Socket RCD

14 Nov 2007
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United Kingdom
Good afternoon.

I have install a double socket in my cupboard for my chargers and other use such as lawnmower and outdoor use.

As I have a combi powered by a ring main, immersion heater cable is disused but still connected to consumer unit. I've reused this cable and extend to new socket. All work great. But I noticed I need to put this on a RCD as it doesn't have one.
Can I move this to RCD side or buy a RCBO and swap it if I don't have a live bar tag for MCB to move over?


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Can I move this to RCD side or buy a RCBO and swap it if I don't have a live bar tag for MCB to move over?
Yes you can (it is possible).

An RCBO would be the better option as it won't disconnect the other circuits because of a fault outside.

It should be tested; do you have the necessary equipment?
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Or alternatively if the new cable installed is not buried within wall, you could install an RCD socket outlet. But as already quite rightly mentioned, testing is required.
It should be tested; do you have the necessary equipment?

How would I need to test it?

I've moved to MCB over to RCD as luckily I have a spare live tag. I also moved the neutral to RCD side neutral bar. I've tested it with a plug in tester and shown correct polarity. The new cable is only 2 metres to new socket with MF joint between existing cable from consumer unit.

In theory you need a RCD tester as it should trip within 40 ms and clearly that is a tad too fast to do with a stop watch. The test button on the RCD is for mechanical testing to ensure it has not stuck, and there is no requirement for the test resistor to be set to 30 mA, so although it trips with the test button you don't know if it trips either in the required time or current.

Proper RCD testers start at around £120 mark, however if you are testing yourself you also need to test the loop impedance, the Martindale EZ150 will test loop impedance however it starts at 1.7Ω and that is over the fail point so looking at around £170 for the loop impedance tester, before you use these however you should test before even turning on these will cost around £100 I have looked for cheapest I could find, not trying to scare you. It is debatable if with an insulation tester that you need the loop impedance meter as you should be able to calculate the results. But to inspect and test you are looking at £220 to get the testers.

I am sure many do work without testing, and many use the cheap plug in tester like the EZ150 at around £50. And also many only test the RCD using the test button, however this does not make it right, with a large firm with many testers you can compare the results by testing a socket in the office with all the meters, it is very unlikely all meters will malfunction at the same time, so if the readings are about the same the meters are OK. But for one person on his own he needs to send the meter for calibration, or own two so he can compare. This means for DIY really doing your own inspection and testing is not economical viable. And inspection and testing will likely cost as much as getting some one to do the whole job for you.

We have talked about this many times on this forum. And the question is should we tell people it's impossible to DIY and do a proper job or not? I think we will be lucky to get most DIY people to buy the EZ150 you can get cheap socket tester for under £5 but they do very little. So you have to do a risk assessment, is it worth the risk to DIY? I can't answer that, only you can answer that.

I looked at rewiring mothers house, £2500 to get some one in, and that includes all the materials, for me to do it need to replace my meters £500 and pay the council £100 + Vat last time I looked could be more, so that means in real terms £1500 for them to wire house and they will take one week I will likely not be finished in a month, so I got a firm in to do it, and I am an electrician. It's a lot of money I know, but wanted to be able to rent out the house if mother did not come home.

So what do you think?
Then if you did have the correct test meters (which can be hired BTW), you need to understand how to use them, then understand the results you have measured and know if they are compliant.
You've at least used a plug-in tester, and you've thought the project through, so you're a long way ahead of many DIYers.
You've at least used a plug-in tester, and you've thought the project through, so you're a long way ahead of many DIYers.

Cheers, Ive moved the 16a MCB to RCD side, and the neutral to RCD neutral bar, tight all connections, made sure all existing connections are tight, apart the main one which obliviously is live. I also moved the cover for the gap where the MCB used to be.
Earth is sleeved and correctly connected to their terminals. Used my socket tester and all is good enough for me.
It is comfortably charging my power tools batteries.

But to inspect and test you are looking at £220 to get the testers.

Do you have the list of testers, their price, and where to get them please? This is a lot more reasonably priced than I thought.
Your best bet is eBay.

You should read about testing so that you know what the various types of testers do.

Mainstream makes of testers are Megger, Fluke, Martindale, Kewtech, Metrel _________________ (other suggestions from other people welcome).

You can do well with lesser known makes - I picked up some excellent bargains with this make

I suspect because not many people have heard of them. Also they don't look as if they could withstand the same physical abuse as a Megger or a Fluke, but then if you aren't a professional electrician you won't be slinging it into the back of a van or using it as a football during a break on site.

You can buy a multifunction tester, or 3 separate ones - if you aren't fussed about them being the same make you could probably pick off bargains as and when they appear.

Look for ones which are calibrated - if they aren't ask the seller if he will accept your bid on the basis that if you win you want the deal to be contingent on it passing calibration. You may have to/should pay for that, but if a seller seems reluctant to consider it at all then be suspicious. Yes, it might be that they just CBA, or it might be that they know there's something wrong.

TBH - re the one I showed as an example of that make, if "certificate of conformity" means it has a current calibration certificate then £150 is a good buy.
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