Replacing 60A CU with 100A

[srj321]

Hi

Forgive my ignorance on this but hopefully someone can supply what I hope is an easy answer.

Currently my CU has a 60A sticker on it. If I want the CU changed to a 100A CU (getting some additional things added such as induction hob and electric shower and need more connections on the board) is this something a suitably qualified electrician can do or is it more complicated than that.

Thanks

srj321

 

[JohnD]

An electrician who is a member of a self-certification scheme can do it. He will inspect your existing installation and may find other work that needs doing to bring it to a proper standard. This is likely to include the main earth and bonding. The older your installation is the more likely it is to need other upgrades. Have any additional electrical work in the Kitchen and Bathroom or outdoor circuits done at the same time as it is notifiable under Building regulations and will be more expensive if done separately.

Most people have a split-load CU fitted with one RCD to protect several circuits (such as sockets and showers) but if you can afford it, RCBOs provide one RCD per circuit which is a better solution.
Be sure to have a CU fitted which is larger than you currently need. The extra cost of larger plastic box and some fresh air is not much but will be handy in future.

Get recommendations for a local electrician from friends and neighbours. Ask which Scheme he is a member of before he comes round. Do not have it done by anyone who will not issue the proper documentation.

 

[srj321]

Thanks for the response.

Sounds relatively straight forward then with the right electrician. Was worried that I would need to contact my electricity supplier to somehow upgrade the supply into the property to enable it to cope with the increased demand - and was getting worried that this would delay/add to the cost of doing all the bits and pieces required.


srj321

 

[JohnD]

Have a look at the Company Fuse. it will probably be marked 80A or 100A (however this is the max fuse that can be fitted, it might only have a 60A cartridge inside). if the fuse ever blows (e.g. when you are using electric hob and shower at the same time) if you ring then they will be round quickly to replace the fuse, and may well fit a larger one.

Also look at the Earthing arrangements. If you can post a pic showing the main fuse, the service head, the meter and your consumer unit, and the wires between them (especially any green and yellow ones) we may be able to spot something and make suggestions. You can often get a better more modern earth fitted by the company if you need it.
//www.diynot.com/forums/viewtopic.php?t=99672

There ought to be 10mm main bonds going to your incoming gas and water pipes. This is an easy DIY job or your electrician can do it and charge you for crawling about on the floor.

 

[Adam_151]

Any chance of a picture? is it an old wylex standard unit fitted with re-wireable fuses

In addition to being rated at 60A total, a lot of the time the maximum fuse allowed to be fitted was 30A and with modern showers taking upto ~45A, they can't be fitted on a unit like this (the wiki has some lovely pictures of slightly chrispy ones )

Yes, it won't be a problem for any competant electrician, but this is notifiable work, so check that he is registered with one of the 5 full scope electrical certification bodies (NICEIC, NAPIT, BRA (ECA), ELECSA or BSI), standard things apply like get recommendations from friends and family if they have had any electricial work done, don't just get one quote etc, ask him what brand of CU he plans to use, MEM, MG, MK, HAGER, WYLEX, CRABTREE, SQUARE D are recognised as being reasonable quality, makes such as PROTOUS, CHINT, VOLEX, not as much so!

Ask him which standard he is working to, BS7671:2001(2004), or BS7671:2008, its acceptable to work to either at the moment, but the transistion period ends in June, others might disagree with me, but if you are having a CU change done, I'd perhaps say it was sensible to work to the new standard (which requires more RCD protection), because the last thing you want is to end up requireing an inspection in 18 months time for whatever reason, and finding it no longer complies with the current standard and a CU change is recommended again!

 

[srj321]

Here are a couple of photos.

One of the cu and one of the actual supply into the house - not the greatest of photos but bit of a squeeze trying to get in there.





Not sure what you mean johnd about the Company Fuse. Is that identifiable from my photo?

Thanks once again for all your input.

sr321

 

[JohnD]

The Company fuse (main fuse, supplier's fuse) is inside that black ?plastic thing that the thick red cable comes out of. It has a label stuck over it telling you not to touch it, so the rating marking may be obscured.

Can you get down and see how the G&Y are attached to the service head? Is it all plastic, not cast iron?

I hope one of the G&Y goes into your CU.

There appear to be 5 cables going into that rectangular Henley block, I was expecting either 4 or 6. Where does the other one go? Stand back and take a wider pic.

 

[srj321]

ok

Had a look at the company fuse - having scraped the label and seen nothing I then noticed in very small embossed writing at the bottom 60A written on it. So that answers that question.

The service head would appear to be all plastic (guessing that is more up to date than cast iron).

The G & Y cables loop behind the board but I can see that there is a connection to the CU with it.

Just tried to take a wider picture - not a lot of room underneath to get it all in and the battery on the camera has gone flat - so will have to wait for an updated one. What I have realized though is that there is a seperate little fuse board with 3 MCB's on it which I haven't managed to capture on my previous photos (sorry) - so does that explain the 5 cables from the Henley block?

Also just been chatting to a friend who is training to be an electrician and was told that I would need to confirm with my supplying company whether I have the right supply cables to support a higher company fuse as you can't see the supply cables as they are currently all tightly wrapped up in tape. Is this right or will the electrician I get in just be able to whip out that 60A fuse and put in a bigger one (or is it something only the supplying company can supply?)

Thanks once again for all your input.

 

[JohnD]

Only the distribution co can change the company fuse. It will depend on the incoming cable size, but they are quite generous.

there are calculations to estimate what the current demand will be (based on the idea that you are unlikely ever to turn on everything at the same time) but lots of UK houses work happily on a 60A fuse.

Having storage heaters or a big electric shower puts a big load on it.

If you incoming cable is quite old it probably has a flexible steel armour round it, wrapped in tarry cloth tape to resist rust.

BTW the Henley block casing has two junction blocks inside it, one in front of the other. So you would expect all the front cables to be black, and all the back ones to be red. But looking at your pic I'm not sure if that's how its been done the sheathing has been cut back too far so you can see the coloured insulation. Maybe it is an optical illusion. Or maybe it is not the same design as i am used to

If they have been mis-connected it could be very dangerous.

 

[srj321]

Time to give them a call then.

Is the distribution company different to the supply company? Just been looking at a recent bill and it only shows that npower as my supply company. If I do have to arrange it through npower I don't hold out much hope as my previous dealings with them haven't inspired me with confidence.

 

[dannyboi2003]

There appear to be 5 cables going into that rectangular Henley block, I was expecting either 4 or 6. Where does the other one go? Stand back and take a wider pic.

If you look very closely (took me a few minutes to see it) the neutral from the meter has been wired using a grey/red tail (you can just see the red where the tail connects to the henley) its just a little naughty whoever wired it like that and then didn't properly identify it, there are then 4 more cables going from the henley up to the CU's.

 

[JohnD]

... the neutral from the meter has been wired using a grey/red tail ...

Good grief!

Is the distribution company different to the supply company?

Yes, but you don't need to worry about that. your supplier is responsible for passing on the request. If they don't act correctly when you phone them, send a brief letter to the address on the bill. in my experience, letters are carefully tracked and passed on, unlike phone calls which can be fobbed off or mis-handled.

 

[ban-all-sheds]

Also, when phoning, always ask for the name of the person you speak to, and the name of their line manager/supervisor.