How do RCDs work and how often should they be tested?

Man holding an automatic switch of differential current. The device protects human life from electric shock. It combines an automatic switch plus a protective shutdown device.

An RCD (Residual Current Device) is an electrical safety device that protects people from electric shocks. It detects imbalances in the electrical current and quickly shuts off the power supply to prevent harm.

According to NSW Safework’s guidance on RCDs, a competent person must conduct regular workplace RCD testing to ensure they work effectively.

RCDs are safety devices that protect from electric shock and reduce the risk of electrical fires. They constantly monitor the flow of electricity through a circuit
and cut electricity supply to prevent shocks if they detect an imbalance. Following guidelines set in AS/NZS 3760, the frequency of RCD testing will range from daily to two years, depending on the type of test and industry.

The requirements around safety switches or RCDs differ from state to state. This article will explain how RCDs work and how often they should be tested.

How do RCDs work?

RCDs  monitor the flow of electricity. In a normal situation, the amount of current flowing in will equal the amount flowing out.

If they detect an imbalance (such as current leaking to earth), they immediately cut the electricity supply, preventing serious electric shock or fire hazards.

Since 1991, the NSW government made it mandatory for RCDs to be installed in all new homes or renovations involving changes to existing wiring.

RCD tests in Australia

There are two main tests for fixed and portable RCDs – the push button and operating time tests. The required frequency of these tests is described in AS/NZS 3760:2022.

Push button test

The push button test checks if the RCD is functioning correctly and will activate if there is an earth leakage. When the button is pressed, it creates an imbalance that triggers the RCD to disconnect the circuit, ensuring the safety of those nearby. As per AS/NZS 3760:2022, It’s recommended that this test be performed every three months for portable devices and every six months for fixed devices. For factories, workshops and other high-risk settings, a push button test must be done before every use or every day, depending on what is longer.

Operating time test

During the operating time test, a technician will measure the trip time of the RCD to check that electricity cuts off within the required time. An instrument records readings based on guidelines. A qualified test and tag specialist must perform this test.

How often should RCDs be tested?

RCD testing may vary based on your industry. Lower-risk environments like offices and residential buildings may have slightly longer testing intervals than higher-risk industries such as workshops, construction sites and factories.

The general interval for push button tests for portable and fixed RCDs in most environments is six months. An exception here is portable RCDs in factories, fabrication facilities and equipment used in commercial cleaning, where the push button test should be conducted daily or before every use. In environments where the equipment or supply cord may or may not be in hostile settings, portable RCDs should be tested every three months.

Operating time tests for RCDs range from six months to two years, again depending on the industry. Equipment used in commercial cleaning requires an operation time and push button test every six months, while portable and fixed RCDs in factories, workshops, fabrication facilities and equipment in hostile settings must be tested every 12 months. Testing is required every two years for low-risk settings such as hotels, accommodation houses, etc.

Once the test is conducted, a tag is affixed to the device identifying details of the tester, whether it has failed or passed the test, the date of testing and the next test date. Regular RCD testing ensures compliance with AS/NZS 3760.

Types of RCDs

There are two main types of RCDs used in Australia:

Portable RCDs

These devices can be plugged into a standard power outlet to protect any appliances or tools connected to them. They are typically used for outdoor electrical equipment or when a fixed RCD is unavailable. For example, portable RCDs on construction sites can help protect workers from electric shocks while using power tools or equipment. Events and festivals also use portable RCDs to safeguard performers and guests from electrical dangers in temporary setups. They are often used where water and electricity intersect to reduce the risk of electrical hazards.

Fixed RCDs

Fixed RCDs are installed directly into the switchboard of a building and protect the entire electrical installation or circuit, including power outlets, lighting circuits and hard-wired appliances.  If it detects an imbalance between the live and neutral currents, which may indicate a leakage of current that could pose a hazard, the RCD automatically disconnects the power supply. Fixed RCDs are used across industries, including construction, manufacturing, healthcare and hospitality.

What’s the difference between an RCD and a circuit breaker?

An electrical switchboard showing an RCD (safety switch) on the left. Notice the orange test button above the safety switch. The circuit breakers are on the right.

An RCD and a circuit breaker are both safety devices used in electrical systems, but they serve different purposes.

A circuit breaker protects an electrical circuit from damage caused by overcurrents (such as lightning strikes) or short circuits. It automatically shuts off the circuit when it detects a high current that exceeds the safe limit, preventing overheating and potential fires.

On the other hand, an RCD protects people from electric shocks and electrocution by detecting current leakage. It monitors the balance of current flowing into and out of a circuit and trips when it detects a difference, indicating that electricity may be flowing through an unintended path, such as a person.

Importance of RCD testing

RCDs are essential to prevent electrical shocks. Testing them regularly ensures your business complies with NSW electrical testing requirements and WHS requirements to minimise workplace risks.

RCD testing also ensures your electrical devices continue to work safely, reducing the risk of equipment downtime and protecting staff.

Who can test RCDs?

RCD testing must only be conducted by a licensed, competent and qualified person with the necessary training and experience to ensure RCDs function correctly. 

Property and business owners should verify that the individual performing the test holds the appropriate certifications and is familiar with NSW’s current safety standards and regulations.

Need RCD testing? Hire a qualified RCD testing company

In summary, RCD testing may range from daily to every two years depending on your industry. Higher risk industries will require more frequent testing to ensure safety and compliance.

Precision Test and Tag has been providing high-quality, reliable RCD testing services across Sydney for over a decade. We follow all standards and regulations for RCD testing, microwave, and emergency lighting testing, keeping our costs reasonable.

Our comprehensive test reports provide detailed information on any potential hazards found during the RCD testing process.

Contact our team today to discuss your RCD testing needs.

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Craig Boyle

Craig has been practising as a test and tag technician for almost 10 years. He's one of the most experienced and qualified test and taggers in Sydney with qualifications for RCD testing, emergency light testing and appliance testing

About Precision Test and Tag

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Precision Test and Tag is a leading provider of electrical test and tag services across Sydney for all kinds of businesses. This includes microwave oven testing, offsite testing and tagging, 3-phase testing and emergency light testing.

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