If you’re wiring an EV charge circuit, RCD selection should follow the charger specification and the current BS 7671 framework rather than guesswork. In simple terms, a Type A device is suitable where the EV charger provides 6 mA DC fault detection, while a Type B device is used where that protection is not built in or where the manufacturer specifically requires it.
EV protection devices form part of our wider Consumer Units range, including EV-ready boards, heat-pump boards, PME units and surge-protected enclosures.
Quick Answer: For EV charger installs, use a Type A RCBO if the charger includes 6 mA DC detection (RDC-DD). If not, or if the datasheet specifies it, install a Type B RCD. Always protect the EV point with a ≤30 mA double-pole device and add surge protection per Amendment 2.
| Device Type | Use It When | Typical EV Use Case |
|---|---|---|
| Type A RCBO / RCD | The charger includes 6 mA DC detection (RDC-DD) | Most modern domestic EV chargers |
| Type B RCD | No 6 mA DC detection is built into the charger, or manufacturer specifies Type B | Older chargers, specialist installs, some commercial / 3-phase setups |
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The Quick Answer
- Use a Type A RCD/RCBO when the charger provides integrated 6 mA DC fault detection (RDC-DD per BS IEC 62955).
- Use a Type B RCD when the charger does not provide 6 mA DC detection, or the manufacturer explicitly requires Type B.
- In all cases, the EV point must be individually protected by a ≤30 mA device that disconnects all live conductors (double-pole on single-phase). Pair with surge protection per A2.
Related reads: What Is an EV Consumer Unit? · What Surge Protection Does an EV Charger Install Need?
When a Type A Is Enough
Most modern Mode 3 chargers ship with an internal 6 mA DC detection module (RDC-DD). In that case, BS 7671 allows a Type A device for additional protection.
- Pick a Type A RCBO that disconnects line and neutral.
- Installer favourite: High-Immunity Type A Mini RCBO (6–40 A)
- Outdoor/IP jobs: IP65 A-Type RCBO EV Kit
- Use a Type 2 SPD on the EV circuit or in the EV board.
- On PME earthing, add PEN/PME fault protection to avoid rods.
Installer’s Pick: Our IP65 A-Type RCBO EV Kit is ready for outdoor installs, fully compliant, and UK-stocked for next-day delivery.
In practice, many installers choose a Type A device for domestic EV circuits, although BS 7671 also allows Type F in suitable setups where DC fault protection is already provided by the charger.
When a Type B Is Required
Fit a Type B when no 6 mA DC detection is provided inside the charger, or when the EVSE datasheet calls for it. Type B detects AC, pulsed DC and smooth DC.
- Single-phase & three-phase options:
- 2-Pole Type B RCD (domestic / single EV)
- 4-Pole Type B RCD (3-phase / commercial)
- B-Type EV Kit (63 A RCD + 40 A MCB)
- Still include a Type 2 SPD for surge compliance.
Installer’s Pick: The B-Type EV Kit (63 A RCD + 40 A MCB) is ideal when the charger lacks RDC-DD. Fully 18th Edition compliant and in stock.
How to Check the Charger for 6 mA DC Detection (RDC-DD)
- Read the EVSE datasheet — look for “integrated 6 mA DC detection”, “RDC-DD (BS IEC 62955)” or similar.
- If present → a Type A RCBO is acceptable.
- If absent / unclear → specify a Type B RCD to stay compliant.
RCBO Sizing for 7 kW & 22 kW
- 7 kW single-phase — typically a 40 A Type A RCBO. Options:
-
22 kW three-phase — use a 4-pole device sized per design current:
- 4-Pole A-Type RCBO
- Or a 4-Pole Type B RCD if no RDC-DD in EVSE
Upstream Devices & Selectivity
A downstream Type A can be blinded by DC if there’s an upstream Type AC on the same path. Keep the RCD hierarchy clean:
- Do not place a Type AC upstream of a Type A EV device.
- For series RCDs, use time-delay/selective types upstream where discrimination is needed (e.g. 100 mA A-Type Time-Delay).
- Always give the EV circuit its own 30 mA device.
Regulation Reminder: For EV charging equipment, BS 7671 requires protection against DC fault currents. Where that protection is not provided by the charger, a Type B RCD is required. Where the charger includes suitable DC fault protection, a Type A or Type F device may be used.
Common Mistakes to Avoid
- Using Type AC on EV circuits — not acceptable for modern EVSE.
- Single-pole RCBO — EV protection must disconnect line + neutral.
- No SPD — Amendment 2 expects a Type 2 SPD.
- PME with no PEN protection — add a PEN/PME device instead of rods.
What RCBO Should You Use for an EV Charger?
For many 7 kW domestic EV charger installs, the usual choice is a double-pole 40 A Type A RCBO where the charger includes built-in 6 mA DC fault detection. If the charger does not include that protection, or the manufacturer calls for it, the correct approach is typically a Type B RCD instead.
The important point is not just current rating. You also need to confirm the charger’s DC fault protection, pole configuration, and the manufacturer’s installation instructions before selecting the final protective device.
FAQs
Do EV chargers need a Type B RCD?
Not always. A Type B RCD is required where the charger does not provide 6 mA DC fault protection. If suitable DC fault protection is built into the EV charger, a Type A device is commonly used instead.
What RCBO should I use for a 7 kW charger?
Typically a 40 A Type A double-pole RCBO. Options: A-Type RCBO — WRT or High-Immunity Mini RCBO.
Is surge protection mandatory on EV circuits?
Yes — under Amendment 2, SPDs are required unless a risk assessment says otherwise. For EV installs, fit a Type 2 SPD.
Do Tesla or modern chargers still need an RCD?
Yes — all EVSE must have RCD protection. If RDC-DD is built in, use a Type A RCBO; otherwise a Type B RCD is required.
What size breaker for a 22 kW three-phase charger?
Depends on design current/cable. Commonly a 32–40 A 4-pole device. Options: 4P A-Type RCBO or 4P Type B RCD.
Products & Kits That Deliver
- Type A RCBOs: Mini High-Immunity RCBO · A-Type RCBO — WRT · IP65 A-Type RCBO EV Kit
- Type B RCDs: 2P Type B RCD · 4P Type B RCD · B-Type EV Kit
- EV Boards & PME: 4-Way EV Unit (A-Type + SPD) · PME Load-Balancing Board · IP65 PEN Unit
- Surge Protection: Surge-Protected Enclosures · 3-Phase SPD
Browse collections: Type A RCBOs · Type B RCDs · PME Units · SPDs · EV-Ready Consumer Units
Final Word
Match the RCD to the charger’s DC protection: Type A with RDC-DD, Type B otherwise. Add a Type 2 SPD, ensure double-pole disconnection, and include PME protection on TN-C-S supplies. Do this and your EV installs pass inspection first time.
👉 Ready to spec? Compare our EV-ready consumer units, stock up on A-Type RCBOs, or secure compliance with Type B RCDs for installs without RDC-DD.