A protective mechanism that constantly monitors the balance of current between the active and neutral conductors. If the outgoing current does not exactly match the return current, the device assumes the difference is leaking to earth through a fault or a person. It then trips the circuit in milliseconds to prevent fatal electric shock.
The residual-current device keeps tripping every time the boiler kicks in, so we likely have a degraded heating element.
While circuit breakers protect cables from overheating due to overload, residual-current devices protect humans from electrocution.
Also heard as
- RCD
Related terms
RCD
Residual current device: trips when the current going out on the live conductors does not all come back.
Earth fault
Fault in which a live conductor makes unintended contact with earth or with earthed metalwork.
Touch voltage
Voltage a person bridges between a hand on faulted metalwork and their feet or other hand during a fault.
Leakage current
The small amount of current that escapes through insulation to ground under normal operating conditions.