WSB5L Series RCCB | 6kA/10kA Residual Current Circuit Breaker

The 6kA or 10kA figure is the rated short-circuit making and breaking capacity of the RCCB itself—the maximum prospective fault current it can safely withstand and clear without being destroyed. Although RCCBs are primarily residual-current devices, they must still survive short circuits on their terminals, which is why this rating is specified. In practice they are almost always backed up by an upstream or in-series MCB/breaker.

During a short circuit, extremely high current flows through the RCCB's terminals and conductors before the upstream protection operates; the RCCB must be able to carry and interrupt this without rupture, fire, or failure. A 6kA/10kA rating ensures the device can survive fault currents typical in domestic and light-commercial boards. If the available short-circuit current exceeds the device's rating, it must be backed by a suitably rated upstream breaker.

All live and neutral conductors pass through a toroidal zero-sequence current transformer. In a healthy circuit the vector sum of the currents is zero, so no flux is induced. If current leaks to earth (or through a person), the incoming and outgoing currents no longer balance, producing a residual flux that the CT senses and triggers the internal trip mechanism within milliseconds.

The WSB5L series is typically available in Type AC (sinusoidal AC residual currents) and Type A (also pulsating DC residual currents) versions. In modern installations with LED lighting, drives, chargers, and IT equipment, Type A is strongly recommended because such loads can produce pulsating DC leakage that Type AC devices may not detect correctly. Confirm the required type with the local wiring rules.

The WSB5L clips onto a standard 35mm DIN rail inside a distribution board. Connect the incoming live and neutral to the marked line terminals and the outgoing circuits to the load terminals; both conductors must pass through the internal CT. Do not share or bypass the neutral, and use the correct torque for each terminal. Pair it with an upstream or series MCB rated within the RCCB's conditional short-circuit rating.

The "T" button manually injects a known residual current to verify the trip coil and electronics respond correctly. Press it monthly and after any maintenance; if the device fails to trip, replace it immediately. The test button does not test the wiring or earth electrode itself—only that the RCCB is functional.

First isolate loads one at a time to find the leaking circuit, remembering that small leakage from many devices can accumulate. Long cable runs, surge protective devices, and damp environments also contribute. Switching from Type AC to Type A, using a higher rated sensitivity (e.g., 100mA) upstream, or choosing an S (delayed/selective) type can resolve repeated unwanted trips while still protecting downstream 30mA devices.

It is manufactured and type-tested to IEC 61008-1 for household and similar residual current circuit-breakers without integral over-current protection. CE marking shows conformity to applicable EU directives, with additional regional certifications available per market. The standard defines the residual operating values, time delays, and short-circuit endurance tests.

Use the WSB5L RCCB when one device needs to protect a group of downstream MCBs (common in mains or sub-mains distribution), because it has no built-in overload protection. Use an RCBO when a single final circuit (e.g., a cooker or shower) needs both earth-leakage and over-current protection in one module. An RCBO also provides selective tripping so one faulty circuit doesn't cut out an entire board.

It is used in residential distribution boards, commercial sub-boards, and light industrial panels as the main earth-leakage protection. The 6kA version suits smaller, lower-fault-level supplies, while 10kA is chosen where the upstream transformer can deliver higher fault current or where future-proofing is desired. It is well suited to protecting socket circuits, outdoor circuits, and equipment in damp or high-risk locations.