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SILICON CHIP www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc. (Hons.) Technical Editor John Clarke, B.E.(Elec.) Technical Staff Ross Tester Jim Rowe, B.A., B.Sc Nicholas Vinen Photography Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Kevin Poulter Stan Swan Dave Thompson SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Warwick Farm, NSW. Distribution: Network Distribution Company. Subscription rates: $105.00 per year in Australia. For overseas rates, see our website or the subscriptions page in this issue. Editorial office: Unit 1, 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. Fax (02) 9939 2648. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Publisher’s Letter Electricity is a boon; electricity is a killer! This month we have an article which highlights a hidden hazard of domestic electrical systems whereby the plumbing in a house can become lethal. How can this be? It is mainly due to corrosion and it turns out that your average plumber is more aware of the problem than most electricians. Why is that? Because if a plumber replaces a length of copper pipe in your house or needs to remove or replace your water meter, he can be exposed to the risk of electrocution. The reason for this is that heavy electrical currents can flow in your water pipes and through your water meter. If the water meter is removed, there may be the full 230VAC applied between the two pipe ends! If the plumber is unfortunate enough to touch the two pipe ends, he could be electrocuted. Fortunately, most plumbers are aware of this and before they even think about removing a water meter, they bridge across it with a heavy jumper lead – to provide a continuous path for the hazardous current. They should do the same thing if they need to replace a length of copper pipe elsewhere in your plumbing. You can read about how this hazard comes about in the article, starting on page 14 but even if you don’t read it, you should be aware of the basic message. In short, if you lose the Neutral connection from your home’s switchboard to the power pole in your street, your water pipes could hold this lethal threat. Nor will you know anything about it unless you do some checks. All of your electrical appliances will continue to operate normally, by the way. Perhaps you may be thinking that because you have RCDs (Residual Current Devices or safety switches) installed in your switchboard that everything is ‘hunky dory’. Well, the RCDs may well protect you and your loved ones if one of your appliances develops an electrical fault but they will not give any protection against the hazard of electrical currents flowing in your water pipes. “Oh, well”, you might be thinking, “provided no-one disturbs the water pipes, nothing further can happen”. Well that could be a tragic conclusion because the loss of the Neutral connection can also ultimately lead to all the pipes in your household becoming “live” and lethal. You could be electrocuted next time you take a shower. Think that is far-fetched? There have been several cases of this happening in the last few years. Ignorance is not bliss! Indeed, the impetus for this article came about because of a letter from one of our regular correspondents whereby some of his close relatives living in a rental premises complained to the landlord about getting ‘tingles’ in the shower. The landlord regarded it as trivial and passed it off, saying that the previous tenants had lived with it for six years. But our reader knew better and advised his relatives to complain to their electrical retailer. And just as well that they did – they had lost the Neutral connection at the power pole and were living with the substantial risk of electrocution. Now I am not advocating that people should be tampering with their electrical systems in any way. But people should know about our MEN (Multiple Earth Neutral) system and how it can develop a hazardous condition. Furthermore, I believe that people who know about this are fundamentally safer than the vast majority of the population who are completely ignorant about the workings of electricity. If you ever hear about anyone getting ‘tingles’ from their water taps, make sure that they advise their electricity retailer immediately. They will get an immediate response and the problem will be fixed. Leo Simpson Recommended and maximum price only. 2  Silicon Chip siliconchip.com.au