RCD Protection Requirements in Commercial Buildings

What You Need to Know

AS/NZS 3000:2018 changed the game for RCD protection in commercial buildings. Every final subcircuit rated 32 A or less that feeds socket outlets, lighting, or hand-held equipment now needs a 30 mA residual current device. That threshold used to sit at 20 A. The 2018 edition pushed it to 32 A, which captures the majority of circuits in a typical commercial fit-out.

This memo covers what needs RCD protection, what qualifies for an exemption, and the RCD types you can actually install. If you wire a commercial building today and skip the RCD on a 25 A lighting circuit, the installation fails compliance.

• Clause 2.6.3.2.3 requires 30 mA RCDs on all final subcircuits rated 32 A or less that supply socket outlets, lighting, direct-connected hand-held equipment, or fixed wired equipment presenting increased shock risk (AS/NZS 3000:2018, Cl 2.6.3.2.3)
• Type AC RCDs are banned in Australia for new or altered installations from 1 May 2023 - Type A is the minimum (AS/NZS 3000:2018, Cl 2.6.2.2.2)
• Type B or Type F RCDs are required for circuits feeding EV chargers, solar inverters, variable speed drives, and UPS systems - any equipment that produces smooth DC fault currents (AS/NZS 3000:2018, Cl 2.6.2.2.2)
• Lighting circuits must be distributed across multiple RCDs - a single trip must not black out an entire floor (AS/NZS 3000:2018, Cl 2.6.3.2)
• Exemptions exist for lifts, centralised air conditioning, fire pumps, and drainage systems - but only where RCD disconnection would create a greater danger than the earth leakage current itself (AS/NZS 3000:2018, Cl 2.6.3.2.3)
• Switchboard replacements trigger RCD requirements for all connected circuits (AS/NZS 3000:2018, Cl 2.6.3.2.5)
• Repairs to existing circuits do not trigger a mandatory RCD retrofit - a like-for-like replacement of a single outlet or fitting in the same location counts as a repair (AS/NZS 3000:2018, Cl 2.6.3.2.5)
• Adding socket outlets to an existing circuit requires the RCD at the origin of the new wiring only - you do not need to retrofit the entire existing circuit back to the switchboard (AS/NZS 3000:2018, Cl 2.6.3.2.5)

Take a two-storey office building with 20 final subcircuits per floor. Under the old 20 A threshold, your 25 A and 32 A circuits sat outside the RCD requirement. Under the current rules, every one of those circuits rated 32 A or less needs a 30 mA RCD.

On a typical floor with 8 lighting circuits and 12 GPO circuits, you need to spread the lighting across at least 3 RCDs. If one RCD trips, only 2 or 3 lighting circuits go dark - the rest of the floor stays lit. That distribution matters for emergency egress and day-to-day operations.

For the mechanical plant room, the story changes. A centralised air conditioning system fed by a 3-phase 32 A circuit can qualify for an exemption if an RCD trip would shut down the entire HVAC system. But you need to document why the exemption applies. Write it on the drawings, note it in the switchboard schedule, and keep a record that shows you made a deliberate, compliant decision - not an oversight.

The ban on Type AC devices catches some contractors off guard. If you have Type AC RCDs left over from a previous job, they cannot go into any new or altered installation. Type A is the minimum. For buildings with VSD-driven fans or EV charging stations in the car park, you need Type B or Type F devices on those specific circuits.