EV chargers are one of the most common causes of RCD confusion on modern installations. Some installs require a Type B RCD, others don’t - and getting it wrong can mean failed inspection, callbacks, or unsafe protection.
This guide explains exactly when a Type B RCD is required for EV chargers, how DC leakage affects RCD performance, and what BS 7671 actually expects installers to provide.
Quick Answer: Type B RCD protection is required for EV chargers unless the charger includes certified DC leakage detection that limits DC fault current to 6mA. Without that protection, a Type A RCD may be blinded and fail to trip.
Browse compliant protection options here: Type B RCDs.
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Why EV Chargers Can Produce DC Leakage
EV chargers are fundamentally power electronics. Internally, they use rectifiers and control circuitry to convert AC supply into DC for battery charging.
This process can introduce:
- Pulsating DC leakage
- Smooth (continuous) DC leakage
- High-frequency fault currents
If smooth DC leakage exceeds 6mA, standard RCDs can become DC blinded and fail to operate correctly.
BS 7671 Rules for EV Charger RCD Protection
BS 7671 requires EV charging equipment to be protected against DC fault currents that could impair RCD operation.
Compliance Note: Where an EV charger does not include certified DC leakage detection, Type B RCD protection is required to ensure correct disconnection under fault conditions.
This applies regardless of charger power rating or whether the installation is domestic or commercial.
When Is a Type B RCD Required for EV Chargers?
You must install a Type B RCD where the EV charger:
- Does not include built-in DC leakage detection
- Cannot guarantee DC fault current below 6mA
- Is supplied from a dedicated circuit
- Is installed on a PME supply without alternative protection
If the charger includes certified DC protection, a Type A RCD may be acceptable - but only where the manufacturer explicitly states this.
When in doubt, specifying Type B removes ambiguity and future-proofs the installation.
EV-Ready Protection & Consumer Unit Options
Many installers now use pre-configured EV protection kits and boards to simplify compliance and reduce install time.
Common EV protection approaches
- Dedicated consumer unit with Type B RCD
- EV kit with integrated RCD, SPD and isolation
- Surge-protected boards designed for EV circuits
Relevant installer-ready options include:
FAQs
These are the most common questions installers ask when specifying RCD protection for EV chargers.
Do all EV chargers require Type B RCDs?
No. Only chargers without built-in DC leakage detection require Type B protection.
Can I use a Type A RCD on an EV charger?
Yes - but only if the charger includes certified DC fault current protection.
Why is DC leakage such a concern?
Because it can prevent standard RCDs from tripping during a fault.
Is Type B safer than Type A?
Type B offers broader protection where DC leakage is possible, but it is not required on every circuit.
👉 Installing an EV charger? Use compliant Type B RCD protection