Extending cables to move consumer unit

[huw169]

I am converting 2 flats into a house.
The upstairs flat has recently been rewired, but the lower flat is original.
I am putting a new big consumer unit (Crabtree 18way) downstairs, but I need to extend the cables from my upstairs CU to the downstairs CU.

My electrical chap has suggested 2 ways to do this:-

1 - Find the first and last connection point on the circuits and replace with longer cables from there.

2 - Extend each cable using a junction box and route to the new CU.

I am not really happy with either of these. Option 1 means digging some walls out upstaris, and option 2 is just messy - although once I put the floor boards back it will not be seen - I will just know it's there (do you know what I mean??)

Do any of you guys know of any products that have multiple connection for extending a bundle of cables? I guess I'm really after a more elaborate and rated chocolate block (one big junction box)

Any ideas??
Many thanks

 

[rebuke]

In place of the upstairs CU you could put in a large adaptable box, some DIN rail, and some DIN rail mount connections - box it in a cupboard and you're sorted. Not sure if there's anywhere better, but most electronics companies such as RS, Rapid, Farnell etc will sell the connections (electrical wholesalers in general only sell the DIN rail itself in my experience). You can get gray and green/yellow ones, so you can make nice batches of 3 for each connection etc.

Remember, whatever you do if it involves screwed connections will have to be accessible - you can't bury it under the floor unless using crimps or some other permanent connection...

 

[ban-all-sheds]

I am putting a new big consumer unit
.
.
My electrical chap....

So who is installing the CU - you or your "electrical chap"?

option 2 is just messy - although once I put the floor boards back it will not be seen

Shouldn't have JBs under floor boards really - I'm surprised your electrical chap suggested it.

I'm also surprised that he doesn't know about crimping, or DIN rail mount through terminals.

I have my doubts about his competence - you might like to consider getting someone who knows what he's doing.


[EDIT]Doh![/EDIT]

 

[huw169]

Crimping sounds the best idea, as whatever I do will not be accessable. The wall that the current upstairs CU is on will not be there soon.... so no chance of a box.

I didn't know about the screwed terminals under the floor. How does that work with lighting circuits being run off JB's in the roof?

It wont be me installing the CU so not to worry there. All of this work will be Part P approved and signed off, but I am doing all the 'donkey' work.
Just learning really - isn't that what these sites are for?

Many thanks for the comments, at least I'm more informed to ask better questions.
Cheers
Huw

 

[rebuke]

If it's in the loft, and the loft is accessible via e.g. a hatch then it's OK - if boarded and the JBs are under then it's questionable...

If you have standard screw terminal JBs under a floor for e.g. downstairs lighting, then that is against the regs, since you cannot get to it for inspection and maintenance. If there is e.g. an inspection hatch, then as long as this can be opened without e.g. lifting carpet that would be OK.

 

[huw169]

Thanks Rebuke
Makes sense. Crimping is definately the way forward.
I'm glad you mentioned that JB's are not goof for downstairs lighting as I would have used them as they are used upstairs, but my loft is boarded out

 

[ColJack]

nevermind, must read the post more carefully...
didn't see the bit about the soon to be disssapearing wall..

 

[comms]

I've used these in the past to extend circuits to a new cu location.

http://web6.automationdirect.com/adc/Overview/Catalog/Terminal_Blocks

Sat inside a nice adaptable box on a length of dinrail or I once used old cu (gutted it apart from dinrail) & loop'd conductor extensions out to new cu location 3mtrs away.

 

[huw169]

Thanks comms.

I might be able to take the cables to a nearby built in wardrobe and put a junction box in there.
I'll check it out once I get the cables exposed.

Thanks for all the comments guys.
Huw

 

[huw169]

Just sitting here thinking to myself...........

Couldn't I just have the current CU relocated to the fixed wardrobe (assuming there is enough slack in the cables) and run a single beefy cable from a single circuit off the new CU downstairs?
This would mean the new CU would be a lot smaller and the path to the new CU could be a lot smaller in diameter?
Is this possible, or considered bad practice?

I'll give my electricial chap a call tonight to discuss, but i like to be prepared.
Thanks
Huw

 

[rebuke]

I don't think there's anything in the regs that would forbid it (you'd probably have to run the supply to upstairs CU in SWA or in earthed metal conduit so you don't have to RCD protect it), although it would certainly be unusual...

 

[huw169]

Yeah, the more I think about it the less i like it.
The crimping works.

Just to finish up then........
This is a 'phase 1' piece of work, and i may in the near future end up relocating the stairs - which will mean that the understairs storage where the new CU is going would dissappear.

Is there any issue with extending the cables such that there is sufficient length so I don't have to extend them again later?
Can I coil them up in the roof space?
I seem to remember from my physics that coiling cables can create heat.....

 

[rebuke]

Hmm, not sure about what the regs say - I guess grouping factors would come in (any heat generated in a cable will be multiplied by the fact it's touching x coils of itself).

Assuming you use T&E or similar there won't be issues with magnetic fields, since you have both L and N in the same cable so they cancel each other out (if you did it with singles then you would potentially be generating various magnetic fields which could cause induction in other cables and interference with things etc).

Would it not be easier to put the new CU in somewhere that will remain after you've relocated the stairs, that way you don't have to relocate things multiple times?

 

[huw169]

Hmm - see what you mean.
There is nowhere else for the CU unfortunatly - well, nowhere that will be out of site anyway.
Thanks for your help.
Huw