For continuation of Discussion from General Area.

SJT:

The Romex name isn't used here, but a similar PVC-sheathed cable is the most common method for wiring residential systems. It's commonly called "twin & earth" (i.e. 2 conductor plus ground).

Steel conduit -- either set into the wall or run on the surface -- is common in industrial applications, but would be far too labor-intensive and expensive for residential work, although you might find it in some very old (1930s) residential wiring. Wiring from the 1930s/1940s may also be a lead-sheathed cable.

These days we also have PVC conduit, which is common in light commercial systems, and also useful in domestic situations where a little more protection is needed for the wiring, such as in a shed or garage.



[This message has been edited by pauluk (edited 06-24-2003).]

pauluk:
Please correct me if I have any of the names wrong.


Three Core

Twin and Earth

Twin and Earth, Red-Red for lighting switch circuits


Compression Glands


[This message has been edited by ThinkGood (edited 06-26-2003).]

Yep, that's the stuff!

The twin-&-earth -- "T&E" -- is officially designated 6242Y, and the 3-core plus earth is 6243Y.

The T&E with twin red conductors doesn't seem to be used that widely. It's available only in the smaller gauges for lighting switch drops, but most of the time the regular red/black is used (Regs. require the black to be taped or sleeved red when used as a switch return).

More cables can be seen here.

Paul,
I've never seen that Earth + Two Reds cable before.
I've seen a cable with two single Reds, used as a switch wire as you described, but it never had an Earth wire with it.
Hmm, bare earth wires, are these still used in the UK?.

we have simuimar wiring in france also

yeah french regulation requred a switched leg to be red or purple but in usa it is little diffrent we use red black et white( it is remarked for loop leg) and that wires i use it few time and i keep a piece with me i know few of my freinds here cant belive what european wire look like they were little suprised


merci marc

So that's what SWA cable looks like. Is the jacket XLPE too? http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Armoured_SWA/index.html

What is regulation burial depth for SWA?

I don’t think the US has an equivalent to the gasketed direct-burial splice boxes. http://www.tlc-direct.co.uk/Main_Index/Cable_Accessories_Index/Cable_Joints_1/index.html

The striped tape is cool! I know places where that tape would give a US inspector convulsions. http://www.tlc-direct.co.uk/Products/TLTAPEGY.html

Bjarney,
I would imagine that regulation depth would be 2-3 feet, depending on where it is laid.
With direct burial, as you may already know, there is a requirement to bed cables into sand, that has no stones in it, this has caused the failure of lots of U/G cables.
XLPE, has become quite popular in NZ, as an alternative to PVC serving, it's cheaper and it does not degrade under sunlight.
But, it is hard to work with when cold(As I have found) and can be hard to pull through conduits, as most lubes, can affect the insulation, we have to use KY jelly with our cables over here, anything else is too risky at 11-33kV, if the insulation is compromised!.

You know I've never stopped to think about whether the outer jacket on SWA is XLPE or some other type of plastic! It is difficult to work cold though.

A couple of years ago I had to install an underground feeder to a shed/workshop in January, and it was one of those rare English days when the temperature remained down at almost freezing point until well into the morning. It took ages to get that stuff where I wanted it to go, and even longer to terminate the cable into its gland at the outside end.

Here are some notes on Underground Cables.

As long ago as 1966 the "Regs" specified a minimum depth of 18 inches, so if you read those notes you'll see that they sometimes take a step backwards.

I've never liked the idea of underground junction boxes (not for direct burial anyway -- underground in a manhole is OK).

Trumpy,
Yes, our cables still have a bare earth wire (from pictures I've seen in an Australian catalog, it looks as though yours have green/yellow insulation throughout ?). However, the Regs. now require all bare earth wires to be sleeved with green/yellow insulation when exposed at junctions and outlets.

Cable with no earth conductor was widely used for lighting circuits in the past, but from 1966 onward the Regs. required an earth at all points, so twin cable with no earth was soon withdrawn from the market. Do the NZ rules allow you to run a switch drop with no ground? Even if the mounting box is metal? The argument here was that even if the fitted switch assembly was entirely plastic that an earth terminal should be provided in case somebody replaced the switch with a fancy brass one later.

Marc,
There's another subtle difference in a switch loop here. In the U.S. you would normally re-identify the white wire as black and use that as the feed to the switch, with the black as the return to the lamp, yes?

In British wiring, it's normal to use the red wire as the feed; the black (normally neutral) is then re-identified red and used as the line to the light.

BJ,
I never really liked the adoption of green/yellow for grounding here, and prefer the original plain green. Some of the conductor insulation and sleeving in use for ground wires these days is really more like yellow with just a thin green stripe along it. I don't like that at all -- Plain yellow is used as the standard color for our B-phase.



[This message has been edited by pauluk (edited 06-28-2003).]

Paul,
Thanks for you reply,
I was figuring: That January is the middle of the UK winter, it's the middle of our Summer.
But on the subject of cable types and regarding that link, concentric cable, is what we call Neutral-Screened, you can only use the outer screening as an Earthing(or if you are really slack in your quote, a Neutral)Conductor.
But, Paul, trying to bend any large diameter cable in cold conditions, has a risk all of its own, I posted a topic a while ago about installing a 300mm2 Al cable, and believe you me, the cable did not like being bent at all, this cable had XLPE insulation on it(as all cables of this size do), It wasn't the Al conductors in the cable that didn't like being bent,it was the outer and the core insulation that was moaningabout being bent, we've had XLPE cables split on us in really cold temperatures.
XLPE is nothing but a s**t-bag, to try and run in cold areas.
Regarding our LV cables, we have used the sheathed Earth conductor since the early 70's, I hope that our Australian folk can back me up on this!.
This method(to a certain extent) cuts down on Earth-Leakage currents, through the length of the cable.
Paul, over here in NZ, We are required to run an Earth continuity conductor to all points on a circuit, regardless of wether they are required or not, makes sense though, in the example that you gave, I have lost count of the times that I have sworn and cursed the Electrician that fitted the Double insulated light fitting and chopped off the Earth wire.
(Again I would ask for the input of the AUS sparkies to let us know how it is over there).

Paul,

Just a question to satisfy my curiosity. I was cruising the TLC website and I wondered if their prices are reasonable by your standards? Are they the "trade counter" price or are they marked up considerably. I know the mail order places in the US tend to be a rip-off.

Also, as you probably know, electricians get a discount from the wholesalers here.

Peter

Bjarney,
The outer sheathing of the SWA cable referred to in your link is PVC.
SWA cables should be terminated in brass cable glands that grip the wire armouring, & an earth tag which enables a crimp lug with earth wire to be attached.
We are still permitted to use the wire armouring as a circuit protective conductor (EGC in US terminology) in most circumstances. However it is increasingly common for 3 core cables to be used instead of 2 core in single phase circuits to provide a copper cpc/earth wire in addition to the wire armouring.

Trumpy,
I would like to see our T&E cables changed to incorperate an insulated earth core, but it's true they are bare. Incidentally, we have been required to insulate & identify bare earth cores at terminations since the mid to late 1960's. Originally plain green sleeving or tape was used, after Dec 1977 green & yellow was the only colour acceptable for identifying earth wires.
Green & yellow sleeving is widely available, & at less than £4 for 100M it is not expensive.

Paul,
I don't understand your dislike for the adoption of g/y as the colour for earth wires.
We both know it was done for sound safety reasons, colour blind people. A striped conductor stands out to all.
Whoever came up with the idea of g/y as the international code for earthing cables was a genius. One day even the US will adopt it.

I understand what you are saying about some cables only having a thin stripe(s) of green on a yellow base. G/Y cables are supposed to have not less than 30% of either colour, & not more than 70% of the other colour, if you understand what I am trying to say.
I only use British made, BASEC approved, branded (AEI, Pirelli etc.) cables & these are usually fine, but I have noticed some earth sleeving appears to be more than 70% yellow. Either way it still has 1 or more green stripes, making it apparent that the conductor is for earthing.

Peter,
TLC isn't too bad compared to some mail order prices, probably on a par with a lot of the "Big Orange" type stores, although there's often a lot of variation between different products so it's hard to be specific.

They're certainly not as cheap as the big wholesaler that I generally use: BDC Electrical . The latter often has extra deals on discount cable etc. which is handy. They're also strictly trade-only, whereas TLC will sell to anyone.

David,
I've never been entirely convinced about the colorblindness argument. Sure, I can see how having just one-striped conductor out of three (or more) makes it easy to identify no matter what, but was it really necessary?

I was always under the impreession that the most common form of color-blindness is the inability to distinguish red from green, and that bnth colors would appear the same to an afflicted person. If someone saw two wires which appeared to be the same color, wouldn't he go and ask for some help?

I can't help wondering just how much trouble the old red/black/green system actually caused to colorblind people trying to wire a plug prior to 1970. Probably not half as much confusion as was caused to the numerous people who were totally lost by the introduction of brown and blue at the same time.

Paul,
I've just waded and driven through 2-3foot of snow to come up with an answer to your Colour-Blindness question!.
Yes, another Fault Call-out, to repair a 3-phase Lathe, that kept on blowing HRC fuses.
R-class, they were and there was a dead short to earth.
Got my Avo-Megger on the case and found that there was a transposed Phase and Neutral, caused by the use of the Blue wire as a Neutral, in a Delta(mesh) connected system(it was hooked into a 3-pole MCB at the supplying board), I only found this because of the low reading to Earth, hooked it up the right way and he was turning like never before!
Turning Brass of all things!, but who am I to argue!. .
One of the easiest Faults calls I've done in a wee while, if you discount the snow!!!.
And if you're wondering why I mentioned two lots of Circuit Protection, that's because it was hooked up that way!!!!.

[This message has been edited by Trumpy (edited 07-05-2003).]

I'm not quite following what had been done here. Was it a blue phase which had been erroneously connected to the neutral by someone following the "flex" code?

Sorry Paul,
At the time of posting that message, I was in a bit of a panic here, as the roof timbers were creaking and carrying on, with the weight of all the snow on it.
What resulted, was I only told some of the story,here's the rest!.
What had happened was, the owner of the Lathe, had hooked it up himself and he thought that with having a Blue wire, a Yellow wire and a Red wire at the lathe, as well as the Earth wire(Green), that he would hook up the Red and Yellow wires as per normal(he still had an empty B terminal, when I turned up).
The Blue wire(that he thought was a Neutral) was joined to the frame of the Lathe, with the Earth wire, when I asked why this was so, he replied, "because it's like that at the switch-board".(Older MEN switchboards, here used to have the Main Neutral and Earth solder lugs on the same stud on the Neutral Busbar, along with the Range Neutral)
Must have gone off, with a big bang!.
Regarding the fusing, the HRC's fed the MCB and then to the Lathe sub-circuit, which also had no isolator.
I have since been back to fix all of this up, it's fed via HD Flex and a chemical-proof isolator(because of the cutting fluid).

That just goes to illustrate the perils of the British/Commonwealth systems usiung blue as both phase C and neutral in different circumstances. Maybe those who don't really know what they're doing shouldn't be messing around with the wiring, but we all know that they're going to anyway.....

I think that when the standardized European colors were being agreed upon that the committees should have chosen something other than blue for neutral, and preferably a "neutral" color such as black, white, or gray.

Looking at ECN's compiled list of colors then in cmmon use, I think I might have voted for gray. Black was neutral in the UK and Ireland, but a phase most everywhere else, so that's out. White was used as neutral in some places, but had only just been taken out of British regs. as an acceptable phase color a few years earlier.

Gray was already in use as neutral in several countries and appears to have not been used as a phase elsewhere at that time.

Paul,
It would be a GOOD idea, if the WHOLE world, just moved to ONE single standard wiring colour, but I can't see that ever happening.

I think the best option is to just leave the color codes alone. "If it ain't broke......."

It's unthinkable to mess with the color codes here in the U.S. Most people have enough trouble with the one we use allready!!

At one time [>40 years ago] there was a similar problem with reversed phase and
equipment ground in some North-American systems. Type-SO flexible supply cord is furnished with black, red, white and green insulated conductors. Before the grounding conductor was universally green, {if you can imagine back in the stone age} some used white for equipment grounding. Of course the problems were the same as in Trumpy's lathe case.




[This message has been edited by Bjarney (edited 07-08-2003).]

Scott,

So when did the NEC first actually specify that an EGC must be green? (If not bare.)

How did the general use of colors say 40-50 years ago differ from today? Was the BOY system in use for 277/480 (was the 277/480Y even in use then, or were these systems just 480 delta?).

paul — In the 1953 NEC Handbook the green/bare permission/use limitation is stated. Reidentification was permitted "by paint or other effective means."

Living in a rural area, I came across local 480Y/277V in plants that had medium-voltage service, and in sports-field lighting. The first significant recommendation I found in text is the classic 1955 Industrial Power Systems Handbook, by Donald Beeman.

In many older plants and commercial/institutionals, coloring is black-black-black(-white)+bare or metal raceway. Differing voltages having distinct phase identification varies, but I’ve found it in 1957-vintage institutional/research facilities.

Thanks Scott.

So presumably where all phases were run in black they used tags or something similar for phase identification, where necessary?

I seem to recall a thread a while back discussing that in many areas red was used for the wild-leg on 4-wire deltas in the past, before the NEC requirement for it to be orange.