Have you recently bought an electrical vehicle? Ensure your EV charger meets the highest safety standards with RCD protection. Understand the role of RCDs in preventing electric shocks and fires for a safe, efficient charging process.
Yes, and it’s mandatory that EV chargers in Australia be installed with RCD protection in place [1]. EV charging pulls more power than a normal power point does, so it’s exposed to specific hazards that your electrical appliances wouldn’t have to deal with.
In a normal charge, an EV charger pulls a heavy and continuous load for hours. A typical single-phase charger would require 7.4 kW (32 A) of power, while three-phase high-speed AC chargers pull 22kW of power.
Loads that demand such an amount of power typically require their own dedicated circuit with built-in protection.
Since having a dedicated RCD protection is mandatory for all EV chargers, your existing switchboard might not be equipped to house this device and handle the current pull safely.
This guide walks through the AS/NZS 3000:2018 Amendment 2 rules, the DC leakage hazard behind them, and the practical difference between a Type A and a Type B RCD.
Your home runs on 230V AC, while EV batteries store direct current (DC). This difference in current is why EVs have an onboard inverter that converts AC from EV chargers, particularly high-speed AC chargers, to DC before it charges the EV batteries.
When charging your EV, a small amount of current leaks out of the car’s inverter (the device that converts AC to DC) and back into your home’s AC wiring. It’s mostly very minimal and negligible, but once DC leakage reaches about 6mA, it “blinds” your switchboard’s residual current device (RCD).
If your RCD’s internal sensing is blinded by 6mA DC leakage, it gets swamped with the interference and stops responding properly to AC faults. Should anyone accidentally touch the faulty wiring or earthed appliance body, the switch that’s supposed to trip and protect them may simply not fire.
The AS/NZS Wiring Rules elaborate on EV charging in a dedicated section, as it’s a standalone power point system that should be treated differently from any other household power circuits.
Section 7.9 of AS/NZS 3000:2018 Amendment 2 covers all EV charging installations and has installation requirements and notes on purchasing compliant RCDs [2].
All EV chargers must have their own dedicated sub-circuit that runs directly from the switchboard [3]. That means you can’t simply branch off an existing power point using an extension cord or share it with your household lighting.
High-current loads like EV chargers must not share circuits with other loads, since they can pull their full rated current for hours on end.
That circuit needs 30mA AC protection, the same baseline shock protection every modern circuit gets [1]. On top of that, it needs 6mA DC fault detection specifically to stop the blinding problem above, either built into the charger itself or added at the switchboard.
And where more than one car charges from the same board, like a strata garage or a driveway with two wallboxes, each one needs its own dedicated protection device rather than sharing.
Knowing whether your EV charger has an RCD built in is vital in deciding whether you need to upgrade your switchboard or simply wire a dedicated power point.
If it does. Most current smart wallboxes such as Tesla’s Wall Connector, Wallbox Pulsar Plus, and similar units have an internal module called an RDC-DD (Residual Direct Current Detecting Device). This device watches for DC leakage and cuts power the moment it crosses 6mA, before it ever reaches the switchboard’s own RCD.
With that protection already in the charger, a standard Type A RCD or RCBO at the board is compliant and sufficient.
If it doesn’t. Older and simpler wallboxes without any internal sensing and residual DC protection need a standalone Type B RCD fitted at the switchboard instead.
A Type B unit can sense DC leakage directly without getting blinded by it, so it does the RDC-DD’s job from the board rather than from the charger.
|
Charger has built-in RDC-DD |
Charger has no DC detection |
|
|---|---|---|
|
What’s needed at the board |
Standard Type A RCD/RCBO |
Dedicated Type B RCD |
|
Relative cost |
Lower |
Meaningfully higher |
|
Physical size |
Standard |
Larger, more specialised |
Type B RCDs are highly specialised and detect smooth DC and high-frequency components on top of standard AC and pulsating DC. It’s basically an upgrade to Type A RCDs, making it more expensive and it may take more space on the switchboard.
That’s why most manufacturers now build RDC-DD sensing capabilities directly into the EV chargers themselves, shifting the cost of DC protection and proper installation into the charger circuits instead of your house’s switchboard.
Most EVs have household-ready charging cables called “trickle” cables that you can plug into your wall socket to charge your car at home. Household trickle chargers often draw 10A to 15A and are useful for emergencies, but we don’t recommend relying on standard plug-in chargers for daily use.
A standard wall socket is usually on a shared circuit with whatever else is on that part of the house, and it almost certainly doesn’t have 6mA DC detection behind it.
On an older switchboard with ceramic fuses, one RCD covering half the house, pulling a continuous 10A or 15A load for six or eight hours at a time induces thermal stress in the socket and its wiring, and we’ve seen the melted faceplates that result from using high-current devices such as EV chargers for prolonged periods.
Portable EV charging cables should only be treated as a backup for when you’re driving out of town and are running on a low battery. At home, Bright Force Electrical can install a proper dedicated EV charger with RCD protection in place.
If your switchboard is running outdated ceramic fuses and has no sensitive overcurrent protection installed, we recommend a switchboard upgrade before any upgrades or RCD installations.
Read more about our complete guide to upgrading your switchboard for EV charger compatibility.
You can, occasionally, with the portable cable that comes with the car. Portable cables must not be used for day-to-day charging.
That’s because a standard household RCD installed on switchboards lacks the 6mA DC detection, and the common rail where it’s installed may not be designed for hours of continuous heavy draw.
A Residual Direct Current Detecting Device (RDC-DD) is a safety module installed within EV chargers that detects DC fault leakage. It’s embedded inside your EV charger and disconnects it from the power supply once it detects the 6mA residual DC.
Using an EV charger with RDC-DD built-in will prevent DC leakage from blinding your switchboard’s Type A RCD, so your house stays protected from electrical faults.
Your switchboard needs to be upgraded if it still runs ceramic fuses or it doesn’t have enough space to house a new RCD. Also check if it does not have a main safety switch.
Learn more about whether your switchboard needs upgrading to accommodate an EV charger by calling us at 1300 724 942 to get started.
No. The Tesla Gen 3 Wall Connector has built-in 6mA DC protection, so under the Australian standard it only needs a standard Type A RCD or RCBO at the switchboard behind it.
Wiring an RCD to your dedicated household EV charger is a no-brainer. Aside from the obvious electrical safety precaution, it’s a mandatory requirement in Sydney when wiring a dedicated EV charger at home [1].
For your EV wallbox installation, inspection, and repairs, call Bright Force Electrical on 1300 724 942 and book a licensed Sydney Level 2 electrician for a compliant, upfront fixed-price installation.
Our technicians are in-house and licensed; there’s no call-out fee during business hours, and every job comes with a CCEW and our lifetime workmanship warranty.
Did you enjoy reading our article “Renovating in Sydney? Here’s Why Bright Force Electrical Is the Right Choice for Electrical Work”? We have many related articles you may also be interested in reading, like the below:
