What is an RCD?
A residual current device, or safety switch, protects you from the most frequent cause of electrocution – a shock from electricity passing through the body to the earth. It can also provide some protection against electrical fires.
RCD’s are an essential safety device installed in every workplace and household.
How does an RCD work?
The Safety Switch constantly monitors the flow of electrical current in a circuit, when it detects an imbalance in the flow of current it immediately disconnects the supply of electricity in the circuit. This prevents exposure to harmful levels of electrical current and can save lives and prevent serious injury when an individual is exposed to electric shock.
In an office space, the safe operation of the safety switch is set at 30 milliamps and 0.3 seconds, this means, when someone is exposed to electric shock the RCD must disconnect power in 0.3 of a second when it senses an imbalance of 30 milliamps or more.
RCD Standards in New South Wales
In New South Wales, as outlined in the Code of Practice for Managing Electrical Risks in the Workplace, “a person conducting a business or undertaking (PCBU) has the primary duty under the WHS Act to ensure, so far as is reasonably practicable, that workers and other persons at the workplace are not exposed to electrical risks arising from the business or undertaking.”
RCD’s are an engineering control measure put in place to mitigate the risk of electric shock where that risk cannot be eliminated or substituted.
Under WHS Regulation 38 – Review of Control Measures
The NSW Code of Practice specifies that a PCBU must ensure circuits where portable electrical equipment can be connected are protected by appropriately rated residual current devices (RCDs) (as required by the WHS Regulations) that are properly tested and maintained.
In general, this means almost every power point in the workplace needs to be protected by an RCD.
What is RCD Testing?
RCD’s are maintained through periodic testing of the device to simulate the imbalance in current and to ensure it immediately disconnects power within the required time frame given the amount of current.
Workplace injuries and fatalities can be prevented by the use of properly installed and maintained residual current devices.
How often should an RCD be tested?
The frequency of RCD testing depends on the type of environment and equipment.
In general, for office spaces it’s every 12 months but for factories and workshops it’s every 6 months. This is determined by whether the environment is deemed to be a ‘hostile environment’ or not.
Table 4 from The Australian Standard: AS/NZS 3760:2010 In-service safety inspection and testing of electrical equipment provides guidelines for – Indicative testing and inspection intervals for electrical equipment.
What happens if the RCD Fails?
If an RCD fails to disconnect the supply of electricity in the circumstances its designed too, the risk of injury or death increases significantly as an individual can be exposed to >30mA’s current for longer than 0.3 seconds.
If it’s the result of faulty wiring and it fails to disconnect, the risk of fire in an installation will increase significantly as well.
What are the costs of not doing RCD testing?
RCD’s are found to be about 97% reliable, this improves when they are tested regularly as required.
The costs of not doing RCD testing can be numerous: increased risk of harm and reduced safety in the workplace, increased risk of fire or damage to the property. In the unlikely event that someone is injured, or the property is damaged, not only is there potentially a human cost but also insurance implications.
RCD Testing can be completed at an insignificant cost when considering the above.
Can anyone perform RCD Testing?
No, certain types of electrical equipment must be regularly inspected and tested by a competent person to identify damage, wear and detect electrical faults.
If you are a business or employer (or other PCBU) you must make sure that electrical equipment is regularly inspected and tested by a competent person if the electrical equipment:
Is supplied with electricity through an electrical socket outlet (‘plug in’ equipment), and used in an environment in which its normal use exposes the equipment to operating conditions that are likely to result in damage to the equipment or a reduction in its expected life span, eg conditions such as exposure to moisture, heat, vibration, mechanical damage, corrosive chemicals or dust.
Definition of a ‘competent person’ for inspection and testing
A competent person is someone who has acquired – through training, qualification or experience – the knowledge and skills to carry out inspections and testing of electrical equipment.
The relevant Australian standards are:
AS/NZS 3760: 2010 –
In service safety inspection and testing of electrical equipment, outlines
inspection, testing and tagging methods
AS/NZS 3012: 2010 –
Electrical installations – Construction and demolition sites, outlines regular
inspection and testing requirements. The Workplace Regulations and Code of
Practice state that only an “appropriately trained individually” can carry out
In general, a competent person is a licensed electrician or an apprentice working under the direct supervision of a licensed electrician.
What to do next?
If you are unsure of whether your installation complies with the NSW Code of Practice and Workplace Health and Safety Regulations, then it is best to speak to a professional commercial electrician in Sydney who can provide RCD Testing assistance to ensure your installation is upto date and compliant.