Twin and Earth American style

[Mark Wright]

Can anyone tell me more about Twin and Earth American style?

What's it's full name? NM?
Is it always flat?
Do you add a sheath to the ground/earth cable?
Thanks

 

[Mark Wright]

This kind of speculation has led some people to believe that it's a requirement for all cables to contain a CPC. (Even on this forum!)
As you say, the only real design advantage is the reduced cost.

All cables should contain a CPC shouldn't they?

 

[nicebutdim]

All cables should contain a CPC shouldn't they?

No.

Surely you've encountered, if not installed, numerous cables that didn't contain a protective conductor?

Edit: to expand upon this, common examples would be 4 core 3 phase cable or insulated and sheathed singles, such as meter tails.

 

[Lucien Nunes]

Amongst the countries that use a flat cable:

USA: Bare earth, same CSA as line conductor
AUS/NZ/IE/RU: Insulated earth, same CSA as line conductor
UK: Bare earth, reduced CSA
JP: Insulated earth, reduced CSA

Japan is about the only example I can find with a smaller, insulated earth. Granted, they don't often use it and it's strange in other ways (the green CPC is bonded down the outside of the other two so it can be zipped off at the terminations). But it sort-of completes the square of permutations.

Obviously there are countries / systems that normally use round cables, such as NYM-J in Europe, where the earth is usually insulated and same size.

 

[Mark Wright]

Amongst the countries that use a flat cable:

USA: Bare earth, same CSA as line conductor
AUS/NZ/IE/RU: Insulated earth, same CSA as line conductor
UK: Bare earth, reduced CSA
JP: Insulated earth, reduced CSA

Japan is about the only example I can find with a smaller, insulated earth. Granted, they don't often use it and it's strange in other ways (the green CPC is bonded down the outside of the other two so it can be zipped off at the terminations). But it sort-of completes the square of permutations.

Obviously there are countries / systems that normally use round cables, such as NYM-J in Europe, where the earth is usually insulated and same size.

Great bit of info

 

[Dustydazzler]

The interesting thing with Romex is the outer sheath / jacket is much harder than our PVC , it looks more like LSF cable.
I wonder if it has similar properties to LSF / LS0H cable

 

[Mark Wright]

I've said it before but the old White sheath stuff seems tougher to me.

There was some old White sheath - Black and Red stranded resting on a hot pipe for about 20years and it had hardly done anything to it - would probably be ok for another 20. I suspect the Grey wouldn't have lasted.

 

[Dustydazzler]

I've said it before but the old White sheath stuff seems tougher to me.

There was some old White sheath - Black and Red stranded resting on a hot pipe for about 20years and it had hardly done anything to it - would probably be ok for another 20. I suspect the Grey wouldn't have lasted.

Could be LSF cable which is much tougher than Pvc

 

[Mark Wright]

Was the old get anywhere(B&Q) White sheath cable LSF? think its just PVC but might be wrong.

 

[Dustydazzler]

Was the old get anywhere(B&Q) White sheath cable LSF? think its just PVC but might be wrong.

yes There used to be some god awful pvc in the big DIY sheds that was white and near impossible to strip. it was the worst cable every produced

 

[brianmoooore]

Ordinary white PVC sheathed T&E was around long before LSF was even invented (as was I).

 

[norcal]

At one time non metallic sheathed cable commonly known by the brand name "Romex®" formerly made by General Cable, now made by Southwire, had a 16 AWG ground wire in 12 and 14 AWG sizes, sometime after the adoption of the 1968 NEC, it was required that the grounding conductor in 10,12,14, AWG sizes that the grounding conductor be the same size as the insulated conductor in those sizes, 6 and 8 AWG NM cable have a 10 AWG grounding conductor, my house which was built in a factory in 1943, was wired with a early NM cable, plated copper conductors, insulated with rubber, covered in cloth, with a spiral paper wrap over each individual conductor, jute string fillers wrapped with a asphalt covered cloth sheathing, the stuff is still in pretty good shape considering how many years since it was manufactured, although it's been of service since around 1980.

 

[RetiredNY]

Pretty much all YOuTube sparks in America and Canada refer to that cable as ROMEX , which I believe is a brand name. It is much harder than pvc twin and earth , it is much more like our LSF cable. Yes the NM stands for Non Metalic.
It comes in a wide variety of gauges much like our twin and earth does where the line and neutral come sheathed and with a bare copper earth / cpc / ground wire.
Yes it is always flat with The main difference being they have a White for Neutral and Black/Very dark grey for Live.
Also from what I can tell you are not allowed to wire Romex surface mounted , it must either be in the fabric of the building Or run in a conduit.
This guy waffles a fair bit and even muddles up his colours but he explains the different sizes , and colours of Romex common in his area

As an American electrician since 1986, I've never actually encountered the brand name "Romex" although that is what everyone calls it. Just like cotton swabs are called Q-tips and adhesive bandages are called Kleenex Our code calls it NM for non-metallic sheathed cable. Prior to the 90's the outer sheath was any color, I've seen white, black, and power blue and tan, but most of it was all just white, come manufacturers would use black for their larger gauges.

American / Canadian terminology for everything is so bizarre, not to mention they can mix lighting and receptacles ( sockets ) on the same circuit and can have receptacles ( sockets ) in bathrooms

also the fact the the bigger the gauge on the wire the smaller it actually is , this had be stumped for ages when watching American YouTube stuff.

In the US and Canada we use radial circuits only, no ring mains. And we don't have fuses in our plugs, save for some holiday decorations which typically use such small gauge wire they must fuse is lower than our receptacles 15 or 20 amp circuits.

Thanks for the info.

Thanks, I assume it's naked like us for cost? but also the Earth/Ground is normally of a smaller size/diameter than the Live and Neutral.

But I would be interested in there is some other thinking behind the ground being bare. I mean I have known people in the UK say it's for safety incase a nail is driven into the cable.

Cost is likely a factor but I've never seen an NM cable with an insulated ground wire. I have seen MC cable, which is a steel or aluminum clad cable which does insulate the ground with green, but that cable was first introduced to cater to the hospitals which by code requires insulation on the ground.

yes There used to be some god awful pvc in the big DIY sheds that was white and near impossible to strip. it was the worst cable every produced

We do have a PVC based NM cable called "UF" which stands for underground feeder, allowed for direct burial which is a bear to strip. NM cable is quite easy to strip (or un-sheath) but UF is more like the PVC was poured around the insulated conductors and ground, whereas NM cable's sheath is more like a hollow flexible tube.