VIR Wiring in Conduit

[kens999]

Hi, Just joined this forum - excellent info here. I have a 1950's house that the previous owner has 're-arranged' the original downstairs radial circuits into a ring. The other circuits in the property are in PVC and seem to be OK.

This 're-arranged' downstairs ring is mainly old VIR, rubber in cotton covering, in conduits buried in the concrete floor. From what I've seen so far it isn't crumbling yet, but it will have to go pretty soon. I have a few questions....

Is it legit to replace this wiring with pvc singles in the conduit? Presently the conduit is actually providing the earth (arggh) but I hope to be able to pull live/neutral and earth through.

and

How much of a nightmare is pulling the old VIR out of the conduit going to be. There are some runs as long as 3m with a right angle bend at each end where the conduit drops down the wall, turns under the floor and the same at the other end 3m away. Any golden rules or tips with this...


Thanks in advance

Ken

 

[bernardgreen]

Can I assume this is metal conduit.

One neighbour 1960's DIY re-wired his house pulling PVC into existing metal conduit.

First the VR did crumble as it was pulled leaving debris clogging conduits.

Then a nightmare to sort out the problems.

A sharp edge in the conduit damaged the cable leaving the neutral exposed and in near contact with the conduit meant a RCCB trip when the floor flex as furniture was put back in place.

Then get all the conduit earthed in case of any other damaged cables, was probably a requirement as well.

Highly NOT recommended and possibly not permitted.

Bernard
Sharnbrook

 

[Spark123]

Luvly stuff the old VIR!! The best way I found to pull new cables through was to tie them to the old cables, tie to one leaving a gap between the strands, tie the next wire to this and the third wire to the second, hence they are stepped. Wrap the wires in insulation tape so they don't catch. Have someone effectively pushing the new wire into the conduit and someone at the other end pulling the slack. It depends how sharp an angle as to wether you will get around the 90deg bends, if they are pre-fab or bent using a conduit bender they shouldn't be too bad. Of course the conduit size and how many conductors you are pulling through will have some bearing on how difficult it is. Some yellow conduit gunk may not go a miss either. Last time I did some of this I tapped the conduit boxes M4 and earthed to them.
Also I'd advise you to read the Wiki on Part P, its one of the grey areas as to wether notifiable or not.

 

[JohnD]

Unless it is the expensive thick tube conduit with threaded ends and screw-on fittings, you will probably find the elbows and boxes can be taken off easily. this makes it much easier to pull your cores through. This kind of conduit does not give a reliable earth but you can re-earth it at every fitting, and put the joints back together.

You might also consider discarding all the conduit except the drops in the walls.

IIRC the old conduit boxes fit a 2BA machine screw, you can still buy these.

 

[Spark123]

Sorry I wasn't clear, there was no earth screw in the back of them so I drilled and tapped a hole in the box M4 to connect an crimp for an earth, the screws which hold the covers on were some sort of BA thread.