Residual Current Devices: A Crash Course in RCD's
Residual Current Devices - better known as RCD’s - are life-saving devices that protect against electrical shocks and fires. RCD’s are more sensitive and provide a higher level of protection than standard fuses or circuit breakers, with ratings measured in milliamps (mA) instead of amps (A).
But with many different types of RCD available, selecting the correct model can be a confusing process.
With the help of our simple guide, we'll make it easy to choose the right model for the job.
What Are RCD's?
In simple terms, RCD's monitor the electricity flowing through equipment and devices. They measure the current flowing in versus the current flowing out - and shut off the power if they detect an imbalance.
RCD's can be triggered by things such as faulty electrical equipment, water seeping into electrical connections, burnt-out sockets, or a person cutting into a live wire.
RCD’s provide three types of safety protection:
- Fault protection: Any tripping current that relies on the resistance of the earth path (Regulations 411.4.204, 411.5.1, 531.2)
- Additional protection: RCD's with a tripping current of less than 30 mA (Regulation 415.1)
- Fire protection: A tripping current of less than 300 mA (Regulation 422.3.9)
What Are the Different Types of RCD's?
While ‘RCD’ is often used to describe any device that provides residual current protection, there are three specific types:
1) Fixed RCD’s are fitted into the consumer unit (fusebox), and provide the highest level of safety for one or multiple circuits. There are two types of fixed RCD's for use under varying standards:
- Residual Current Circuit Breaker (RCCB) without overload protection (BS EN 61008, BS 4293, BS EN 62423)
- Residual Current Circuit Breaker (RCBO) with overload protection (BS EN 61009)
2) Socket-Outlet RCD’s feature built-in residual current devices and can be used instead of traditional socket-outlets (BS 7288)
3) Portable RCD’s plug into any standard socket-outlet, allowing electrical appliances to be connected directly to the RCD (BS 7071)
How Do You Select the Right RCD for the Job?
RCD's are required to comply with strict electrical and safety standards as identified in Regulation 531.3.3 of BS 7671:2018.
Where it is needed, equipment manufacturers must also specify (or make available) the correct type of RCD as a requirement under UK law. As it's not possible for electricians to know which equipment will be connected to an installation in the future, it's best practice to consult with clients to determine the most suitable RCD type.
Expert Electrical can also assist in selecting the correct type of RCD from a range of popular models and brands.
Need Expert Advice? We Can Help
RCD's are an essential component of electrical safety, and it's critical to use the right model for each type of installation. We supply a wide range of RCD's and RCBO's from many of the UK's leading brands, ensuring that you're always meeting the latest standards - and your customers stay safe.
We encourage you to view our extensive selection of residual current devices, or if you need some expert advice, contact a member of our friendly and knowledgeable team.