RCD Fault Protection – Gardens, Bathrooms, Kitchens

An RCD monitors the algebraic sum of the currents in the line and neutral conductors (the residual current) at the point at which it is installed in a circuit, and mechanically interrupts the circuit when this sum attains a predetermined value (the rated residual operating current ).

The following definition is given in Part 2 of BS 7671:

‘Residual current device (RCD).A mechanical switching device or association of devices intended to cause the opening of the contacts when the residual current attains a given value under specified conditions.’

‘Residual current device’ (RCD) is the generic name for a range of devices including:

RCCB (residual current operated circuit-breaker without integral overcurrent protection)
RCBO (  residual current operated circuit-breaker with integral overcurrent protection)
SRCD (socket-outlet incorporating an RCD)
Portable RCD
An RCD formed of a suitable association of devices including current transformers, a residual current sensor, a test button and a circuit-breaker.