Fire risk

 

 

 

In fires that BRE has been informed of where the PV systems have been the cause of the fire, these fires have generally resulted from poor installation or the use of wrongly specified, incorrect or faulty equipment.  Specifically, there have been reports of installations of AC isolator switches being used mistakenly in DC circuits resulting in a build-up of heat within the switch enclosure and leading to a fire.  Other incidents have resulted from the use of faulty inverters or faulty DC switches or the absence of isolator switches.  Any switching or connection faults on the DC side of a system can result in the generation of a high temperature arc or high resistance fault which could start a fire.  DC arcs can be difficult to extinguish and pose a risk to fire-fighters attempting to suppress the fire.

Current MCS guidance [ref. 5] for the installation of PV systems recognises the potential risks from fire and includes some recommendations for prevention/mitigation of these risks, although further guidance is a topic still under discussion within MCS.  Clearly good design and proper routine testing, servicing and maintenance are essential for risk management.

In the event of a failure of the AC supply to a building, (for example due to a local power cut, or a fire) the inverters are designed to shut down automatically.  However, the solar DC supply (from panels to the DC isolator) will still be live during daylight.  It may therefore still be necessary to manually isolate the DC cables and components from the PV panels which will otherwise remain live.

If a fire damages the DC cables from the PV array, for example by burning off insulation, then there will be risk of electric shock from the exposed DC conductors, in particular to fire-fighters.

Poorly installed panels may obstruct or restrict use of roof windows as means of escape.

Concernshave been raised regarding the presence of heavy metals within some specific types of PV cells, and whether such metals can be or are released during a fire [e.g. ref. 15].  Therefore, while such risks are considered to be low, caution is needed, as with any fire involving electronic elements, in dealing with fire damaged components and residues since a variety of heavy metals and other toxins may be present.

Many PV systems feed energy into the electricity grid at times when it is not required by the building.  Reports are now indicating that, where such a feed in is occurring from a number of distributed sources, this can cause voltage fluctuations in the grid. Fluctuations are known to have the potential to cause fires in sensitive equipment, such as television sets

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