Why would it be limited to 13A? As I have already mentioned, there is a ring circuit, from a 30A MCB in the house CU. This feeds a CU in the garage, which has a lighting and a power MCB adding up to less than the 30A supply fuse. Two cables from an MCB in one box are the supply for the second box. I am asking if this setup is allowable, obviously the 30MCB would be replaced with the CU replacement, presumably with an RCBO.
Ah - well I wasn't replying directly to your very first post - I saw that things had moved on so I picked it up part way through.
And in the post I replied to, you wrote
can a garage be run off a 32A ring...
which I took to mean as a spur from a ring final.
It looks as though you haven't got that - I think what you're saying is that you've got 2 parallel cables supplying the CU from a dedicated fuse in the CU?
That's not a ring final. You probably weren't to know, but when you start talking about a ring in 2.5mm² cable from a 30A fuse, you are talking about a circuit which may only supply sockets and FCUs, not a CU, which is why there was initial confusion and "no you can't do that".
It sounds as though what you have is a radial, wired with 2 cables in parallel.
Intrinsically there's nothing wrong with 2 x 2.5mm² cables on a 30A fuse, but the use of twin & earth in buried conduit is very dodgy, the chances of it having been done in a way which complies with the Wiring Regulations are slim to none, as are the chances of finding an electrician prepared to use if from one new CU to another new CU which he'll be signing off.
My objection here is not that I dislike the answer, but that I would like a little more more information than 'no'. The ring setup is amply protected mechanically by being under paving, and the total current requirements of the garage to not exceed the current carrying capacity of the two cables. On what grounds are you stating 'no'?
It was on 2 grounds, but now that the ring/radial confusion is gone we are left with one.
The cables are not amply protected mechanically, because being under paving it's more likely to be attacked at some time by kangos and mini-diggers than if it was in a flowerbed, and they'll go straight through pvc conduit and through steel that's been buried for more than a few years.
Armoured cable really is the only way to go.
I corrected the initial post to 4mm2 long before you replied,
See above - you hadn't (and still haven't) corrected the post I quoted.
and even if I had not surely it's simple enough to state whether or no multi-stranded cable in good condition is recommended for replacement or not.
Well - I was trying to be even terser than previous replies.....
Sorry 'bout that.
These seem more like regulations questions than house specific questons to me.
And the reason you think you don't have to comply with the regulations is what, exactly?
I have no idea where you are coming from there. I did not suggest at any point that I do not need to comply with the regulations, and am clearly endeavouring to find out what the regulations say with regards to my questions.
You seemed to be saying that you didn't want regulations to be a consideration in any replies.
Is the described circuit a case of recommended improvement or required rewire to fit the CU. The question seems plain enough. The described circuit has multi-stranded cable as opposed to the solid core that seems to be sold these days, and the socket outlets are on the skirting board as opposed to the new specifications of however high from the floor etc.
As each room is decorated the sockets would be raised and if recommended the wiring replaced with the newer colour coded solid core stuff.
Do the cables run down the walls from above, or up from under the floor? If the latter how will you raise the sockets if you don't replace the cable? Is there enough slack in all of them?
Plus replacing all or significant sections of a circuit really should be tested.
Your breaking of my post into these little chunks in order to give terse uninformative answers appears to have resulted in a contradiction to the last no. I have already specified the CU is being replaced with one that has RCD protection, I now have no idea if you are telling me it can then feed the garage CU or not..
You can't reuse that old cable run to the garage.
You can supply the garage from an MCB in the house CU, but you'd be better off having the electrician split the tails and run SWA from a switchfuse to the garage, don't come off the house CU at all.
Is this a regulation or a suggestion or a personal preference?
The regulations require buried cables to be protected. By far and away the cheapest and most practical way to do it is to use armoured cable.
I'm basically wondering how much additional work is likely to be required based on the following-
But really that question can only be answered by the electricians who have been to see the job, discussed what you want to do, and formed their opinions.
As long as the old cables are sound they can stay, but no reputable and competent electrician would consider replacing a CU without testing the old circuits first, so things could change anyway.
As ever, personal recommendations are always the best way to find a reputable tradesman, but if you're having to go ahead without much in the way of those, or references, don't put any store by registration itself - sadly it is possible to become registered with woefully inadequate qualifications and zero practical experience. You don't have to spend long here to see people cropping up who are registered and "qualified", but who are clearly seriously incompetent in reality and who should not be charging for their services.
You are looking for someone to install CUs, run a supply to a garage etc, and it may surprise and dismay you to learn that it is quite possible to become a "certified electrician" without ever having done those things before, and without having acquired any of the practical skills needed to do it without half-destroying your house in the process.
It's your money, £'00s of it, and you have every right to ask prospective tradesmen what their qualifications and experience are.
Just being listed here is not a good enough guide. No genuinely experienced electrician, with the "full set" of C&G qualifications will mind you asking - in fact he will wish that everyone was like you.
I feel sorry for people who have been misled by training organisations and (shamefully) the Competent Person scheme organisers into thinking that a 5-day training course, a couple of trivial examples of their work and some basic understanding of how to use test equipment will make them an electrician, but not sorry enough to agree with them trying to sell their services to Joe Public.
