Residual Current Device (RCD) Testing

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RCD Testing

Residual Current Device (RCD) testing not only ensures the safety of an electrical installation but also ensures that the installation runs perfectly without risk of damage to other sensitive electric components.

Residual Current Devices are also known as GFCIs or Ground Fault Circuit Interrupters. These safety features are put in place to prevent an electrical installation from being overwhelmed by excess electrical loads.

These devices can help prevent shocks, fires, and even damage to electrical equipment. A certified installer will use specialised testers to check these devices and make sure that they are working as expected.

If you have been wondering how RCDs work, then this guide is just for you. Read below to learn more about these important safety systems, and the importance of timely maintenance checkups for new and old electric installations.


RCDs are a group of switches that control the flow of electricity in the case of extreme imbalances. For example, in the case of a storm surge, lightning strike, or heavy load from the grid, these special switches can redirect the current and cut it off from the supply to the main electric installation in your home.

The benefit of these switches is that they can prevent electric shocks and fires. They are the first line of defence against electric imbalances and are vital for ensuring the integrity of the entire electrical installation.

Without Residual Current Devices, any installation would be at the risk of being overwhelmed by huge currents. If there is no RCD in place and there is a surge of high voltage, then you would be looking at intensive damage to the main electrical installation and likely a complete failure of sensitive electrical equipment.


RCD testing is just as important as the devices themselves! RCD testing not only ensures that the safety components are working as intended but also makes sure that the system is working at full efficiency with no current leaks.

Here is what you can expect in a typical RCD test by a professional electrician:


Before testing the system, the RCD component is separated from the main installation to ensure that it can be tested safely. The RCD system is isolated so that it cannot cause any damage to the main installation if it turns out to be faulty.

An electrician will calibrate the RCD tester to ensure that it provides accurate readings in the context of current, load duration, and response time.

Testing Process

The RCD test involves several steps and is conducted to make sure that the RCD system operates within the specified parameters. For example, the system must trip within a specified time frame without any lag for it to be deemed acceptable. If there is a considerable delay in the disconnection of the switch, then this would indicate that the RCD system needs to be repaired.

The first step is to visually inspect the RCD system. A certified electrician will use their trained eye to visually inspect the components of the RCD system. The inspection is done to make sure that there are no obvious signs of damage to the system.

This damage can either show on the components themselves, or the wiring that leads from the main electrical installation to the RCD system.

The second step is to run a functional test. This test involves triggering the RCD system to ensure that it disconnects or “trips” at the right time. Timing is everything in these systems because a delay in the time that it takes for the system to disconnect can result in severe damage to the electrical installation.

An RCD can be triggered using a manual test button or specialised test equipment that sends a load to the RCD system to purposefully trip it.

The third step is to conduct a trip test. This test involves calculating the tripping time for the RCD system. The tripping time can vary but is usually set in milliseconds so that the system can quickly disconnect from the main to save the electrical installation. The final step is to run a rated current test. This test verifies that the RCD trips right at or below the residual current rating.

Duration of Test

RCD test duration can depend on several factors. For example, the testing time can depend on the number of RCDs installed in an installation. Large homes or commercial properties usually have a lot of RCDs installed to protect the electrical installation.

Small homes, on the other hand, have few RCDs so they can take less time to test. Usually, a typical standard RCD test can take anywhere from a few minutes to about half an hour. This time includes preparation time, setup time, testing, and documentation.


The only way to ensure the safety of an electrical installation is to have it checked out by a professional electrician. These electricians are the only trained and experienced personnel to handle testing procedures using the British Standards.

However, how do you know when you need to run RCD or similar electric tests?

In the case of RCD testing, this test can be conducted every six to twelve months, or according to regulatory requirements and industry standards.

As per the wiring regulations BS 7671:2018, every commercial property’s electrical installations must be regularly inspected and tested every 5 to 10 years to rule out any defective electrical work and safety hazards.

This means that if your electrical installation is around or beyond the five-year mark, you should call in a professional as per their provided schedule to have the system checked for faults.

Please keep in mind that all electrical equipment depreciates over time and can wear down or accumulate damage. When this happens, even a small fault as a defective RCD component or an exposed wire in the RCD system could potentially jeopardise the entire installation.

Testing is also part of the regulations. For example, landlords who are renting out property will be held responsible for the testing of the RCD systems along with the electrics as per the wiring regulations for commercial properties and businesses.

For residential properties, electric testing may also be done before a new tenant comes in. This is done to ensure the safety of the electrical installation and to make sure that there is no risk involved with the current configuration of the installation.

RCD testing doesn’t take up a lot of time but is incredibly crucial in protecting your electrical equipment. Failure to follow protocol can result in a lot of unwanted risk and severe consequences to both your life and your assets!


RCD and general electrical inspection cover a few important procedures. The most basic one is a visual test that property owners can also conduct on their own.

While RCD systems can be too complex for the average Joe to test, property owners can use their keen eyes to detect faults in the electrical system beforehand to ensure the safety of their installation.

In some cases, these faults can also highlight issues in the RCD components. For example, in the event of electrical surges, if the power does not disconnect, it could indicate a problem in the RCD. On the other hand, if the RCD system works but there is a delay in the disconnection, then this too can cause systemic issues.

You can detect faults caused by electrical imbalances caused by a faulty RCD system in various electrical components like lights, switches, fans, dimmers, sockets, small and big appliances, machinery, etc.

Here are a few common warning signs of a failing electrical system that could be caused by faulty RCD components:

  • Flickering lights or buzzing noise from lights/fixtures.
  • Excessive breaker tripping, specifically when turning on high-wattage appliances.
  • Electric buzzing, small sparks, or discolouration around the socket or socket board.
  • Excessive voltage imbalances.
  • Frequent burning out of lights, switches, or small appliances like bells, chargers, etc.
  • Smoke and burning smell when turning on appliances.
  • Frayed wires and electrical shocks.

If you notice some or all the signs mentioned above, it is probably time to call Calder Electrical.

These warning signs may not look alarming but may indicate a larger safety issue within the electrician installation.

Over time, these issues will typically lead to problems which is why it is recommended that you get in touch with a professional and certified electrical team as soon as possible.

Here are some of the most important electrical testing procedures:

Visual Inspection

As mentioned above, one of the most basic ways to begin electrical testing at your property without a professional is to inspect the installation visually.

Please keep in mind that the differences between the visual inspection conducted by a layperson and a professional will be huge!

While you may conduct a visual inspection on your own, a professional inspection will provide way more useful information. Furthermore, professionals use their years of experience, intuition, and understanding of electrical equipment to carry out a detailed visual inspection.

For example, a frequent voltage imbalance, flickering lights, or burning smell during the operation of high-voltage appliances can all indicate problems in the installation. These problems can also be caused by a faulty RCD system that isn’t tripping in the event of imbalances or unusually high loads.

During the visual inspection, a certified electrician will make notes and create a Visual Inspection Report (VIR) that will provide an overall general summary of the electrical installation.

A VIR will provide a general report on the efficacy and safety of the electrical installation. The report can also highlight problematic areas. For example, if the electrician visually inspects the RCD components and finds problems, they can document the issue, present it to the stakeholders, and provide corrective measures.

Electrical Installation Condition Report

Electrical Installation Condition Reports or EICRs are what the industry uses as a standard for detailed electrical inspections.

An Electrical Installation Condition Report (EICR) is the testing procedure of choice because it can help outline potential flaws in the system and provide a full look into the efficiency of an electrical installation.

EICR was previously known as the Periodic Inspection Report (PIR) and is used to thoroughly assess all electrical systems within the property.

The EICR checks the current condition of multiple systems using various electrical tests. For example, the report will cover aspects of the RCD components, the wiring in the RCD system, general electrical wiring, accessories, equipment, and any other component connected to the main line.

An EICR is generated using functional testing. A functional test is when every electrical component is thoroughly checked and documented using industry standards. Documentation also helps in creating an effective testing and maintenance schedule.

The benefit of Electrical Installation Condition Reports is that they are conducted at regular intervals and provide a complete picture of the health of the installation.


The only way to ensure the efficacy of RCD systems and an electrical installation is to opt for an experienced and certified electrician who is trained to perform electrical tests using industry best practices.

Here is how you can get a certified electrical company for electrical installations, RCD, and general testing, maintenance, and inspections:

  • Go to the Competent Persons Register – a database of the Competent Person Schemes (CPS) – and search using the name of the person or business you’re looking for. Type in “Calder Electrical” and you’ll see it listed under the NICEIC registered businesses.
  • Make sure that you conduct a thorough analysis! We recommend that you check the reviews of the installer to ensure that they are experienced and have great reviews on their professionalism, service, and after-service.
  • For the best experience, talk with the electricians in the company to make sure that they understand your expectations. Professional installers, like Calder Electrical, always keep property owners in the loop so that they know exactly what to expect from the visit.
  • Ensure that the electrician takes liability for the installation and is insured by the electrical installation company. For example, Calder Electrical provides fully trained and experienced individuals who conduct work using the latest regulations and industry-leading best practices.


We have been providing electrical services to residential, commercial, and industrial properties for over 40 years and are specialists in all aspects of electrical installations, maintenance, and testing.

All our work is fully insured, and we work to meet the standards set by the NICEIC to make sure all your electrical installations meet the current regulations, and all the notifiable work is signed off by the local authorities.

If you have unplanned issues within your home or business, we can provide a call-out service to rectify and solve any problems such as circuit tripping, loss of power, broken items that need repairing, or to check if you feel something is unsafe or a potential hazard.

Our team can generate a Visual Inspection Report (VIR) to identify anything visual that does not comply with the standards or looks unsafe, as well as a full Electrical Installation Condition Report (EICR) where we will identify and test each circuit to make sure they are not deteriorating and are safe for use within the current standards and regulations set by the BS 7671.

We can also provide PAT testing of appliances to make sure that any items such as kettles, computers, and microwaves are safe for use in the home and workplace.

Contact us here or call us at 0800 612 3001 to get in touch with our professional electricians for more information on RCD testing and the importance of regular electrical maintenance and testing for your property.

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