House Rewire and new consumer unit

poriet · 14 Nov 2014

I have an old house which needs a decent electrical system and a modern consumer unit. I'm not a spark, but I have done lots of rewires over the years and I even have an old Which? book about electrical rewiring.
Despite dire warnings from all directions, I intend to go ahead with this. Mains electricity hasn't changed in the last 30 years and rewiring has little to do with electricity: it's about digging up floor-boards and knocking holes in walls.
I will be inhabiting this house on my own and it wont need certificates when it's sold as it will probably be demolished: the land is worth more than the house. Meantime, I'm turning it into an eco-home full of crazy 'green' ideas. Nobody but me would want to live there, so many of the caveats relevant to DIY electrics don't count.
However, connecting the supply cables from the meter to the consumer unit is something I would get a competent person to do: I'm not sure how that's done and advice and info on electrical stuff is sparse on the Net. The Net is awash with info about everything, but not electrics.
I suppose the question is: what is so complicated about a rewire that makes the World and his wife insistent you don't do it?

Bruce

Jackrae · 14 Nov 2014

Statutory obligation, invalidation of insurance, danger to buildings, danger to others, danger to self.

EFLImpudence · 14 Nov 2014

CLICK

sparkwright · 14 Nov 2014

You seem to think you'll find it easy to rewire this house.

It also seems like you are going to do it regardless of what anyone says.

Why don't you send pictures of everything as you put it in (and I do mean everything - cables under floor, connections, chasing etc) and we can tell you if you're doing a good job, or a load of ****e, as whatever the case may be.

poriet · 14 Nov 2014

OK,
Thanks for the replies, anyway.
(Doesn't anyone go to bed these days? )
Yes, I think I intend to go ahead, BUT I did ask for some common sense answers before.
BTW, I read Dale Carnegie's book years ago and , if memory serves, found it gibberish. I don't recall him saying anything particularly innovative. He waffled a lot about loving people and then about God ( who I don't believe exists.) In any case, having friends and influencing people has nothing to do with being a nice guy: Billy Graham was an out and out fraud, completely contemptuous of people and was loved by millions. Go figure.

Of course it will invalidate insurance and risk life and limb: so does climbing, scuba diving and ( if memory serves) sex. But only if it's done wrong. I have wired up lots of stuff in the past and it didn't go wrong. So what is so different now?

Sparkwright: I don't imagine it will be easy, but I cant see it being any more tricky than the last time I rewired part of a house many years ago.
I appreciate your offer of looking at the work I've done. I will endeavour to do just that and if it really is awful, I hope I'm man enough to take that on board.

Cover me lads, I'm going in......

Taylortwocities · 14 Nov 2014

You are right, its not complicated. Any fool can do it.

Just buy a couple of rolls of cable and off you go.

Have a nice time.

ban-all-sheds · 15 Nov 2014

poriet said:
I suppose the question is: what is so complicated about a rewire that makes the World and his wife insistent you don't do it?

Nothing particularly complicated.

But chock-full of things which someone whose level of knowledge is encapsulated in "Mains electricity hasn't changed in the last 30 years and rewiring has little to do with electricity" won't even know exists.

For a circuit to supply a given load, how would you go about deciding what cable and protective device to use? (No, you can't just copy what's there because it's going to become your responsibility and what's there might be wrong.)
Do you know which circuits can be ring finals and which cannot, and what the advantages and disadvantages of each are? (No, you can't just copy what's there because it's going to become your responsibility and what's there might be wrong.)
How do you calculate maximum demand and how can diversity be used?
Can you correctly identify all components and connections of a circuit by method of testing or otherwise? In doing so can you identify or recognise anything wrong or dangerous with the circuit? You cannot assume that what's currently installed is OK, and you need to check it before starting work.
Do you understand how the way in which cables are installed affects how much current they can carry? (No, you can't just copy what's there because it's going to become your responsibility and what's there might be wrong.)
Where cables need to be joined, how should this be done / not be done and in what circumstances are different methods acceptable?
Can you identify extraneous conductive parts, and do you know the requirements for main and supplementary bonding of them?
Which circuits should be RCD protected?
What about the testing that you should do on your existing installation before you change the CU, if you want to be sure of avoiding grief from new RCDs tripping?
And what about the tests you should carry out after the installation? What sequence will you do them in and at what point will you energise the installation, and for each test do you know what is being measured, why it is important, how you would carry out the test, and with what equipment, and what sort of results you would expect to get if everything was OK?
How do you propose to isolate the supply so that you can install the CU?
Do you believe you are qualified to issue an Electrical Installation Certificate for the replacement?
Are you aware that you'll need to apply for Building Regulations approval in advance, and as part of that you'll have to say how you'll ensure that your work complies with P1?

Doing a complete rewire is not a trivial job, and almost certainly it involves knowing far more than you think it does.

Asking questions here can be a useful part of a learning process, but they are not a substitute for proper structured studying. The key term there is "learning process" - you cannot learn all the things you need to know just by asking questions here. It isn't structured enough - it won't provide you with a way to progress where each step builds on what you learned before.

You can't carry out a job of this magnitude by asking whatever random questions happen to occur to you, what if you get something wrong because you have no idea your knowledge is wrong? What if you miss something because you simply have no idea it even exists, and just don't realise you don't know it?

//www.diynot.com/wiki/electrics
//www.diynot.com/wiki/electrics:books
http://web.archive.org/web/20080213151445/http://www.kevinboone.com/electricity.html
http://www.google.co.uk/search?q=uk+house+wiring+(basics+OR+101)
http://www.tlc-direct.co.uk/Book/1.1.htm[/list]I suggest you get stuck into the last link right away - it won't give you design ideas, and unfortunately it doesn't refer to the current edition of the Wiring Regulations, but it's free, and will still give you a good grounding which you can augment with more up to date publications.

garlicbread · 15 Nov 2014

poriet said:
However, connecting the supply cables from the meter to the consumer unit is something I would get a competent person to do: I'm not sure how that's done and advice and info on electrical stuff is sparse on the Net.

Bruce

I dont think you will find many 'competent persons' willing to connect the tails up to an intsallation someone else has installed.

ban-all-sheds · 15 Nov 2014

poriet said:
advice and info on electrical stuff is sparse on the Net. The Net is awash with info about everything, but not electrics.

Ok - admittedly only some of these will be relevant to the UK.

But 46.5M hits is not what I would call "sparse".

poriet · 15 Nov 2014

I think some of you guys are really enjoying this: giving some upstart amateur a good kicking. I'd like to say you've hurt my feelings, but at my age I don't have any left

I did find a wiki of all things which gave a really nice diagram overview of the system. Theres a bloody big switch which isolates the supply from the CU. My guess, and it is only a guess, that, if you turn it off, you can connect the tails to the CU without burning your fingers. Turning it back on again is a real leap of faith and would concentrate the mind wonderfully.
Blowing a 100A fuse is dodgy. What I would do, if it could be done, is to replace the 100A fuse with a much smaller one before I turned it on. If it blew, no real harm done: if it didn't, you probably got it right and could replace the 100A. Now, how many of these awful bungling amateurs would bother doing that?

To be fair to people like me this is not 'Electrical Forum dot whatever', where they deal with people in the trade and amateurs get short shrift. This is a DIY forum and this part is called Electrics UK. If the only advice you can give to DIYers in this field is 'dont', then maybe you should change the name ever so slightly.

AndyPRK · 15 Nov 2014

This thread could get interesting

Firstly look at "safezones". This will tell you where you can put cables in walls.
Basically they should go in a straight horizontal or vertical to an accessory (switch or socket) .

No you wouldn't lower the main fuse before you turn it on.

You could do some tests, or just turn all the MCB's off, and power up in turn.

ANyway what did you want to know ?

OwainDIYer · 15 Nov 2014

poriet said:
Turning it back on again is a real leap of faith and would concentrate the mind wonderfully.
Blowing a 100A fuse is dodgy. What I would do, if it could be done, is to replace the 100A fuse with a much smaller one before I turned it on.

Before you connect your new installation to the mains you test it using a test meter. This gives you some assurance that it won't go BANG when you make it live.

JohnW2 · 15 Nov 2014

poriet said:
Blowing a 100A fuse is dodgy. What I would do, if it could be done, is to replace the 100A fuse with a much smaller one before I turned it on. If it blew, no real harm done: if it didn't, you probably got it right and could replace the 100A. Now, how many of these awful bungling amateurs would bother doing that?

They may have thought of that, but they may also have considered the fact that they are not allowed to interfere with the DNOs fuse (which should be sealed, to prevent such interference).

In any event, the physics doesn't work quite as you imply. Whether the fuse is 5A or 100A, the initial current which flows through it in the event of a serious fault will be exactly the same (potentially 'hundreds of amps), depending only on the impedance of the fault path. If the current is 'hundreds of amps', the 5A one would probably blow fractionally more quickly, but the initial bang/explosion/whatever would not necessarily be all that much different.

Furthermore, as has been said, you would hopefully undertake tests on your wiring, to ensure that a bang/explosion wasn't going to happen, before you applied power (through any rating of fuse).

Kind Regards, John

ban-all-sheds · 15 Nov 2014

poriet said:
Theres a bloody big switch which isolates the supply from the CU.

And you've got one have you?

My guess, and it is only a guess, that, if you turn it off, you can connect the tails to the CU without burning your fingers.

Be honest (at least to yourself) - do you really think that doing major electrical design and installation by guesswork is a sensible idea?

Turning it back on again is a real leap of faith and would concentrate the mind wonderfully.

Be honest (at least to yourself) - if after you'd rewired your house and replaced the CU you were to be so unsure whether you'd done it properly that you didn't know if there would be a catastrophic bang the moment you applied the power to it, do you really think you should have been doing the work in the first place?

Blowing a 100A fuse is dodgy. What I would do, if it could be done, is to replace the 100A fuse with a much smaller one before I turned it on. If it blew, no real harm done: if it didn't, you probably got it right and could replace the 100A. Now, how many of these awful bungling amateurs would bother doing that?

What an ironic question. Trust me - nobody but an awful bungling amateur would think that they should temporarily put a smaller fuse in in case they'd done such an awful bungling job that it might go bang.

This is a DIY forum and this part is called Electrics UK. If the only advice you can give to DIYers in this field is 'dont', then maybe you should change the name ever so slightly.

But that isn't the only advice you've been given.

Did you look at the questions above? Are you able to answer them?

Which of the following mean something to you:

Zs, Ze, EFLI, R1+R2, r1+r2, Ib ≤ In ≤ Iz, supplementary equipotential bonding, Reference Method C, TN-C-S, IR testing....

?

You need to learn. There is no reason to think that you would be incapable of learning, but learn you must. Unlike DIY decorating, or gardening, or plumbing etc, where people don't die from paint runs or mismatched wallpaper, or struggling shrubs, or leaky pipes, electricity takes no prisoners - it is not your friend, it is locked in an insulated prison waiting to get out and kill you. You have to be as competent as a professional electrician if you want to do a job of this magnitude.

skotl · 16 Nov 2014

The OP is keen to do his own gas work, too;

//www.diynot.com/forums/plumbing/would-welcome-help-with-boiler-fault.344877/#2579637

So if the electrics don't get him, the gas might.

---

By the way, Bruce, the only question that I can see you asking in this thread is "what is so complicated about a rewire that makes the World and his wife insistent you don't do it?" and it seems that you have received consistent and clear advice. Even b-a-s's response was detailed and helpful(!).

You don't like the responses, but that doesn't make you right and everyone else wrong. If you are going to go ahead, then it can't hurt to do a little research, right? I'd start with the book that b-a-s referred to in his final link.
Then, if you have specific questions, people on here might be inclined to answer. But continuing to argue against the responses you received for your first question seems pretty pointless.

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House Rewire and new consumer unit

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