engineer-in-wonderland
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An Engineer in Wonderland – Domestic wiring madness?

cc-plug.jpg Years of experience, and quite probably many tragedies, have made the UK wiring regulations what they are – good, sensible rules – albeit written in a somewhat impenetrable form. For all the right reasons, no power sockets or wall-mounted switches are allowed in bathrooms, and light fittings near the bath, shower and hand basin must be special water resisting types. However, what I find a little nuts is that there seem to be no special rules for the room immediately under the bathroom – normally the kitchen.

More than once, someone who has had a flood in the bathroom has told me the kitchen light fitting was “really hot” to touch when they got up to poke a hole in the ceiling to let the water out. Now maybe I am missing something here, but I suspect it would be possible to get a very nasty belt off a light fitting full of water, particularly with a soaked ceiling, water running down the walls, and pools on the kitchen floor. None of these people I know have been shocked during their experience, but this seems down to good luck rather than design. Can anyone tell me if there is a technical reason why light fittings beneath the bathroom do not have to be waterproof? Or if there is some reason that the situation I describe above is intrinsically safe? I don’t think the answer: “people should know better and turn the power off” counts, as protection of the ignorant seems to be one of the purposes of the wiring regs. ‘Alice’ (Picture – Leonid Mamchenkov, under Creative Commons Attribution Licence)

Tags: flood, hand basin, kitchen floor, missing something, Wonderland

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12 Comments

  1. Peter Smith
    May 29, 2008 18:15

    As many other commenters have pointed out, a RCCB is the simplest (and safest) course at the moment. I certainly agree with Robin Brand about double insulated gardening tools; not only is there a danger from a nicked cable, they can get wet in a garden, and wet plastic can deliver a reasonably severe shock.
    In any case, why all this paranoia about safety? A little danger adds spice to life. You’re far more likely to die in a RTA than as a result of getting an electric shock in a flooded bathroom – or, for that matter, cutting wet grass.

  2. Cliff Woodcraft
    May 08, 2008 14:07

    My concern is with MCBs, which now replace wire fuses in distribution panels. Experience has shown that they are vulnerable to nuiscance tripping when incandescent lights expire and following brownouts when supplying high surge loads such as banks of computers. This tripping damages the MCB contacts and can cause them to weld closed: I have seen this. I know of an MCB exploding, causing injury when being manually reset. As a result my employer adopts a policy of replacing MCBs after every 3 trips. They also suffer from very slow operation if any fault current is insufficient to actuate the magnetic actuator, having to wait for the thermal mechanism to operate. Until these problems are resolved, I think I will stick with fail safe wire and cartridge fuses for home.

  3. Alice
    May 07, 2008 15:19

    I agree that some folk have an unreasonable desire to put totally unsuitable fittings in bathroom ceilings – my home’s previous owner had installed two cheap metal framed downlighters in zone 2, without even bothering to connect the earths at either end of the cables.
    I now have a nice low-energy electronic ballast IP6x fitting that cost just shy of £100.
    However, I disagree that fittings with greater ingress protection have to be expensive – particularly in comparison to an RCBO.
    After all, a lemonade bottles, Tupperware and toy submarines are all waterproof and cheap, so it can only be lack of demand that stops fitting manufactures making floodable fittings in quantity – particularly as they could be designed not to be completely waterproof, but to drain downwards and keep the contacts dry.
    ‘Alice’

  4. Auntie G
    May 06, 2008 16:38

    To paraphrase Bill Clinton – “it’s money stupid”, the cost of a completely waterproof light fitting would be prohibitive – a RCBO is all you need. I am more concerned about the amount of people that install totally unsuitable fittings into bathrooms and as they rust, because of the ingress of steam, they degrade and become dangerous.

  5. Cushie
    May 01, 2008 15:10

    Following on from Peter Smith’s comment. The light fittings would also not just have to be IP44 rated like bathroom fittings but would have a greater ingress protection as it would need to be protected from more than just splashes of water. Now how often do you see a light fitting in your local hardware store that would meet that requirement?

  6. Carl Williams
    May 01, 2008 14:27

    I think the issue is more one of British Bathrooms than electrical, per-se – elsewhere in Europe, bathrooms seem more often to be built with waterproof floors having proper drainage, in the not unreasonable expectation of the occasional flood and a disinclination, in the event of same, to redecorate, replace collapsed ceilings etc. On the other hand, elsewhere in Europe, one often finds a more relaxed attitude to electrical safety, so I guess it probably evens out. RCCBs on the lighting circuit certainly did their job when water poured through my own kitchen ceiling, so would seem to be a good idea if you have a leaky bathroom.

  7. 'Alice'
    May 01, 2008 13:33

    Thanks for your responses.
    I am starting to get the idea that not everything can be legislated against.
    But surely there has to be protection against flashes of stupidity, as even people who should know better do foolish things.
    A fine engineer I used to know, with a background in grid power transformers, still picked up the live end of his hedge trimmer cable when he cut through it – in pre-RCD days.
    I suppose surviving one of those incidents trains people never to do it again.
    It also occurs to me that evolution doesn’t favour those beguiled by electric carving knives.
    As it happens, I know of a conscientious electrician who at least has a go at talking all of his customers in to having RCBOs on all circuits, despite the added cost.
    I too have too few circuits in my house, and when I get a competent person in to rewire it, I may well ask for an RCBO on the lights under the bathroom.
    And when I buy an umbrella, it will have a spike on top and 2m of trailing copper braid.
    Just in case.
    ‘Alice’
    alice@electronicsweekly.com

  8. David Kelly
    May 01, 2008 13:06

    In the latest 17th edition of the wiring regulations, due to come into force on the 1st July 2008, sockets will be allowed in bathrooms providing they are more than 3m horizontally from zone one, in addition all new bathroom circuits must be protected by 30mA RCD.
    A change in regulations for safe zones will effectively see many lighting circuits fitted with RCDs, and good practice is to have these on separate RCDs or RCBOs (combined MCB and RCD), All domestic sockets will need additional protection by 30mA RCDs. So many of the concerns will to be taken care of.
    In regard to Robin Brand’s post, the electrician should have fully tested the installation and issued a completed a full Electrical Installation Certificate, complete with schedule of tests and schedule of test results.
    I too have seen work done by approved contractors with earths left unconnected!! This should be reported to the registering body concerned as clearly the required testing has not been carried out.

  9. Peter Smith
    May 01, 2008 12:30

    I suspect the reason it’s not mandatory is fiscal, rather than technical. Society is unlikely to consider the cost of fitting millions of homes with waterproof electrical fittings in the kitchen, on the off-chance of saving someone getting a shock, an efficient use of resources. A bit like fitting all umbrellas with a lightning conductor.

  10. Cushie
    May 01, 2008 12:06

    I think this is all down to bad plumbing, your bath and sink should have an overflow so this doesn’t happen.
    The reason in a bathroom that the IET apply these measures is that in a bathroom the bodies resistance is likely to be significantly reduced so the normal precautions are not adequate to protect against electric shock so you place items out of reach or use barriers.
    If you have a flood above your kitchen you would not normally be stood in a vessel of water whilst playing with the electrics. Or maybe you do whilst holding a pointy metal object to make a hole in the ceiling?
    Also regarding the previous comment about the electric garden tools, use an RCBO.

  11. D Valentine
    May 01, 2008 11:33

    An increasing number of homes are getting additional protection from RCD devices. You might think that this would cover the wet kitchen light problem. However, their position in the consumer unit often protects sockets olny. I have only ever seen one RCD fitted in any consumer unit. I have lived in a house where the RCD blacked out the entire house when the toaster had a problem. Very annoying and potentuially dangerous if trying to exit the house at night in emergency (fire?). I now have a house with an RCD that has been wired to omit the lighting circuits. Neither are really a satisfactory solution. But at least an improvement on the no RCD situation. A better solution might be to use 2 or more RCDs in a consumer unit. Or to specify RCD protection on circuits in flood prone areas.
    However, I do not think that additional regulations are going to achieve anything. Competent and conscientious electricians are what is needed. Regulations provide the spirit of safety, but their implementation is always down to the man (or woman) doing the work.
    I recently moved house. The old consumer unit had too few circuits, all protected by wire. I had some additional building work planned that required wiring. I therefore engaged a fully certified electrician to fit a new larger consumer unit with circuit breakers and RCD. I am a mere ‘electronics’ engineer and not certified for domestic wiring.
    I returned home on completion of work to find the consumer unit cover loose. The breakers were were not correctly aligned to the bus bar. After removing the cover to investigate further, I found THREE earth wires were not connected at all. Had I just accepted the work, this would not have come to light until some other (potentially lethal) fault occurred. A further loose earth wire fell off during my remedial work.
    More regulations needed? You must be joking. They have already failed to protect the customer. My solution was to take several photographs showing the standard of the electrical work and enclose it with a significantly smaller payment than that previously agreed. I suspect this will ensure more care is taken by this company on the next installtion, wherever that may be.

  12. May 01, 2008 10:57

    How about another anomaly – quite a serious one – on mains equipment capable of cutting its own power supply cable, such as hedge trimmers & electric carving knives. These generally have a double insulated design, i.e. are not earthed and have a corresponding two wire supply cord. The double insulated philosophy is presumably that two insulation breakdowns in the same place are unlikely – but this is false for such equipment, as if the user accidently nicks or cuts into the power cord, the blade is liable to become live, and with no earth wire will remain so!