Test your RCDs regularly to be protected against electric shock

(11/12/2009)

An RCD is a Residual Current Device. Usually it is a big switch in your fuse board but it can be next to the fuse board or somewhere else. It is usually as wide as two of the normal switches and it has an on/off switch and an important little plastic button with a ‘T’ embossed on it. Without going into the boring technical stuff what it does is monitor the flow of electricity around the circuits it is guarding. As soon as it gets even a minute sniff of anything not in perfect balance it switches off in milliseconds. An RCD tripping could be saving a life.

You know those things you can buy to plug the lawnmower into at the socket, so that it will switch off if you mow through the cable before you get an electric shock? Well it is almost exactly the same as one of those. Almost, but better. And it is protecting you indoors, and on more than one socket. In up to date homes there will be an RCD looking over everything. Or two, or three if you are lucky.

Like all industries, electrical stuff is shrouded in myth. The RCD is at the heart of many of those and they’re not all good but please read on. You might hear stories that make you not want to have one, for example that they cut out too often. There’s a common story that carries the threat of your freezer defrosting while you are away on holiday. Let me try to persuade you otherwise: An RCD cuts out because it is doing its lifeguard job. It does it with science and doesn’t make a conscious decision to disrupt your evening or cause an unwanted thaw. That little gadget is constantly checking and fantastically sensitive to even the smallest problem.

You could easily forget it is there until one day it finds a fault. It only takes a tiny fault for your RCD to safeguard you and cut off the electricity. I’ll put that into perspective by telling you that when you are boiling your kettle it is probably using more than 280 times more electricity than that tiny fault which will cause your RCD to operate, but normally your kettle is using it safely. If you have an electric shower then we could be in the realms of a thousand times and more. All fine so long as the kettle and the shower are working well but we need the electricity to cut off much sooner if there is a problem. So, that’s why RCDs are super-sensitive. If your RCD is working properly it will cut your kettle off long before you are in danger.

The imbalance that an RCD finds might be something like some water getting into a socket. Water and electricity: not a great combination but common enough. That’s why your electrician isn’t just putting up that new garden light. It might be where one of your cables is wearing out and starting to break open. Or it could be a mouse chewing away in the loft. Or how about a baby trying to bottle feed the little holes in a socket or post soggy toast into the DVD player? Without your RCD that warm milk might do more than just damage the wallpaper. RCDs save lives. Amazing bits of kit.

Because of the bad press that the RCD was getting, the Electrical Safety Council commissioned an investigation into the reliability of RCDs in homes. They tested 607. What they found was that they are very reliable in long term use but that homeowners were not testing them. To test one, every two months or so all you have to do is press that little button with the T on it. The switch should ping down. If it doesn’t, then it might not be working and could be hiding all manner of fire and shock hazards. In which case, call a NAPIT registered electrician. The good news is that 96% of the RCDs tested were fine and dandy. To switch back on, just pull it all the way to the bottom (if there is room to spare on yours after it has pinged), and push it back up.

But what of the four percent that weren’t fine? This is mind-blowing; six of them had been deliberately shorted out, which means blown up, to prevent them from working. OK, so that’s just a statistic on paper but a working RCD offers preventable death by electric shock when your hair dryer starts playing up, and the risks involved in shorting one out are risks not to be taken. The rest were genuinely faulty.

It turns out that an overwhelming number of people are not testing their RCDs regularly. Go on, go and hit the button. Do it with your smoke alarms. Make it a habit and don’t look upon it as a chore. But if the switch doesn’t go down then do call a registered electrician because you might have a problem. This type of problem is advanced electrical work so you might do well to call an electrician who knows how to test and inspect. Electrical fault finding is a bit different from putting up a light.

Registered Electricians work to a strict code of practice dictated by a huge book of regulations. They are required to pass an exam about them every time they change significantly. These days, most new work must be protected by one of our magical RCDs which means that you need to be ready to hear it and to have one. But before you say no to a new RCD for the sake of your freezer, there are a couple of nice ways of preventing you from worrying about it defrosting while you are away. Your electrician will know those little gems if he is up to date with the latest electrical regulations. They’re not a secret and it is a regular exam question for them.

But if yours does trip, it might be something simple causing it so first unplug everything right out of the sockets and try to re set the RCD into the up position. Don’t just switch the sockets off, pull out the plugs. That’s an important trade secret just shared with you. Nine times out of ten it is an old appliance that is causing the trip, so you might only need a new toaster and not an electrician. If that doesn’t work then it is a fault finding mission for an electrician.

If you don’t have an RCD then your electrician may well be able to put one in for you without changing the whole fuse board. The new fuse board is the best way to go though, because you’ll get more than one protective RCD and as well as that your NAPIT electrician will carry out a full inspection of your household electrics which will tell you about any problems found. You’ll be walked through what to do if it ever trips and shown how to test it. You’ll also get a set of certificates with all the test results on.

But which ever route you take to acquiring RCD protection, you will get the peace of mind of knowing that you and your family are much safer and better protected against electric shock. Worth having.

Related categories:  Circuit breakers MCB, MCCB, ACB   Residential   Surge and lightning protection