Type A vs Type B RCDs and RCBOs for EV Chargers
Quick answer: Use a Type A or Type F RCD for an EV charging point where suitable protection against DC residual current is provided by the charging equipment, normally through an RDC-DD. Where that DC protection is not provided, a Type B RCD is required.
Whether you need an RCBO, RCCB or separate MCB arrangement depends on the charger, consumer-unit design and manufacturer’s instructions. The EV charging point must have individual residual-current protection not exceeding 30 mA and the RCD must disconnect all live conductors.
Selecting protection for an EV charger involves more than choosing a current rating from the charger’s maximum output.
The installer must establish:
- Whether the charger provides suitable DC residual-current detection.
- Whether a Type A, Type F or Type B RCD is required.
- Whether the circuit will use an RCBO or separate RCD and overcurrent device.
- Which live conductors must be disconnected.
- The charger’s design current, cable capacity and manufacturer’s requirements.
This guide explains how Type A and Type B devices differ, when each is used and how to choose an RCBO or RCD for a domestic or commercial EV charging circuit.
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What Type of RCD or RCBO Does an EV Charger Need?
The RCD type depends on whether the charging equipment provides suitable protection against DC residual current.
| EV Charger Protection | Permitted RCD Type | What to Check |
|---|---|---|
| Suitable DC fault protection is provided by the charger | Type A or Type F | Confirm RDC-DD functionality, applicable product standard and manufacturer’s instructions |
| No suitable DC fault protection is provided | Type B | Select the device according to the supply, charger and circuit arrangement |
| Manufacturer specifies a particular device | Follow the stated requirement | Check the current installation manual for the exact charger model |
The term Type B charger should not be confused with a Type B RCD. Charger connector types, charging modes, MCB curves and RCD classifications are separate systems.
What Is the Difference Between Type A and Type B RCDs?
Type A and Type B refer to the residual-current waveforms the device is designed to detect.
Type A RCD or RCBO
A Type A device detects alternating residual current and pulsating DC residual current. It is widely used with electronic equipment, including EV chargers where the required smooth-DC protection is provided separately by the charger.
Type B RCD
A Type B device provides wider residual-current detection, including smooth DC and higher-frequency components within its product specification.
This means Type B is suitable where an EV charger could produce DC residual current that is not being detected and controlled by an RDC-DD or equivalent function within the EVSE.
| Feature | Type A | Type B |
|---|---|---|
| AC residual current | Yes | Yes |
| Pulsating DC residual current | Yes | Yes |
| Smooth DC residual current | Requires separate suitable DC detection for the EV application | Covered within the Type B operating characteristics |
| Typical EV use | Charger with suitable RDC-DD functionality | Charger without suitable built-in DC protection |
👉 Compare Type A RCBOs and Type B RCDs.
What Is 6 mA DC Detection or an RDC-DD?
An RDC-DD is a residual direct-current detecting device used with Mode 3 EV charging equipment. It monitors DC residual current and initiates disconnection through associated switching equipment where the relevant operating threshold is reached.
RDC-DD functionality is commonly incorporated into modern EV charging equipment. Where suitable protection is provided, BS 7671 permits a Type A or Type F RCD instead of requiring a Type B device.
Check the charger documentation for wording such as:
- Integrated 6 mA DC residual-current detection
- RDC-DD
- Compliance with BS IEC 62955 or BS EN 62955
- Protection against DC fault current provided within the EVSE
- Required upstream RCD type
Specification reminder: Do not select the upstream RCD solely because the charger description mentions DC monitoring. Confirm that the documented functionality satisfies the EV manufacturer’s stated upstream protection arrangement.
Does an EV Charger Need an RCBO or an RCD?
An RCBO combines residual-current protection and overcurrent protection in one device. An RCCB provides residual-current protection only and must be coordinated with a separate overcurrent protective device such as an MCB.
Either arrangement may be suitable when correctly designed:
- RCBO: Combines earth-leakage and overcurrent protection for the individual EV circuit.
- RCCB plus MCB: Separates the residual-current and overcurrent functions.
- RCD within the EV charger: May provide the required residual-current protection where permitted by the equipment design and manufacturer’s instructions.
An RCBO is often convenient for a dedicated EV circuit because it keeps the circuit individually protected and avoids relying on a shared 30 mA RCD serving unrelated circuits.
The correct question is therefore not simply “Does an EV charger need an RCBO?” It is:
Where are the required residual-current and overcurrent functions provided, and do they comply with the charger and circuit design?
Does an EV Charger Need a Double-Pole RCBO?
The RCD protecting EV charging equipment must disconnect all live conductors.
For a single-phase circuit, that means both line and neutral must be disconnected by the residual-current protective arrangement.
Installers should distinguish between:
- A device that switches and disconnects both line and neutral.
- A device that switches only the line but includes a switched-neutral arrangement elsewhere.
- A product described informally as “double-pole” despite having different protection and switching functions across its poles.
Check the manufacturer’s technical data rather than relying only on the product title or module width.
For a three-phase charging point, the RCD arrangement must disconnect all applicable live conductors, including neutral where present.
What Size RCBO or Breaker Does an EV Charger Need?
The protective-device rating must be selected from the charger’s design current, cable current-carrying capacity, installation method, ambient conditions, voltage drop and manufacturer’s instructions.
Common examples include:
| Nominal Charger Output | Approximate Current | Common Protective-Device Range |
|---|---|---|
| 3.6 kW single-phase | Approximately 16 A | Often 20 A, subject to design |
| 7 kW single-phase | Approximately 30–32 A | Frequently 32 A or 40 A, depending on the charger and design |
| 11 kW three-phase | Approximately 16 A per phase | Often 16 A or 20 A per phase, subject to design |
| 22 kW three-phase | Approximately 32 A per phase | Frequently 32 A or 40 A, subject to design |
These are typical examples rather than fixed rules. A 7 kW charger is not automatically paired with a 40 A RCBO, and a 22 kW unit is not automatically paired with a particular four-pole device.
The manufacturer’s maximum protective-device rating and installation instructions must also be checked.
Should an EV Charger Use a B-Curve or C-Curve RCBO?
The B or C marking on an RCBO normally refers to the overcurrent tripping curve. It is unrelated to whether the residual-current element is Type A or Type B.
For example:
- B32 Type A RCBO: B-curve overcurrent characteristic with Type A residual-current detection.
- C40 Type A RCBO: C-curve overcurrent characteristic with Type A residual-current detection.
- Type B RCD: Type B residual-current detection, which is a different classification entirely.
The overcurrent curve should follow the charger manufacturer’s instructions and the circuit’s starting-current, fault-current and disconnection-time requirements.
Do not choose a C-curve device simply because the circuit supplies an EV charger. Confirm that the earth-fault loop impedance and protective-device operating characteristics remain suitable.
Can an Upstream RCD Affect EV Charger Protection?
DC residual current from EV charging equipment can affect the operation of unsuitable upstream RCDs.
The complete hierarchy should therefore be reviewed, not just the final EV device.
- A Type AC RCD should not be placed upstream where DC components from the connected equipment could impair its operation.
- Shared upstream 30 mA RCD protection can create unwanted tripping and poor circuit discrimination.
- Where RCDs are installed in series, their types, time-delay characteristics and residual operating currents must be coordinated.
- Any upstream non-delay RCD arrangement must also satisfy the applicable all-live-conductor disconnection requirements.
Where possible, give the EV charger its own clearly identified protective arrangement rather than placing it behind a shared domestic RCD.
What Other Protection Does an EV Charger Need?
Choosing the correct RCD or RCBO does not complete the EV circuit design.
The installation may also need consideration of:
- Open PEN protection: Where a charging point is connected to a PME earthing terminal.
- Surge protection: According to the installation, potential consequences of overvoltage and BS 7671 requirements.
- Overcurrent protection: Matched to the charger and cable design.
- Isolation and switching: According to the equipment and installation arrangement.
- Load management: Where the available supply capacity cannot support unrestricted charging.
- Earthing arrangement: Including PME, TT and any connected generation or storage system.
These functions may be built into the charger, provided within a dedicated EV consumer unit or distributed across several correctly coordinated devices.
👉 Browse EV consumer units and protection kits or compare PME fault detection units.
How to Select an RCBO or RCD for an EV Charger
Before ordering the protective device, work through the following checks:
- Identify the charger model. Obtain the current datasheet and installation instructions.
- Confirm the DC protection. Check whether suitable RDC-DD functionality is built in.
- Select the RCD type. Use Type A or Type F where permitted, or Type B where the charger does not provide the required DC protection.
- Choose the protection arrangement. Decide whether the circuit will use an RCBO, an RCCB with MCB, or protection incorporated within the EVSE.
- Confirm all-live-conductor disconnection. Check the actual device switching arrangement.
- Calculate the current rating. Base this on the charger, cable and circuit design rather than charger power alone.
- Check the overcurrent curve. Follow the charger manufacturer’s requirement and verify disconnection conditions.
- Review upstream devices. Avoid an incompatible RCD hierarchy.
- Coordinate other protection. Include PEN, surge, isolation and load-management requirements where applicable.
Installer summary: Do not select an EV RCBO from the charger’s kW rating alone. Confirm the charger’s DC detection, required RCD type, pole arrangement, maximum protective-device rating and circuit design first.
Browse EV RCDs, RCBOs and Protection Boards
- EV RCBOs
- Type A RCBOs
- High-Immunity RCBOs
- Type B RCDs
- EV Consumer Units
- PME Fault Detection Units
- EV Surge Protection Boards
Use the charger manufacturer’s instructions and the circuit design to confirm whether you need a Type A RCBO, Type B RCD, separate MCB or a complete pre-built EV protection unit.
EV Charger RCD and RCBO FAQs
What type of RCBO should I use for an EV charger?
Where the charger provides suitable DC residual-current protection, a Type A or Type F RCBO may be used if it also meets the charger’s current, pole and overcurrent requirements. Where that DC protection is not provided, a Type B RCD arrangement is required.
Does every EV charger need a Type B RCD?
No. A Type B RCD is required where suitable protection against DC fault current is not provided by the charging equipment. Many modern chargers provide RDC-DD functionality that permits a Type A or Type F RCD.
Is a Type A RCBO enough for an EV charger?
It can be where the charging equipment provides the required DC protection and the RCBO meets the manufacturer’s other requirements. Type A alone should not be assumed suitable without checking the charger documentation.
Does an EV charger need its own RCD?
Each charging point requires individual residual-current protection not exceeding 30 mA. That protection may be installed upstream or incorporated within the EV charging equipment where the applicable requirements are met.
Does an EV charger need a double-pole RCBO?
The RCD arrangement must disconnect all live conductors. On a single-phase circuit, this means line and neutral. Confirm the product’s actual switching arrangement rather than relying solely on the phrase “double pole”.
What size RCBO is used for a 7 kW EV charger?
A 7 kW charger commonly draws around 30–32 A, so 32 A and 40 A devices are both encountered. The correct rating depends on the charger’s instructions, cable design, installation method and applicable correction factors.
Should an EV charger use a B-curve or C-curve RCBO?
Use the overcurrent curve specified or permitted by the charger manufacturer and confirm that the circuit meets the required disconnection conditions. The B or C curve is separate from the Type A or Type B residual-current classification.
Can I use an MCB instead of an RCBO for an EV charger?
An MCB can provide overcurrent protection, but it does not provide residual-current protection. A suitable RCD would need to be provided elsewhere in the arrangement, including within the EVSE where permitted.
Do bidirectional EV chargers need a different RCBO?
Bidirectional charging equipment may have additional manufacturer and system requirements because power can flow between the vehicle and installation. Use only the protective arrangement specified for the exact charger and operating mode.
Does a three-phase EV charger need a four-pole RCD?
The RCD must disconnect all live conductors applicable to the charging circuit. For a three-phase system with neutral, this commonly means a four-pole switching arrangement.
Does a Type B RCD replace PEN fault protection?
No. Type B residual-current protection and open PEN protection address different hazards. Both must be considered separately where applicable.
Type A or Type B: Which Should You Choose?
Use a Type A or Type F RCD where the EV charger provides suitable protection against DC residual current. Use a Type B RCD where that protection is not provided or where the manufacturer specifically requires it.
The final specification must also account for:
- Whether an RCBO or separate RCD and MCB arrangement is being used.
- Disconnection of all live conductors.
- The charger’s design current and protective-device limits.
- The required overcurrent curve.
- Any upstream RCDs.
- PEN, surge, isolation and load-management requirements.
👉 Ready to spec? Compare EV RCBOs, Type A RCBOs and Type B RCDs.