ECN Forum Forums Photo Discussion Forums Photos for General Discussion U.S. Romex vs. U.K. "Twin & earth"

Is it really?

Most of our job specs require solid for sizes smaller than 8 AWG so I am pretty much used to it.

In some ways I find solid easer as it does not turn into a giant mess when you have to pull a loop out of a pull point.

But it is clearly a personal choice.

Bob

[This message has been edited by iwire (edited 04-16-2006).]

I don't know, we have outdoor/underground cable called UF that has the same construction as the 'T&E'

The paper makes for easy stripping so I hope it stays.


Yeah we have the same issues so giving a definitive rating is difficult without knowing how the cable will be used.

Unfortunately, these traditional colors have just been phased out (no longer permitted under our Regs. for new work since 4/1/06). The new version is this:




No. Only the smallest 1.0 sq. mm size (used primarily for lighting circuits) has an earth the same size as the other conductors.


2.5 sq. mm is just a tiny fraction smaller than #13.

Click here for AWG/metric conversion chart

Having now worked with both Romex and T&E, I can safely say that the Romex is easier to strip.


As far as British T&E is concerned, the 2.5 pictured above plus the two smaller sizes are always solid. 4 sq. mm (about #11 AWG) and upward is stranded. (Although with the reduced earth, the 4 sq. mm cable actually has a solid 2.5 earth conductor.)

However, stranded was used for smaller sizes of T&E before we changed to metric sizes around 1970. For example, here's a piece of 7/.029 from the 1960s:



The old designations specified the number of strands and the diameter of each strand, thus 7/.029 is 7 strands of 0.029" each. That gives a conductor CSA of 0.0045 sq. in., equivalent to approx 2.9 sq. mm or somewhere between #12 and #13 AWG.

Here are the comparative sizes of all three cables for reference. Top to bottom: 2.5 sq. mm T&E, 7/.029" T&E, #12 Romex:


Note the reduced earth still on the old cable: Only 3 strands but each of larger diameter than those in the live conductors.

Here's another old stranded cable, 3/.029 which works out to 0.002 sq. in. CSA, approx. 1.3 sq. mm or #16 AWG. This is a 3-core without earth, which is all I could find in my scrap box:


Under the old system, only the smallest T&E of 1/.044 wasn't stranded (near enough 1 sq. mm or a fraction smaller then #17 AWG).

P.S. Yes, the strands on the old cable were tinned. They changed to bare copper with the move to metric-sized cable about 1970.




[This message has been edited by pauluk (edited 04-16-2006).]

Paul, if you have any of that red and black cable laying around, send it to me. Even a sample to show my guys would be cool, but I'd love to have some in useable lengths.

If shipping, which I'd cover, isn't prohibitive, I'm serious. Otherwise, I'm just kidding.

We also had 1/.064

I remember on a project having to resort to using a hunk of 4 x 2 and a sledgehammer trying to straighten out some very big solid core pyros. Give me stranded any day.

Bob,
A lot of the specs in this area call for stranded and if they do permit solid it is often only up to #12. If they speced solid #10, I would give them two prices. A price ~20% higher for the additional labor requried to use solid 10 in conduit and the lower price using stranded.
Don

Sample lengths are about all I have left of the "old" red/black T&E I'm afraid. Details coming to you by e-mail Larry.......


That's an interesting one. When did Australia switch to metric-sized cables?

The old British cable sizes pre-metric can be seen listed here, along with current ratings and other data (taken from IEE Regs. 1966 edition):
https://www.electrical-contractor.net/pc/IEE1966_T3.JPG

Don I had already been thinking of you in this thread, I know you had said you guys stay away from solid.

We do not, that I know of price it differently.

Its all in what the labor force is used to working with.

If we priced dwelling units with EMT the price would go up as our guys are not used to that, for guys in your area it's just another day.

For us solid does not slow us down, but we use more than the code required size boxes and are used to the solid.

I just started a job Monday that is 100% EMT that is very unusual for us and it is a nice change from the typical cable work we do. With an average of four guys we got in a little over 5000' since Tuesday.

Its all 3/4" and 1" for branch circuits in a large retail store. All 20 amps circuits are speced 10 AWG but they did not specify solid or stranded. As it is up to me we will be using stranded.

I read an article in a trade mag that said solid provides a slight energy savings over the life of an electrical system. I have always figured that is why the engineers around here have a thing for solid.

Bob