Earth sleeve

[swampydrill]

Im sure most can tell i am no electrician but i have been running a few cables etc etc. One question about earth cable, i keep fitting earth sleeves but why does cabling not come with 3 coated cables rather than 2.

 

[JohnW2]

Im sure most can tell i am no electrician but i have been running a few cables etc etc. One question about earth cable, i keep fitting earth sleeves but why does cabling not come with 3 coated cables rather than 2.

In some countries they do.

The most likely answer is simply cost - if insulation of the earth wire is not 'needed', then it's cheaper not to insulate it!

There is also an argument that by having a bare earth wire, if the live one becomes damaged in some way it is more likely to come in contact with that bear earth wire, thereby causing a fuse to blow or a breaker to trip. However, I suspect that £££ is the main reason.

Kind Regards, John

 

[crystal ball]

Keeps the overall size down too, but as John says it is most likely cost

 

[EFLImpudence]

i keep fitting earth sleeves but why does cabling not come with 3 coated cables rather than 2.

OR -

Why do we fit the sleeving?

I know it's been discussed before but I'm not convinced.

 

[crystal ball]

Me neither, right PITA when up a ladder and you drop it, or rummaging through the toolbox for a length, back to the van again!!!

 

[ericmark]

I would say tradition. We started with a lead clad cable with two cores inside the lead, when this was replaced with rubber outer coating it was black but when the rubber was replaced with plastic they actually used lead coloured plastic and made it look as much like the original lead as they could. As with many other histological items the originals are lost in time and if we were to start from scratch likely we would come up with something very different.

The Ali-tube cable is very like the original lead cable, the live wires are completely surrounded by an earthed outer, however it costs more, so it has very limited use. It can be buried in walls without RCD protection, it can be dressed very like the even more expensive mineral insulated cable, it is somewhere between the two with the heat it can take, easier to terminate than mineral but cost is the main problem.

 

[JohnW2]

OR - Why do we fit the sleeving? I know it's been discussed before but I'm not convinced.

As you know, I'm not convinced, either.

I suppose that one simple regulatory answer is that the regs require that a CPC be 'identified' by G/Y, at least at the terminations. However, that's really redundant/unnecessary if a bare conductor could not be anything other than a CPC and, in any event, would only be a reason for a token bit of ('identifying') G/Y sleeving, rather than sleeving all of the exposed bare conductor.

The other reason discussed and, I suppose, the main 'electrical' reason I do it, is that one never really knows exactly what happens to the conductors when they are 'scrunched' into a back box (particularly a fairly shallow one), so that there is a (small) possibility (particularly in the case of a conductor linking faceplate to backbox) that the scrunching up could result in a bare CPC coming into contact with one of the terminals, or terminal screws, of the accessory concerned. The same risk does not exist with most designs of JB, so I am then often tempted to omit the sleeving, particularly for very short bits of CPC.

The impression I get is that an increasing number of countries are coming to require insulated CPCs.

Kind Regards, John

 

[JohnW2]

....As with many other histological items ...

Your software appears to be misbehaving again!

Kind Regards, John

 

[bernardgreen]

Insulating the CPC would make it less likely that current leaking from a damaged Live conductor would have a route to ground. Hence the earth leakage device would not operate even if the area around the damaged cable was live.

 

[Mikefromlondon]

From my point of view, it is safety and would deter anyone hoping to use it as a 3rd conductor like in a two way switch wiring, and there are people who would do that, instead of using a dedicated 3 core + E wire for a two way lighting. Cost would be l factor too, so imagine someone ends up using an insulated earth wire as one of the feeds for a two way wiring and a an unsuspecting electrician comes across this insulated conductor with green/yellow insulation, he would think it sure is an earthing and may handle it without thinking only to possibly get a shock from it when he realises that someone has used that to carry live feed to a two way lighting circuit and omitted the earth altogether!

But remember most flexible cables have all 3 conductors sleeved and are of equal CS.

 

[JohnW2]

Insulating the CPC would make it less likely that current leaking from a damaged Live conductor would have a route to ground. Hence the earth leakage device would not operate even if the area around the damaged cable was live.

Indeed. As you will be aware, I made that point at the start but, as I have also said, despite that there appears to be a growing number of countries which are requiring insulated CPCs.

Kind Regards, John

 

[crystal ball]

I have seen the bare CPC used as a conductor plenty of times, even sleeved red in one instance

 

[JohnW2]

From my point of view, it is safety and would deter anyone hoping to use it as a 3rd conductor like in a two way switch wiring, and there are people who would do that, instead of using a dedicated 3 core + E wire for a two way lighting.

If the CPC were insulated, one could say that it would be much safer for anyone who used it as a live conductor than is the case with it bare.

Indeed, provided the ends of the G/Y conductor were appropriately over-sleeved, and provided that whatever were at the two ends of the cable had CPCs from some other cable, then I think it would actually be reg-compliant. Oversleeving of a G/Y for use as something other than a CPC is, as far as I am aware, only 'forbidden' for singles.

KInd Regards, John

 

[crystal ball]

According to Wiki ROI regs banned uninsulated CPCs in 2013

 

[JohnW2]

According to Wiki ROI regs banned uninsulated CPCs in 2013

That doesn't surprise me. I believe that has been the case in Australasia for quite some time, and that other countries are gradually following suit.

Kind Regards, John