RCBO

An RCBO consolidates earth-leakage and overcurrent protection into a single device. Practically this means one module per branch, cleaner wiring, clearer labeling, and better selectivity at the final-circuit level. With a shared RCCB upstream, a single fault can de-energize several circuits; with per-circuit RCBOs, only the affected branch trips, reducing collateral outages and simplifying fault-finding. In retrofit boards where DIN space is limited, RCBOs are often the only way to meet code while adding protections.

For most single-phase final circuits, 1P+N is the preferred choice: it measures residual current through both line and neutral and disconnects the circuit with minimal space. A 2 pole RCBO can be used where simultaneous disconnection of both conductors is required by local practice or where system topology demands it. For three-phase loads, select a 3 phase RCBO (3P or 3P+N/4P) sized to the load current, inrush profile (curve B/C/D), and the residual-current type (AC/A/F/B) specified by the equipment.

RCBO 30mA is the common choice for personnel protection on final circuits because it reliably detects leakage currents that pose shock risk. Upstream devices (e.g., submains) may apply 100 or 300 mA for fire protection and selectivity, but only where local code permits. Always follow national wiring rules and AHJ guidance; where medical or special environments are involved, more stringent requirements may apply.

No additional MCB is needed on the same branch: an RCBO already includes the thermal-magnetic overcurrent element of an MCB. Upstream feeders and submains still require appropriate overcurrent protection sized to their conductors. When comparing rcbo vs mcb, remember the RCBO has both residual-current and overcurrent protection; the MCB has only overcurrent protection.

Use a separate RCCB when you want one device to protect several downstream MCB-protected circuits (e.g., for cost or legacy reasons). The trade-off is reduced selectivity: a leakage fault in any one circuit will trip the shared RCCB. Per-circuit RCBOs avoid this by localizing the trip to the affected branch, which is preferred in critical or high-availability areas.

Yes—follow the equipment manual. Some EVSEs include internal DC monitoring and specify an external Type A RCBO; others require a Type B device to detect smooth DC. PV inverters vary by topology; the manufacturer will specify Type A/F/B as applicable. Where DC components exist, using the wrong type can result in blind spots or nuisance tripping. When in doubt, confirm with the supplier and the AHJ before selection and submittal.

Curve B is suitable for predominantly resistive or low-inrush circuits (lighting, receptacles). Curve C balances nuisance-trip immunity and protection for mixed loads and small motors. Curve D is intended for high inrush equipment such as transformers and certain machinery. Match the curve to the expected inrush and coordination with upstream protection so that downstream faults trip local RCBOs first.

Wiring diagrams are provided per model family and pole option. As a rule: route both line and neutral through the RCBO sensing core; follow terminal markings; respect torque values; and keep neutral segregation to avoid cross-return paths that can cause unwanted trips. You can place an illustrative diagram in your documentation set or on the board door schedule for maintenance clarity.

Press the TEST button monthly (or per local regulation) to verify residual-current trip. Visually inspect terminations for discoloration or loosening, re-torque per datasheet, and replace any device that fails to trip or shows mechanical damage. In dusty or corrosive environments, increase inspection frequency and consider enclosures with higher IP ratings.

Yes. An RCBO addresses leakage and overcurrent; an AFDD adds arc-fault detection to mitigate fire risk, while an AC SPD handles transient overvoltages. Coordinate installation order and protection levels according to the manufacturer’s guidelines and local codes to maintain selectivity and performance.

RCBOs are typically rated for −25 °C … +55 °C operation with derating above standard ambient or altitude (e.g., >2,000 m). Enclosure grouping and thermal rise can also impact effective current carrying capacity; consult the datasheet’s derating curves and apply margins in tightly packed boards.