DC Isolators and Solar Safety Switches: What AS 5033 Requires and Why Some Installers Skip It

Does your solar system legally need a DC isolator on the roof? Every solar array must have a compliant way to disconnect its DC power at the array, not just at the inverter, but since AS/NZS 5033:2021 a rooftop switch is no longer the only way to achieve that. Some newer systems use plug connectors or other disconnection devices instead, which is why two compliant Sydney installations can look quite different on the roof.

⚡ Quick Answers: DC isolators and solar safety

• What does a DC isolator do? It disconnects the DC power flowing from your panels so the array can be isolated for maintenance, fault finding or emergencies.
• Is a rooftop isolator always required? No. The 2021 edition of AS/NZS 5033 allows other compliant disconnection devices, and small systems under 120 volts DC with panels within 1.5 metres of the inverter are treated differently.
• Does turning the isolator off make the roof safe? No. The cables between the panels and the isolator stay live whenever there is daylight.
• What signage is mandatory? Isolators need a PV ARRAY D.C. ISOLATOR label, systems with multiple isolators need a warning to turn all of them off, and the switchboard needs the green PV marker for firefighters.
• Why do some quotes not include a rooftop isolator? Often legitimately, because the design uses a different compliant disconnection method. The question to ask is how the array isolates, not whether there is a switch.

1. What a DC isolator actually does

Solar panels produce DC power whenever light hits them, and that side of the system cannot simply be switched off at the meter. The DC isolator gives electricians and emergency services a defined point to break the circuit between the panels and the inverter.

Without a compliant disconnection point, anyone working on the system, your roof or a fire around it is dealing with live conductors they cannot turn off. That is why isolation gets its own section of the standard rather than a passing mention. Our overview of the AS 5033 solar rules covers where it fits in the bigger picture.

2. What AS 5033 requires

Under clause 4.3.3 of AS/NZS 5033, every PV array needs a means of isolating the DC source at the array itself. The standard is deliberately flexible about the device: it can be a switch, a circuit breaker or, in some designs, plugs and connectors that meet strict requirements.

There is also a specific carve out for small systems. Where the DC voltage stays at or below 120 volts and the panels sit within 1.5 metres of the inverter, the disconnection arrangement is simplified. Typical Sydney rooftop systems run well above that voltage, so most still need a dedicated disconnection device.

3. Why some installers skip the rooftop switch, and when that is fine

Before 2021, the rooftop DC isolator was near universal, and weathered isolators became one of the most common causes of solar fires. The 2021 revision responded by allowing alternative disconnection methods, so a modern system without a visible rooftop switch is not automatically cut rate work.

The line between compliant and corner cutting is whether a proper disconnection method exists at all, with the right ratings, enclosures and labels. If an installer cannot show you how the array isolates, that is the red flag, and it is one of the things checked in a CEC compliant installation.

4. The signage that must be on your system

The standard is strict about labels because the next person at your switchboard may be a firefighter. Every DC isolation point needs a PV ARRAY D.C. ISOLATOR sign, and where a system has multiple isolators that do not operate together, a warning must state that all of them need to be switched off to isolate the equipment.

Your main switchboard also needs the green PV marker showing there is solar on the roof, and plug type disconnection points carry their own warning tags about testing for zero current before unplugging. Missing or faded labels are among the most common findings in an electrical safety inspection of an older solar system.

5. The catch: the isolator does not make your roof dead

Switching the DC isolator off stops power reaching the inverter, but the panels keep generating in daylight and the cabling between the panels and the isolator stays live. There is no switch that turns off the sun.

That is why solar work belongs with licensed people even after isolation, and why rooftop isolators must be weather protected, with outdoor units needing higher temperature ratings and shrouding so water cannot pool in the switch. A cooked or waterlogged isolator is a fault waiting for a wet week.

6. When solar changes your supply requirements

Adding solar to an older property can expose a supply problem that was never obvious before. When an installer sizes a system for maximum export, or when a battery is added later, the total load on your main fuse and consumer mains can exceed what they were built for.

The main service fuse is a network asset — it sits on the supply authority's side of the meter and only a Level 2 ASP can apply to have it upgraded. On Ausgrid, the standard residential fuse is 63 amps. On Endeavour Energy it is typically 80 or 100 amps depending on the area and the tariff. A larger solar system or an added battery may require a fuse upgrade before the network will approve the connection, which is lodged by the ASP as part of the power supply upgrade process.

The consumer mains — the cables running from that fuse to your main switchboard — also need to be rated for the new load. If your home still has the original aluminium or undersized mains from the 1970s or 1980s, a solar or battery addition is often the trigger that brings them to light. Replacing consumer mains is Level 2 ASP work, and getting it right the first time means the network approval goes through cleanly without re-inspection delays.

7. Metering and the grid connection step

Connecting solar to the grid is not just an on-site wiring job. Every system that exports power needs a bi-directional meter — one that records what goes out as well as what comes in — and that meter change is lodged through your electricity retailer with the network's approval. In New South Wales, both Ausgrid and Endeavour Energy have moved toward smart meters for solar connections, which means the old spinning-disk meter almost always needs to come out.

The metering work sits at the boundary between your retailer's responsibility and the Level 2 ASP's. The ASP installs and certifies the metering equipment and confirms the point of connection is safe and compliant before the retailer activates export. On a straightforward new residential system this is a routine step, but on a property with an older switchboard, an undersized meter panel, or a private power pole that needs work, the metering step can uncover issues that delay connection if they are not identified up front.

Our guide to Ausgrid and Endeavour defect notices explains what happens when a network inspection finds a problem at your meter or point of attachment — a situation solar installations occasionally trigger when the inspector gets eyes on the property for the first time.

Where your distributor fits in

Isolation requirements come from the standard, but connecting solar to the grid also involves your distributor's approval and export settings, which differ between networks. We compared them in our Ausgrid vs Endeavour solar approval guide, and you can check your network area in seconds with our postcode checker before you get quotes. Battery additions bring their own layer, covered in our NSW battery compliance guide.

How High Demand Electrical helps

We inspect and certify solar DC isolation as part of our electrical safety work across Sydney. That includes checking isolator condition and weatherproofing, verifying the signage set, testing that the disconnection method actually isolates the array, and fixing what fails, from a single degraded isolator to a switchboard upgrade that brings the AC side up to standard. If your system needs more supply capacity to grow, our power supply upgrade and Level 2 teams handle the network side as well.

DC Isolator FAQs (Sydney)

My isolator is cracked and faded. Is that urgent?

Yes, treat it as a priority. Degraded rooftop isolators let water in and are a known fire cause. Have it replaced and the rest of the DC side checked at the same time.

Can I turn off the DC isolator myself?

You can operate it in an emergency, the shutdown procedure should be on a sign at your switchboard. Leave any work beyond switching to a licensed electrician, since parts of the system stay live in daylight.

Do older systems have to be upgraded to the 2021 rules?

Not retrospectively. A system compliant when installed stays legal, but any significant alteration or repair must meet the current standard, and unsafe components must be fixed regardless of age.

Who checks all this when solar is installed?

Your installer certifies the work, and the system also needs distributor approval to connect. An independent electrical safety inspection is worth it when buying a house with existing solar.

Does adding a battery always require a supply upgrade?

Not always, but it often does on older properties. The key factors are your current main fuse rating, the size of the battery inverter, and whether your consumer mains are rated for the combined load. A Level 2 ASP assessment before you commit to a battery brand can save you from finding out on installation day that extra network work is needed.

Get your solar isolation checked

Book an electrical safety inspection covering your solar DC isolation, signage and switchboard, or get in touch with our team. Every job includes a site assessment before scope and pricing are confirmed.