Glossary · Maintenance and diagnostics
Residual current circuit breaker (RCCB)
Also known as: Residual current device (RCD), RCCB
German: Fehlerstromschutzschalter
In electrical installations, a residual current circuit breaker (RCCB) is a switching device that disconnects a circuit when the difference between the currents in the live conductors, the residual current, exceeds its rated value, for example because current flows to earth through a fault or a person. An RCCB without integral overcurrent protection is covered by IEC 61008-1.
- Maintenance
In one sentence
An RCCB disconnects a circuit when current leaking to earth exceeds its rated residual current, protecting against electric shock and fire.
Example
Socket outlets in the control cabinet for service laptops are protected by an RCCB with a rated residual current of 30 mA.
How it applies
- Engineering: Designers select the type (for example AC, A, F or B) according to the expected residual current waveform; frequency converters can produce smooth DC residual currents that require suitable types.
- Maintenance: RCCBs must be tested regularly with the test button and, as required by national rules, with measuring equipment. A tripping RCCB points to an insulation fault that needs diagnosis, not to a device that should be bypassed.
- Safety: An RCCB provides additional protection against electric shock but does not replace basic protection or overcurrent protection. It does not trip on a fault between two live conductors.
- Documentation: The manual should explain the test procedure and interval, what to do after tripping and which type is installed. Warnings about Electrical hazards stay necessary.
RCCB vs. miniature circuit breaker
A miniature circuit breaker protects against overload and short circuit. An RCCB detects residual current. A combined device with both functions (RCBO) is covered by IEC 61009-1. In North America, similar protection is provided by ground-fault circuit interrupters (GFCI).