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What is a RCD and how does it work?

Sarah Allen

There are 3 types of RCD in workplaces across Australia. Fixed, Portable and Socket Outlet RCD’s. All RCD’s are identified by the presence of a “test” button. If it doesn’t have a “test” button then it’s not a RCD.

RCD’s are found in the switchboard and can be installed on all or only some power or lighting circuits depending on site requirements. Each protected circuit is protected by one RCD, however there may be multiple lights or socket outlets on that circuit. Fixed RCD’s have been proven as the most effective method of protecting against severe electric shock.

RCD’s may look like a power board, double adaptor or other plug in device. They plug in to a socket outlet and portable electrical items are then plugged in to the portable RCD. Portable RCD’s are commonly used where no Fixed RCD’s are present. Portable RCD”s only protect the user of the equipment plugged in to the portable RCD.

Socket Outlet RCD’s are added to socket outlets at the time of manufacture and installation, and are fully incorporated in the wall socket outlet. The RCD in the socket outlet only protects the user of the equipment plugged in to the socket outlet.

All types of RCD continuously monitor the electric current that travels through the circuit it is protecting. As soon as a RCD detects a leakage to earth (as an example, when a person touches a live part), a correctly functioning RCD “trips” and shuts off the power to the circuit in milliseconds.

RCD will not eliminate the possibility of an electric shock being sustained. Humans are conductors of electricity, and coming into contact with a live wire or damaged appliance can result in electricity following the path of least resistance to earth – through the individual. However, quickly shutting off power to the circuit significantly decreases the severity of injury or death.

WHS regulations specify regular RCD testing and AS/NZS 3760:2010 specifies the maximum “trip time” a RCD must switch off the power to the circuit along with the recommended frequency of testing.

Book an RCD test today!