by contractors using heat producing equipment. Hot works such as welding, flame cutting and similar activities should be avoided unless there is absolutely no alternative. Our guidance on Fire Safety: Hot Work and Historic Buildings provides further advice

Safe access for emergency services

The design of the PV installation should also consider mitigation measures to ensure it doesn’t hinder the emergency services from dealing with a fire.

The main risks to the emergency services from PV arrays are:

• Electric shock
• Burn injury from energised panels or exposed cabling
• Injury through a roof collapse due to the increased load on the roof
• Slips/falls due to reduced roof space

To mitigate against these risks, the following should be considered when designing a system:

• The provision of additional isolators in a prominent location readily accessible to owners and firefighters to isolate the DC side of the PV system near the panels to ensure the safety of firefighting personnel.
• Signage on the building of the presence of a PV array can be useful as it won’t always be obvious at ground level that there is an array.
• Additional signage and labelling provided at the cut out and metering position.
• For pitched roofs, a border around the array should be kept free of panels to allow ladder access.
• For flat roofs access, a border around the perimeter needs to be kept free of panels to provide access.
• For large arrays access corridors may be required between the panels.
• Panels should be kept away from fire escape routes.

Protection against lightning

When installing a new PV system, consideration must be given to the possible effect of a direct or indirect lightning strike as these can cause fires in PV systems. To ensure the system will be protected, a risk assessment should be undertaken by a suitably qualified specialist. Where required, a professionally designed, installed and maintained lightning protection system should be used.

Our lightning protection guidance provides advice on the design, installation and maintenance of lightning protection systems. The guidance includes briefing on the British Standard European Norm BS EN 62305, risk assessments and what is relevant for historic buildings.