Solar system fires have been blamed on inferior design, low-quality components, poor installation or all three of these factors.
The hub of the issue is that the systems which fail are designed to operate at up to 1000 volts DC, which is inherently dangerous.
Any fault on a high voltage DC circuit can result in a dangerous DC arc.
DC arcs are the root cause of all solar system fires.
The DC wiring in conventional (string) solar systems runs under the solar panels on the roof down to the inverter. The circuit in a typical 4kW DC solar system has about 30 separate connections. Each of these is a potential point of failure. A 100kW system could have 350 potential failure points.
A DC arc fault occurs when there is a flow of electrical energy through an air gap in the wiring. Although air is regarded as a poor conductor, a high potential (voltage) difference between contact points in close proximity can cause the air molecules to break down and carry a charge. The arc fault and resultant fire is intense, generating enough heat to melt copper, which has a melting point of 1085°C.
Poor installation can be a factor but there are many possible causes of a DC arc fault irrespective of the quality of the installation. The two main causes are compromised insulation on one or both of the DC cables or, a connection in the DC circuit is compromised.
Possible contributors to a DC arc fault include loose connections, corrosion, water ingress, animals (insects, rats, possums, birds) damaging cables, extreme weather events, accidental (crawling through a roof space, drilling through a wall to hang a picture) damage, intentional damage or vandalism, failure of plastic fitting and enclosures and moisture build-up within sealed components.
There is no way to eliminate all the potential causes of DC arc faults in a DC solar system as it is the operating voltage itself that creates the risk.
As the system ages, faults will inevitably occur, and when they do, dangerous situations leading to DC arc faults can occur.
AC Solar systems (that incorporate microinverters) and some DC optimised systems eliminate or minimise the fire and safety risks associated with DC arcs.
Information about safer solar technologies can be found here.
Microinverter and some DC optimised solar systems are immune to DC arc faults and are therefore as safe as other electrical wiring running through your house or business.
If you have a conventional DC solar system installed it will almost certainly have unprotected DC cabling running from the solar panels on the roof down to the inverter. The string inverter is normally mounted on the wall adjacent to the main switchboard.
A fault of any sort on this DC circuit has the potential to result in a fire.
It is strongly recommended that conventional DC Solar systems are inspected by a CEC accredited solar installer every 12 months. However, even having the system regularly inspected will not eliminate the risk of DC arc faults, which can be caused by a wide variety of factors that can occur at any time. For example, a DC arc fault can occur simply by a rodent biting through the cable insulation, water entering any part of the circuitry, or corrosion at any of the various DC cable connections.
There are three types of solar systems commonly available in Australia: conventional DC solar systems, DC optimised systems, and microinverter-based systems.
The type of system is determined by the type of inverters that have been installed.
Conventional DC solar systems generally have a large inverter and several electrical switches mounted on the wall adjacent to the main switchboard.
DC optimised systems are similar to conventional DC systems, however a DC optimiser is also installed under each solar module.
Microinverters systems do not have a large wall mounted inverter as the inverters are located under each solar module.
The best way to establish the type of solar power system you have installed is to consult with the company that supplied the system or to seek advice from a CEC (Clean Energy Council) accredited solar installer.
Yes, safer solar technologies are readily available and can be retrofitted to existing DC solar systems to eliminate the risk of DC arc faults.
This involves replacing your existing string inverter with either microinverters or a DC optimised system. It is not normally necessary to replace the solar modules themselves – just the inverter.
Contact a CEC accredited solar installer or click here to lodge an enquiry and we will arrange for a suitably qualified installer to contact you.
Solar panels are connected in series to create long “strings”. Each string of panels is connected to an inverter which transforms the DC electricity produced by the panels into appliance-friendly AC electricity.
The facts around fires started by DC solar systems speak for themselves.
Some solar installers do not wish to risk losing a sale by acknowledging the risks involved with conventional DC solar systems.
We recommend you ask your installer about safer solar technologies (microinverters and DC optimisers). If the installer doesn’t offer these options then we strongly suggest you seek quotes from alternative suppliers who understand the risks and the full range of technologies available.
Yes, in the same way that seatbelts and airbags add to the cost of cars, safe solar technologies cost more than cheap DC solar systems.
There are other benefits of safe solar systems that justify the additional cost, including higher energy yield and greater overall reliability.
The Clean Energy Council and various Electrical Safety offices in Australia recommend regular inspections of solar systems to reduce the risk of a fault.
However, while inspections can reduce the likelihood of a DC arc fault an inspection cannot prevent DC arc faults. An inspection can only pick up obvious faults, it cannot prevent rodents biting through the cable insulation or water entering any part of the circuitry or simply detecting corrosion of any of the various DC cable joints – all of which can cause a solar fire.
If you have moved into a new home or business premises with rooftop solar, or you are unsure, have it inspected immediately to determine what type of solar system you have and whether there are any obvious safety risks.
Call your fire and emergency service immediately.
You should also notify your electrician or the company that installed the solar system and request them to attend and make the system safe.
No, around 70 percent of all solar systems installed in Australia still use conventional DC solar technology, though safe solar technologies are growing in popularity as the risks associated with DC solar systems become more widely understood.
Current Australian standards do not prevent solar companies installing conventional DC solar systems with unprotected DC cabling.
These systems are common because the components cost less to buy compared with DC solar systems with DC optimisers or AC Solar systems.
In other countries around the world, standards are already changing to prevent the installation of these systems and it is likely that over time, Australian standards will also change to require safer solar technologies, that eliminate DC arc faults, to be used in all systems.
In the meantime, it is a case of buyer beware.
Some insurance policies do not provide protection against fires caused by DC solar systems. This means that the damage to your solar system or your house/business may not be covered.
You should consult with your insurance provider on whether your policy covers damage to your solar system and property as a result of a solar fire.