Why Does Your Sydney Solar System Need Two DC Isolators?

Why does your solar system have two separate DC isolator switches instead of just one? AS/NZS 5033 sets out isolation requirements at both ends of the solar circuit, one disconnection method at the PV array itself and a separate load break disconnection device at the power conversion equipment, meaning the inverter or the gear right beside it. The two points work together so a technician can isolate the system safely from either end, and in a limited set of circumstances the standard actually allows the rooftop switch to be left out altogether.

⚡ Quick Answers: Solar DC Isolators

• What are the two isolation points in a solar system? One disconnection method at the PV array, up near the panels, and a separate load break disconnection device at the power conversion equipment, which is the inverter or the switchboard area beside it.
• Can my installer leave out the rooftop isolator? Yes, but only where the panels sit within 1.5 metres of the inverter, the circuit stays under 120 volts, and a compliant disconnection device is fitted right at the panels instead.
• Why do I need an isolator at the inverter as well? AS/NZS 5033 requires a load break disconnection device at the power conversion equipment so the DC circuit can be broken safely while current is still flowing, not just opened once everything is already switched off.
• Does having more than two strings of panels change anything? It can. The standard uses a decision tree based on how many strings you have, whether each one is individually fused, and where they are joined together, to work out if an additional load break disconnector is required.
• Does switching both isolators off make the whole system dead? No. The panels keep generating electricity in daylight, so the wiring between the panels and the first isolation point can still carry voltage even with everything switched off downstream.
• Who checks all of this has been wired and labelled correctly? A Level 2 ASP or a CEC accredited solar installer, typically as part of a proper electrical safety inspection of the system.

1. The array side isolator: breaking the circuit at the panels

Where the calculated maximum voltage of your PV circuit goes above 120 volts, AS/NZS 5033 requires a disconnection point right at the array, positioned so it sits adjacent to the modules, stays readily available, and is protected against weather within 150mm of the edge of the panels it serves. This is the switch most homeowners picture when they think of a solar isolator, sitting in a weatherproof enclosure near the roofline.

Instead of a simple disconnection point, an installer can fit a load break disconnection device directly at the array, and in that case a separate switch at every individual string is not required. Either way, the positive and negative conductors are isolated together, never as two unrelated switches that could be opened independently, and the whole point must be clearly labelled so the next person who sees it understands exactly what it does.

2. The power conversion equipment isolator: the second break point

The second isolation point sits at what the standard calls the power conversion equipment, which in a typical Sydney home is simply the inverter. AS/NZS 5033 requires a load break disconnection device here too, capable of breaking the DC circuit safely under load rather than only when current has already stopped flowing.

This requirement can be met in one of two ways: a physically separate load break switch installed next to the inverter, or a load break device built into the inverter itself, provided both the device and the inverter conform to the requirements covered in our guide to AS 4777.2 inverter settings. Grid connect inverters themselves must be installed in line with AS/NZS 4777.1, which is part of why solar wiring sits so firmly in licensed electrician territory rather than being a project for a handy homeowner.

3. When the rooftop isolator can be left out

Before the 2021 update to the standard, a visible rooftop DC isolator was close to universal on Sydney homes, and weathered, UV damaged isolators went on to become one of the more common causes of solar related fires. The current standard responds to that by allowing a narrower exception rather than a blanket switch at every array.

A separate array side disconnection device is not required where the calculated circuit voltage is under 120 volts, the panels sit within 1.5 metres of the inverter, and the panels are connected directly to a disconnection device that meets the standard. Outside of those specific conditions, the general isolation requirements apply in full, so a missing rooftop switch is not automatically a compliance shortcut, and it is exactly the kind of detail an electrical safety inspection should confirm rather than assume.

4. Why more than two strings of panels changes the isolation requirement

A single string of panels wired straight to the inverter is the simplest case, but plenty of Sydney roofs run two or more parallel strings to make better use of available space and orientation. Once you go past two parallel strings, AS/NZS 5033 uses a decision tree to work out whether an additional load break disconnector is needed on top of the array side and power conversion equipment isolators already covered above.

The answer depends on three things: how many strings are paralleled, whether every string carries its own fuse, and whether the strings are joined together right at the load break disconnector near the inverter. Get any of those wrong and you can end up with a system that looks compliant from the ground but cannot actually be isolated the way the standard requires in an emergency, which is precisely the kind of fault that turns up during a thorough electrical safety inspection, covered in more detail in our solar signage and labelling guide.

5. What this means if you are buying, selling or upgrading a solar system

If you are about to buy a property with solar already installed, or you are adding batteries or extra panels to an existing array, the isolation setup is one of the first things worth having checked rather than assumed. An older system fitted before 2021 almost certainly has a rooftop isolator, while a newer one may rely on the narrower exception instead, and neither approach is automatically wrong on its own.

What matters is whether the actual wiring matches one of the compliant configurations the standard allows, whether every disconnection point is labelled correctly, and whether the power conversion equipment side has its own proper load break device rather than relying on the array side switch alone. A smart meter upgrade or any work that touches your switchboard is also a sensible moment to have the isolation arrangement reviewed at the same time, since the switchboard and the solar isolation points usually sit close together.

Why it's Level 2 ASP work

Deciding which isolation method applies, sizing a load break disconnector correctly, and working out whether an extra disconnector is needed for multiple strings all call for a genuine reading of AS/NZS 5033 and AS/NZS 4777.2 together, not a guess based on what the last job looked like. Where that isolation work intersects with your point of supply or your main switchboard, it also needs the kind of authority a Level 2 electrician holds, well beyond the scope of general household wiring. High Demand Electrical treats solar isolation with the same discipline we bring to switchboard upgrades and disconnect and reconnect services, because getting it wrong leaves a system that cannot be made safe quickly if something goes wrong.

How High Demand Electrical helps

High Demand Electrical is a licensed local team, not a call centre, and we check solar isolation setups as a standard part of every electrical safety inspection we carry out across Sydney's West, South West and Sutherland Shire. If your system was installed years ago and you are not sure whether it still meets current isolation and labelling rules, or you are adding panels and need the existing array side and inverter side isolators reassessed, our team can walk you through exactly what is fitted and what, if anything, needs to change.

We also handle the switchboard side of solar work directly, including the kind of switchboard upgrades that often go hand in hand with adding a second string of panels or a battery. If you are weighing up a full isolator overhaul against simpler repairs, our guide to DC isolators and solar safety switches covers the basics, and our guide to solar DC cable wiring rules explains the wiring requirements that go alongside every isolation point.

Solar DC Isolator FAQs (Sydney)

Do I need a visible switch on my roof for my solar to be compliant?

Not always. AS/NZS 5033 allows the rooftop disconnection device to be left out where your panels are within 1.5 metres of the inverter, the circuit stays under 120 volts, and a compliant disconnection device is fitted right at the panels instead. See our electrical safety inspection service if you want this confirmed for your own system.

What is the difference between the array isolator and the inverter isolator?

The array isolator disconnects the circuit up near the panels, while the load break disconnection device at the power conversion equipment, usually the inverter, breaks the DC circuit safely at the other end, under load rather than only once current has stopped. AS/NZS 5033 requires both points to be addressed, whether through separate switches or a device built into the inverter itself.

Can I switch my solar off myself if I need to work near the switchboard?

You can operate a correctly labelled isolator yourself, but switching it off does not make the panels or the cabling between them and the isolator safe to touch, since the panels keep generating in daylight. For anything beyond simply turning a switch, call a licensed electrician rather than opening covers or working on the wiring yourself. See our disconnect and reconnect services for jobs that need the supply isolated properly first.

Why does my system have more than two load break disconnectors?

Once a solar array runs more than two parallel strings, AS/NZS 5033 uses a decision tree based on string count, fusing and where the strings are joined to determine whether extra load break disconnectors are required on top of the standard array and inverter side isolators.

How do I know if my existing solar isolators are still compliant?

The only reliable way is to have a licensed Level 2 electrician physically check the isolation points, labelling and wiring configuration against the current version of AS/NZS 5033, since the rules changed materially in the 2021 update. See our electrical safety inspection for a proper assessment.

If you want your solar isolation setup checked, upgraded or brought up to the current standard, get in touch with High Demand Electrical's electrical safety inspection team for a full review, or talk to us about a switchboard upgrade if your solar and your switchboard need attention together. Call 0402 559 777 to discuss your system, and keep in mind every job needs a proper site assessment before we can confirm scope or pricing.