Changing a CU

[Muriz]

Hi all,

I am new to this website and have just passed my 17th and looking to get some experience under my belt.

My first job is to change a CU at my parents home as some practice. Hoping to get some advice here.

The exsisting installation is unlike anything i've seen before. looks ancient.

It is a 2 bedroom house, the existing board has only 3 very old fuses. from my initiall examination im assuming there is 2 rings and a lighting circuit or 2 lighting circuit and 1 ring.

Im looking for some advice on how to go about doing this job.

Sorry for the long post, hope you will take time to read.

Cheers.

 

[Bez]

More info needed I reckon, size of tails, no of circuits on each fuse, any bonding in place(highly doubtful)

I reckon at the very least your first job is to upgrade the tails and get some bonding in to your new board. I would disconnect everything at the board and from there you can work out what does what. Then you can see what size CU you need and go from there.

If you're really unsure is there anyone you know (electrician) that could oversee what you are doing, at least that way you have someone to ask if you get stuck.

 

[Dane]

If the boards that old, there is a chance of no CPC on the lighting circuits too

 

[Bez]

If the boards that old, there is a chance of no CPC on the lighting circuits too

Good Call

 

[M107]

post a few piccy's of the current set up, more advice can be given then.

 

[Evans Electric]

Are those cables rubber or PVC Muriz ?

 

[Dane]

Fused Neutral on the service head as well is a possibility

Wooden back box's on the circuit, good sign of age of installation.

 

[tom1]

you may find borrowed neutral on lights as well

 

[Dane]

I do think, if youve only just passed ure 17th edition, a Full CU change could be a bit much for a first job?

Although place to start is visually check it everything above is something to be checking, pictures on the forum always help too. the more the better some members prefer pictures lol

 

[markysparky]

Prob good if you feel confidents to isolate circuits by pulling and seeing what doesn't work.Then visually check a few bits like, sockets, bonding, light sw and a few ceiling roses. This will give you an idea what the current wiring lokks like. Maybe after that dead test a circuit if you feel competent. what qual and experience do you have prior to 17th?

 

[GreekIslandLover]

The thing I guess we should mention is that this work is notifiable to the local building regs office, and an electrical installation certificate will be needed.

Burocracy aside, if you have never changed one before I'd really advise getting the assistance of someone who has. The board must be properly isolated before you start taking it to bits. You've got to check it's dead after isolating it too. It's pretty easy to kill yourself, and that slightly worries me. Don't mean to sound patronising!

 

[Andy™]

anything like this?

wouldnt give her a price to change it without a re-wire. those VIR cables started crumbling when i opened the cover! didnt get any further work, probably someone else probably changed it. good luck to them!

 

[Evans Electric]

Its you that goes round putting Spec's work right then !!!

 

[Andy™]

Its you that goes round putting Spec's work right then !!!

someone has to do it!

 

[Muriz]

thanks for the advice guys, ill take some pictures of the job and gather all the info that may be useful. I,ve done many minor jobs and installed new circuits so far as well as testing. i have observed a few jobs on replacing CU's and wired up plenty whislts training but this board it beyond anything i've seen before.

Yes Andy, something similar to that picture.

Once again thanks for all the replies.

 

[paul b b]

Hi Muritz,

I would stick a tester on the cables befor you do a cu change, just to check the insulation if nothing else.

if you have 3 circuits you may have, 1 ring, 1 lights and a cooker circuit.

if the cables are in good order i would do the change for your assesment. or rewire the house for your assesment.

oh and dont forget the bondings!

as regards to the tails you may find that the fuse is a 60A so 16mm will be fine, though if they are old change them aswell.

paul

 

[SPECIAL LOCATION]

thanks for the advice guys, ill take some pictures of the job and gather all the info that may be useful. I,ve done many minor jobs and installed new circuits so far as well as testing. i have observed a few jobs on replacing CU's and wired up plenty whislts training but this board it beyond anything i've seen before. Yes Andy, something similar to that picture.

Once again thanks for all the replies.

Hello Muriz....

welcome m8, few quick points.

1/ If you have passed your 17th you obviously understand the basics of what the regs require.

2/ You understand safe isolation, cable ratings, capacities etc...

3/ You understand concepts of how circuits work.

4/ You understand the basic essential tests,

Polarity, earth continuity, Ins Res, Earth loop, RCD times ect...

5/ You understand earthing types, TT, TN-C-S (PME), TN-S

6/ So although it may look a bit of and odd-bod, keep all of your "basics" learnt at college in mind, and approach things in a SAFE & systematic logical way!

7/ A CU.. no mater how old is just a bunch of fuses collected together in one place with a single main isolating switch near by as well!

8/ Ask any questions on here....

I mean ANY questions... even if they seam a bit daft... ASK THEM... you will get proper answeres.....

cuz if any one tries knocking you down or belittling you... the Mods & Admin will sort them out.

9/ So go for it.... As the others have said.. stick a few photos up

make it easier for us to help.

10/ oh ******... me brains stopped againGuinnessBlushing

I cant remember what I was going to put there!!!! :|

headbangGuinness

 

[GreekIslandLover]

How old is the house, and is there any evidence of a previous rewire? I ask, because I've seen the very minimal number of circuits in old Victorian terraces, and to be honest a rewire is the only reccomendation I've been able to make.

It's worth looking at what circuits you have, and what appliances are being used etc. I.E. are there loads of appliances in the kitchen and only one ring? In that case it may be worth looking at adding a circuit for this purpose.

If you only have a few circuits, then it's probably a good idea to fit RCBO's. Reason being that the regs require you to consider minimal disruption in case of a fault. For example, if a light bulb goes ping and the RCD pops you'd lose all power to the house! Similarly, if somebody spills water into the kettle base (been on callout for this frequently) you lose power to the entire place including the lights.