Electrics in a cloakroom - can I DIY?


Postby orsoch » Thu Feb 10, 2011 4:57 pm

Hi DIY Doctor,

I am a newbie hoping to tap in to the wealth of knowledge on your forum.

I am updating the cloakroom in our 30's house with new loo and sink. I want to do as much as possible myself as builders are very expensive where we live and money tight.

A builder has told me that the internal wall light switch (which has been there since 1937!) is illegal and must be moved outside the room or converted to a cord pull and that he is forbidden from doing the work without having an electrician come in and check the earth bonding. Since we had a new boiler from British Gas a couple of years ago and all the earth bonding was OK'd at that time I am a little puzzled. Regulations have changed and that British Gas are rubbish was his response.

Am I being frightened into not doing it myself? Am I allowed to keep the switch inside the room? Can I move to a cord pull myself? Does this invalidate my house insurance should I burn the house down as a result of my DIY?

I have done basic wiring in the past and am competent at wiring in lighting, extending cirucits etc. by the way, so moving a light switch is within my capability and I judge to be low risk.

Thanks for any advice you can give.

regards,

Chris
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Postby ericmark » Sat Feb 12, 2011 4:02 am

In a bathroom it would be normal to use a pull cord or have the switch outside the room. But these rules do not include a toilet or utility room even if they have a sink. The only rule is the items must be suitable for the room. So if there is a likely hood of splashing water than the switch should be IP65 or at least an IP rating to suit the environment.

Careful with word competent this means better than skilled in that you are able to not only protect yourself but also others. And as a competent person you will need to test the earth loop impedance and complete the minor works certificates.

The gas people often use a device that does test the earth loop impedance but does not give a reading but just lights a series of lamps to show if the socket is within limits for a standard B32 MCB supplied ring main. An electrician will use a meter giving a reading and will have to calculate what the pass limit is for the circuit being tested. So the gas guy is just testing to make sure he is safe where the electrician is testing to ensure both he and you are safe.

As an electrician we inspect and test that often we get to know the pass limits so to anyone watching it is not always apparent that we have measured the impedance and checked the size of the MCB. The letter in front of the number i.e. B6 tells us the current that will trip the magnetic part of the MCB. In the case shown it will be 30A and we know that 230/30 = 7.6 ohms and we look for a reading below that limit. However with a socket on a ring main we look for 1.44 ohms so each circuit is different.

The whole idea of just fitting a bit of cable without testing has now gone. Every installation is tested and in the main it is common sense and visual inspection. Very few houses comply with the latest regulations and where nothing has been added that's OK. But as soon as one alters anything then the alteration must comply it seems amendment 1 to BS7671:2008 is going to relax the requirements but as it stands it is hard to do any alteration without falling foul of the regulations. Any cable buried in a wall less than 50mm has to be either a special type of cable or protected with a RCD.

So for example in a house with no RCD in the consumer unit then to extend the wire to a light switch would need Ali-tube cable not normal twin and earth. As to if a electrician would comply with regulations is down to him but he would be correct to say it needs special cable. However at the moment one can only buy the cable by the reel and it is expensive. So electricians tend not to carry the special cable. So will tell the customer he needs to fit a RCD which involves a consumer unit change. That means he does not need special cable and he gets paid more. Likely though better anyway as then next time any alteration is required the RCD is already fitted so simple.
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Postby orsoch » Mon Feb 21, 2011 1:03 pm

Thanks for all your advice on the subject. I'm a little way from having to do the electrics but will certainly take heed when it comes to doing it.

regards,

Chris
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Postby wookey » Sat Mar 12, 2011 10:11 am

As was just explained you need to use physically protected cable or change the CU to comply with the regs and you're not allowed to change the CU without involving building control. So given that you only wanted to move the switch because you were told it no longer complies by far the easiest thing to do is leave it where it is. It's not doing any harm. The risk hasn't risen because the regs changed, so if you were happy before, then remain happy.

In practice if you just move it, using normal cable of the right size, no-one will be any the wiser, and you'd have to be fairly incompetent to make the situation worse.
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