Extending circuit cables into new CU

[Bill Alty]

I'm a time-served electrician but served my apprenticeship and all my working life in one factory or another, so I readily admit I have no experience of the domestic side of the business, ie, wiring houses.

The factory where I served my time was brilliant and the apprenticeship very varied. We had our own power house onsite with four "normal" turbine/genny sets and two "specialised" sets providing a certain part of the factory with whatever it required - can't remember now because it's been 33 years and many thousands of beers since then :o)

One day I might be installing a new socket for a copier in an office, the next day I might be jointing a 6,600V feeder cable to one of the 20 substations we had onsite and, having had such a varied and brilliant apprenticeship, I'll be buggered if the guvmint are going to tell me I can't install a new consumer unit under my own stairs!!!

So, what's the best/approved method of extending the cables from my old consumer unit into my new one?

Thanks, Bill.

[Owain]

If you just need a few extra inches inside the new CU then crimps. If you need to take lots of cables a longer distance then DIN rail terminals in an appropriate enclosure.

Owain

[Bill Alty]

Ah, thanks Owain. That, I can work with :o)

[Andrew Gabriel]

I'd suggest a service connection block, a.k.a. "Henley" block. Another advantage is that this way you can split the tails into both the old and new CU's, allowing plenty of time to move circuits across, before eventually disconnecting and removing the old CU.

Also, check your meter carefully. Some have an unsealed cover on the terminal connections to your tails, so you can replace them without breaking the meter seal. Breaking the meter seal in not a good thing to do. Breaking the seal on the main cutout so you can pull the fuse and work on the tails without them being live seems to be less frowned upon, although strictly still not allowed.

[Tim S]

Bill Alty wibbled:

;->

eg, on a temporary circuit I did:

Tim

[Bill Alty]

cables by about a foot each, so for me I think Owain's suggestion of DIN rail terminals in a suitable enclosure is the way to go.

Thanks anyway mate

[Bill Alty]

Excellent idea!

The meter is sealed but the service fuse isn't so I can pull that to work on the tails. I've got a 100A DP isolator that I can run the tails into from the meter and then out to the Henley's and on to both CU's.

Thanks Andrew.

[Owain]

Owain

[Owain]

I claim no originality for it, it's been done before and by better than me.

"Moving consumer unit 4 feet down" including detailed postings by Stefek Zaba and the late Andy Hall

Somebody here did it and posted links to good photos

Owain

[Tim S]

Bill Alty wibbled:

Sorry - I didn't see Owain's reply at the time.

I'm using DIN for a number of lighting junction boxes - if it's any help, RS own brand DIN terminals seem as well built and less expensive than many others.

OTOH crimps are regarded as a permanant solution, so it would be a matter of a suitable enclosure to house 10 sets of joints.

Cheers

Tim

[Tim S]

Owain wibbled:

Hehe :)

[Andrew Gabriel]

Maybe you are thinking of:

[John Rumm]

Coming to this party a little late, there is not much to add to what the others have said. There may be some stuff that is of use to you here however:

not the subject at hand, some of the stuff on use of an independent supply may be of use:

[Dave Plowman (News)]

Just remove the seal on the meter if you need to fit new tails. Much better than using a connection block. I did this when fitting a new CU some years ago - and despite many meter readings since then no one has noticed.

[Bill]

In message , "Dave Plowman (News)" writes

I did the same a few years ago when my fathers CU died a death in quite a spectacular way. Even phoned up the supplier to own up to it and to ask them to re-seal it, they never have.

[Owain]

Did you find the grouping factor for the trunking an issue, or not relevant for such a short distance?

Owain

[Arthur 51]

I think 'Mandy' will help you out with that.

Arthur

[Andrew Gabriel]

The trunking was already there so I didn't worry about it, although it crossed my mind. The total (ungrouped) capacity of those cables is about 200A, and there's only 100A supply (and in reality the total load probably never exceeds 30A and none of the cables are normally likely to be carrying more than 30% of capacity).

[John Rumm]

CU wiki article? I just realised there is not much detail on the section about extending existing circuit wires, and the din enclosure is not mentioned at all at the moment.

[Andrew Gabriel]

Yes, that's fine.

One comment I would make in hindsight - the DIN rail connector sizes are measured for a specific cross section of conductor, and you'll struggle to get even a hair's breath extra in one. If I was doing it again, I'd bump all the DIN rail connectors up to the next size up from what you might expect is needed. Also would have made it easier if there was more space in the box above the connectors