Moving the consumer unit

[gigcoyle]

I have an old flat (ca 1830) which I'm planning to largely gut and refurbish. The CU is currently close to the mains feed and meter but above the combi boiler. I had problems with the RCBO wires coming a bit lose and tripping constantly, probably due to the temperature cycling up and down. It took the electrician a while to figure that out but they also noted that the CU is no longer compliant and the RCBOs are discontinued, so if one does fail getting a replacement wont be easy. I checked the latter and it seems its correct. I'd like to move the CU to a better location when I refurbish but that will mean running a ~10-15 m feed from the mains connection (physically simple enough with the way its wired). I just wanted to check what guage cable should be used and if someone can recommend something. I'm assuming it'll have to be 10 mm2 or over but what form as well (flat twin & earth? separate L, N and E lines or is there flexible circular 3 core we can use). ANy advice welcome. Thanks

NB I'm not proposing doing all of this work myself - I'll get an electrician in but I want to know what's need to comply with the regs and best practice before I start. the last electrician I dealt with wasn't great and I had to report them to trading standards

[Neelix]

If you aren’t going to do the work why ask about the cable. Get a couple of sparkles to come and take a look

Routing a cable, the cable sizes and protection need consideration as do extending cables

AND you’ll need a spark for most of this

[Someone-Else]

To add to what Neelix said, if someone said xx cable, you buy it and the electrician who does the job says its too small, you will have just wasted your money.
There is more to moving a consumers unit that it appears, and since you obviously are going to get an electrician to do it (as you should) why worry about it, that's what you pay him/her for.

[dewaltdisney]

SE, is it important to get a work conformation ticket in this case to satisfy building regs?

DWD

[Neelix]

SE, is it important to get a work conformation ticket in this case to satisfy building regs?

DWD

Absolutely.

[gigcoyle]

Why do people always do this - all I want is some guidance on what's needed so I am informed before we start. I've had some bad experiences with tradesmen who thought they could bamboozle a poor single woman and rip her off. I'm a physicist, I'm competent to build and repair electrical equipment, off-grid DC up to mains, so I understand the technical side I'm just not involved in domestic installations to be fully up to speed with the regs and best practice (since I did my basic training maybe 20 years ago now). I did a lot of the initial work on the house when I bought it, 25 years ago, all of it signed off, the electrician complemented me on the neatness and quality of my work! But it now needs fully refurbished and the things we've lived with brought up to the current regs.

NB all I really want to know is what type of cable is usually used and an idea what gauge, I'm going to reassess the load as I haven't done that for a while but its only a two bedroom flat

[dewaltdisney]

Don't fret, we cannot know your level of competence and we have to try to advise with a best guess to keep you safe. I know very little about electrical work so I am not able to help but from a general standpoint it would appear that you just need to know the Regulation required cable thickness. You are not alone in trades trying to rip off people, it is a sad reflection of the times. I try to do everything myself but electrical can kill you so I get my little Ukrainian chum in to do anything. I am sure that now you have clarified your position one of our competent members will advise.

DWD

[ericmark]

In theory, we need to be able to isolate elsewhere, so we need an isolator not built into the consumer unit, which I have, so I do not need the DNO to visit in order to work on my consumer unit. However, it seems this is not always the case, and the only person who can remove the DNO fuse, is the DNO, so often step one is to get DNO to fit an isolator.

There is nothing stopping you from DIY the CU change, one can tell the LABC, and they can after paying their fee, in Wales £100 plus vat, allow you to do the work, if they feel you have the skill, and of course the test equipment. I have done this myself, they wanted to see my C&G 2391 and Degree etc, if I had not satisfied them I had the skill, I would have also needed to pay for a third party inspection.

So as a rough estimate it will cost around £250 to hire the test equipment and pay the council fees. As to how strict they are on the qualifications, I don't know, Flintshire were harder to satisfy as Cheshire, and Liverpool were very helpful, so it does seem a bit of luck as to what the inspector wants.

Theory I did not need an extractor fan in bathroom as windows opened, but the Flintshire guy insisted one was fitted.

I would say write out a detailed plan, so he can't after the work is done, say he wants something extra, when it came to fitting a new CU in this house, I used a registered electrician, just too many hoops to jump through, the main one being having to wait for the inspection before you can turn power back on.

[ericmark]

(since I did my basic training maybe 20 years ago now)

Sorry, did not realise you were so young. Did mine in the 70s, yes we now use metric cable sizes, 7/0.029 cable is well gone. It seems prudent to use 25 mm tails, fit a SPD, and also type A RCBO's and lighting is normally 1.5 mm, ring finals 2.5 mm, cooker 6 or 10 mm and shower 10 mm, there is some debate between ring finals and radials, in the main looking at volt drop.

It has been accepted, since the volt drop moved to 4% to 5% for non lighting, that a 32 amp ring final has no more than 106 meters of 2.5 mm sq. Moving to radials, it depends on the overload rating, for a 20 amp radial with 2.5 mm sq the max length is 32 meters, one could use 4 mm sq, which will allow 55 meters, but getting three x 4 mm sq into some sockets can be a problem, so I favour the ring final.

[gigcoyle]

Don't fret, we cannot know your level of competence and we have to try to advise with a best guess to keep you safe. I know very little about electrical work so I am not able to help but from a general standpoint it would appear that you just need to know the Regulation required cable thickness. You are not alone in trades trying to rip off people, it is a sad reflection of the times. I try to do everything myself but electrical can kill you so I get my little Ukrainian chum in to do anything. I am sure that now you have clarified your position one of our competent members will advise.

DWD

:D thanks, sorry if I got a bit peeved, I should have waited until I'd had another coffee

[gigcoyle]

(since I did my basic training maybe 20 years ago now)

Sorry, did not realise you were so young. Did mine in the 70s, yes we now use metric cable sizes, 7/0.029 cable is well gone. It seems prudent to use 25 mm tails, fit a SPD, and also type A RCBO's and lighting is normally 1.5 mm, ring finals 2.5 mm, cooker 6 or 10 mm and shower 10 mm, there is some debate between ring finals and radials, in the main looking at volt drop.

It has been accepted, since the volt drop moved to 4% to 5% for non lighting, that a 32 amp ring final has no more than 106 meters of 2.5 mm sq. Moving to radials, it depends on the overload rating, for a 20 amp radial with 2.5 mm sq the max length is 32 meters, one could use 4 mm sq, which will allow 55 meters, but getting three x 4 mm sq into some sockets can be a problem, so I favour the ring final.

Well I'm not young but a wee bit younger ;-)

Thanks, the existing rings and radial wiring are pretty new and up to spec, it just the consumer unit I want to move.

[Someone-Else]

Why do people always do this

I would say that is because you did not give all the relevant information in the first place, and your comment of

I'm assuming it'll have to be 10 mm2

does not instil any confidence in me, nor does

what guage cable

But the answer you seek is 25mm and you will need an isolator if it is to go the distance you suggest.

(since I did my basic training maybe 20 years ago now)

Sorry, but basic training in what? Let me guess, panel wiring? (You do not do "basic training" to become an electrician.)

[gigcoyle]

Wow. Okay I said 10 mm2 or over, thanks for answering my question - what type of cable would you recommend?

I build mains powered equipment for my job as a research scientist as well as 24/12V DC off grid powered systems. I never said I was an electrician, I’m a physicist. I’ve been trained for low voltage systems and testing by Select, they did a bespoke course for us, and we had other courses on testing and the applicable regs. We also had a review of work we’d done already and they recommended some changes to how we constructed some things, overall my work was pretty good and safe. I did a short course on domestic wiring as part of my degree studies, as well as other practical skills in fabrication (using lathes and other equipment). I’ve never done anything without ensuring it’s done safely and properly tested and certified. There’s a separate isolator after the meter so it can be switched off. I’ve never worked on the CU myself, I leave that to a professional but I can do some prepping and wiring.

[Neelix]

Wow. Okay I said 10 mm2 or over, thanks for answering my question - what type of cable would you recommend?

Wow.

Did you not read any of the responses?

[gigcoyle]

Hi Neelix, sorry for the slow response. I did read your responses and as I explained I just wanted to have some information before I started speaking to electricians and progressed the job. I have the skills to do some work myself (cost is a limiting factor most of the time so it makes sense to utilise my skills as far as possible) but it is far to easy for tradespeople to dismiss me and I have had people try to rip me off in the past, apparently, just because of my gender and not being trained in the specific area of domestic installations.