Switch on to safe RCD specification
Alan Boutall, design manager at GreenBrook Electrical, tries to cut through the marketing hype and help contractors choose the right RCD for a particular application.
It is now 33 years since the first ‘Powerbreaker’ was introduced to the UK market, and since then new product types have been introduced and market demand has grown significantly. The need to combine advances with technology in the home, with an increased emphasis on safety, has made RCDs an indispensible part of any electrical installation. However, with the new RCD requirements introduced by the 17th edition wiring regulations we’re now overwhelmed with ‘reference guides’ - most of which provide a thinly-veiled sales pitch.
Luckily, the BEAMA Guide is a truly independent handbook, which remains available from the association free of charge. The guide pre-dates the changes to the regulations and therefore looks at the options for RCD protection from a completely objective standpoint. Why is this important? Because every application is different, so a one-size-fits all approach to installing RCD protection simply is not viable. Instead, specifiers and contractors need to be able to make informed decisions based on what is practical, what is financially reasonable and, above all, what offers the highest level of protection from electrocution for the end user.
These are the considerations that have driven product development of RCDs since their introduction all those years ago and there are now three generic types of fixed RCD on the market. For domestic use the main product types are consumer board modules, which replace the consumer box fuse, 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. Installed in just the same way as an SRCD, FCUs have only the RCD buttons, a fuse holder and provision for a cable to be wired in direct, making them ideal for applications such as hand-dryers in public toilets. In addition to these fixed RCDs there are also a number of portable products on the market ranging from plugs which 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. On a building site, for example.
As far as the legislation is concerned, the consumer board module is the quick fix for domestic installations and, in many cases, this is certainly the most straightforward option as it protects the end user and their appliances with a single device for a whole zone. However, it may not prove the easiest choice to live with for the family that eventually makes its home in the property.
The biggest issue they may face is nuisance tripping, with a single faulty or vulnerable device causing the whole zone to trip and thereby knocking out other appliances. A small price to pay for the safety benefits of having an RCD in place, you might think. But what if there is a freezer full of food or a tank full of fish within that zone? It is easy to see how this situation could quickly become unacceptable and prompt the user to disable the RCD and expose themselves to the risk of having no RCD in place at all!
The alternative is to include individual RCDs at the points of use, which allows the end user to immediately identify any faults. This also makes it easier for the end user to test the RCD every time they plug in an appliance because, as a legal requirement, all point of use RCDs have a test button incorporated in their design and regular testing is strongly recommended. While this is also true of consumer units, their inaccessibility makes frequent testing a much more difficult – and therefore less likely – prospect.
It is also worth noting that, while both consumer unit and SRCD products can be retro-fitted, if the house in question requires only a partial update, the SRCD may offer more of a quick fix. This allows the contractor to update the sockets that are being replaced without disruption or additional cost to the end user.
Like any other safety precaution, RCDs work best when used appropriately, which means making informed decisions about all the choices for each individual installation.
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