Replacing an old CU with a new one

[Naz1977]

ok, so might as well change my CU whilst I am doing some other work to the house.

Current house:

2 bed bungalow, Kitchen with Electric cooker at the moment. Dining room and sitting room.
Electrics are about 70yrs old.
No ring main at the moment and the sockets are just star connection.

Planning on doing a small extension at the moment with a full floor added above probably in about 18 months.

So how do I go about re-wiring the house?

I am thinking the number of MCB/RCDs that I need:

1) Ring main for the kitchen and the new diner ( It is open plan kitchen/diner)
2) Cooker
3) Kitchen/Diner Lighting + Fan
4) Ground Floor Ring Main
5) Ground Floor Lights ( to supply the old diner, Sitting room and the bedroom).
6) Bathroom Lighting
7) Bathroom Fan and Shaver Socket
8) Shower
9) Garage ( Feed to the Garage CU which will have to be installed as it is not even got a CU at the moment in the garage)
10) First Floor Ring Main ( for future)
11) First Floor Lighting ( For Future)
12) First Floor Bathroom Lighting ( Future)
13) First Floor Bathroom fan and shaver Socket ( Future)
14) First Floor Shower

Am I thinking about the right number of MCB/RCDs?

Now with all the new CUs that I have seen, they seem to come with a number of MCBs and 2xRCDs.

If I am to use the above for my electrics, which circuits need to be connected to the RCDs and do I need more than 2xRCDs?

So I am thinking about either:

http://www.screwfix.com/p/bg-16-way...bs/7300g#product_additional_details_container

or if I want to have a few more options for future expansion ( Perhaps outside lighting, or outside electrics ) then go for an 18 way?

 

[EFLImpudence]

You really must involve a registered electrician before you start so that HE can tell you what to do and supervise so that HE is able and happy to issue certificates and sign that everything complies.

A DIY forum is not the place for designing your entire installation from afar one point at a time because you don't know what to do.

 

[flameport]

As previous reply - given the questions you are asking, doing this yourself is not going to happen unless you want to spend months/years first learning all the stuff you don't yet know but really need to.

Electrics are about 70yrs old.

Doubtful, and if they really are, the installation is unsafe and must not be used.

Am I thinking about the right number of MCB/RCDs?

No, you appear to have far too many - an entire circuit for a fan and a shaver socket? Lighting for one bathroom?
Two electric showers and electric cooking is a total bust in a domestic property unless you have a three phase supply.
Even with all gas, it's still likely to be a problem.
Garage may not need it's own CU and even if it does, it would not be connected to the house CU with the other circuits.

Now with all the new CUs that I have seen, they seem to come with a number of MCBs and 2xRCDs.

They are sold in DIY sheds to people who have no clue what they are doing.
Proper installations would involve an empty unit and suitable items purchased separately to install in it.

which circuits need to be connected to the RCDs and do I need more than 2xRCDs?

Probably all of them and you can't normally fit more than 2 RCDs in those dreadful '17th edition' consumer units anyway.

 

[ban-all-sheds]

Am I thinking about the right number of MCB/RCDs?

Who can say, when you haven't said how many RCDs you are planning to use?

But, in any event, what others have said is spot on. Rewiring a house, installing new CUs, outside supplies, submains etc is not a trivial job, and I can assure you that 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. You've already shown that you have some dodgy misconceptions - 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?

 

[ericmark]

I can see why some one wants to plan out what they need, however I find it hard, I have argued with my son many times. I will give one example, do you have the fridge/freezer on a dedicated supply (Its own RCBO) or do you supply them from a general ring? If on its own supply less likely to trip, but if it does trip, your less likely to notice it has tripped. I have had two RCD's since around 1992 and it seems to have moods, it will go years without tripping, then trip 6 times in one week with no fault found, but mother has never had a RCD or RCBO trip, maybe they are more modern so less likely to trip, but fact remains, some people get away with one RCD for whole of house, it seems to be more down to luck than design.

So two problems, you pay out for loads of stuff not required, or you don't use enough stuff and you get problems as a result. There is no right way, it's down to the local electrician who knows the area and has worked in a property like yours before to advise on right level of protection. Get a quote, then consider it, and maybe ask on here about items you are unsure about, but get an electrician first to look around and advise.

 

[Doggit]

As others have said, whilst there's no real problem doing the work yourself, in order to get it signed off, you need to agree the layout with the person that's going to do the testing and then issue the electrical safety certificate. Some here will advocate final ring mains, and others radial circuits so that faults and testing are easier.

So, to get your mind round the problem.

Kitchen ring
Cooker
Ground floor ring main
Ground floor lighting
Ground floor shower
First floor ring main
First floor lighting
First floor shower

But if you haven't done any electrics before hand, then you're going to need to get your electrician to show you how to install the sockets and back boxes, or just do the donkey work to install the wiring, and then let the electrician finish the job off. And you'll need to agree with your electrician as to the quality of the CU and the fittings etc. He may be happy with you doing the donkey work, but wiring up and testing sub standard cheap items, may not go down so well with him.

 

[Naz1977]

Hi

Thank you for all the replies.

Maybe I should have said:

I used to work as a leccy ( Well apprentice leccy) about 10 yrs ago. But obviously things/regs/standards have changed since then. I have the 17th edition wiring regs and all the books. But I don't have the experience.

Have wired many back boxes and light boxes and ... in the old days.

The system which is used where I am ( York) is a TT circuit.

Two electric showers and electric cooking is a total bust in a domestic property unless you have a three phase supply.

Well not all three going to be used at the same time. And the plan is to replace the electric cooker with Gas one in near future. They use far too much electricity. But the fan oven will still be electric probably.

an entire circuit for a fan and a shaver socket? Lighting for one bathroom?

Maybe I am over complicating things a bit then. I like the idea of making things modular so it is easier to isolate things when need to work on instead of taking down the whole lighting circuit for example.

do you have the fridge/freezer on a dedicated supply (Its own RCBO) or do you supply them from a general ring

At the moment it is plugged into the Kitchen main ring. Which is protected by RCD.

Kitchen ring
Cooker
Ground floor ring main
Ground floor lighting
Ground floor shower
First floor ring main
First floor lighting
First floor shower

I assume the first and ground floor shower only refers to the actual shower feed rather than the lighting/fan for the bathroom? so lights/shaver/Fan will take their feed from the gounrd/first floor lighting circuit?



I am planning on burying all cables inside trunking so that it is easier in future if I ever need to replace/rewire. I don't like the idea of clipping to the wall. Does it mean I can get away with MCBs or do I still need to use RCD for the sockets? do the cables in the floor/roof voids need to be also protected or can they just be cliped to the joists as lons as they are at least 50mm away from roof/floor board?

I am planning on using RCDs:
Kitchen Ring main
Showers x2

MCBs:
Ground and Firstfloor sockets
Ground and First floor lighting
Cooker

 

[ban-all-sheds]

I used to work as a leccy ( Well apprentice leccy) about 10 yrs ago. But obviously things/regs/standards have changed since then. I have the 17th edition wiring regs and all the books. But I don't have the experience.

Nor do you have the competence to sign an EIC, so who is going to do that?

And when you apply for Building Regulations approval, what will you say will be the way you'll ensure compliance with Part P?

Well not all three going to be used at the same time.

How will you ensure that?

I assume the first and ground floor shower only refers to the actual shower feed rather than the lighting/fan for the bathroom? so lights/shaver/Fan will take their feed from the gounrd/first floor lighting circuit?

You're the one trying to do the design - surely you must know stuff like that?

Does it mean I can get away with MCBs or do I still need to use RCD for the sockets?

You "have the 17th edition wiring regs and all the books", but asking that tells us that you either cannot or will not read them.

I am planning on using RCDs:
Kitchen Ring main
Showers x2

What sort of RCDs?

This latest post of yours just proves the truth of what I said earlier:

Rewiring a house, installing new CUs, outside supplies, submains etc is not a trivial job, and I can assure you that 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. You've already shown that you have some dodgy misconceptions - 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?​

 

[Naz1977]

Nor do you have the competence to sign an EIC, so who is going to do that?

And when you apply for Building Regulations approval, what will you say will be the way you'll ensure compliance with Part P?

An electrician will provide a certificate once he has done his testing. However he is very busy and before I get him across to go through the requirements, I wanted to make sure I am on the right path when I discuss things with him.

An electrician's job is not that complicated. After all this is why they have apprentices doing all the donkey work for them and then they come and connect their test equipment and do the testing.

I will dig out my books and read them again as it has been over 10 yrs since I last used them since some people seem to not want to give advise and help rather just tell you go and get a leccy and pay £3000-5000 for a rewire!

I will then get him across and see what he says.

 

[ban-all-sheds]

An electrician will provide a certificate once he has done his testing.

But what about these (highlighted) clauses in the EIC:

I being the person responsible for the Design, Construction, Inspection & Testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2015 except for the departures, if any, detailed as follows:​

given that he isn't doing that?

An electrician's job is not that complicated.

It's more complicated than you know.

After all this is why they have apprentices doing all the donkey work for them and then they come and connect their test equipment and do the testing.

You are not this electricians apprentice. He has no formal supervisory or directing relationship with you. He cannot be said to be responsible for what you do.

I will dig out my books and read them again as it has been over 10 yrs since I last used them since some people seem to not want to give advise and help rather just tell you go and get a leccy and pay £3000-5000 for a rewire!

Because that's the best advice, particularly when you can't be bothered to even try to do properly what you have decided you can do.

 

[Iggifer]

I will dig out my books and read them again as it has been over 10 yrs since I last used them since some people seem to not want to give advise and help rather just tell you go and get a leccy and pay £3000-5000 for a rewire!

Crack on then, because I think your attitude will have alienated almost anybody that was willing to help you here.

 

[Echo the husky]

I will dig out my books and read them again as it has been over 10 yrs since I last used them

10 years?! You need to work to the current regulations!

An electrician's job is not that complicated.

I disagree entirely.

 

[Doggit]

In my area, you pay the fee for a building control notice, and they just pass the fee over to a Leccy company that will come in and just test the installation, so the design will have been done by the buider/diyer, not the tester. I don't know if they are then happy that there is just an electrical safety certificate, and aren't bothered about the design, but it does seem odd.

I was reading down the recent posts, and as I got to the "an electricians job isn't that complicated" I laughed and thought, boy you've just dropped yourself in it. Responses as per expected.

NAZ, read up, check the current regs, have a chat with your electrician, and then come back, and a little of the pique may have subsided by then. I will finish by suggesting you just bed the cables in, as you're never going to have to take them out again if you've done the job properly, and it'll be MCBs on all the circuits although some her would suggests MCBOs on the showers. The RCDs are for earth faults, and not the same as MCB. You do have a lot more reading to do I'm afraid.

 

[flameport]

about 10 yrs ago. But obviously things/regs/standards have changed since then.

10 years ago would have been the final revisions of the 16th edition, and while the 17th did introduce various changes, the majority of the basics such as circuit design are exactly the same.

In my area, you pay the fee for a building control notice, and they just pass the fee over to a Leccy company that will come in and just test the installation, so the design will have been done by the buider/diyer, not the tester.

What happens when this company arrives and finds large parts of the installation are not compliant with BS7671?

 

[Doggit]

What happens when this company arrives and finds large parts of the installation are not compliant with BS7671

No Idea; it was a chat I was having the local BCO, so I'll ask him next time I see him, but that's what I was trying to suggest in my post.