Earthing to 1st floor flats

[phillipdj]

Hi, I've come across this strange setup on a set of flats I'm doing work on and wondered what people think.

There are 4 flats on the 1st and 2nd floor (ground floor is a shop) with their own supply from the street. The supply enters the building from underground at the bottom of the stairs, a DNO cable supplying a 3x100a cutout, but there is also a 25mm earth coming from under the street to the MET. There is a PME sticker, then the supply goes to a big old switch. (first pic)

Then there is a 4 core SWA to a cupboard upstairs with the distribution boards in it, which feeds another 3x100a cutout. In that cutout the earth and neutral terminals are linked, and then tails as normal to the meters. (second pic)

It seems like tn-s to the first cutout then tn-c-s to the second cutout, but I don't think the SWA sheath or big switch are earthed.

 

[mattg4321]

The 25mm earth going to the 'street' probably goes to an earthing plate buried in the trench the cable comes through. This would form part of the DNO's PME system.

 

[SJD]

Just to check, are you saying the white-coloured cable from the top of the first switch, is the same black-coloured cable entering the bottom of the second cutout? The sizes seem different, but that might just be the photos.

 

[phillipdj]

Yep, it's the same cable, I think it's 16mm 4-core swa, it's glanded at the switch, but I have no idea how it's terminated in the second cutout

 

[Wilko]

Are you saying - DNO cable cutout is TNS and then internally in the building the N and E are recombined? Which would not be right at all, I’d have thought.

 

[phillipdj]

i think they are both dno cutouts as they are before the meters, but now I'm wondering if neutral and earth are joined at both cutouts and as mattg4321 said, the earth cable is just a link to a pme plate. so I guess my question is, should the met at the first cutout be linked to the swa sheath? even though it's not really my job to do it