If you work with electrical installations in Australia, you’ll know that AS/NZS 3000 is the Wiring Rules we live and breathe. Within it, Clause 2.6.3 is one of the most important because it deals with additional protection by residual current devices, or RCDs. Over the years, this clause has been clarified through amendments and rulings, and it has a direct impact on how we design, install, and upgrade switchboards and circuits. Let me walk you through what it really means in practice and how it applies on site.

RCDs in domestic and residential installations

The first and most critical point to understand is that for domestic and residential installations, every final subcircuit must be protected by an RCD with a rated residual current not exceeding 30 mA. This is not limited to socket outlets, which is how many electricians used to interpret the rule years ago. Today it includes lighting circuits, fixed appliances such as ovens and hot water units, and even air conditioning circuits. If it’s a final subcircuit in a home, it needs 30 mA RCD protection. That’s the baseline expectation inspectors will have when they review your work.

What changes in non-domestic installations

When we move outside the residential space and into commercial or industrial environments, the rules shift slightly. Clause 2.6.3 still requires broad RCD coverage, but there are exceptions written into the standard for certain kinds of plant and equipment. Lifts, centralised air conditioning, fire pumps, and drainage systems may be treated differently provided they are not located within or supplied from a residential living unit. These exceptions are narrow and need to be read carefully, but they’re there to make sure critical plant isn’t tripped unnecessarily while still balancing safety requirements. Amendment 2 of the Wiring Rules tightened up the wording around these non-residential exemptions to remove the grey areas that had been causing debate.

Alterations, repairs, and switchboard replacements

A big source of confusion in the industry has been how RCD requirements apply when you’re not installing brand new circuits but working on existing ones. Clause 2.6.3 and its associated guidance make a clear distinction between repairs, alterations, and switchboard replacements. If you’re repairing an existing circuit, you generally don’t need to retrofit it with RCD protection, because the work doesn’t change the way the circuit is structured. But if you’re altering or extending a circuit, or if you’re replacing a switchboard, then you must bring the affected final subcircuits up to the current RCD requirements for that type of installation.

This means if you alter one circuit in a home, you don’t need to retrofit the entire installation with RCDs, but the altered circuit itself must be upgraded. With a board replacement, the circuits connected to that board will usually need RCD coverage. Inspectors want to see clear documentation on exactly what you changed so it’s evident why you applied RCDs to some circuits and not others.

Location of the RCD and the exception rule

The Wiring Rules also make it clear that RCDs should normally be installed at the origin of a final subcircuit, which in most cases means the switchboard. There is, however, an exception written into Clause 2.6.3.2.3.2 that allows the RCD to be installed at the outlet itself under certain conditions. This is only permitted if the wiring to that outlet has additional mechanical protection that meets the requirements in Clause 3.9.4.

It’s a narrow pathway but it does exist, and regulators have issued rulings to confirm exactly how it applies. If you ever use this approach, it’s important to record your justification and make sure the installation is labelled appropriately.

Choosing the right type of RCD

Another key change in recent years relates to the type of RCDs we’re allowed to install. Type AC RCDs, once the default, are no longer permitted in Australia for new or altered installations. This came into force in May 2023 and reflects the reality that many modern appliances and devices create DC residual currents that Type AC units can’t detect.

In practice, this means Type A is now the baseline RCD for most circuits. In situations where you have EV chargers, solar inverters, or variable speed drives, you may need Type B or other specialised devices. Checking manufacturer specifications is now an essential part of circuit design, not just a box-ticking exercise.

Common traps to watch out for

There are some common traps worth mentioning. Hard-wired appliances like hot water units and rangehoods are often overlooked, but they are final subcircuits and require RCD protection in homes. Similarly, smoke alarms, ceiling sweep fans, and exhaust fans have been explicitly clarified as “lighting points” under Amendment 1, which means they also fall under the RCD rules.

On the non-residential side, it’s easy to misinterpret the exceptions and apply them too broadly. Always check whether the plant is part of a residential supply or located in a living unit before assuming the exemption applies.

Why documentation and labelling matter

The regulators have also made it clear that documentation and labelling are crucial. If you leave a circuit without RCD protection because it legitimately falls under an exemption, label it clearly and record it in your job documentation. That way, anyone coming after you understands the rationale and inspectors can see you made a deliberate, compliant choice.