Difficulty in replacing a FT lighting wire (no CPC)

[js.b1]

I am encountering difficulty in replacing one FT lighting wire, no CPC. It has been run in concrete, with hessian embedded, on crap-block-coke wall, with chicken wire overlay & plaster.

Removal may damage flock lined wallpaper on the other side. It is the sole 2-core cable drop to a switch, although I notice another switch & light the other side which begs the question of how that receives a supply or return with no other cable.

The alternative is 4mm^2 6491X to the architrave backbox, right back to the CU (or a locally FTE rewired lighting circuit). No class-1 lighting device, metal backbox needs an earth.

Is this still regarded as good practice?

I notice the following document suggests doing the same...

will need manual rejoining to BS7671 :-)

Interesting PDF used by NICEIC ECA etc.

Thanks.

-- JSB.

[meow2222]

Wouldnt it be easier to replace the pattress/screws/switch?

NT

[js.b1]

Thanks, flush architrave boxes are metal unfortunately.

Stripped out an LED camera & attached to cable rods. There are 2 cables - for the light-drop and light+switch. Cables are not just set in cement on the wall, but through the wall, up the other side, against the wall & against joists.

Cable colour & wiring differs from the others, route is odd. I guess the builder did these for his use - cement to protect the cables before he put the staircase in against that area.

Easy replacement impossible, so ran 4mm 6491X for CPC.

-- JSB.