“Huge win” for solar, with rooftop DC isolators no longer mandatory

In what has been hailed as a big win for the residential solar industry in Australia, the requirement for all installations to include a rooftop DC isolator has been removed, paving the way for less complex installations and potentially making rooftop arrays less vulnerable to faults or fires.

The updated solar installation standard, AS/NZS 5033, largely removes the requirement to install rooftop DC isolators for average residential rooftop systems, in return for a number of alternative measures to ensure the safety of others, including first responders, working around live solar systems.

The mandatory use of rooftop DC isolators – a safety measure to readily isolate the system’s panels in the case of a fault or emergency – has long been a point of contention in the industry.

The requirement is unique to Australia, and was criticised for adding complexity and cost to rooftop solar installations for what many saw as negligible returns on safety – at least in the case of most average-sized grid-connected residential applications.

As James Patterson explained in this article last year – published at the time Patterson was installation compliance specialist for standards at the Clean Energy Council, before leaving to work at Safe Solar Systems – it’s a complicated issue.

“Extra DC connections and additional places for water to seep into enclosures pose a genuine risk. But so does not having a method for non-electricians (such as emergency services personnel) to isolate live cables,” he said.

Nevertheless, after what one insider described as nine months of “torturous” negotiations – and that’s on the isolator issue alone – Standards Australia says it assessed different requirements around the world against Australian conditions, identified achievable safety outcomes, and determined a number of different solutions the industry can choose to best suit their installations.

For those who do not wish to install a rooftop DC isolator, and if the PV array is more than 1.5 metres away from the inverter, installers instead need to build into the design a designated point of disconnection at the array, which can just be simple plug and socket set-up.

Using this approach, installers also need to ensure that when the cables pass through a ceiling cavity, they clear the ceiling by at least 600mm, to avoid posing a hazard to emergency services workers in the case of a fire.

A further requirement, and perhaps the one potential sticking point in the changed rules, is for extra labelling from the installers, which means they have to provide a diagram showing the path of the DC cables through the building, laminate it and fix it to the wall.

Sandy Atkins, who is ex-Clean Energy Council and co-chaired the committee behind the revision of AS/NZS 5033, said solar technology was rapidly changing and the previous version of the standard was now limiting for installation professionals.

“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,” said Atkins.

The Smart Energy Council described the updated installation standard as a “huge win” and the the culmination of many years’ work to remove the “unsafe and unnecessary” isolators in Australia.

“The Smart Energy Council had long argued that rooftop DC isolators are a significant point of weakness in the safety of solar installations,” an email from SEC CEO John Grimes said.

“It was pure madness that Australia was the only jurisdiction in the world that mandated their use. Well from today, not anymore!”

Glen Morris, who chaired the rooftop isolator sub-committee, welcomed the update as “rooftop isolator freedom day,” but also warned that those opting to take advantage of the new standard must comply with all of its requirements, not just remove the isolator on the roof.

(For those interested, Morris is holding an industry crash course for the new standard, through his business SolarQuip.)

The CEC Tech Team said in emailed statement that it was preparing an advice document to assist accredited people in interpreting the changes, while also encouraging feedback to continue improving the standard through future versions.

“Since the dust is still settling from the announcement of the publishing of the standard late last week, there has been a mixed response to the changes inherent in the standard, particularly around Rooftop DC Isolators (RTIs),” the team said.

“Critically, it is important to remember that this is one of many changes inherent in the standard, which aims to provide a higher level of safety, functionality and better align with the technological developments in the solar industry.”

Beyond the loosening of the rules around DC isolators, there are other changes being introduced as part of the 2021 revision to AS/NZS 5033, including around the prevention of water ingress, which Patterson told One Step Off The Grid would prevent more fires than anything else.

The new rules call for either a break in the conduit for the wiring, or a drip release system, which means that should water find its way inside the conduit tubes due to any number of possible aberrations – a crack, an error at installation, condensation due to climate – then that water can spill out before pooling around electrical components like an isolator switch.

Further, the changes to AS/NZS 5033 also align with international standards by doing away with the limitation of 600V for panels for houses, bumping up the maximum PV array voltage for residential systems to 1000V.

Another positive that Morris said was “making everyone smile at the moment” was a revision allowing for installations to have longer strings, and therefore require less paralleling, which again makes for less complicated work for installers.

Meanwhile, new rules for the testing and certification of integrated DC isolators – that is, isolators that are integrated in a solar inverter – are another story entirely. Watch out for that one in tomorrow’s edition.