Type B 20A RCBO with 30mA earth leakage protection, combining MCB and RCD functions in a single module for Wylex NX consumer units.
An RCBO combines the overcurrent protection of an MCB with the earth leakage protection of an RCD in a single device. The Wylex NHXS1B20 provides individual 30mA protection for a single circuit, meaning a fault on one circuit does not trip the protection for every other circuit on the same RCD — the most common complaint with split-load consumer unit designs.
The shift from split-load consumer units to full RCBO boards has been one of the most significant changes in UK domestic electrical installations. An RCBO board gives every circuit its own earth leakage protection, eliminating the problem of a single fault tripping half the house.
In a traditional split-load board, circuits are grouped under shared RCDs. A fault on any circuit in the group trips the RCD and disconnects every circuit in that group. With RCBOs, each circuit has independent protection — a fault on the kitchen ring only affects the kitchen ring, not the lighting, sockets, and everything else on the same RCD.
The Type B characteristic trips between 3 and 5 times the rated current, making it suitable for resistive and lightly inductive loads — standard socket outlets, lighting circuits, and immersion heaters. For circuits with higher inrush currents (such as some motor-driven equipment), Type C RCBOs are required.
The Wylex NHXS1B20 is the RCBO that electricians reach for when fitting Wylex NX boards. Individual circuit protection is now the expected standard for new installations and upgrades, and the single-module width means a full RCBO board does not require a larger enclosure than a traditional split-load design.
| Rating | 20A |
|---|---|
| Type | Type B (overcurrent) |
| Earth Leakage | 30mA |
| Breaking Capacity | 6kA |
| Width | Single module (18mm) |
| Compatibility | Wylex NX series consumer units |
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