Fire safety and solar PV

The UK solar industry’s meteoric rise to the top of the European solar totem pole has seen half-a-million homes across the UK fitted with solar panels. But for fire services, that means half a million homes that present a number of different challenges when compared to the average home. The presence of solar panels can fundamentally change a firefighter’s approach to tackling a blaze, irrespective of whether the fire is PV-related or not. 

First and foremost, it is important to put the scale of risk associated with solar-related fires into perspective. As with any electrical appliance, solar panels can present a fire risk – albeit an extremely small one

According to the latest figures from the Office of National Statistics, there were 8,531 accidental fires caused by faulty electrical equipment in 2011-12.  

BRE Global, who the Department for Communities and Local Government (DCLG) charged with solar PV fire investigation activities until 2015, reports that over the last two years it has only been notified of eight incidents involving solar modules which concerned fire and rescue services. 

Ray Noble, director of Solar BIPV, explains that the actual risk of a fire caused by solar PV is “incredibly small”. He stresses that “there are obviously a lot more house fires caused by faulty electrical components (TVs, kettles etc.) than there are from anything to do with solar. Solar is probably less likely to start a fire than other electrical appliances. The way that things are made and the standards that we apply tend to better than some of the cheap electronics you can buy.” 

Andy O’Leary, business development manager at Sibert Solar goes further, stating that there is “zero” risk of fire associated with PV “if the correct installation methods and materials are used”. He adds: “The ‘fine-tuning’ of good-practice/recommendations put forward in documents such as the PV Installation Guide help to mitigate the propensity of fires occurring directly due to a PV installation, but evidence has shown that they can and do happen, particularly where poor product selection has taken place, or where DC string cable termination methods have resulted in series-arcing breaking down, and ultimately setting fire to plastic insulation materials.”

The vast majority of solar fires are a consequence of installer fault – through poor install practices, incorrect equipment or poor products. 

So what can go wrong? 

One of the more common mistakes installers make is erroneously installing an AC isolator on DC circuits. This can lead to an extremely significant build up of heat that can eventually melt the isolator switch and trigger a fire. 

O'Leary explains: “Solar PV installations tend to involve relatively high levels of DC voltage and current during normal operating conditions. Making and breaking DC is not as simple as when dealing with AC as the current is constant/direct and doesn’t oscillate through a zero value point (AC = alternating current/sinusoidal waveform that passes through zero 100 times per second, for 50hz AC supply). Because of this fact, making or breaking DC tends to be done either on-load or off-load. 

“During daylight hours, the PV array is always producing power ‘on-load’ unless the inverter is switched off or the DC output from the PV array is made ‘open-circuit’ thus rendering any current flowing (and therefore, power) effectively to a zero value. When a DC current is passing between two conductive points, if they are separated at all then the DC current will try to maintain its contact with both conductive parts – this is manifested as an ‘arc’. DC arcs can be quite fierce and involve a high degree of energy being emitted as heat and light,” says O’Leary. This can break down insulating materials over time and create a serious fire risk.

Solar from a firefighter’s perspective 

Research commissioned by the DCLG and carried out by BRE on fire safety and solar electric/photovoltaic systems, identifies the major obstacle facing firefighters: “In contrast to the power used by conventional mains electrical equipment, the power that PV systems generate is DC (direct current) and parts of the system cannot be switched off. DC installations have a continuous current, making them more hazardous (volt for volt) than normal AC (alternating current) electrical installations.”  

The issue is that a household’s AC supply can easily be shut off by firefighters, however, the DC current supplied by the solar panels will also be generating as long as the sun is out. 

How a firefighter approaches a house fire in a property with solar installed

According to Kent Fire and Rescue Services

  • Conduct a risk assessment to identify if any solar thermal (ST) of photovoltaic panels (PV) were or likely to be affected by fire
  • Identify the system fitted (we would treat as PV if not clear)
  • Isolate the main consumer unit
  • Identify the location of inverter and isolation switches and isolate
  • Inform personnel about the existence of the system in place and highlight the hazards present (electrical and risk of collapse)
  • Any fires within the inverters would be extinguished with a dry powder extinguishing agent

Additional control measures would be applied when appropriate:

  • Ladder contact with PV systems would be avoided
  • A safety officer would monitor for signs of collapse
  • A cordon would be established below panel arrays
  • Avoid application of firefighting water directly on to the PV array
  • Electrical rated gloves would be used for any contact with components of PV arrays and wiring
  • Consider covering the PV panels to reduce the generation of DC power
  • Seek specialist advice where necessary

Andy O’Leary outlines why the relatively new phenomenon of solar panels in the UK could result in avoidable damage to properties. He says: “Whilst the danger of an actual DC electric shock is considered minimal (certain specific circumstances must be in place for this to be a real danger), the fact remains that, from a risk assessment point of view, the fire service often struggle with the level of uncertainty that the solar PV system can present to them. 

“Firefighters need to consider the additional roof loading of the array, especially when the purlins/rafters etc. are fire-damaged or water-laden. They also need to consider the fact that DC string cables may be running down through the property from a system that, during daylight hours, is producing voltages anywhere between 400VDC to 1000VDC, and currents between 1A and 10A, depending on the nature of the installation and the irradiance present,” says O’Leary.

“Furthermore, solar PV modules are manufactured to include a number of potentially hazardous chemicals and materials which may be released as a side-effect of the fire damage. All of these considerations, and more, can lead to the fire service deciding that the level of risk and uncertainty is too high to justify dealing with the property fire at all – resulting in some instances where properties have been literally left to burn out.”

How can the solar industry help the fire industry? 

In May last year, MCS held a PV installations and fire safety event at the Fire Service College at Moreton-in-Marsh. The event was attended by 20 different fire services as well as a number of solar industry players. 

One of the main concerns raised by the Fire Services in attendance was the absence of fire detection measures in roof spaces – where the vast majority of inverters are installed in residential properties. Responsible solar installers should consider fitting fire detection equipment to accompany any inverter installation in a roof space. 

In addition, the Fire Services present at the meeting expressed concerns over the identification of cable runs in order to protect firefighters when cutting open roofs or ceilings to ventilate and check for fire spread. Another major concern expressed by Fire Services is the use, and siting, of external isolation switches. 

O’Leary echoes these concerns, explaining where he thinks the industry can improve in fire safety: “Several steps have already been taken to advise best-practice installation techniques to solar PV installers. Such recommendations include making sure that string cable connectors being used are suitably certified (TUV/IEC standards apply here in Europe) but, perhaps more importantly, making sure that one connector manufacturer’s plugs are not used with another connector manufacturer’s sockets. Male/female MC4-compatible type connectors for example. 

What’s more, at the moment there is no national database which tells firefighters whether a property has solar panels or not. Writing in Solar Power Portal, Solar Business Focus UK’s sister publication, Canadian Solar’s Greg Spanoudakis explains: “In the absence of any kind of national database of systems, the responsibility falls to the owner of the system to inform the local fire department about the location and type of PV on their buildings, preferably as soon as the system is installed and at the very latest when the emergency call is made. Here, the more information that can be shared with the department regarding the wire routing, setup, isolator switches, inverters and supply stations the better.” 

Asked what the industry could be doing to help, Noble agreed that the industry should be moving towards a more thorough registration system. He says: “I would say that the industry needs to move to a point whereby every person who installs any part of the PV system is fully trained. You can’t fit unless you’ve been on a training course and you’ve been updated on regular refresher courses. The reason for that is that technology is moving on fast. A good, sustainable industry will ensure that everybody that works in solar is fully trained and up to date with the various technologies – that would prevent most of the problems.” 

Summarising, Noble adds that the message to homeowners must be clear: “Solar doesn’t cause fires. My advice to a customer will always be: go to a good quality, reputable installer and you will not have a problem.”