Residual current device (RCD) coverage is the single most important shock-protection measure on a commercial board, and the one most often non-compliant on pre-2007 installations. AS/NZS 3000:2018 requires personnel-protection RCDs (typically 30 mA Type A) on virtually all final sub-circuits, and where solar inverters or DC-fault-capable EV chargers are present, Type B is required upstream of them. Millar Electrics audits existing commercial boards against current code, designs and installs the right combination of RCD or RCBO protection, and produces documented test results suitable for insurer and ESV audits.
What modern code requires
AS/NZS 3000 §2.6 covers the residual current protection requirement for final sub-circuits. In commercial premises virtually every power circuit, most lighting circuits and any three-phase final sub-circuit requires 30 mA RCD protection. Special applications (medical body-protected areas to AS/NZS 3003, certain hospitality wash-down zones) require 10 mA protection. Type B is required ahead of solar inverters and certain EV chargers per the manufacturer's installation manual and the Wiring Rules; get this wrong and the protection won't trip on a smooth DC fault.
RCBO per circuit vs grouped RCDs
Grouped RCDs (one RCD protecting multiple circuits) are cheaper but trip every protected circuit on any one circuit's fault, which is operationally disruptive on a commercial board. RCBO-per-circuit (an RCD and circuit breaker in one device) provides individual circuit selectivity, simpler fault-finding and better discrimination. For new commercial installs and most upgrades, RCBO-per-circuit is the preferred approach. Where board space or budget rules it out, we group circuits in functional clusters so a trip doesn't take out unrelated systems.
Testing and documentation
We test every RCD on completion under load using a calibrated tester, with trip current and trip time recorded against the AS/NZS 61009 / 61008 specification windows. The test results form part of the handover documentation, with photographs of every termination and the updated circuit schedule. For ongoing testing we recommend the regime under AS/NZS 3760, typically 6-monthly or 12-monthly under a maintenance contract, with documented test history retained for insurer audit.