We finally opened the mysterious box in the hall...

[Triffle]

Triffle are you saying the lower cable going through the doorframe is going outside and is the supply coming in.
If so then i was getting mixed up, I wrongly asumed that new cable went to thenewer cut out, maybe they renewed your supply to there for some reason.
Just noticed the left what i thought was a Henley box is actually joined to the fuse, so that makes that a "Cut out " with a seperate Henley block for the Earths, my apologies

Yep the cable lower right is coming in from outside, through the doorframe as you say. And thanks for the extra info (I hadn't noticed myself that the left box was joined to the fuse!)

To clarify:

Looking at my other photos, I've just noticed... is that the split concentric coming into the top of the Henley Cut Out next to the consumer unit? It is all beginning to come clear...:

 

[333rocky333]

Yes it iooks like it is a a split concentric which is why I thought wrongly that was the lower cable through the doorframe.

Hard to tell from the pic but it appears the hall top cable may be a split concentric too, just they have slid that oversleeving, over the bunched individual strands, Green solid colour sleeve indicates it was done early 70s or earlier, as Green and yellow was introduced early 70's.
Due to the difficult route from that box to the under stairs cupboard, is likely why they chose to renew the newer lower cable only up to that old location.

Further info for you, Split concentric is mainly used by the Regional Electric boards, i dont recall ever seeing an electrician use it.

As for Concentric which only has an Inner and a ring of outer cores, I think its use is regulated and mainly forbidden for use even by electricians.

Its rare to see split concentric terminations exposed like you have in the hall , as there usually hidden within a cutout fitted by the electric board (as your understairs pic above).

Heres a pic of a load of Concentric cables in a block of flats, all the Outer cores are bunched in heat sleeve and used for Neutral as well as Earth, this is something only the Dno are allowed to do.

Main1

• 333rocky333
• 20 Jun 2015

 

[jelliottelectrical]

Further info for you, Split concentric is mainly used by the Regional Electric boards, i dont recall ever seeing an electrician use it.

As for Concentric which only has an Inner and a ring of outer cores, I think its use is regulated and mainly forbidden for use even by electricians.

I’ve seen split con used lots, and have installed it myself a number of times. As it isn’t armoured it has to be treated as twin and earth. I have used it for submains myself many times, either clipped direct or on tray

Straight con can only be used for combined neutral and earth which is forbidden for use in any installation. I only know of once install that is wired with a combined neutral and earth throughout and it required permission from the home office!

Though I do know a linesman who wired a supply to his shed in 35mm2 hybrid (straight con with an aluminium core and copper neutral/earth) with a separate 16mm earth

 

[SimonH2]

CONCENTRIC is one main core with a ring of outer cores usually EARTH
SPLIT CONCENTRIC is one main core, a ring of outer cores and ALSO a ring of Neutral cores

Err, that's not right is it ?
Yes, concentric is one core with one layer of smaller cores (generally not insulated) around it.
Doesn't split con also have one core and one layer of smaller cores round it - but this layer has cores which are split into two groups (insulated blue for neutral and uninsulated for earth).
Eg: https://www.elandcables.com/cables/concentric-and-split-concentric-cables#range

 

[jelliottelectrical]

Err, that's not right is it ?
Yes, concentric is one core with one layer of smaller cores (generally not insulated) around it.
Doesn't split con also have one core and one layer of smaller cores round it - but this layer has cores which are split into two groups (insulated blue for neutral and uninsulated for earth).
Eg: https://www.elandcables.com/cables/concentric-and-split-concentric-cables#range

Yes you are correct, though i seem to remember there are more blue cores than bare

 

[SimonH2]

The blue cores are probably smaller CSA so that with the insulation they are roughly similar in diameter to the bare ones. Thus there'll be more of them to get the same combined CSA.

 

[333rocky333]

Err, that's not right is it ?
Yes, concentric is one core with one layer of smaller cores (generally not insulated) around it.
Doesn't split con also have one core and one layer of smaller cores round it - but this layer has cores which are split into two groups (insulated blue for neutral and uninsulated for earth).
Eg: https://www.elandcables.com/cables/concentric-and-split-concentric-cables#range

Yes you seem to be right, never realised that, only ever seen it when already terminated with the outlet bit sheathed over