Type B RCD
A Type B RCD is a switchboard safety device that cuts power to an EV charger if it detects an earth-leakage fault, including DC faults a Type A RCD may miss
Type B RCD Overview
Key Specifications
- Function: Trips on AC and DC earth-leakage (residual current) faults
- Sensitivity: 30mA (Acti9 iID)
- Rating: 40A
- Forms: Type B RCBO (with overcurrent protection) or Type B RCCB / RCD
- Poles: Single phase dual pole (Smart EV Chargers RCBO); 4-pole, 400/415V (Acti9 iID)
- Board Space: 3 spaces for the RCBO vs 5 for Type B RCD + MCB (Smart EV Chargers); 8 x 9mm modules (Acti9 iID)
- Standards: AS/NZS 61008-1, IEC/EN 61008-2-1, IEC/EN 62423 (Acti9 iID)
- Mounting: DIN rail in the switchboard
- NZ Price: $250 (Smart EV Chargers RCBO) to $771.40 inc GST (Acti9 iID 4P, Electrical Direct)
Installation Guidelines
- • Have the RCD installed by a registered electrician as part of the charger circuit
- • WorkSafe recommends an RCD for home EV charging and names Type B as the most appropriate type
- • Check whether your charger already has DC leakage protection built in; if so, a Type B device may not be needed (Smart EV Chargers)
- • Use a single-phase device for single-phase supplies and a 4-pole device for three-phase supplies
- • Allow switchboard space: an RCBO saves room compared with a separate RCD and MCB
Benefits
- • Detects DC fault currents that can blind a Type A RCD
- • Cuts power automatically on an earth fault, protecting against electric shock and fire
- • An RCBO adds overcurrent protection in one device
- • Saving board space can avoid a switchboard upgrade or sub-board (Smart EV Chargers)
Considerations
- • Not every charger needs one: some, including all the chargers Smart EV Chargers sells, have DC leakage protection built in
- • The 4-pole Acti9 iID costs about three times the single-phase RCBO
- • Stock varies: the Smart EV Chargers single-phase RCBO was out of stock on 5 November 2026
About Type B RCDs
A residual current device (RCD) switches off the electricity automatically if it detects a fault, protecting against electrocution and fire caused by earth faults. There are several types. WorkSafe says the most appropriate one for electric vehicle charging is a Type B RCD, which can handle the different kinds of faults that an EV and its charging equipment (EVSE) can place on household wiring. The more common Type A RCDs already installed in many homes are not suitable to protect against all of those faults.
WorkSafe recommends asking your electrician to install an RCD when a home charger is put in, and suggests insisting on one if the electrician does not advise it. Smart EV Chargers explains that a fault in an EV can send DC current back into the switchboard, which can blind a Type A breaker so that it does not trip when needed. It also notes that a Type B device is not required with chargers that already have DC leakage protection built in, as all the chargers it sells do.
Two forms are sold in New Zealand. A Type B RCBO combines the residual current protection with overcurrent protection: Smart EV Chargers lists a 40A single-phase, dual-pole Type B RCBO at $250, which uses 3 switchboard spaces instead of the 5 needed for a separate Type B RCD and MCB (out of stock on 5 November 2026). For three-phase supplies, Electrical Direct lists the Schneider Electric Acti9 iID 4-pole 40A 30mA Type B residual current circuit breaker (A9Z51240) at $771.40 inc GST.
More Information
WorkSafe home charging guidance and New Zealand Type B listings:
Type B RCD Advice
A Type B RCD is fitted in your switchboard as part of a hard-wired charger installation, so talk to your registered electrician about whether your charger needs one. Browse other EV parts or find an EV service centre near you.
