WSB1LE-125 2 Pole Earth Leakage Circuit Breaker

A 2-pole earth leakage circuit breaker is a DIN-rail RCBO that simultaneously switches and monitors both the line (L) and neutral (N) conductors of a single-phase circuit. It combines residual-current (earth-leakage) protection, overload protection, and short-circuit protection in one unit, protecting people, equipment, and cables in 230 V single-phase installations.

L and N conductors both pass through a toroidal differential current transformer. In normal operation the current in L equals and opposes the current in N, so the net magnetic flux is zero. When current leaks to earth (through a person, damaged insulation, or damp wiring), the balance breaks and the toroid detects the residual current, triggering the trip mechanism. A separate bimetal handles overload and an electromagnet handles short circuit.

A 2-pole device switches both L and N simultaneously, completely isolating the downstream circuit from the supply on both conductors. This is safer for maintenance, required for certain installations (e.g., bathrooms, kitchens, gardens), and prevents back-feeding through neutral that can occur if only L is switched. It is the standard choice for new single-phase final circuits.

The "125" denotes the maximum frame current — the highest current the device's terminals, housing, and internal busbar are rated to carry. The actual rated current (e.g., 40 A, 63 A, 80 A) is set by the internal trip unit. A 125 A frame allows future upgrade of the trip rating without replacing the whole device, providing flexibility for load growth.

The WSB1LE-125 2P is typically available in 30 mA sensitivity, which is mandatory by wiring regulations for socket outlets, portable equipment, bathrooms, gardens, and any circuit where a person can touch live parts. Higher sensitivities (100 mA, 300 mA) are used for upstream distribution or fire-prevention circuits where personnel risk is lower.

The unit clips onto a standard 35 mm DIN rail in the consumer unit or distribution board. The supply L and N are connected to the marked input terminals, and the load L/N to the output terminals. The device must be mounted vertically, with the line side at the top, and the upstream short-circuit level must not exceed the rated breaking capacity (Icn) of the RCBO.

The test button injects a simulated residual current via an internal resistor to verify that the trip mechanism still operates. Press it once a month; the device must trip immediately. If it does not trip, the unit has failed and must be replaced. The test button must never be used as a routine on/off switch.

An RCCB only detects residual current and has no overload or short-circuit protection, so it must always be paired with an upstream MCB or fuse. An RCBO like the WSB1LE-125 combines both functions in one DIN module, saving board space, eliminating the wiring error of pairing the wrong RCCB and MCB rating, and tripping only the affected circuit rather than the whole RCCB group.

Nuisance trips are most often caused by high-frequency leakage from LED drivers, UPS, inverters, or VSDs; by capacitive leakage on long cable runs; by damp or aged insulation; or by transients. Solutions include using Type A/F RCBOs for electronic loads, splitting the load across multiple RCBOs, using 100 mA or S-type (time-delayed) devices upstream, fitting upstream surge protection, and insulating or replacing damp cables.

The WSB1LE-125 series is built to IEC 61009-1 and carries CE marking. Typical applications include residential consumer units, apartments, villas, offices, retail shops, hotel rooms, kitchens, bathrooms, and single-phase sub-boards in light-industrial settings where combined earth-leakage, overload, and short-circuit protection is required in a compact DIN-rail form factor.