# RCD types for V2L — Type A, F, B and smooth DC detection (RDC-DD) > A power-electronic source like a V2L inverter can produce residual currents a plain Type AC RCD will not clear. **BS 7671 §722.531** drives the answer: at least a **Type A** RCD at the connection point, plus protection against **smooth DC** — either a **Type B** RCD, or a **Type A/F** RCD combined with an **RDC-DD** (BS IEC 62955). The common case is “Type A plus an RDC-DD”. The product standards define the device; **BS 7671** decides the application, and the disconnection must be **proven by test**. **Safety frame.** This is education, not an instruction to carry out work. Work connecting V2L equipment to fixed wiring is safety-critical and may be notifiable under Part P. It must be designed, installed, inspected and tested by a competent person to the current edition of BS 7671. Vehicle manufacturers generally do not sanction back-feeding fixed wiring from V2L outlets; follow manufacturer instructions. ## In short - **BS 7671 §722.531**: at least **Type A** at the connection point, plus a means to handle **smooth DC**. - Smooth DC protection comes from a **Type B** RCD, or a **Type A/F** RCD **plus an RDC-DD** (BS IEC 62955). - **Type F** handles mixed-frequency residual currents from single-phase inverters; **Type B** handles a higher-frequency range plus smooth DC. - A V2L source's prospective fault current and disconnection times differ from the grid — **MCB selection and disconnection must be proven** by a competent person. - Product standards are device **ratings**, not the design verification. **Where this stops:** This explains which device type applies and why. The actual selection and the disconnection-time verification are competent-person work, proven by test. ## Why a plain RCD is not enough An ordinary Type AC RCD responds only to alternating residual current. Power-electronic sources and chargers can produce **DC or higher-frequency** residual currents that can blind such a device. That is why an EV/V2L connection point needs a more capable type, and a way to handle smooth DC. **Figure: RCD selection for an EV / V2L connection point.** Each connection point needs RCD protection of the type and rating BS 7671 requires for a charging point; protection against smooth DC comes either from a Type A/F RCD plus an RDC-DD, or from a Type B RCD. _A decision flow. Every EV/V2L connection point needs additional RCD protection of the type and rating BS 7671 requires for a charging point. Because a power-electronic source can produce smooth DC residual current, you then choose one of two routes: Route A is a Type A (or Type F) RCD combined with a residual direct-current detecting device (RDC-DD to BS IEC 62955); Route B is a Type B RCD (to BS EN 62423). BS 7671 §722.531 permits Type A, F or B at the charging point; the common case is “Type A plus RDC-DD”. A plain Type AC RCD is not adequate where DC or higher-frequency residual current is possible._ ## The two routes to smooth DC protection - **Route A — Type A (or F) RCD plus an RDC-DD** to BS IEC 62955, which trips on smooth DC so the upstream RCD is not desensitised. This is the common case, often embedded in the EVSE. - **Route B — a Type B RCD**, which itself responds across a higher-frequency range plus smooth DC. **Type F** sits between A and B, handling the mixed-frequency residual currents typical of single-phase inverters. Which to use is a design decision against §722.531 and the actual equipment. ## Don't forget the fault current is different A V2L inverter delivers a much lower prospective fault current than the grid, so MCB selection and disconnection times that are fine on the grid may not be on V2L. The product standards rate the device; the **competent person proves the disconnection by test** in both source conditions. ### How this is made and proven compliant **What governs it:** BS 7671 §722.531 (RCD type and smooth DC detection at an EV connection point); Product standards: BS IEC 62955 (RDC-DD), BS EN 62423 (Type F/B), BS EN 61008/61009 (RCCB/RCBO), BS EN 60898-1 (MCB) **Who may do it:** A competent person selects device types and proves disconnection by test, for both the grid and V2L source conditions. Notifiable under Part P (England). **How compliance is demonstrated:** Select at least Type A + smooth DC detection per §722.531; Prove RCD operation by test in both grid and V2L modes; Verify disconnection times against the V2L source's (lower) prospective fault current ## FAQ ### Do I need a Type B RCD for V2L? Not necessarily. BS 7671 §722.531 allows Type A or F with an RDC-DD (smooth-DC detection), or a Type B. The common case is a Type A RCD plus an RDC-DD — often built into the EVSE. ### Is a Type A RCD enough on its own? A Type A is the baseline, but you also need to handle smooth DC (Type B, or Type A/F + RDC-DD). And the disconnection must be proven by test for the V2L source, whose fault current differs from the grid. ### Can I rely on a socket tester to confirm RCD protection? No. A floating V2L output can pass a socket tester yet give no RCD protection until a neutral-earth bond exists. RCD operation must be proven by test in V2L mode. --- _Author: Martin — qualified UK electrician (BEng Mech Eng; vehicle mechanic)._ _Last reviewed: 14 June 2026. Written against: BS 7671:2018 + A4:2026._ _Status: published. General information, not project-specific design advice._ _[How we source this](/methodology) — evidence hierarchy, confidence flags and source policy._ ## Sources 1. BS EN 62423 (Type F/B) and BS IEC 62955 (RDC-DD) — BSI — https://knowledge.bsigroup.com/products/type-f-and-type-b-residual-current-operated-circuit-breakers-with-and-without-integral-overcurrent-protection-for-household-and-similar-uses-2 (cited by reference only) 2. BS 7671:2018+A4:2026 §722.531 — IET/BSI (cited by clause only)