I'm not sure if the Regs allowed separately bare earths.

[MFS Electrical]

That is for you to decide the level of what you feel is still okay to be left in service, me personally I would be suggesting that should be rewired. You also need to consider was it actually compliant at the time of installation or a later ad hoc addition.

I couldn’t agree more if you yourself are in any doubt as to whether or not it ever complied then as its you signing the Cert you have to make the decision

 

[westward10]

For interest it says much the same in the 15th Ed.

 

[MDJ]

I've been on this job to do an inspection before fitting a new RCD OR RCBO board. In most of my career until now the CPC is inside the T+E cable. This property has a separate CPC all through out the building. Only where there has been modifications, modern wiring has been used. If I can prove the ZS is good, is it ok to connect to this system. It's seems to be mainly the lighting that is wired in single sheathed cable which has been ran in conduit. I am hoping if anyone has any information regarding the regs about separate bare earth running through the property. There is a risk of borrowed neutrals if changing to an rcd or rcbo board. The customer does not want a Rewire but wants spots fitted and sockets moving. I have convinced him to change the board, now I am worried about nuisance tripping. However if you could advice about the earth mainly would be a great help. Personally I feel the wiring was good for it's day.

View attachment 44940

I would be giving the customer a quote for a full rewire as well, what a mess, buckle clips, bare earths and double insulated singles, 1950s -60s wiring, must be 60-70 years old now

 

[Lucien Nunes]

Common cable types explained...

VIR: Vulcanised India Rubber. Single-core unsheathed cables used in conduit. Rubber insulation has an outer fabric layer impregnated with a preservative compound. Tinned copper conductors, stranded in all but the smallest size. Conduit was normally black-enamelled. Domestic installations often used 5/8" or 3/4" slip conduit that was not threaded at joints but clamped by the fittings, a.k.a slip conduit. Continuity required enamel coating to be scraped off and was considered unreliable with cheaper fittings.

TRS: Tough Rubber Sheathed. Construction generally similar to modern T+E, rubber insulated cores with or without a bare CPC, inside a rubber sheath. Usually black, occasionally white. Tinned copper conductors, stranded in all but the smallest size.

Lead sheathed twin: Rubber insulated cores with or without a bare CPC, inside a grey lead metallic sheath that serves as CPC unless a copper CPC is included. Tinned copper conductors, stranded in all but the smallest size. Original work will be jointed in metal junction boxes with continuity clamps that connect the lead sheaths together, rather than bakelite ones.

Imperial sized PVC and PE insulated twin / twin + earth: Construction generally similar to modern T+E but with imperial sized conductors, either tinned or plain copper, stranded in all but the smallest size. Some early plastic-insulated cables used polyethylene insulation which has a smooth, waxy appearance and may be semi-transparent.

Aluminium conductor: Construction generally similar to modern T+E. Conductor soft and brittle regardless of whether copper-clad. Cladding was to improve contact at terminations, plain Al makes poor terminations that tend to go high resistance unless special precautions are taken.

Imperial sizes:
Example: 7/.029 (note position of decimal point carefully)
7 strands of 0.029 inches diameter.
CSA (0.029/2 x 25.4)² x pi x 7 = 3.0mm²

Normal strand diameters: .029, .036, .044, .064, .083
Normal strand counts: 1, 3, 7, 19, 37

Common domestic applications:
Lighting circuits: 1/.044 or 3/.029
Power radials: 3/.036 or 7/.029
Ring finals: 7/.029
Cookers and submains: 7/.044
Tails: 7/.044 or 7/.064

There were other / older systems for specifying cable size, e.g. 3/18 meaning 3 strands of 18SWG. These were not normally used after WW2.

 

[Midwest]

Why not with bare earths? I can understand rewiring aluminium cables lead sheathed cables and TRS but as long as the PVC cables that are in use in the installation test ok ie good insulation resistance and the earth is actually from the CU and not a water pipe I don’t really see a problem with the bare earths? Is there some sort of requirement to replace a system that still works and is effective? As I said Regs aren’t retrospective so why would you be saying don’t do it? He is going to upgrade the CU and the bonding so I don’t think it’s any different to connecting to Red and Black PVC? It’s old cable and yeah it’s not to current standards but what is the reason to replace it if it tests out ok and the cable is in generally good condition?

It'll be ok when the house burns down; the new metal CU will be holding up the only remaining wall.

 

[sham]

It'll be ok when the house burns down; the new metal CU will be holding up the only remaining wall.

I was thinking that a RCD board would be a good idea given the circumstances.

 

[sham]

That is for you to decide the level of what you feel is still okay to be left in service, me personally I would be suggesting that should be rewired. You also need to consider was it actually compliant at the time of installation or a later ad hoc addition.

Have suggested it, he has plastered and decorated it. His even fitted a bar. I feel that in these circumstances that an rcd board would be a good idea. As long as I have a good reason . I can even write it down on the cert. What do you think.

 

[Midwest]

I was thinking that a RCD board would be a good idea given the circumstances.

RCD's don't sort all things. Just ask the AFDD's manufacturers

 

[sham]

When someone opens the board, It has 5 neutrals and 5 live cables and only one earth going out, this can be confusing. It will look look like none of the lighting is earthed.

 

[westward10]

If it were me I would not be replacing the board.