A Complete Guide about Residual Current Devices

Residual Current Devices

All electricians are familiar with residual current devices (RCDs). These devices are widely used for fault protection and additional protection in most consumer units or electrical distribution boards.

Residual Current Devices

Residual current devices are devices that people use for the safety of switches. They are designed and developed to protect basic forms such as;

  • Fire Protection – for currents not more than 300 mA
  • Fault Protection – in case of tripping currents
  • Additional Protection – for RCDs affording less current, usually 30 mA

RCDs are the safety devices one must use or work on electricity.

How Does These Devices Work?

  • Every RCD has an iron core. Electricity passes through the coil to the iron core, producing a magnetic field.
  • Current flows back to the RCD, pass around the coil and goes to the live wire.
  • So, two magnetic fields produce current. Both currents must be the same and cancel each other.
  • If there is any fault, electricity may leak.
  • Then an RCD detects the leakage and disconnects the circuit.

An ELCB device detects the earth leakages and imbalances of the current in both fixed and portable environments. During such issues, devices automatically disconnect the circuits when the leakage reaches the level of 30 mA and does not pass the electricity. Above 30 mA, there might be dangerous electric shocks. This mechanism helps and protects people from fire and electric shocks. For electrical system solutions and ELCB, RCD, RCCB, and Circuit Breaker related issues, you must find an authentic, trustworthy, and reliable service provider who can provide you with responsibility.

What to Keep in Mind?

During the installation of circuit breakers and RCDs, you and your electrician must consider the installation requirements and parameters. Remember that

  • You are regularly checking your circuits to avoid any sudden shock or leakage.
  • Suitable RCD is installed according to the appliances.

Types of Load on RCDs

Type of RCD Usage (Domestic / Industrial) Brief Description Type of Load an RCD can Bear
Type AC Usually industrial AC applications Resistive, capacitive, and inductive Electric showers, hob, oven, heater, halogen lighting, and tungsten lighting.
Type A Usually industrial AC applications Single phase with electronic components Inverters (single phase), power supplies, induction hobs, charging equipment for electric vehicles, IT equipment, multimedia equipment, and lighting equipment such as dimmers and LED drivers
Type B Usually industrial AC applications Three phase electronic equipment Inverters for speed control (three phase), lifts, welding equipment, chargers for electric vehicles EV, escalators, uninterrupted power supply (UPS), and industrial machines.
Type F Usually industrial AC applications Frequency controlled equipment Air conditioners, power tools, dishwashers, tumble driers, washing machines, and appliances with motors.


How to Wire an RCD?

Before looking for the answer to this question, you must look at several other factors like manufacturers, different models, and devices. These factors vary, so the steps to perform the task also vary. There can never be a universal way to wire an RCD.

Keep in mind that all brands have different methodologies. All manufacturers use different numbers and letters. Terminal locations also vary from model to model. It is highly recommended that you check the manufacturer’s guidance manual for your specific device to ensure accuracy and consistency.

Precautionary Measures

You must take extra precautions when working with the consumer units or removing an RCD from a fuse box. Working with electrical units and circuits can cause a lot of dangerous problems. If you are unaware of such work, you must always get help from a professional electrician and qualified person to avoid any risks and inconveniences.

Testing Requirements for an RCD

It is highly recommended that you check RCD regularly. You must check fixed and socket RCDs almost every three months, but test the portable RCDs whenever you use them. Testing is easy and quick as most models have a built-in button. If the case is the opposite, you can check and test it easily with a tester. When you test your device, it should trip and switch off immediately. If it does not happen, your device requires further investigation.

Step by Step Guide to Test an RCD

Below are the key steps you must follow to test your residual current devices (RCDs).

  1. Plug a small appliance into the socket and ensure it is working properly. Do not switch it off.
  2. Ensure that electricity is connected to the RCD and the main switch is on.
  3. Turn off all other electrical appliances.
  4. Press the test button on your residual current device. Keep your finger away from the device.
  5. Check if your device is working.

Reasons for RCD to Get Tripped

There are a lot of reasons that might cause an RCD to trip and switch off the supply to the circuit. These reasons include;

  1. Old, damaged, and faulty electrical wirings
  2. A blown light bulb
  3. Moisture in your electrical bulb or appliances
  4. Incorrect current rating within an RCD
  5. An incorrect or faulty electrical appliance is plugged into the electrical circuit.
  6. Poor weather conditions like heavy rain, thunderstorm, and lightning.

Measures to Take When an RCD Trip

It is necessary to take some measures when an RCD trips. First of all, you must switch off all electrical circuits that are protected and secured with a tripped RCD. Once you ensure the circuit is switched off, you must reset the device and turn it on again. During this process, you can identify the basic cause of the trip. If the cause is simple, you can easily rectify it.

If your circuit tips again and you cannot identify the cause, you must switch off the circuit until you diagnose the problem. If you cannot check and investigate yourself, you must call an electrician or a qualified professional for further assistance.

If you observe multiple circuits trip the RCD, remember that it may be the sign of a neutral fault. In that case, you must identify the fault to rectify it as soon as possible.

Final Words

Never compromise on the electrical issues of your home of office. Ensure that all circuits, breakers, and appliances are operating perfectly. If there is any issue, you must investigate it as soon as possible and rectify it with the assistance of an electrician.

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