The RCD testing guide
April 4, 2023 | Tom B
When was the last time your RCD was tested? Your Residual Current Device (RCD) is a critical safety device that needs to be tested regularly. They are a vital component, which if they become faulty, could lead to injury or even death. If it has been a while, or you need help understanding how to test it, we have put together this guide. Here we will cover what an RCD is, why testing is important, how to test the device, and what happens when the test fails.
What is an RCDAn RCD is a safety device that monitors the electricity flowing through a circuit. If it detects an imbalance it then quickly disconnects the power supply. This is a life-saving feature that is designed to protect people from electric shock. Electricity flows through a toroid in the device, and this creates magnetic fields. In an installation with no problems, these magnetic fields should cancel each other out. By doing this, the device protects a person who may otherwise have received an electric shock. This can happen, for example, if a person accidentally touches an exposed wire or an appliance with a fault.
Why RCD testing is importantRegular RCD testing is critical because these devices can become faulty over time, particularly if they are exposed to harsh environments or are used frequently. Faulty RCDs may not work correctly, which means they may not provide the necessary protection against electric shock. By testing RCDs regularly, you can detect any faults and ensure that they are repaired or replaced as necessary. This helps to minimize the risk of electric shock and ensures the safety of people who use electrical devices.
How we test themThere are two different ways to test your RCD. The first way is through the test button, and the second is a timed trip test with a dedicated RCD tester. Both cases involve interval testing. It is important to note the interval between pressing the test button and when the system is tripped. The smaller the interval the smaller the electric shock sustained by an individual. Australian standards dictate the maximum trip times for various RCDs. A licensed technician will be able to determine whether your RCD is tripping fast enough. Here is how to test your RCD.
Integral Trip - Test buttonPush-Button Test: This is a simple test which involves pressing the "Test" button on the RCD. The button simulates an electrical fault by sending a small current through the RCD, which should cause it to trip. If the RCD does not trip, it is likely faulty and requires further investigation.
Injection Test - Timed TestAn Injection test involves applying a milli-amp current through the RCD measuring the time it takes for the RCD to trip when a current imbalance is detected. This test is more accurate than the push-button test and can help identify less obvious issues with the RCD. A qualified electrician can perform this test using specialized equipment.
When should your RCD be testedAs RCDs are important safety devices they require testing at regular intervals In accordance with AS/NZS 3760:2010, RCDs should be tested via the trip button test every 6 months and Injection testing every 12 months in order to ensure that they are able to detect and respond to a fault as quickly as possible. As well as this, all businesses must have an RCD protecting hostile circuits. Ensuring that you follow these standards test your RCDs appropriately will save lives.
What to do in the event that an RCD fails a testIf your RCD fails a test, you must have it replaced as soon as possible. If any of the following occurs, your RCD has failed its test:
- It does not reset after the test
- It does not trip when the test is triggered
- The device is tripping slowly after the test button has been pressed
- The switch feels floppy after the test.