Queensland has the most comprehensive legislative requirements for the installation and retrofitting of safety switches of any Australian jurisdiction and now has the highest penetration of safety switches in domestic premises of any Australian jurisdiction at more than 63 per cent of homes.
Safety switches can and do save lives. In the last ten years safety switches would have prevented 33 fatalities (56 per cent). Safety Switch, residual current device is a device which is intended to trip out an electricity supply in the event of a current flow to earth. As such, it can provide protection from harmful electric shocks in situations where a person comes into contact with a live electrical circuit and provides a path to earth.
As such, it can provide protection from harmful electric shocks in situations where a person comes into contact with a live electrical circuit and provides a path to earth. Typical reasons of this occurring are with the use of faulty electrical leads and faulty appliances.
An RCD is connected in such a way as to enable it to monitor how much current is entering a circuit and how much is leaving that same circuit. If there is an imbalance of 30mA or over (the minimum current required to kill a human), ie. current is flowing from active, through a person and to ground.
There will be less current leaving the circuit through the RCD than entering. The RCD will detect this and isolate the power, usually within 15 to 20 ms.
The RCD also has over-current detection, that operates in exactly the same way as a conventional circuit-breaker. RCD's ONLY operate if there is an imbalance in the active and neutral, or overcurrent. If you hook yourself up across active and neutral and do not overload the circuit, the RCD *WILL NOT* trip, as there is no imbalance (leakage to earth). However, if you touch an earth and active, it will trip.
For an RCD to trip, there must be leakage of current to earth. It is important to note that a safety switch will not protect all circumstances, such as contact between active and neutral without earth being involved, or between active and active.
There are two main safety switch types commonly in use:
Type 1 Type 2
- used in medical, hospital or patient care situations Used in construction areas, workplaces and homes
. RCD Type1 Test Current Maximum Tripping Time Type 1- 10 mA AC 40 milli-seconds
RCD Type 2- 30 mA AC 300 milli-seconds type 2 switches,
If an imbalance of 30mA or more occurs, the RCD will trip - usually in less than 30 milli-seconds, but typically anywhere between 8 and 30 milli-seconds with a maximum test time of 300 mill-seconds.
The nominal tripping sensitivity for a Type 2 safety switch is 30mA; but sometimes the value is anywhere between 18.5 and 25mA. Warnings If the Safety Switch trips as soon as you use an appliance it is most likely that, that appliance has an earth fault or excessive leakage current.
Testing of residual current devices .
The regulations require that a residual current device installed at a workplace shall be kept in a safe working condition and tested on a regular basis by a competent person to ensure its continued effective operation. A record must be kept of these tests. and Guidelines for testing of residual current devices is provided in Australian 3760 Standards-
In-service Safety Inspection and Testing of Electrical Equipment, which is an approved code of practice under the Workplace Health and safety act 1995 It is also good practice for people to regularly test the units using the test buttons on the devices. Guidance on this is usually provided with the device.
Frequency of testing will depend on the environment in which the device and the equipment is being used, with more frequent testing required for harsher environments.
A legal 'must have'
From March 1st 2008 All Manufacturing Workplaces Must have a Safety Switch Protecting all electrical equipment. This Ensures that everyone within the workplace is protected from death, injury and property damage. Safety Switches and Domestic Rental Properties The law is that all homes built since 1992 must have safety switches installed on power circuits. BY LAW...
If you are building a new home, you must have a safety switch installed on both power and lighting circuits. The law also says that if you buy a property without a safety switch, you must install a safety switch for the power circuits within three months of a property transfer. This applies to any transfer of domestic premises including estate, family law and mortgagee transfers.
Remember – if you buy a domestic residence, or enter into a residential tenancy agreement for a domestic residence you own you have a legal requirement to have a safety switch installed for general purpose socket outlets if there is not already one installed