It MIGHT be acceptable, It was permitted and is still permitted to use the conduit as the CPC, provided that a suitably low earth loop impedance is achieved. There should be flyleads from earth terminal in the box to the earth terminal of the accessories. Metal fixing screws will often provide acceptable earth continuity but it is poor practice to rely on this.

If the single core live and neutral wires are still in good condition and are PVC or polythene insulated they should be fine for continued use. If the wires are rubber/cotton covered than they are probably due for replacement.

What sort of Zs reading do you get from the far point(s) ? If the conduit is rusted out and you can see the singles, or if there is no earth connection to the far end, then it has probably had it. 

However properly jointed conduit can act as the CPC and with PVC insulated singles can last more or less for ever, and a little surface rusting need not immediate condemn anything. The red and black is neither here nor there, but the state of the insulation is - any chance of a photo to set the scene ?
As noted already perished rubber would be a failure, but PVC is likely to be OK unless overloaded, and even waxed cotton if the  ends are in good condition, may well be OK for another half century.

Are you doing an EICR or actually working on it to add extra points etc ?

Mike.

the clients expect me to certifcate an installation

A BS 7671 EICR? - that'll be a report rather than a certificate then? Under BS 7671 certificates are only produced for new work.

   - Andy.

What's the conduit made from?  If it's steel, and it's not rusting away, then that is probably the CPC.

Yes, the first question is whether it is metal or plastic conduit. Clearly there needs to be a CPC. If you work out the CSA of galvanized conduit, it will be more than enough.

FWIW, I have red and black singles in galvanized conduit at home - installed about 40 years ago. It is in good condition and certainly fit for many more years' service.

P.S. I am sure that you will be thrilled to know that there no longer has to be a 2-colour notice - was 514.14.

I started in 1981 in a large factory. We didnt fit a CPC in the conduit or trunking, as the CPC WAS the conduit and trunking. Benefits of that was that pretty much every machine was at the same potential, and, no chance of getting a loose connection from a single cable, these were large machine and conveyors, all bolted together at some point. The fault current was huge, as the substation was inside the factory, with 5Mw furnaces the other side of the wall.

When tested, it would give a far lower Zs than an equivalent CPC using a cable to each machine.

I would say test it, then see how low the Zs is, and be amazed that people 60 years actually knew what they were doing, and find out that the Zs and R2 are far lower than you could ever achieve by adding a copper CPC to each circuit.

I don't think you could make a determination on the condition of the installation without doing the EICR first - that's the point of the EICR.

These are probably V.R.I. cables and probably prepared well, i.e. the ends of the protective braiding was cut back as it wasn't insulation.

I have seen such socket and appliance installations using heavier currents, the outer braiding was subject to embrittlement - the insulation at terminations had hardened and broke up when disturbed. Any house insurance may be invalid, a rewire is preferable or ............. run away!

Jaymack

If it's only 50 years old, it's going to be PVC.  At 60 years, you'd have to look and see.

Even if it's rubber it's not a foregone conclusion that it's perished. I pulled out some rubber insulated & rubber sheathed singles from my own cellar/basement that must have been there since the 1950s at least (complete with round switches on wooden blocks) - and they seemed to be in perfectly decent condition throughout and even passed an IR test without problem.

   - Andy.