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Powerbreaker making Britain safer for 35 years

Richard Shaw, managing director at GreenBrook, the pioneers of the RCD Powerbreaker explains how the idea for the first RCD was born in a pub!

Powerbreaker making Britain safer for 35 years

Who would have thought that a simple customer request could spark one of the electrical industry’s biggest ever safety improvements - the development of the humble RCD. Yet this really is the case.

Now retired, Doug Knight was responsible for developing the first RCDs. He was the engineering manager, and later the technical director at Besson and Robinson, the electrical relay manufacturer that today is part of GreenBrook.

In the 70’s circuit breakers were huge, and had to be included in the original specification of an electrical installation. The original enquiry came from the brewer, Watney Mann. They had a code of practice that stated that the electric pumps in their pubs had to be run off a 110w socket or else be connected to a circuit breaker. We were asked whether it would be possible to create a circuit breaker that would fit into a 13 amp plug and the development process started from there.

Since then, the concept of the RCD has developed so much that it is now a mandatory part of building regulations compliance and the devices are available in numerous formats to suit all kinds of domestic and commercial applications.

The first RCD that Doug produced was a single socket RCD in a unit the size of a double socket using HO7 wiring. However, he kept the development process going and within six months had created an RCD socket within a normal, surface mounted socket unit.

There had been some fatalities with young people dying from electric shocks from microphones in clubs, so safety was high on the agenda in the commercial world and very much on the general public’s radar too. We successfully marketed the RCD sockets for commercial use but people also started buying them for use in their own homes.

At this stage the company joined BEAMA which helped raise the profile of the new-style circuit breaker even further and Doug began looking at the possibility of fitting the technology into a 13amp plug. By this time the prospect of creating an RCD in a plug seemed realistic and there was such industry support and political will behind achieving it too. The result was the Powerbreaker plug-in RCD.

The technology works by constantly monitoring the current flowing in the live and neutral wires supplying a circuit or an individual piece of equipment. Ideally, the current flowing through both wires will remain equal but if an earth leakage occurs due to a fault in the circuit or an accident with the equipment, or if an imbalance occurs, the RCD detects the problem and automatically cuts the power preventing injury or damage. To be effective, an RCD must respond very quickly to even the smallest current leakage, which is why GreenBrook now engineers its RCD units to trip out well within the 200mS recommended time if any current leakage of 30mA or above is detected. Our RCD’s are designed to trip out after only 40 millseconds.

GreenBrook was also responsible for introducing the first double pole RCD in 1988. Broadly speaking, today there are three types of fixed RCD. For domestic use the main product types are consumer board modules, which, following the 17th edition of the wiring regulations are now required in all new installations, and SRCD wall socket units, which replace the standard, unprotected socket outlet. In commercial environments, where there may be a need to wire the appliance directly into the wall without a socket, FCU spur units are also available. These are Installed in the same way as an SRCD, but have only the RCD buttons, a fuse holder and provision for a cable to be wired in direct, making them ideal for applications like hand-dryers in public toilets.

There is still a huge market for portable RCD products - ranging from plugs that can be fitted to individual appliances, adaptors that can be moved from appliance to appliance and in-line RCDs which are best suited to applications where equipment may need to be moved around a lot. For many, portable RCDs and SRCDs remain the safest and most reliable as they protect the user at the point of use. What’s more, they do not present the problems with nuisance tripping associated with consumer board modules.

The use of RCDs is now routine in both commercial and domestic settings and wholesalers and contractors need to recognise their advantages in terms of enhanced safety and added value when compared to standard plugs and sockets. GreenBrook is continuing to develop the concept and is currently working on bringing the next generation of SRCDs to market.


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