Why Does Your Solar Panel Frame Need to Be Earthed in Sydney?

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Why does your solar panel frame need to be earthed in Sydney? AS/NZS 5033 requires the exposed metal frames and mounting structures of a solar array to be earthed once the array's DC circuit voltage rises above 35 volts, which covers almost every grid connected home or business system. This turns an otherwise ungrounded metal frame into a safe part of the installation if a fault ever develops inside a panel or its wiring.

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1. Why 35 volts is the line that matters

AS/NZS 5033 draws a clear line at 35 volts. Where the calculated maximum voltage of the PV DC circuit is greater than 35 volts, specific exposed conductive parts of the array must be earthed. Almost no residential or commercial grid connected string stays below that figure once more than a couple of panels are wired in series, so in practice this requirement applies to nearly every rooftop solar installation across Sydney, not just large commercial arrays.

2. What exactly has to be earthed

The standard is specific about which parts qualify. All conductive PV module frames must be earthed, along with array mounting frames that are in direct contact with the PV DC cables, and any conductive cable support systems or wiring enclosures that are also in direct contact with those cables. Cabling run inside an insulating enclosure, such as insulated conduit, is not deemed to be in direct contact and does not trigger the same requirement on its own. Where the system is connected to a supply arrangement without an earth reference, such as some independent pumping setups, the exposed conductive parts of the associated equipment must also be equipotentially bonded.

3. Approved earthing and bonding methods

AS/NZS 5033 sets out three accepted ways to make an earthing or bonding connection to a PV array frame. A purpose made fitting designed for earthing or bonding between dissimilar metals, installed to the manufacturer's instructions, is one option, provided the fitting actually suits stranded cable or is paired with a small copper plate where it does not. Purpose made washers with serrations or teeth that bite into the surface are another, installed at every connection point between module and mounting frame. The third is a tinned cable lug fixed with stainless steel bolts, flat washers and star washers onto the aluminium frame. Whichever method is used, the connection has to be protected against corrosion, which matters on a Sydney roof exposed to salt air in coastal suburbs as much as it does anywhere inland.

4. The self tapping screw and rivet ban

One rule in this clause leaves no room for interpretation: self tapping screws and rivets must never be used to make an earth connection to a PV array framework. They are common, cheap and fast to install, which is exactly why they turn up on lower quality jobs, but they do not maintain a reliable, low resistance electrical connection on aluminium framing over years of thermal expansion, vibration and weather. An earthing connection that degrades silently behind a panel is one of the harder solar defects to pick up without a proper electrical safety inspection, since the array can keep generating power with no obvious symptom while the earthing path quietly fails.

5. Minimum earth conductor size

The earth conductor running to the array has a hard floor: 4 square millimetres is the absolute minimum permitted under AS/NZS 5033, regardless of how small the system is. The actual size required for a given installation is worked out from the standard's own sizing chart, which takes into account factors specific to the system rather than applying one number to every roof. A conductor sized correctly at installation but later extended or modified without reference back to that chart is a common way systems drift out of compliance over the years.

6. Functionally earthed arrays and the earth fault interrupter

Some solar technologies deliberately earth one side of the DC circuit as part of how the inverter works, known as a functionally earthed array. Where that design is used, AS/NZS 5033 requires a dedicated earth fault interrupter, a device that trips the circuit if current starts leaking to earth through a developing fault rather than waiting for a more serious failure. This is a different protective function from the general frame earthing covered above, and it only applies to systems actually designed this way, so it is worth confirming with your solar installer which earthing arrangement your inverter uses before assuming one protection covers the other.

7. The earth fault alarm for inverters without isolation

Inverters that do not provide their own internal isolation between the DC and AC sides of the system are required to have an earth fault alarm, a visual or audible signal that keeps alerting until someone actually fixes the fault, rather than a single notification that can be missed or ignored. This is a genuinely useful early warning in practice, since a developing DC earth fault can otherwise sit undetected inside a roof space for a long time. Anyone hearing an unexplained beeping or seeing a persistent warning light from their inverter should treat it as exactly that kind of signal rather than something to silence and investigate later.

Why it's Level 2 ASP work

Solar array earthing itself is CEC accredited and licensed electrical work rather than exclusively Level 2 ASP territory, but it becomes part of a Level 2 job whenever a solar connection coincides with other network side work, such as a smart meter upgrade or a change to the point of supply that a new or expanded system needs to proceed.

How High Demand Electrical helps

High Demand Electrical checks array earthing as a standard part of every solar related inspection and defect rectification, not an afterthought bolted onto panel cleaning or performance checks. A licensed local team, not a call centre, we service homes and businesses across Sydney's West, South West and Sutherland Shire, and we routinely find frame earthing issues on systems installed years ago to a lower standard than AS/NZS 5033 now requires. If your array shares a roof or a switchboard with other electrical work, HD Power Pole's guide to solar and lightning protection for a private power pole property covers the separate question of surge and lightning risk alongside this one.

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