Westhomes Wsb5 (L) -40 Series Phase Nuetral Earth Leakage Miniature Circuit Breaker

The WSB5(L)-40 is an RCBO — a residual current circuit breaker with overcurrent protection. It combines, in one modular unit, the earth-leakage protection of an RCCB with the overload and short-circuit protection of an MCB. It protects people and property against both electric shock/fire from leakage currents and damage from overcurrent or short circuit.

A toroidal (ring-shaped) current transformer monitors the sum of currents in the phase and neutral conductors. In a healthy circuit the currents cancel out, so the toroid output is zero. When current leaks to earth — such as through a person or damaged cable — the imbalance induces a secondary current that an electronic circuit detects, triggering the trip.

1P+N means the device switches the phase pole (which has both thermal-magnetic overcurrent protection) while opening the neutral pole together with it, but the neutral pole itself does not carry the overcurrent trip elements. Wiring is straightforward: incoming L to the L terminal, incoming N to the N terminal, and the load connected to the matching L/N output terminals.

The "40" indicates the frame size (rated current) of the RCBO, typically up to 40 A. This frame is well suited to single-phase residential and light-commercial branch circuits such as kitchens, bathrooms, outdoor sockets and garages, where a 40 A feed comfortably covers a mix of circuits.

30 mA residual operating current is the threshold at which the device trips, chosen because it is low enough to prevent dangerous ventricular fibrillation if a person touches live parts. It is the standard "human-protection" sensitivity for sockets and locations with shock risk, unlike 100/300 mA types used mainly for fire protection on distribution circuits.

The WSB5(L)-40 integrates a bimetal for overload, a magnetic solenoid for short circuit, and an electronic residual-current circuit fed by the toroidal CT. Any of the three faults — overload, short circuit or earth leakage — releases a common latching mechanism that opens both phase and neutral contacts.

The TEST button injects a simulated residual current to verify the trip mechanism is functional. Press it monthly (and after any power outage) to confirm the device trips and resets correctly. If it does not trip, replace the RCBO immediately because earth-leakage protection cannot be relied upon.

A standard MCB provides only overload and short-circuit protection, with no earth-leakage function. An RCCB provides earth-leakage protection only and needs a separate upstream MCB for overcurrent. The WSB5(L)-40 RCBO provides all three protections in one DIN-rail module, saving panel space and simplifying selective coordination.

RCBOs are covered by IEC 61009, the standard for residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (Type AC/Type A according to design). The WSB5(L)-40 is designed to this standard and typically carries CE marking for the European market.

Use the WSB5(L)-40 for bathroom/kitchen circuits, outdoor and garden sockets, garages, garden offices, and any socket circuit within 3 m of a bathroom. If it trips repeatedly on the residual-current side (without obvious overload), suspect a damp cable, damaged appliance insulation or accumulated leakage; isolate loads one by one to identify the faulty circuit.