New CU and meter tails etc

[rajshar]

Hi
I don't know if I should ask it here or the main electricians forum. It's about CU change and the work around it and the CU change will be done by a proper registered electrician.

I will try to upload the pictures so you can see what I am talking about. I took two quotations. One just ask for pictures and quoted me for new BG CU with RCBOs, meter tails, upgrade the earth cable as the old one is only 6mm.

The second one visited my house today and after looking at the meter fuse board gave me two quotes, one including materials and one just his labour, testing and certificate charges. He said there is no need to tell Building control as he is registered and his certificate covered it. His quote includes fitting new CU and meter tails. But he said he won't change the earth cable as that is coming out of cut out and he isn't allowed to touch that. He also told me that the tails from the cutout to the meter and then to the fuse board are 16mm. The cutout fuse is rated 100A. The length of tails from cutout to meter is about 60cm and from meter to the fuse board is about 120cm including all the bends. Is all this acceptable? I know that I can ask him to fit 25mm tails to the CU but who is responsible to change the tails from cutout to the meter and who is supposed to change the earth cable for bonding from cut out to the gas pipe.

I have an appointment scheduled with British Gas to fit an isolator between the meter and fuse board as the first electrician asked for it. Can British Gas electrician change the tails and earth bonding cable from cutout while fitting the isolator?
Sorry for a long description and questions.
Thanks

 

[rajshar]

Thanks Strima.
The suppliers installer will fit the correct cables if he deemed necessary. between meter and isolator and between cutout and meter as anything after cutout to meter is the suppliers responsibility.

Now I could be completely wrong but isn't that with a 100 amp fuse the 16mm tails aren't suitable as they have maximum rating of 80amp. We had smart meter fitted April 2020. I am just wandering that why they didn't upgrade the right tails or downgrade the cut out fuse that time. That time I knew nothing about any standards or regulation otherwise I would have asked the installer for this and would have arranged for an isolator at the same time.
The other issue is the earth cable. Now we don't have the earth conductor or earth block. The earth cable goes direct to the fuse board from cut out. The current earth cable doesn't comply even with 16mm tails. I believe it should be 10mm in the current settings and if upgrading to 25mm cable it should be 16mm. Even this wasn't pointed out to us by the meter installer. May be it's not their job to change the cables but at least during the installation, they should be inspecting that equipment is in compliance. Or is it that my equipment is still in compliance because new regs don't apply retrospectively. Anyway when suppliers installer comes to fit isolator and decides that 16mn tails are good enough, shouldn't then who ever is responsible, change the cut out fuse to the correct rating. Although upgrading the tails should be the best option.

Now some electricians have no problem to upgrade the earth cable and some just getting out of it by saying they don't touch the cutout as this 2nd electrician said. It also makes me wonder that how he was going to change the CU without any isolation because he didn't knew that I had arranged for an isolator to be fitted. I think I should at least ask one more quote and see what he/she can or can't do.

All this brings up new questions. All the CUs come with 100 amp isolators. Do we still need an isolator inside the CU, if one fitted outside, if yes should it be lower rating than the 100amp?

Thanks.

 

[brianmoooore]

100A is the max. rating of the cutout fuse holder. 100A fuses were common several years ago, but the DNOs have been changing them to 80A when the opportunity arises on 'normal' supplies.

 

[rajshar]

Earlier telextrix said that BG CUs are good. Sorry I didn't meant that BG boards are bad. It's that he was going to get the BG CU from Screwfix and all the prepopulated BG CUs with RCBOs they sell come with Type AC RCBOs. I want Type A RCBOs and I was thinking to get the wylex ones from TLC. Anyway now I found that TLC does sell BG brand Type A RCBOs as well and it comes around £107 pound cheaper than Wylex, it's not that big difference.. Now it's just a struggle to chose between Wylex and BG.
Thanks

 

[rajshar]

Thanks brianmooore. So do you think that when smart meter was fitted, they would have changed the fuse. Do they not put any notes etc about the rating of the fuse as I don't see anything to indicate. Do you think that someone should have pointed out that earth cable needs changing.
Thanks

 

[Vortigern]

It is not necessarily the case the earth cable needs changing. The braided earth is supplied from the DNO and it is their equipment. The energy supplier (in theory) should not touch the DNO equipment and vice versa. It depends on the fault current likely to occur at the CU. Personally I would not fit BG my experience with them has been they are unreliable and I have had quite a few failures with their RCBO. The earth cable from the DNO supplied earth to the CU can be changed no problem but then there must be a reason to do so such as thermal damage for instance. Why are you changing the CU anyway?

 

[brianmoooore]

Why are you changing the CU anyway?

Haven't you seen the pic? It's an ancient rewireable Wylex, with a fuse cover that's missing/unfittable. On the plus side, it isn't plastic.

 

[Vortigern]

Yes I have seen the pics. I am still interested from the OP as to why he has decided to do this. Personally on a pragmatic level, I wouldn't mandate a CU change on the box alone anyway. Significant improvements to safety could be achieved by doing so it is true. I was really wondering did the OP think this up all by him/herself or was it recommended by someone and if so why.

 

[rajshar]

Vortigern, first why changing the CU. No we aren't changing the CU, we are fitting one because currently we have old fuse box without any RCD protection.
About BG, yes few others have mentioned to go with either Hager or wylex. I am leaning more towards Wylex as with 7 RCBOs the price is just about £100 more. Although I am fully aware that even the best can fail too.

The reason I keep asking about the earth cable is that both electricians who gave quote and searching on Google it comes up that earth cable should be 10mm with 16mm tails or 16mm with 25mm tails. Both recommended changing it although one agreed to do it, the second one said he himself won't do it as it is the distribution networks responsibility. I am just trying to ascertain if it really should be upgraded and if yes then what is the best way to do it. I mean an electrician or the DNO.

Another confusion is that do we still need bonding as water gas supply is in plastic pipes. I just found a special note on the back of water meter booklet. I am attaching the picture of it here. I again don't understand that are they talking about main earth or bonding.

 

[rajshar]

The decision to change to a CU was taken after advice by a former electrician who is my colleague in the railway. We wanted a new circuit in the kitchen and I asked him, how to do it. He asked about the current equipment and then advised to upgrade to a CU. The reasons were given that new circuit in kitchen is notifiable and has to be protected by a RCD and it was best to do the complete upgrade rather than just doing a partial work. Unfortunately he can't recommend an electrician as he isn't from London, so don't know anyone locally. There is another compelling reason. When we bought the house in 2005, we weren't aware about electrical report neither it was mentioned to us by the surveyor and the electrical installation in my home never has been tested. We never had any issues though apart from a one time blown fuse incident due to a faulty socket. That's why we changed the lighting and socket circuits to plug in wylex mcbs. Since then no blown fuse or no tripping of mcbs. I take the wiring is in good condition. At least it has given me an opportunity to educate myself about regulations.

 

[SJD]

If the earthing cable is undersized when I'm installing a new (domestic) consumer unit, I generally just change it if practical & safe to do so, I don't start arguing over who owns which bit, I regard it as part of the job.

 

[Midwest]

If it was my house, I would spend my money on upgrading everything, new CU including RCBO’s, SPD’s, main earth, tails and anything else I could think of.

Which might include a rewire or partial rewire, which is when I might consider an EICR. But then sometimes, just a visual inspection would help you make that decision.

 

[rajshar]

I agree that while upgrading the CU, other cables including earthing and bonding should be upgraded too. That's why I asked it here. I have read some other posts from past in a very similar position and majority advice is that either there should be proper calculations to see if a 6mm earth will suffice or just upgrade to at least 10mm earth as a rule of thumb.

Do you still need bonding in the house when outside water and gas pipes are plastic but inside the house still copper?
Who should replace the earth cable from cutout to CU?
Does one need an isolator inside the CU when a 100amp isolator is fitted outside and if yes then what rating it should be inside the CU?

On closer inspection I found that earth cable is going into a small square size block moulded on the left side of cutout. This blocks cover is being held by a sealable screw. The "do not remove" seal isn't on this earth cable as I thought instead there is silver cable which come out of cutout, and goes underneath into this small block. The earth cable from top of this block goes to fuse box routed behind the ply board. Then another earth cable comes from fuse box for binding to gas pipe and continue on the gas pipe into kitchen under the floor, possibly to the water pipe and hidden out of site. I believe I should be able to unscrew this cover to have a closer look. Could it be the earthing terminal inside this block?

Just found this link in UK power network's site. Can I ask them to inspect the earth cable by requesting a visit or is it unnecessary. I don't know if they will charge a fee if they do any work but the visit and assessment is free.

Earthing | UK Power Networks

Is there an issue with the earthing at your property, do you need Protective Multiple Earthing (PME) at your property or you don't have any earthing at all? Get advice now.

www.ukpowernetworks.co.uk

Thanks

 

[rajshar]

The sealable screw isn't sealed on this earth terminal block or whatever it is called. I unscrewed the cover and took a picture. It seems that any electrician should be able to change the earth cable as the green yellow cable is just connected to the too of this block. The DNO's earth connection with do not remove seal goes to the bottom of this terminal block and doesn't need to be touched. I personally feel it is dead easy for any electrician to upgrade the earth cable here unless there are some caveats to it.

 

[nicebutdim]

It seems as though the first electrician meets your requirements, other than the fact that you've expressed a preference for having a different brand of CU fitted. Why not just ask him for an ammended quote to account for this?

 

[rajshar]

Now before someone condemned me for doing this,vI would like to clarify. I k

It seems as though the first electrician meets your requirements, other than the fact that you've expressed a preference for having a different brand of CU fitted. Why not just ask him for an ammended quote to account for this?

I have asked him if he can provide me a quote either with a wylex cu or deduct the amount of cu and rcbos and I will supply him direct. I have given him the links of TLC for this, not sure if he shops at TLC. I have a TLC store about 2 miles from my home and can pick up the stuff in about 20 minutes.

Sorry to be pandentic but can someone advise me about isolator and it's rating in the consumer unit when a standalone isolator of 100amp is installed before cu or it doesn't matter as these are just main switches and they don't trip on their own and one can have multiple of them.
Also the requirement for bonding when outside supply pipes are plastic.
Thanks