New CU, suit you Sir

[Danimal]

Hello all, I’m looking for logic check on some work I’m planning to do, it’s quite a read so settle in, but please check my logic, anything else I should do or check?

First things first, no I’m not a qualified electrician but am a competent person, well at least more competent than the electrician who originally installed my CU. But if we can do away with the "you shouldn’t be doing this" etc., I know

I want to replace the main CU in the house for a couple of reasons, mainly because I have run SWA out to my shed and my consumer unit is plastic, and seeing as the regulations now call for a steel enclosure, all the better for fitting my SWA gland.

The CU is a 16way unbranded piece of crap filled with a mix of different brands of mcb’s. It’s totally jammed full of wiring, nothing is labelled, and there are no spare earth connections left for the extra circuits I wish to add.

What I have:

1x Hagar SB299U 100A main incomer switch
4x Hagar MT106 6A single pole type B mcb’s (lighting circuits)
Wylex B63 (PSB63-B) mcb (this isolates the feed to the annex’s CU)
Hagar CD263U 63A RCCB (protecting the power circuits below)
5x Hagar MT132 32A SP type B
1x Hagar MT140 40A SP type B (doesn’t appear to be connected)

Electrically my house is as follows:

• TN-C-S Earth system
  
• Domestic supply with incoming meter feed switch (i.e. I can pull apart my CU isolated from live feeds)
  
• Annex with separate CU, Feed from main CU (RCD in the annex CU for annex power sockets)
  
• Shed with separate CU, feed from main CU (or at least will be)
  

To begin I need to figure out what’s what in the box as nothing is labelled so I’ll go around the house make sure everything works, light bulbs etc then switch off 1 mcb at a time and figure out what no longer has power.
I am confused as to why an mcb would have two reds coming out of it but I’m sure ill figure this out as I go through this.

After I’ve labelled up all the reds and unconnected everything, removed the old CU and fitted the new one, a 20 way Hagar VML120 then it should be a straight swop fitting the old Hagar modules back in place, replacing the wylex one with a Hagar MTN163 63A SP type B.

Connecting up the shed SWA cable to a new Hagar CDC263 63A 30mA RCD (I had no idea they were so expensive!!)
I have to have the RCD on the main CU end right? As the SWA cable goes outside?

Before anyone askes as I know this is a matter for hot debate, the shed is 15M away from the house, its 6mm^2 3 core SWA and I’m using 1x core and armour for earth back to the main CU, not a separate ground spike.

I think I have to check carefully what else is connected through the kitchen lights mcb as the misses wants 10 LED spotlights, + 3 more in the hallway. Applying diversity to the numbers I may have to have the kitchen lights on a separate mcb as its all 1.5mm sq cable so I can’t really bump the mcb up to a 10A can I?

What if they were low voltage LED type with transformers, any advice for checking the load with this type?

As far as earth loop test goes, I have a plug that will do a earth loop check, socket&see sok36 I don't have a megger or dedicated tester, so wont be able to check a before and after value for resistance, only a green or red light
I have a decent digital multimeter... I cant check with that can I?
I could probably borrow a megger if I really need one?

I’m sending the wife out shopping for the day while I do this work as there will obviously be no power and can do without being nagged "when’s the power coming back on?" do you think I should hide some money in an offshore account as I don’t think I can afford a whole days shopping let alone get a proper electrician!

Cheers
Dan

 

[bernardgreen]

I am confused as to why an mcb would have two reds coming out of it but I’m sure ill figure this out as I go through this.

Sorry to be brutally harsh but if you are confused by that then you do not have anything like enough knowledge of electrical installations to install a consumer unit.

 

[EFLImpudence]

First of all, although you don't want to hear it, the work is legally notifiable to the Local Authority before you start. They will then decide if you are competent - electrically skilled - to do the work.

As you do not have the necessary equipment for testing then, I think, this would have been doubtful.

You need (someone needs) to complete an Electrical Installation Certificate, Schedule of inspections and Schedule of test results - available on line.
Yes, you do need the proper test equipment.

You seem to know of, but not about, some of the tests necessary - but cannot figure out why there are two wires in some of the MCBs.
You are unsure about the load of LED lights.
The point of using swa is so that an RCD at the supply end is NOT required.



P.S. your present CU looks to have been installed quite well.

 

[Danimal]

I see the way this thread will go now, don't bother with advise just show off how big my brain is etc. I know Part P notification yadda yadda etc etc. I'm a mechanical design engineer by my trade ok so that means I studied harder at school than you, the reason I don't know why two wires come out of a mcb is not because Im stupid its just I don't have experience in the world of domestic electrical wiring. you can be sure ill know the reason why its wired like that by the time I pull the cable out though.
If you look at the annex neutral termination really closely you'll see the conductors around the outside have been nicked to at least half depth by overzealous insulation removal cutting but the so called qualified electrician. I can certainly do this job and to standard better than paying someone as they will rush it to get home for lunch! I don't want to rant about this, I accept what you say fine done. Now as I said at the beginning, only looking to start a discussion about the job, NOT the rules. If you wanna talk rules start your own thread

 

[bernardgreen]

is not because Im stupid its just I don't have experience in the world of domestic electrical wiring.

Installing a consumer unit without supervision and the necessary face to face guidance is not the best way to obtain the experience you need.

do you think I should hide some money in an offshore account

Maybe put it into an insurance policy that will pay out even if the rules are not followed.

 

[Danimal]

Fair enough, Ill do it anyway. Good day gentlemen.

P.S. I had an idea the two wires out the top of the mcb would be two separate circuits, I would have said that's bad practice but apparently not and is legit so there you go, now I know.

 

[EFLImpudence]

I see the way this thread will go now, don't bother with advise just show off how big my brain is etc. I know Part P notification yadda yadda etc etc.

It is one of the few parts of this work which actually is the law.

I'm a mechanical design engineer by my trade ok so that means I studied harder at school than you,

Probably true but you don't know that. A silly and irrelevant thing to say.
So, you didn't study what is necessary for the job in hand.

the reason I don't know why two wires come out of a mcb is not because Im stupid its just I don't have experience in the world of domestic electrical wiring. you can be sure ill know the reason why its wired like that by the time I pull the cable out though.

No one said you were stupid.
I can't do your job and you have shown you can't do mine.

If you look at the annex neutral termination really closely you'll see the conductors around the outside have been nicked to at least half depth by overzealous insulation removal cutting but the so called qualified electrician.

The picture isn't clear enough to see.

I can certainly do this job and to standard better than paying someone as they will rush it to get home for lunch!

It is true you may take more care to do it tidier but you don't know the dangerous bits.
You did say you would have to do it before the wife gets home.
Tell her it's illegal to do as you are doing.

I don't want to rant about this,

Too late.

I accept what you say fine done. Now as I said at the beginning, only looking to start a discussion about the job, NOT the rules. If you wanna talk rules start your own thread

Does that includes the electrical rules (regulations) as well?

Fair enough, Ill do it anyway. Good day gentlemen.

We thought you might.

P.S. I had an idea the two wires out the top of the mcb would be two separate circuits,

By definition, that's not possible.

I would have said that's bad practice but apparently not and is legit so there you go, now I know.

But you didn't.

Have you heard of ring final circuits?
How do you test them?

 

[deadshort]

Can i suggest you think about splitting the tails and install an addition 2 way consumer unit to supply the shed and annex ? And leave the existing consumer unit alone, it would appear to be a Hager unit and the wiring is fairly tidy.
Then you would only need to deal with the testing and certification for the 'additional work'.

DS.

 

[flyingsparks]

Pretty sure this is a wind up guys.

Troll Alert!!!!!!!!

 

[sparkwright]

The unbranded piece of crap, as you put it, is Hager.

No spare EARTH ways? That will be a simple matter of rearranging the earth wires so they are terminated in their respective terminals, in sequence.

An MCB will have two or more reds in it if it is a ring circuit or if it is a radial circuit and the wiring has been branched from here. Nothing wrong with a radial circuit having two or more cables at the MCB.

To fit an SWA to an insulated board, one can terminate the cable to a metal enclosure, and run the inner cable straight through to the consumer unit.

The unprotected side of the cu could have RCBOS fitted instead of the MCBs.

As said, the cu looks reasonable from the picture, and, like most people, I really think you will be better off leaving it be - just a few upgrades.

Unless you are an experienced electrician, which you are not, you would be advised not to rip all this out - though DS is perhaps on the right lines about fitting an additional board.

Though I've got a feeling you will do what you want to do anyway.

 

[winston1]

10 kitchen LED s will be no more than 70w, plus 3 more 91w, so no upgrading to 10 A required. Why 1.5mm cable? 1.0mm is all that is required for lighting circuits. You won't need a CU in the shed, just a 20A way on the CU feeding shed socket(s), and a switched fcu (5A fuse) for the light. Doubt if you need a 63A supply (or separate CU) for the annex either

 

[securespark]

I see the way this thread will go now, don't bother with advise just show off how big my brain is etc. I know Part P notification yadda yadda etc etc. I'm a mechanical design engineer by my trade ok so that means I studied harder at school than you,

If indeed anybody has mentioned their qualifications, it isn't to show off how big our brains are, it is to advise people who think they can do something but plainly don't have the first idea that they should either get someone in who does or do a lot of learning and training before they attempt a job like this.

I can certainly do this job and to standard better than paying someone as they will rush it to get home for lunch! Now as I said at the beginning, only looking to start a discussion about the job, NOT the rules. If you wanna talk rules start your own thread

Your arrogance is breathtaking.

the reason I don't know why two wires come out of a mcb is not because Im stupid its just I don't have experience in the world of domestic electrical wiring.

Exactly. Which is why you should not attempt anything until you have done that learning and training first.

There is so much you need to know about and so many checks to make TO ENSURE YOU AND YOUR FAMILY'S SAFETY.

It's quite one thing to take risks with your own well-being, but another thing entirely to risk others.
Obviously you don't give a damn about that.

 

[bernardgreen]

Your arrogance is breathtaking.

It could permanently stop someone else taking any breaths.

 

[ericmark]

1) In the main in the UK we use ring finals which will mean two wires to one MCB.
2) In the main reason for not using 10A MCB with lights is the ceiling rose is only rated 5A.
3) The plug in tester will as you say test the earth loop impedance, but not line - neutral loop impedance or line - neutral prospective short circuit current.
4) The multi-meter does not use the minimum of 200 mA for low ohms or 500 volt for high ohms so not suitable.
5) Even if you hired a test set you need to convince the LABC that you have the ability, if you can't convince us on the forum very unlikely you will convince him.

This does not mean you can't do the job, the LABC do like the idea of using an electrician on their list to do inspecting and testing, so for a fee you can do the work, but have some one else test and inspect, his report may satisfy the LABC inspector however that means you only have a completion certificate you do not get an installation certificate.

So nitty gritty is although you can DIY it will likely if done within the law cost more than getting the job done for you. To break the law does not only mean you have simply broken the law, it also means the installation has not been tested. I consider myself a good electrician however I have made errors, I hope the inspecting and testing I have done highlighted those errors. However even if I was perfect, then there have been quite a number of RCD's which my tests have shown as faulty, in some cases simply because of the strain caused by the stiffness of cables. So in real terms no ability to inspect and test means you should not do the job.

I have from time to time sent my meters for calibration, and went to hire replacements, the hire charge however is not cheap, mainly as after each hire they need calibrating again which is added to hire charge.

 

[flameport]

but please check my logic, anything else I should do or check?

• Other than the Wylex MCB, there is nothing obviously wrong with the consumer unit.
• Replacement just because it is made of plastic is expensive and unnecessary. If required, SWA can be connected into a metal box adjacent or below the existing consumer unit.
• It is not 'jammed full of wiring', and in any case those same wires will have to go into the new one, so the amount of wiring will not change.
• The components you have will not be a 'straight swop' into a VML120, as that only contains a single busbar.
• A 63A circuit is somewhat dubious, and that certainly would require further investigation. Some consumer units are not designed to have 63A MCBs installed into them.
• As for the testing, all of it is required. A plug in socket tester and a multimeter are not suitable. You can't just assume the existing circuits are all ok either, all of them must be tested and the results recorded.
• For the lighting circuit, the total load is the total in watts, and once that is converted to amps you can then determine if the 6A protective device is suitable or not. It probably will be, but only you can know what equipment is connected to that circuit.
• The connection for the shed depends on various things, but one item to check before anything else is whether the shed has any extraneous conductive parts in it. If it does, then the 3 core 6mm SWA is not suitable.