Rewiring Attic in Edinburgh

Dutch Sparky · Oct 11, 2024

I'm from The Netherlands and currently visiting family in the UK. I used to run an electrical contracting company in the Netherlands a few years back, we did a lot of big houses and industrial stuff. But in he UK materials are different and I'm looking for some advice on selection of materials.

The appartment is about 100 m2 and has a DB with 16 circuits. Few 6 Amp for lights, 20 and 32 Amp for sockets and 40 Amp for showers.

The main issue is that currently the old wire Black-Red has been mixed with the new wire. I was asked to hang a light fixture and I found this old cotton braided wiring. When I checked the attic it all a big mess with cables everywere.

My game plan is to get 2.5mm2 Twin Earth cable and rewire everything. Where we reuse the metal conduit I'll make sure to earth it. But there are also some additions for the showers which cables now run losely over the attic. I would like to run this wire in PVC conduit 20 mm.

Any suggestions?

littlespark · Oct 11, 2024

1.5 or even 1mm for lighting on a 6A lighting circuit will suffice.

2.5 can be used for power sockets, and in UK, we commonly use ring circuits for general sockets.

Have you had much experience with UK wiring systems?

If the cables are old (you say cotton braided? I wonder if it’s VIR? Very brittle insulation?) is the distribution board still old rewirable fuses, or much newer RCD/ RCBO?

MFS Electrical · Oct 12, 2024

Dutch Sparky said:
I'm from The Netherlands and currently visiting family in the UK. I used to run an electrical contracting company in the Netherlands a few years back, we did a lot of big houses and industrial stuff. But in he UK materials are different and I'm looking for some advice on selection of materials.

The appartment is about 100 m2 and has a DB with 16 circuits. Few 6 Amp for lights, 20 and 32 Amp for sockets and 40 Amp for showers.

The main issue is that currently the old wire Black-Red has been mixed with the new wire. I was asked to hang a light fixture and I found this old cotton braided wiring. When I checked the attic it all a big mess with cables everywere.

My game plan is to get 2.5mm2 Twin Earth cable and rewire everything. Where we reuse the metal conduit I'll make sure to earth it. But there are also some additions for the showers which cables now run losely over the attic. I would like to run this wire in PVC conduit 20 mm.

Any suggestions?

You’ll need a building warrant if you’re planning to rewire a flat in Scotland. That could be very tricky if you don’t have Scottish/UK qualifications.

Beware of derating the current carrying capacity of cables when putting them in conduit or trunking, you may find that they are already borderline especially for the shower.

All in all I’d advise enlisting a local electrician.

Dutch Sparky · Oct 12, 2024

Indeed VIR wiring has been used. It does run in metal conduit but the places where the switches etc are, this is not the case.

I have worked with metal conduit but i think this is a little bit much for this attic. I see a lot of Twin Cable+earth loosely on the wooden beams between insulation. Is this the normal way? I'm used to put cables at least in pvc pipe to give it more protection.

If I would have the time I would make everything in metal conduit. It is a home owners association building, there may be future repairs on the roof and people could walk everywhere in the attic also on the conduits.

I was thinking on maybe making one 'highway' bigger conduit in the middle and than junction off from there.

Building warrant I need to check!

Dutch Sparky · Oct 12, 2024

I've been looking into the permit/warrant, I found this text:

"A building warrant is not required for rewiring where it is a repair or replacement works to a level equal to the installation (or part thereof) being repaired or replaced.".

So if we just replace VIR cabling in the same circuits we are OK? I'm not going to add anything to the installation, just replacing cabling.

littlespark · Oct 12, 2024

Twin and earth cable is deemed to have sufficient mechanical protection of the outer grey sheath. So any conduit isn’t needed.

It should be clipped securely.

Dutch Sparky · Oct 12, 2024

Ok, and reusing some of the metal conduit, just adding extra ground wire with it.

At some points previous electricians have make extra holes in the metal junction boxes and just went out with twin pvc. Using a rubber grommet is sufficient? Or are glands required? The boxes are not water proof.

MFS Electrical · Oct 13, 2024

Dutch Sparky said:
I've been looking into the permit/warrant, I found this text:

"A building warrant is not required for rewiring where it is a repair or replacement works to a level equal to the installation (or part thereof) being repaired or replaced.".

So if we just replace VIR cabling in the same circuits we are OK? I'm not going to add anything to the installation, just replacing cabling.

In Theory that’s a good argument but if you will be adding or moving switches or sockets or adding lights you’ll more than likely end up needing a warrant.