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RCD Testing: How to Test a Residual-Current Device (RCD)

RCD testing
RCD testing
Resource: https://www.youtube.com/watch?v=ZaAUg75BR5Y

Testing your RCD or residual current device is an important part of ensuring electrical safety. In this article about RCD testing, we’ll show you how to do it. We will not only explain why you should test your RCD, but also give the steps on how to do it properly.

What is an RCD?

An RCD, residual current device, is a life-saving appliance that protects people from electrocution. It does this by detecting ground fault current and quickly disconnecting the power supply.

Your RCD, whether in a residential or commercial setting, should always be in good working order. A faulty RCD can put you and your family or workers at risk of serious injury or even death.

In order to verify that your RCD is functioning properly, you need to check it regularly. This process is carried by either the owner or, if requiring the use of special equipment, a qualified person.

What is RCD Testing?

Because they are so important, RCDs must be regularly tested to make sure they are working properly. You can test RCD devices easily, even without professional help, since they come with a test button.

There are also advanced RCD tests to check the condition of the device. These tests are generally performed by a professional electrician using specialized RCD testing equipment.

A residual current device test provides these benefits:

  • It helps to detect any errors or faults in the RCD for early repair or replacement
  • It confirms that the RCD is working as it should
  • It ensures that the RCD will protect you in case of an electrical accident
  • Depending on your location, it may help ensure compliance with electrical safety regulations

Below, we look at the RCD testing procedure when using the device’s test button and when using a tester. This will give you an idea of the testing options, including what each method entails.

RCD testing equipment
RCD testing equipment
Resource: https://www.diynot.com

RCD Testing Procedure

As indicated above, there are two ways to test your RCD: with the test button or using an RCD tester. Here is a step-by-step guide on how to do both types of tests.

1. Test Button RCD Test

The RCD test button is located on the front or side of the device and may be marked with the words “T” or “TEST”. To test your RCD with the button, follow these steps:

(Note that this is a procedure to test RCD at board or while connected to the electrical system)

1. Remove/lift the cover on the consumer unit/fuse box.

2. Locate the RCD device that you want to test and identify the test button.

3. Push the test button. The RCD should click and the power should go off. If it doesn’t, then there may be a problem with your RCD.

4. To reset the RCD, switch off the circuit breakers that connect to it, then flip the RCD switch to the ON position.

5. Turn on the circuit breakers and replace the cover on the consumer unit/fuse box.

The RCD button test simulates the imbalance that happens when currents going into and out of an electrical circuit don’t match. The button test is a way to check if the RCD can trip or disconnect power when it detects this imbalance.

2. RCD Tester Test

If you want to go beyond the basic test, then you’ll need a residual current device tester. This is a specialized piece of equipment that can provide a more thorough analysis of your RCDs.

While you can purchase an RCD tester, they are generally only used by professional electricians. If you don’t feel comfortable using one, then we recommend that you hire a professional to test your RCDs for you.

There are two different tests when using an RCD testing device: operating time and trip time tests: here are the two methods of RCD testing explained briefly.

RCD Operating Time Test

The operating time RCD test measures how long it takes for the RCD to trip when there is a current imbalance. Although simple to carry out, this test still requires the use of specialized RCD testing equipment.

RCD Trip Time Test

The RCD trip time test measures how quickly the device can trip when there is a difference in the incoming and outgoing currents. This is generally considered to be the more important of the two tests, as it can help prevent serious accidents.

How to test portable RCD devices using a tester
How to test portable RCD devices using a tester
Resource: https://www.youtube.com/watch?v=hjKLzyFUqxs

How to Test Portable RCD

Portable RCD devices have a test button just like regular RCDs. Because they plug into an electrical socket, you can easily test them for proper working using the operating time test. Here is how to go about it:

1. Connect a working lamp to a power point and leave it on.

2. Switch off all electric appliances and other devices.

3. Plug in the portable RCD device into a power point and make sure that the power is turned on.

4. Push the RCD test button. The power should go off and the lamp should turn off.

5. If the lamp doesn’t turn off, then there may be a problem with the RCD device.

RCD Test Requirements

RCD testing is crucial to ensure the safety of your electrical system. Here are a few tips to keep in mind when testing your residual current devices, whether at home or your business:

1. Always test your RCDs before using them. This will help verify that they are in good working condition and that your electrical system is safe.

2. It’s recommended to test fixed (panel mounted) RCDS and socket RCDs after every three months, portable RCDs every time you need to use them.

3. Because RCD testing procedures disrupt power, it’s a good idea to test all of your RCDs at the same time. This will help minimize any disruption to your electrical system.

4. You may also want your RCDs tested during off-peak hours when there is less demand on the electrical system.

5. Always follow the manufacturer’s instructions when testing your RCDs.


Regular RCD testing is a crucial step when it comes to the safety of electrical systems. By testing your RCDs, you can ensure that they are working properly and will provide shock protection in case of an electrical accident.

And while you can test your RCDs with the test button at any time, we recommend that you hire a professional electrician to test them every three months. The electrician will use specialized testers for a more detailed analysis.

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