Split Concentric Cables Feeding supply to shed

Hello all,

My parents recently bought a house and I've been having a quick look at the electrics. I've recently taken and passed my 17th ed, Part P and 2392 so fear not.

One of things i'm looking at is the supply to the shed. This is provided from a 13amp SFCU off the ring main. The shed is approximately two metres away from the side of the house and I believe the cable being used to feed it is 6mm split concentric (will take a photo soon to confirm), which exits the brick wall, drops straight into the ground, under paving stones and emerges just before the outside of the shed before going in. The ring main is RCD protected.

As far as I know, split concentric can be used for this purpose (Split concentric cable to BS7870), although there is no mechanical protection, it is only required for the parts of the cable that are not buried (in total, that amounts to around 15cm of cable). If I protect the exposed cable using conduit, this won't be an issue.

My preferred option would be to add a new circuit to Consumer Unit and rewire using SWA but my father doesn't want the fuss.

Does the current set-up meet regulations? My only doubt is about the cable because I don't know much about the stuff.

Any advice greatly appreciated! Thanks

Treat split con as if it were T&E and assess the job that way.

Hi Jason, thanks for the quick reply. In that case, it is not suitable. Just out of interest, why would the manufacturers say it is suitable for underground usage if it wasn't? Is there a direct regulation referring to this type of cable too please?

Any cable can be used underground, providing it is given adequate protection and installed correctly, unless of course its SWA.

Split concentric is suitable for direct burial according to the 16th edition. This was sadly removed in the 17th edition.

It's a PIR code 4, I wouldn't worry about it. I installed thousands of metres of split con for external power, buried directly. No ones died yet!

not seen this cable b4. interesting, would a shovel going through it be automatically earthed ?

it would either be earthed, or would produce a N - L fault disconnecting the supply

Thanks for all the replies everyone, much appreciated. Disconnected it from the SFCU and took a photo; not entirely convinced it is split concentric now. Photo attached...

There is one stranded, phase core, with copper strands wrapped around. Whoever terminated it, took some strands and sheathed them in black (neutral terminal) and the others in green (Earth terminal). Aside from the colours, I'm assuming this is not the correct way to terminate the cable?!

Once again, any advice appreciated on what type of cable this is, whether it is terminated corrected and most importantly, if it's fit for use. A Code 4 on the PIR is not a problem in my eyes.

Thanks in anticipation again!

That cable is a straight concentric not a split and is generally used by DNO's as a line conductor (core) and a combined N & E (outer). It is not a 3 core cable like a split concentric. IMO a code 1. Looks like you need to rip out and start again.

Check out regs for PEN conductors page 132 543.4 to see if it satisfies those requirements first before coding.

Straight concentric cable is not permitted in any installations, apart from DNO use of course.

Cheers chaps. Looks like I better start flexing my back for some inevitable lifting of block paving