Cable measurements in NZ

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richms

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#107242 8-Aug-2012 22:15

Ive been trying to get some power cable for car audio stuff recently...

As we know NZ is metric.

So why are places selling cable in gauge (totally meaningless) and AWG (of very little meaning) in NZ?

As they are not defined in the weights and measures act, I could sell anything as 10gauge cable so long as somewhere in the listing I had the actual mm^2 cross section, right?

Since there is a hell of a lot of dodgey speaker cables out there with "gauge" measurements that mean nothing, why are sellers of them allowed to get away without providing the true cross sectional area of the cables?

Who covers this type of stuff in NZ. If I buy some "10 gauge" cable off someone and it ends up being lamp cable, would I have any right of complaint if they had not listed any mm^2 area in the listing?

Richard rich.ms

DarthKermit

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#669948 9-Aug-2012 09:37

There are plenty of AWG (American Wire Gauge) to metric conversion sites on the internet.

Just Google "convert AWG to mm"

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richms

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#669973 9-Aug-2012 10:48

Yeah, but when a unit has no legal basis there is no justification for selling by that size. How can they get away with using meaningless numbers on things like that when its not legal to sell beer by the gallon or firewood by the pound?

Richard rich.ms

John2010

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#670001 9-Aug-2012 11:53

richms: Yeah, but when a unit has no legal basis there is no justification for selling by that size. How can they get away with using meaningless numbers on things like that when its not legal to sell beer by the gallon or firewood by the pound?

So, one assumes, you would also like to see the sale of other things that are also often manufactured to gauge or other imperial measurements banned too?

Just a few examples off the top of my head - sheet metals, metal bars and sections, pipes and pipe fittings, well drilling pipe (length and dia always imperial as far as I am aware), nuts and bolts (imperial is widely used in some industries such as oil & gas for the sake of international conformity), guitar strings (which as far as I know are never metric diameters, but gauge), sail cloth. I'm sure there are many more.

Also, while one may not be able to sell firewood and beer by imperial measure, one can sell it by any other measure one cares to use. For example, beer can be and is sold by "jug" or "glass" neither of which have any "legal meaning, and firewood by "trailer load", "sack", etc all of which also have no legal meaning. Are you suggesting all these measures should be banned too?

My suggestion is, instead of campaigning to limit the products available to the rest of us, that if you prefer metric or legally defined measures, can't be bothered converting from one to the other, or can't be bothered asking the seller if you are unclear, then just buy from sellers who meet your own specific preference.

floydbloke

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#670006 9-Aug-2012 12:04

richms: Yeah, but when a unit has no legal basis there is no justification for selling by that size. How can they get away with using meaningless numbers on things like that when its not legal to sell beer by the gallon or firewood by the pound?

Pubs often sell beer by the handle or jug - I'm not sure if they have to disclose the actual quantity if you were to ask.
Cafes sell coffee by the cup, Often small, medium or large.
Chips by the scoop, certainly at my local takeaway the number of chips (or that should probably be weight) varies from week to week.

Just some examples of what you're querying, I do tend to agree it would generally be fairer to consumers if standard measures were in place though.

Edited: typos

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wellygary

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#670015 9-Aug-2012 12:18

richms: Yeah, but when a unit has no legal basis there is no justification for selling by that size. How can they get away with using meaningless numbers on things like that when its not legal to sell beer by the gallon or firewood by the pound?

I hope you don't own a car and need a tyre for it, because all the rim measurements are imperial.

John2010

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#670022 9-Aug-2012 12:31

Just remembered shotguns too, don't think ever made in metric sizes so they will have to be changed to metric too.

Size is by gauge e.g. 12 gauge or bore e.g. 410 (.410 inch). Furthermore the gauge is not even a linear measure at all as it is determined in a round about way linked to the weight of a sphere of lead that fits in the barrel.

Fortunately, 12 guage works out to be 18.5 mm so not too much of a mouthful if Richms has them all converted to having to be called 18.5mm shotguns. But, even so, we will still be left with a shortage of shot to go in the cartridges because that is only available in imperial sizes - lucky for the ducks.

EDIT: Dang, just looked down to my favourite two magazines on my desk - from USA and NOT metric paper sizes, so they will have to go too. Maybe OK as sold on content not size but once the measure maniacs gat onto the case, who knows?

floydbloke

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#670058 9-Aug-2012 13:46

wellygary:

I hope you don't own a car and need a tyre for it, because all the rim measurements are imperial.

Which is most bizarre with the width being in metric.
(And after a bit of research I 've just found out that the number after the '/' denotes the aspect, not the height in millimetres.)

Did Eric Clapton really think she looked wonderful...or was it after the 15th outfit she tried on and he just wanted to get to the party and get a drink?

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richms

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#670073 9-Aug-2012 14:07

John2010:
richms: Yeah, but when a unit has no legal basis there is no justification for selling by that size. How can they get away with using meaningless numbers on things like that when its not legal to sell beer by the gallon or firewood by the pound?

So, one assumes, you would also like to see the sale of other things that are also often manufactured to gauge or other imperial measurements banned too?

No, just require that they are specified in mm or some other unit with legal standing.

As far as the pint in the pub, it means as much as a large at mcdonalds.

Richard rich.ms

John2010

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#670143 9-Aug-2012 15:38

richms:...
No, just require that they are specified in mm or some other unit with legal standing.

I think you are pushing the proverbial uphill myself because it is not a problem for real life users. I take it that you think it is sensible that a 5/16 inch nut has to be sold as a 7.9375mm one?

You do not seem to realise that electrical wire is manufactured to both metric and non metric standard sizes (just as nuts and bolts are) and they are not equivalents in cross sectional area. The vast majority of users have the sophistication to work with whatever unit the wire is manufactured in when working out volt drop, etc or minimum cross sectional area required - just like most users of nuts and bolts can work out what a 5/16 inch UNC nut is.

If you are an unsophisticated user, as it seems you are, just ask the seller or look at the comparison tables (strictly speaking they are not conversion tables because the standard sizes, just like nuts and bolts, do not convert one standard size to another), you'll soon get the hang of it.

richms

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#670148 9-Aug-2012 15:50

You dont seem to get that the conversion tables have no legal standing, which is what leads to the under sized 10AWG cable being sold and the sellers doing nothing wrong under NZ law as they have not claimed to to be any size that is covered by the weights and measures act.

I have had the following excuses on 3 undersized purchases

"its the outside diameter of the cable, not the copper"

"Its equivalent to 10AWG"

"It means it fits into the 10 gauge terminals"

Because they have never claimed a certain size of cable, they have done nothing wrong. If they dont even say AWG (which doesnt only mean american wire gauge, but "auto wire gauge" and other BS terms) and just call it gauge then its totally meaningless since there are dozerns of different manufacturers of drawplates each with their own numbering.

Richard rich.ms

wellygary

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#670169 9-Aug-2012 16:24

richms:
So why are places selling cable in gauge (totally meaningless) and AWG (of very little meaning) in NZ?

.......which is what leads to the under sized 10AWG cable being sold

....I have had the following excuses on 3 undersized purchases

Because they have never claimed a certain size of cable, they have done nothing wrong.

Hang on, how can it be undersized? undersized to what, how can it be undersized to a non existent standard.....

If metric SI units are the only thing you believe in, why did you buy it in the first place,

richms

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#670172 9-Aug-2012 16:40

the standard exists, its just not a standard that means anything IN NZ, so if it doesnt meet the standard you cant do anything about it as it isnt a legally recognized standard here.

If the sellers had to put the mm^2 equivalent of what they were selling then I would have had a case against 2 sellers of undersized junk cables. As they did not, I had no case.

Therefore my question about why they are allowed to sell things with the only measurement being something that is meaningless.

I'm not the one that only believes in them, the weights and measures act is what only believes in them making any claims in any other units meaningless junk unless the seller provides a size conversion table.

I want to know why sellers of stuff like this are allowed to get away with it.

Richard rich.ms

John2010

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#670183 9-Aug-2012 17:08

richms: You dont seem to get that the conversion tables have no legal standing, which is what leads to the under sized 10AWG cable being sold and the sellers doing nothing wrong under NZ law as they have not claimed to to be any size that is covered by the weights and measures act.

I have had the following excuses on 3 undersized purchases

"its the outside diameter of the cable, not the copper"

"Its equivalent to 10AWG"

"It means it fits into the 10 gauge terminals"

Because they have never claimed a certain size of cable, they have done nothing wrong. If they dont even say AWG (which doesnt only mean american wire gauge, but "auto wire gauge" and other BS terms) and just call it gauge then its totally meaningless since there are dozerns of different manufacturers of drawplates each with their own numbering.

You seem to be getting yourself very confused. For example, when you say "auto wire gauge" I assume you are talking about automotive cable (as far as I know there is no such thing as "auto wire gauge", if there is it is not common). If so you do not understand how automotive cable is specified nor why it is so.

What you have been told and seem to have fobbed off as "excuses" is correct in all cases as automotive cable is correctly specified by the total diameter over the stranded conductor not by the cross sectional area. As an example I will use metric for the sake of clarity, but AWG (which will be American Wire Gauge) works the same - so whichever you were to work in you would still get the wrong wire the way you are going.

If you order 3mm (for example) automotive cable you will get cable that the overall diameter over the wire is 3mm and being automotive it will be stranded, probably 16x0.3mm or 14x0.32mm strands so has a copper cross sectional area of just 1.13 sq.mm.

So referring to what you call "excuses", but which sound to me like explanations by your supplier:

"It is the outside diameter of the cable, not the copper" - that is correct, they are referring to the overall diameter of the strands, not the strands or the solid equivalent.

"It is equivalent to 10 AWG" - they are referring to the total diameter over the conductor and that is correct for automotive wire. But where you seem to have gone wrong is automotive wire that is 10 gauge does not have the same the same area as normal 10 gauge stranded wire, its diameter is 10 gauge. Non automotive 10 AWG stranded wire has the same cross sectional area as a 10AWG solid wire so is greater, and being stranded its overall outside diameter over the conductor is greater than a 10 gauge solid wire.

"It means it fits into 10 gauge terminals" - I hope you can see that explanation is correct and that it is a merit of the way automotive cables are sized. They are sized by overall diameter over the conductor and ampacity, so for normal service one orders automotive cable according to the amperage required to be carried and the diameter of the terminations.

It does seem to me that your supplier has tried to explain to you where you have gone wrong, but you have not understood what was said. I can assure you that the way automotive wire is sized is not going to be sized differently just to avoid your confusion over what it is that you seem to have ordered. It is specified that way for good reason.

Despite your protestations any reputable supplier will tell you what the cross sectional area is of any cable you order, regardless of type (automotive, etc) and give you that in sq.mm if that is what you prefer. If you are confused, just order by sq.mm if that is what you understand.

If, for your application, 10AWG has been recommended - check whether they are talking about automotive wire or not as 10AWG automotive wire will not have the same cross sectional area as normal 10AWG wire.

EDIT: Maybe have a look at Tycab's site http://www.tycab.co.nz/automotive.html to see the way different cables are specified. In your original post you mention speaker wire, that and others such as single core, etc are shown as "Industry Standard", and in the list they state what that means and give the total conductor cross sectional area for each size.