ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Why cables look like they do

Hi!

I had an e-mail discussion with a cable manufacturer recently since I wondered why cables look like they do. I was rather surprised at some of the answers I got.

Solid vs. Stranded. The price difference is only 2% and the manufacturer didn't seem to like solid wires. In their opinion, the only reason to use it was that it was easier to use in some terminals.

I only see solid 1.5 and 2.5 mm2 (#16 and #13) cables in the shops. To my surprise, I was informed that the manufacturer made much (otherwise identical) stranded cables in these sizes. It is sold to camper manufacturers. (!)

Question for the ECN members: Do you prefer solid or stranded?

I also asked why european cables are have a 70°C rating as opposed to the 90°C rating used in North America. There were two reasons: It's cheaper making 70°C 2.5mm2 than 90°C 1.5mm2. In addition, 90°C cables are rather stiff. (They have to add a stabiliser to the softener to keep the softener from leaving the cable at the higher temperature.)

Question for ECN: Are North American cables e.g. Romex, stiff?

I'm starting to think that cables look the way they do simply because nobody questions their design.

Definitely, stranded, it is easier to twist two or more wires together and to a certain extent gives you a better connection, as you have more conductor area touching the insides of the connector of your choice.
By the way, I commonly use both types,but stranded wins with me, hands down.

For residential and small commercial I prefer solid wire. It's easier and cheaper to terminate on switches and outlets.
For larger commercial and industrial I use stranded wire. Most of these places have a lot of vibration from equipment.
I do not consider romex to be stiff. Larger sizes are just harder to handle size 8(appprox. 5.486 mm) or 6 (approx. 6.452 mm). ( size 8 is limited to 50 amps @ 75C and size6 is limited to 65 amps @ 75C.)

[This message has been edited by nesparky (edited 10-19-2002).]

Romex-style cables sold in Britain are solid cores for sizes 1 thru 2.5 sq mm.

Pre-metric cables (before 1970) were stranded in all but the smallest size. The old 3/.029 and 7/.029 sizes are much easier to work with given the cramped space in many British boxes, even though the physical cable size is actually slightly larger than with their modern counterparts.

Hi. I know this is an old thread, but the topic is no less relevant today than it was back then so I don't see why not.

C-H was probably right about it coming down to people's unwillingness to question the authorities. Now, I'll examine the dimensions of some common flexible cords as specified by UL (I don't have access to the standards documents themselves - too expensive for anyone not in the trade - but I managed to retrieve the dimensions of many of the cords from a few manufacturers' websites)...

Compare SJT to ST (or, indeed, their rubber or TPE-insulated counterparts), for example. The 18AWG and 16AWG versions of both have the same inner insulation thickness of 0.03" (0.76mm), with only the outer sheath being 0.06" (1.52mm) thick on ST (except for the 5-conductor variants which further increase it to 0.08" (2.03mm)) versus 0.03" thick on SJT. The category voltage is up to 300V for SJT (and SVT, SPT and NISPT), but 600V for ST. Then compare them to the European H05VV-F, which has a category voltage also up to 300V on any phase, but up to 500V between phases in the cord; its construction is comparable to SJT (or actually has a bit thinner inner insulators in the 0.75/1.0/1.5 sq.mm variants). So H05VV-F is suitable for 231/400Y (or 277/480Y although I don't know of a region actually using the harmonised cables with that voltage) but SJT isn't? If you don't need the extra abrasion resistance and aren't worried about "by-the-book" inspectors then I guess you could use SJT for 277/480Y, save a little cash and be happy.

NISPT-2 is another oddity; what exactly is the point of making a cord with nice thick inner insulators, but a thinner (and therefore easier-to-break) outer sheath than even that of European H03VVH2-F?

But it's SPT-3 that's the real case of "why bother?"; the 18AWG and 16AWG variants have an insulation thickness of 0.06" which is the same as the sum of the inner+outer insulation thicknesses for SJT (as already mentioned), so I think it's a fair comparison. But the 14AWG and 12AWG versions apparently had to increase the insulation thickness to 0.08" and 0.096" (2.41mm) respectively, so these "household use only" cords ended up using as much as or even slightly more PVC than the "suitable for commercial use" SJT. So I can't say I'm surprised that it has no near-equivalent elsewhere in the world. (Mind you, that whole "residential/commerical" distinction was almost entirely stupid to begin with, and I can only say I'm glad it's more-or-less exclusive to North America. But from what I see of them, the UL never were any good at making logical standards.)

Anyway, it's interesting to note that the (modern) Australia/New Zealand TPS cables insulate the earth conductor as well as the circuit conductors (avoiding the use of add-on sleeves, at the expense of a somewhat wider and costlier cable), and that their earth conductors also have at least 7 strands even when the circuit conductors are solid (most likely so that the earth is the last to break if the cable is abused by repeated bending).

Come to think of it, I don't think there's a good reason to bother with the textile-braided cords on clothes irons (etc.) anymore (besides tradition), as there has been a technique to modify PVC (cross-linking the molecular structure via carefully controlled irradiation) not to melt for many years now. Hook-up wire with such insulation (abbreviated as XLPVC) is actually fairly common for internal wiring of equipment (UL AWM style 1430 or similar); I'm quite sure they wouldn't be using it if it wasn't cost-effective, especially in the current economy (well, it's more of a false economy than anything else to tell the truth, but that's another story). It even has the designation "V4" (where "V" is standard PVC, "V2" is high-temperature PVC for up to 90C, and "V3" is PVC for cold conditions) under the harmonised coding system (so H05VV-F for example would become H05V4V4-F), or so I read.

I'm pretty sure a cord using it would be more reliable than the braided type, at any rate (given that the braided cords are particularly prone to kinking - over-tensioning the conductors and in some versions also revealing the inner coloured insulators - and at least some braid types will eventually fray from normal use pretty much regardless of how well-treated). And guess what? Some versions of the braided cords feature XLPVC inner insulators anyway!

I think one of the reasons for choosing braided flex for irons was the added flexibility. PVC sheaths can be ridiculously stiff and that's annoying for something that's moved around a lot.

I definitely prefer solid for two reasons: most continental European (except Italian) manufacturers don't list their equipment for the use with stranded wire at all so you'd have to pigtail in each box (and use extra-deep boxes as officially switch boxes are rated for either one device OR connectors, e.g. Wago or choc blocks) and stranded wire has a greater outer diametre than solid because the strands are round and take up more space than one solid conductor. That's most noticable if you try splicing stranded wires using choc blocks.

In Austria and Germany everything for fixed installations up to 6 mm2 is solid and you can get 10 mm2 solid too. 10 mm2 and up are usually rigid stranded, each strand being roughly the thickness of a 1.5 mm2 solid conductor.

Stranded wire is occasionally used inside panels but rarely anywhere else.

There's no need to twist any wires these days, switches and sockets usually have push-in terminals (the last manufacturers to retain screw terminals were a few DIY-grade botchers where the plastic body of the sockets would give or even break before you could properly tighten the screws) and splices are exclusively made using Wago connectors - 273 series for solid up to 2.5 mm2, 223 for mixing stranded and solid. I haven't seen a professional use the once popular choc blocks for ages (except for connecting pendant fixtures) but I suppose a few conservative ones still might. 6 mm2 and up are usually spliced using fixed terminal blocks or connectors that fit on a DIN rail.

Ragner,
With the case of ironing appliances and other such heating appliances, are cords not sheathed in silicone rubber, in Europe?
What I mean is, any appliances that have directly exposed heating surfaces, where the cord could come into contact with the heating surfaces?
Sure, if you want to leave an iron sitting on it's cord, you get all you deserve, but using 75C or 90° PVC flex around hot surfaces, just seems really stupid.

Some irons might have silicone sheathed cords but traditionally it's cotton braided synthetic rubber-isolated conductors (H03RT-F). No PVC anywhere to be seen.

Cheap soldering irons often seem to have PVC (H03VV-F) and hot plates, toasters and the like usually have H05RR-F (natural rubber).

Well, from my own huge stash of cords saved from the landfill, the older cords (by manufacturing date) are generally more flexible than recent production, even comparing PVC to PVC. So it seems that the manufacturers have had to cut down on the plasticiser content lately to stay price-competitive (and it does at least beat many of the "alternatives"). (I don't even notice the difference in flexibility between 3G0.75 and 3G1.0 cords, by the way.) Perhaps the rubber-cable guys took that as a cash-in opportunity, too? (Even if the rubber itself holds up, it provides relatively little protection of the underlying conductors from oxidation, which can increase resistance and result in overheating even at normal loading.)

I agree that silicone rubber (as better soldering irons usually use) would probably be the best overall choice for irons (very flexible, doesn't fray or kink easily, and can withstand higher continuous temperatures as well), albeit at higher cost.

LongRunner,
Welcome along, mate.

I'll also add:

I have wired up my own extension cords from very early on (certainly early enough to set off the "child safety" brigade's alarm bells, but I had my father who was an electrician check that the earlier ones were done correctly so thankfully, no-one got hurt) firstly out of curiosity and then for "fun" for a while (although I later became more pragmatic about it, so my most recent two were done using salvaged appliance leads, with the rewireable sockets I had on hand fitted onto the cords still with their original moulded plugs) and used 90°C rated flex for most of them because I could obtain it easily. It's not noticeably stiffer than the 70°C (or 75°C to Australia's version of the standards; in this day and age of globalisation, of course, flexes typically bear both the European and Australian approvals on one unit) type, allowing for the normal variability in flexibility of PVC from different makers and manufacture dates - so I can't imagine the difference being noticeable with solid or 7-stranded building wires, then. And if you pick the "right" combination, you can find a round (even 3-core!) cord that's as or more flexible in all directions as a flat cord made more recently by the same manufacturer is in the plane it flexes most easily (and no, I'm not cheating by comparing an ordinary-duty flat cord with a light-duty round cord - not that I would see fit to, given that most of the flat cords are light-duty with the ordinary-duty ones being the exception, while ordinary-duty round cords are common enough; those in this comparison are both ordinary-duty), so it's an embarassment, really. The manufacturer of the cords in question is Well Shin, for the record (and for your information, they can be found attached to the Australian version of the PSU for the Nintendo Wii U* - and presumably the versions for the other markets too).

*Nintendo's classic efforts to make their systems hard(er) to break would explain why they chose the ordinary-duty cord, even though a light-duty cord would be legal for the relatively small unit (as H03VVH2-F is a bit fragile and it doesn't help that the end connectors typically have poor strain-relief). (They already used such a cord on the PSU for the previous Wii, although that time it was from a different manufacturer and noticeably more flexible; the US version, by the way, is equipped with NISPT-2 recalling from a photo I saw before, and I'd bet on VCTFK on the Japanese version although I haven't seen that one. Their official PSUs themselves, incidentally, have some of the best build quality I've seen in small SMPS - although they are not multi-voltage which is a bit unfortunate, and the fixed cords are quite backwards today, now 45 years since IEC 320 was initially published.) Incidentally, I currently have just one other flat ordinary-duty cord for myself - this one with an Australian plug to an IEC C7 socket, and it too is more flexible than the new Well Shin cord. To put that into perspective, I have over 200 total cords in my stash now, of which 25 or so are with C7 sockets, although it's been a while since the last substantial bunch I was given - and the "hoarding" has, consequentially, mostly stopped at present.

(To be clear, I'm using the terms "light"- and "ordinary"-duty in relation to cords with the 300/300V and 300/500V ["downgraded" to 250/250V and 250/440V in Australia, although that change appears to be merely political and the heavy-duty cords, curiously, were up-rated from 450/750V to 600/1000V] category voltages, respectively. Both inner insulation and outer sheath thicknesses differ - so ordinary-duty cords are more durable than light-duty, but somewhat stiffer given the same quality of PVC. I know this to be official usage in the relevant standards, IEC 60227-5 [and 60245-4 for rubber cords] and AS/NZS 3191. H03VVH2-F and H03VV-F are not available with 1.0mm² or larger conductors, nor are they allowed on major appliances even with lower current drain.)

Overall, the European standards make much more sense than the North American ones do, to me at least. The "singular" category voltages given for the North American and Japanese/Taiwanese cable types are, to me, an obvious example of dumbing-down of the rules; the "split" voltage ratings for the European (and Australian) cables make perfect sense when you remember that there are two layers of insulation between any two active conductors in the cable, spreading the voltage gradient - and really, anyone who doesn't get this (quite simple) concept shouldn't be working on anything 3-phase to begin with, thank you very much. AS/NZS 3191 seems to have adapted an already good standard to be even better, for the most part (although I'd personally prefer to stick to the more conservative harmonised voltage rating for heavy-duty cord, and here they have yet to update the braided cords to not expose the inner wires when kinked; this is the standard that defines the braided cords with XLPVC inner insulators, by the way, although elastomer-insulated ones like in Europe are also permitted); one of its more notable additions is PVC cord suitable for intermittent operation ("for an average of 500 hours per annum" quoting from a pirated copy of the standard - not that I would be paying the asking price just for my personal use either way; this system that forces you to pay up-front for the standards documents is a broken system, really - at least, I would surely go broke if I tried to buy all the standard documents of interest to me) up to 105°C (known as "V-90HT"), like with much hook-up wiring (I must say, by the way, that it is a bit of a trap that the hook-up wire - especially UL AWM 1015 [heavy-duty, 600V working] and its double-insulated version, UL AWM 1617 - is just marked 105°C with no indication that continuous usage is still limited to 90°C; this is somewhat akin to only listing the best-case ampacity on building cables sold in UK hardware stores, isn't it?).

(A bit off-topic, but another thing I eventually found out as a result of my extension cord DIY among other items is that HPM's products of the past 15 or so years are terrible; at the time, I was predominantly using HPM's plugs and sockets because, again, they were easy to get - from the local Bunnings Warehouse - and because they're an old Australian brand that most people still seem to trust. Well, so much for that, as the transparent version of their model 7P extension socket once used a particularly low-quality clear PVC that not only discoloured to that yucky yellow-brown quite nastily - with no appreciable provocation, mind you - but also reacted with the cord's insulation, turning it brown - insane! (Clear PVC is, generally, more troublesome than opaque PVC, but Clipsal gets their transparent ones right too.) Then they changed it subtly, somewhat fixing the plastic issue but this time messing up the cord grip dimensions, so it won't hold onto the cord [H05VV-F3G1.0 or the equivalent] that it's supposedly designed for, no matter the position of the plastic securing nut! Only 1.5mm² (ordinary-duty - there aren't any ready-made Australian extension cords that I'm aware of using the equivalent of H05VV-F3G1.5, although I've obtained the 90°C Australian version in orange also from Bunnings and used it for two extension cords for, well, no particular reason at the time although I know now that it will stay noticeably cooler under the full 10A, which would no doubt be beneficial at times in the often hot Australian climate - and in the interest of reducing voltage drop, I would recommend it for cords longer than 10m anyway [and, indeed, 2.5mm² flex for carrying 15/16A beyond 10m if you can obtain it and a compatible plug and socket pair, and/or again to reduce the temperature rise]) cord will be held firmly by that last revision I tried, but this is still wrong. My grandmother's current dwelling is wired with mostly the HPM "Excel"-range switches and outlets, and their cover plates have yellowed quite obtrusively - although, conspicuously, the gridplates are still white; in comparison, the lone Clipsal 2015 (single outlet) there really stands out in its still spotlessly white beauty. Some of those HPM outlets also take rather excessive force to remove the plugs from, and the covers can even break at their clips when trying to remove them. I also have a few 6-way power-boards they made that clearly couldn't stand up to even modest UV exposure...yeah, I think those are quite enough reasons to justify avoiding them now. At this stage, I'd take one of the better imports over recent HPM any day of the week - speaking of which, one outlet in the bathroom here has a notable history:

• Originally a Clipsal 2015, which (along with most of the other original switches and outlets in this house) was in (I think) the "Desert Sand" colour option. (Subsequently, in the year 2010, the remaining Desert Sand switches and sockets were replaced with the usual White Electric because the originals clashed with the current paint colours.)
• I wanted to charge two electric toothbrushes at once, without having to continue using a double-adaptor (ugly things that they are). Courtesy of Dad's stuff, I was able to get a Clipsal 2025 double outlet to install - that simple swap I could already handle fine.
• But then some "handyman" had a crack at moving it over to the left to make room for a new mirror, of course in a horribly botched manner with a potentially extremely dangerous result (it was "supported" by a wood-screw with an oversize head, into the plasterboard alone, only on the left side, resulting in the outlet eventually being able to be pulled right out of the wall with little effort at all).

Well, at least I knew that Bunnings would likely have a selection of mounting hardware with which I could make a robust repair thereafter. (This stage was after Dad lost his battle with cancer - so I was on my own, not that I needed assistance by then.) I got some suitable screw-plugs to fit to the wall, and now for the interesting part: The outlet, made by Deta who popped up here quite recently. As any electrician here in Australia will immediately notice, their "6000" series is a dead ringer for the ever-popular Clipsal 2000 Series - in fact, it's so close that the surrounds can be interchanged between the two, more-or-less. (Deta still have yet to replicate the multi-gang surrounds, though.) I'm not sure if Clipsal actually mind that much, though - given that the two brands aren't sold alongside each other (Clipsal refuse to sell their products to the general public, although at a point 10-12 years ago the white 439 [10A plug], 438 [10A extension cord socket] and 418 [10A side-entry plug] could be found repackaged by Ring-Grip, so I used a few of them) and the line is well over 20 years old - but intellectual property issues aside, Deta even appears to have made a small improvement to the clip-on parts; even on Clipsal's stuff, the surrounds can be bloody hard to pull off at times, depending on the manufacturing tolerances - although they at least don't usually break in the process. If you're curious to know more about it then I'd be willing to post some photos, along with further general comments. The little-used corner mounting holes really came in handy in that situation, and although I was forced to omit the lower right mounting point, the end result still feels solid enough.

And I wouldn't want to finish off this post without this quick-fire question: For 2-core flat cords, do you prefer the sheathed types (NISPT; H03VVH2-F and H05VVH2-F; VCTFK) or the "figure-8" types (SPT, H03VH-H, VFF etc.), overall? To sum up the basic pros and cons of each:

Sheathed

• Looks nicer in-situ (IMO)
• Inner insulated wires are colour-coded, so are easily differentiated at a glance
• While the sheath may occasionally break, at least you survive so long as the inner insulators remain intact
• Can't mount a clamp-on ammeter for current measurement without cutting in and accessing the inner cores
• If you fail to clamp the sheath properly, it can pull back - this may expose the inner cores (this is particularly irritating for Australians, as local plugs designed for these cords are stupidly hard to find - well, HPM's side-entry plug will work with it, but I've already told you what I think of them...)

Figure-8

• Gunk can accumulate in the "valleys" between the cores
• Sometimes you get a stripe for coding, sometimes ridges. Not quite as prominent as the brown/blue or black/white combo.
• If the insulation breaks, you're in serious danger
• A clamp-on ammeter can easily (and quite safely) be mounted simply by splitting the two cores apart
• A bit quicker to connect, with no "stripping off the sheath" step

And if a flex in the figure-8 overall form but with 2 discrete insulation layers (the inner layer providing the colour-code) was made, it would provide most of the "best of both worlds" (except aesthetically), albeit at slightly higher cost.

(For the unitiated, as I understand it the insulation on figure-8 mains leads is designed to the "reinforced insulation" standard - and it probably does meet the dielectric strength requirement at least, comparing the SPT variants to the inner insulators of SVT, or the 300VAC light-duty hook-up wires. Note, by the way, that you should not take the military-standard rating of 600VAC for some hook-up wires as indicating applicability to mains voltage, as those are only for intermittent duty and making the insulation significantly thinner than needed for a 300VAC safety agency rating (which tends to go with a 1kVAC military rating!) will also reduce the breakdown voltage below the minimum needed to withstand surges on the mains supply - which also explains why almost no mains cables are rated for less than 250V even in 100-120V countries.)

So I've added two polls for you to answer; the second is about if you too have noticed the trend to stiffer cords, as I noted before.

Overall, which type of flat cord do you prefer? single choice
	Sheathed (e.g. H0xVVH2-F)
	Figure-8 (SPT and similar)
Votes accepted starting: 07/04/15 09:59 AM
View Results

Were older (within reason) cords more flexible, as a general trend, than recent production? single choice
	Yes
	Not that I've noticed
Votes accepted starting: 07/04/15 11:47 PM
View Results

Many people actually believe that H03VH-H is no longer legal for mains voltage and in DIY stores it's usually labelled "42 V max." although at a closer look the original 300 V marking is still there. I don't think equipment manufacturers ever used it since the 70s, the Italians probably kept it around a bit longer than the others (e.g. on table lamps) but that's it. Austrian and German H03VH-H has unmarked conductors as far as I know. I occasionally use it for nostalgia's sake but that's about it.

Most Schuko plugs aren't designed for H03VVH2-F or the likes either so I usually fold back the outer sheath to provide a better grip. On some plugs you can flip the cord grip and turn the convex side towards the cord, gripping even very thin cords.

When you're used to working with H05VV-F, you could indeed be forgiven for thinking that H03VH-H was meant to be speaker wire (although the coded version does make a nice and durable - and very affordable - lead for speakers with passive crossovers).

By the way, the sole Australian plug to IEC (60)320 C15 cordset currently in my stash uses the CSP (chloro-sulfonated polyethylene IIRC) synthetic rubber formulation; all of the elastomer-insulated cords specified by AS/NZS 3191 can run at a conductor temperature of 90°C, although H03RT-F is still common on clothes irons (and H05RR-F on cooking appliances and radiant heaters) as the harmonised cords are still perfectly legal to use here. It was made by the Australian division of Burton Corporation, one of the few manufacturers nice enough to date-code their cordsets as routine; this one was made December 1994 and is still in good condition. I also have a standard C13 cordset made by the same company the following September, with normal H05VV-F3G1.0 (also nice and flexible). Both are 2m long.

My conclusion? The better-quality PVC insulation is just as flexible (at room temperature - and remember that there's also the "V3" grade with enhanced low-temperature flexibility) as the elastomers (apart from silicone rubber of course which is in a class of its own). So there indeed seems to be some element of "cashing in" on the part of the rubber cable guys (although the rubbers also have the advantage of greater abrasion resistance, for heavy-duty professional usage).

Also, the harmonised "R" material designation is intentionally vague - it just covers any natural and/or synthetic rubber formulation with a temperature rating of 60°C, although the most common modern versions appear to use EPR (ethylene-propylene rubber). (A higher grade of EPR that can stand up to 90°C is also specified, with the "B" designation.)

R is only synthetic rubber, natural would be N.

No, N is for neoprene/polychloroprene, used as the outer sheath of H05RN-F and H07RN-F for its excellent water resistance (for service outdoors and in otherwise wet areas). And again, there's a higher grade "N4" for 90°C operation (the North American "HPN" [Heater Parallel Neoprene] cords, designed for immersion heating elements, are also insulated with something similar; its dimensions are equivalent to SPT-2 in 18/16AWG and SPT-3 in 14/12AWG, although with #34 strands in all sizes where SPT-3 has coarser #30 strands in the larger sizes to reduce the price - typical penny-pinching if you ask me). I've checked and I haven't seen any cords still made with natural rubber - which is pretty much entirely obsolete technology anyway (certainly, it's anything but durable compared to the modern materials).

My only major complaint here is that, in my view, plated conductors should be made mandatory with the common elastomers, even where not required by the manufacturing process itself (some synthetic rubber formulations still require plated conductors, while others including EPR can be manufactured with bare copper conductors); while bare copper cores have marginally lower initial resistance, as noted earlier the most common synthetic elastomers provide only minimal protection from oxidation, so by the end the ultimate resistance ends up far higher than the resistance of tinned (or nickeled, silvered etc.) conductors will ever be. The plastics, fluoropolymers (PTFE, FEP, etc.) and silicone rubber all provide far better protection, so bare copper cores hold up fine under them (except at service temperatures above 150°C).

If you doubt me, you always have the option of checking on the manufacturers' websites. To the best of my knowledge, low-quality electrolytic capacitors are the only thing in electronics that still use natural rubber for their seals (as it's cheaper than synthetic rubber and will last through the warranty period). The high-quality ones (mostly from the Japanese brands at present) use synthetic rubber, although Nippon Chemi-Con and Nichicon still advise a maximum 15-year expected service life but that's probably for legal butt-covering as much as anything else to be realistic.

EDIT: I am replying to you, Ranger, only I accidentally used the "reply" button provided for the topic.

Perhaps my info was outdated then.

In my experience any type of rubber has a limited shelf life, more so than plastics used in wire/cable/cord production. Rubber either gets brittle or soft and sticky with age, although some rare specimens live to surprising ages (I have a fully intact extension lead with black, grey and red cores, i.e. pre-1965). One vacuum might even still have pre-WWII flex.

Or, more likely, that info was wrong to begin with.

By the way, I do have a piece of grey H03VH-H2X0.75 (or the Australian Standard equivalent? The text failed to print properly on this sample, unfortunately...) with the ridges identifying the neutral core, although it wasn't actually in use on the mains. It is indeed very flexible, although a good H03VVH2-F2X0.75 cord isn't exactly unmanageable under any normal circumstances.

Also, here's another poll, this one aimed specifically at the USA and Canada... (I'm not about to suggest such a changeover for the fixed wiring cables, as that would only create more confusion, for probably no tangible benefit anyway.)

For convenience, here is my list of suggested replacements, for the PVC cords:

• SPT-1 --> H03VH-H (2-core only) is the closest match, but I'd usually prefer to use H03VVH2-F (2-core) / H03VV-F (3-core)
• SPT-2 --> no direct equivalent; I suggest using H03VVH2-F or H05VVH2-F (2-core, 0.75-1.0mm²) / H03VV-F or H05VV-F instead
• SPT-3 --> no direct equivalent; I suggest using H05VVH2-F (2-core, 0.75-1.0mm²) / H05VV-F (1.5mm²+ and all 3-core) instead
• NISPT-1 --> H03VVH2-F (or for 3 cores, use H03VV-F instead)
• NISPT-2 --> H03VVH2-F or H05VVH2-F (or for 1.5mm²+ and/or 3-core, use H05VV-F instead)
• SVT --> H03VV-F (or H03V2V2-F for heat resistance to 90°C)
• SJT --> H05VV-F (or H05V2V2-F for heat resistance to 90°C)
• ST --> H07VV-F? (although not included in IEC 60227-5, the equivalent of it is quite common here in Australia; otherwise you could choose one of the rubber cords)

And for the rubber cords:

• HPN --> ??? (a hypothetical equivalent would be designated something like H03N4H-H, but I'm not aware of any such cord actually being made)
• SV --> no direct equivalent; use the replacements given for SJ... instead
• SJ --> H05RR-F, H05RN-F, H05BB-F etc.
• S --> H07RN-F, H07BB-F etc.

I thought about the TPE-insulated cords (SVE, SJE, SE) but I don't know of any Harmonised equivalents to them. Earlier versions of AS/NZS 3191 did have some but as of the 2008 revision, they were deleted.

Any other questions? (One that comes to my mind is, would they be happy to use the "split" voltage ratings, or would they feel the need to dumb them down again?)

Do you think they should adopt the Harmonised flexes in North America? single choice
	Yes, and eventually phase out SPT/NISPT/SVT/SJT/etc.
	Yes, but continue producing their own types
	No (why not?)
Votes accepted starting: 07/21/15 04:20 AM
View Results

Cable types for fixed wiring are still something where harmonisation hasn't really caught on. Even most EU countries still largely use national types, although some are fairly similar. Even Austria and Germany, countries that share a common electrical history during WWII, cables aren't 100% interchangeable. While they look essentially the same, the Austrian versions have thinner isolation and especially outer sheaths.

I suppose harmonising cord types all over the world (i.e. adopting exiting harmonised types in countries that don't use them) would mainly benefit manufacturers and international wholesalers.

Quite right there, Ranger.

I also see that still, no-one has voted on my most recent poll in this thread. (I can understand there, I was quite torn about it myself.) I've now decided on option 2: Adopt the harmonised flexes, but keep producing their own traditional types (albeit in decreasing volume) for repairing older appliances with.

It did seem to me (like others) a little unnecessary when the Brits decided to harmonise their colour code for fixed wiring with the rest of Europe, but otherwise stuck with their same cable constructions; if you're going to change, why not also harmonise your cable designs with another part of the world? Anyway, as the fixed cables go the Australian ones seem better-designed than most others; with (as noted before) stranded earths even when the active(s) and neutral are solid, and typically all but the smallest (1mm2) are stranded throughout, like the older (pre-metric) British twin+earth cables.

Stranded wire is only any good if your devices and connectors are rated for the use of stranded wire without ferrules or other terminals. Most designed for the central European market aren't, so using stranded building wire introduces additional labour costs. Coarse stranded wire as is common in Scandinavia is only used for sizes of 10 mm2 and larger here. In Germany cables up to 16 mm2 have solid conductors! I hate to imagine working with them, solid 6 mm2 is annoying enough in tight spaces!

AFAIK Britain and Norway are the only countries in Europe that still allow reduced-size earth conductors smaller than 16 mm2 and the only two that commonly use bare earth conductors in building wiring (Ireland started requiring full-sized isolated earth conductors a year ago I think but I'm not sure if that's already affected actual wiring practices).

Then there's the divide between flat and round cables for building wiring - the UK, Norway and a couple of Eastern European countries predominantly use flat, the others round cables. Not much harmonisation there to see.

16mm2 solid core?! That's about 4.5mm in diameter of solid copper. Those Germans must be out of their minds!

In Australia our multi-core fixed cables have full-size earths up to 2.5mm2, then 4mm2 cables have a 2.5mm2 earth, 6mm2 through 16mm2 have earths two sizes smaller (2.5mm2 through 6mm2), 25mm2 through 70mm2 have earths three sizes smaller (6mm2 through 25mm2), and 95mm2 and up have earths four sizes smaller. (Given that the size steps get relatively smaller as the absolute size goes up, it's actually 25mm2 that gets the proportionally smallest earth there.) All modern versions have insulated earths, though bare earths can be found in older buildings.

We also get the options of flat or circular cables, the latter having tougher sheathing (usually coloured orange) and available in either 450/750V or 0.6/1kV ratings (up to 6mm2, above which it's 0.6/1kV exclusively). The flat cables are rated 450/750V (older versions were 0.6/1kV) and go up to 16mm2. Also worthy of mention are "twin active" flat cables (with red and white cores) commonly used for switch drops, and "SDI" (single-core double insulated) which contains just a single insulated and sheathed core (most often with red inner insulation, but occasionally also black or white). SDI is usually rated 450/750V up to 16mm2, and 0.6/1kV for 25mm2 and up. (Are cables similar to SDI used in other countries?)

Yep, apparently Germans are a bit masochistic! I recently saw a picture of what looked like a terminal box inside a lamppost and someone commented: "Ever tried wiring three 5G16 mm2 solid conductor cables into one of these?" and several others chimed in sympathetically.

I rarely have to work with larger cables so I'm not entirely sure but I think from 25 mm2 and up you can go done one size with the earth (and neutral), so 25/16, 35/25 etc.

Flat cable was and to some extent is used in most Eastern Bloc countries as well as in Norway, the UK and Ireland, although Ireland seems to have switched to round German style NYM a few years ago. Then there's ribbon cable, three, four or five solid conductors with fairly thin conductor isolation and an even thinner outer sheath, with only a small bridge of sheath between the conductors. Sort of like zip cord but with a lot more space between the conductors. It's used in new brick and concrete construction and can be glued or nailed to the raw brick walls and plastered over. Round cable or conduit usually requires trenching walls or pre-installing conduit in the forms while ribbon cable doesn't. The Germans mostly use NYIF with rubber sheath and that deteriorates wuite badly and crumbles if you try to work with older wiring. The Austrians had PVC-sheathed but always preferred conduit anyway. These days ribbon cable is rarely used and outrageously expensive (two to three times the price of round). Due to the thin sheath it mustn't be used anywhere near metal and combustible materials.

SDI seems to be a British thing mainly. In Germany it's commonly used for equipotential bonding and the likes, obviously with a yellow/green conductor.

I've never seen any equivalent to twin-active cable here, either the blue conductor is used as an active instead of neutral or a cable with more cores is used. Some Germans simply use 5-core (4+earth) by default.

Curious, isn't it, how countries can differ so drastically in at what point reduced-size earths are allowed (in British 2C+E and 3C+E flat cables, the 1mm2 is the only one that actually has the same-size earth, everything larger has smaller earths). And I believe some European rules may even demand a larger earth in smaller cables (or singles in conduit)? Would sure be interesting to know how they worked them all out. (Flexible cords pretty much anywhere seem to all have same-size earths.)

I can understand keeping cables away from sharp metal, but any metal? That one's new to me. With a restriction like that, it's a wonder they still bother making it at all, especially given such inflated pricing.

Having double insulation on an earth wire seems a bit unnecessary too. And it's possible to get British 2C+E (and prior to 1966, 2-core without earth) with two brown (modern) or red (older) wires, but most electricians there seem to just use the normal kind (brown+blue now, red+black historically) and over-sleeve the "neutral" core.

If you'd ever seen NYIF you'd know why it has to be kept away from anything that could damage the flimsy rubber sheath! I've seen rolls that were so badly mangled on the shelf in the store that I wouldn't buy them at any cost!

http://c.heimwerker.de/fa/_processed_/csm_stegleitung_detail_ef635d81a7.jpg

1 mm2 is considered too small for fixed wiring in all European countries except the UK and Ireland as far as I know, on grounds of insufficient mechanical strength. In Austria it was banned soon after WWII if it was even legal after 1938 (introduction of the German regs. in occupied Austria).

I've never heard of up-sized earths being required, only suggestions that they might be a wise idea in some very specific applications. e.g. data centres.

Not having any exposed earth wire in boxes does make some sense to me and I assume that's the whole point of isolated earth conductors. The British require sleeving, which adds unnecessary labour costs, probably exceeding the manufacturing costs of fully isolated earth wires. Ireland started requiring full-sized isolated earth in 2013 and seems to have switched from T&E according to British Standard to NYM according to German DIN VDE.

With any large sort of cable running next to or through metallic surfaces, you end up with induced and eddy currents, respectively, especially over long runs.
This is why things like cable trays/ladders are equi-potentially bonded together and earthed.
With respect to cables making entry to equipment, these days, especially where high frequency drives are concerned, you must use an EMC type cable gland, not just the normal nylon one.
I've investigated numerous stray voltage problems, where this has been put down to Eddy currents flowing in metallic parts of the installation, caused by the lack of bad screening/wrong gland used.

With this type of cable the sole concern is mechanical damage though. The main fear is that non-bonded steel like studs or wire lath could be energised by a damaged cable. It's really only designed to be embedded in plaster on a brick, block or concrete wall or ceiling. I'd say the outer sheat is maybe half the thickness of comparable cables or even less and it's rubber, a type of rubber that doesn't have all that much tensile strength and cuts easily. I've seen rolls of that wire on a store shelf that I wouldn't have used any more because the sheath looked so badly chafed!

This picture should give you an idea what I'm talking about:
http://cdn-reichelt.de/bilder/web/artikel_ws/C600/NYIFJ315.jpg

In new construction the cable is either nailed or glued to the rough walls before plastering.
https://upload.wikimedia.org/wikipedia/commons/7/7f/Stegleitung.jpg

Well, C-H noticed over a decade ago that, for whatever reason, the conductor sizes <1mm^2 don't follow the same Renard series used for 1mm^2 through 25mm^2.

(For the bigger wires, I can understand transitioning to finer steps, to enable more precise sizing and minimize wastage; but I'm not sure about 0.5mm^2 and 0.75mm^2.)

If we extend the Renard series below 1mm^2, that gives 0.63mm^2 -- or 0.6mm^2 if rounded off, like with 1.5mm^2 and 6mm^2.
0.63mm^2 flexible conductors could be assembled from 20/0.2, or 35/0.15 (I definitely prefer the finer strands, especially in H03VV-F and H03VVH2-F); if rounded off to 0.6mm^2, then 19/0.2 or 34/0.15 would also work.

This just happens to be very close to an imperial size (to BS 2004) used by old flex in the UK (and Australia, going from memory) -- which is nominally 0.001 square inches (0.67mm^2), made from 23 strands of 0.0076" (about 0.193mm) diameter.

I believe some 0.25mm^2 flex (constructed as 14/0.15) also exists (or did in the past), and was used on a few low-power devices in the UK (with a 1A plug fuse); presumably, it's been ditched for breaking too easily. However, it could still fit into the Renard series, if you add 0.4mm^2 (which could be made from 23/0.15) along with 0.6mm^2.

Anyway, to get the all-too-obvious question out of the way:
If 0.5mm^2 flex is allowed by the relevant standards, why is it so little-used? (Mostly, it seems to be on either appliances that demand a highly flexible cord, e.g. electric blankets; or else very cheap-and-nasty items, including a few low-end fans I've seen.)
Perhaps because, for tensile strength and fault currents, it's a bit borderline...

I've seen some UK flex that feels like doorbell wire but it's most definitely pre-metric (early 60s). I've got it on an old Robuk tape recorder but I don't remember what size fuse sits in the plug. I definitely didn't replace the plug with a Schuko because I didn't feel confident plugging this in without additional protection!

I've seen some 0.5 mm2 IEC C7 cables and they were very easily damaged so I can guess why the size isn't too popular. It's probably also borderline regarding short-circuit protection in countries with 20 A socket circuits like Belgium and France.

Here in Australia, standard practice seems to be using C16 breakers on outlet circuits (I know my home has them). In some other buildings we even have C20 breakers (or British-style rewireable fuses in older installations) -- plus a 20A outlet (admittedly rare in residences) that also accepts our 10A (and 15/16A) plugs!
(As if we weren't "living on the edge" enough already... I also happen to have downloaded a flyer for Prysmian's "Flat Xtra" cables, which calculates their route lengths based on "mean" instead of maximum trip currents. )

Considering that a B16 breaker is the most that proper practice would allow with 0.5mm^2 wires (AFAIK), and that C-curve takes up to twice the current to trip magnetically -- I'm not that impressed with the Australian way.
Personally, I'd then stick with up to a B16 (or C8) if there's any chance of plugging in a 0.5mm^2 flex; if I could be confident of 0.75mm^2 (or my suggested 0.63mm^2) as the smallest that will ever be connected, then B20 or C10 would also be fine.

For lighting circuits, on the other hand, C-curve breakers seem sensible...

I believe one common argument is that if the overcurrent protection doesn't serve as earth leakage protection disconnection times can be much longer, even going into the thermal overload range of the fuse/MCB rather than the magnetic trip. That's often cited with laypeople plugging in multiple extension leads, occasionally exceeding 50 m of 1.5 mm2. Besides, most wiring regs worldwide only apply to fixed wiring and flexes are governed by different standards (that obviously need to take fixed wiring designs into consideration).

C16 is fairly common for commercial and even domestic socket circuits in Austria where sockets and lights are on separate circuits. If there are mixed circuits it's usually B or sometimes C13, mostly out of habit. Around 1980 the regs were updated with reduced ampacity tables, banning the use of 1.5 mm2 and 16 A L/U trip curve MCBs and Diazed fuses under most circumstances (except cables directly buried in masonry walls, concrete or run underground). That update was followed by the introduction of L/U 12 A MCBs that quickly became the de-facto standard for domestic general-purpose circuits and small commercial lighting circuits. The introduction of B/C curve MCBs in the early 1990s saw slightly higher ratings due to the faster overload trip (1.45 times rated current rather than 1.6-2.1 depending on the size) but most electricians had grown accustomed to the smaller size and went with B13. C13 are rare, although sometimes helpful because even a regular home PC can trip a B-curve MCB if plugged into a switched power strip along with a lot of peripherals and then switched on at the power strip. That's even true for B16.

The German regs only had a more moderate ampacity reduction and manufacturers eventually offered huge discounts on B16 MCBs due to the quantities they're sold in - a B16 single pole is usually 1.99 while a B10 is between 4.99 and 9.99 there.

Yeah, there's only so much we can do... (Though I would like if the standards considered fixed wiring and flexible cords in conjunction, rather than separately.)

I wish product engineers would include better inrush limiting, too. (Generally, they seem to have been concerned mostly just with protecting the product itself from damage.)
Anyway, if we want to discuss that further I'd suggest going to another thread...