Australia removes much-criticized DC isolator mandate

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From pv magazine Australia

The Australian solar installation standard AS/NZS 5033 has now been updated, removing the mandate for DC isolators to be installed on household solar systems if other safety measures are followed. The changes will come into effect in six months.

The update comes after much lobbying from various corners of industry who claim DC isolators, intended as a safety measure to disconnect solar system’s panels in case of a fault or emergency, actually made systems more vulnerable to fires and faults. Committee El-042, the group responsible for the rule change, received more than 680 submissions during the public comment stage of the rule change after it closed in June.

DC isolators in Australia

DC isolators were mandated in Australia in 2012 through the Australian Standard for PV installations, AS/NZS 5033. This made Australia the only country in the world requiring rooftop DC isolators. Since then, they have been proven by inspection data to be the largest single source of conventional DC solar system failures. DC isolators have also been criticized for making the solar system’s installation process more complex.

While AS/NZS 5033 recommends owners have their PV system inspected regularly and annually for system components like DC isolators, regular inspections were not required under state and territory electrical safety laws. Another disadvantage of isolator components is that they can degrade from environmental exposure due to specific installation methods and product type, increasing the likelihood of water ingress and ultraviolet radiation damage and, as a result, DC isolators may need to be replaced within the life of the panels of a PV system.

DC isolators have been blamed for many solar-related fires.Image: Safer Solar

Rule changes

Sandy Atkins, who co-chaired the rule change committee, said the decision was made to remove the DC isolator mandate in Australia though because technological changes meant the standard was now limiting for installers. “At the time the 2014 standard was written, solar panels were at most 250W per panel, but technology is quickly changing, and it’s not unusual for panels to be greater than 400W,” Atkins said.

“If you still want to use DC isolators then you can, but if you don’t, the standard allows for other solutions such as disconnection points,” Atkins said.

The committee arrived at its decision after comparing different requirements around the world. In addition to the DC isolator change, it updated several other rule components, including requirements for microinverter installations and DC conditioning units, which it says will enable greater use of technology across larger panels and support better safety outcomes. It also lifted the 600V limit for panels on houses to align with the international standard of 1000V.

A 2020 report from Australia’s Clean Energy Regulator assessing the safety risks associated with rooftop PV has found a significant decline in the number of sub-standard solar systems no greater than 100 kW, with just 1.7% of inspections of 2018 installations classified as unsafe (0.7%) or potentially unsafe (1%). Water ingress in DC isolators was identified as the biggest threat and the most common cause for PV systems to be labeled unsafe.

Safety under fire

Proud as Australia might be about breaking residential solar records year on year, the rise in installations has coincided with an increase in fires. According to statistics from Fire and Rescue NSW, solar PV related fires have increased five-fold in the past five years. Isolation switches have been blamed for causing almost half of solar module fires.

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