Converting AWG to European Wire Standard

It depends on a number of things like different standards, de-rating factors and good old fashioned rounding errors (like to the next wire size even).

You could try the American wire manufacturer websites and perform the calculations on converted AWG wire figures, but I would suggest you go directly to the European wire manufacturer websites and use their data directly (referencing back to your specific requirements) as you are using metric to begin with.

Either way here the following example site has some of the information you need.

http://www.generalcable.co.nz/newzealand/nzPublicPages/Resources/Technical_Info.aspx

Thanks. Therin lies the rub. I did pretty much what you suggested up to a point. That is how I discovered all the normal metric sizes happen to fall in between the AWG sizes. Playing it safe by rounding up yielded wire sizes way larger than needed. Trouble is the inspecting authority wants detailed plans before construction starts and if the percentage loss is calculated as 3.01% its a reject. They do not care if the next size up drops the loss to 1.9% or 2.1%. The end user cares because the cost of all that extra wire could double the cost. Nor have they said they will allow a tolerance range of say 3.0% - 3.2% In the real world I know that it isn't going to matter. When the DC circuit changes from 28.4V to as low as 25.0V depending on whether or not the charging circuit is working, you actually get a bigger percentage change. Unfortunately the pencil pushers don't work that way.

In the website you supplied I found the following note:

"With the exception of when a PVC sheath is used in conjunction with PVC insulation, all materials are rated for a continuous conductor temperature of 90 degrees Celsius (PVC/PVC 75 degrees Celsius)."

This suggest that purely PVC cabling has a rating at 75C. I made a point of asking and was told the cable is marked 85C but no manufacturer given. However the real guessing game comes from trying to determine what Lloyds is using as their temp standard. They take the position that they are not going to do our calculation work for us nor tell us how we should do our job. In other words they won't be helpful. They expect us to submit our design and they merely say approved or rejected.

Arre there no calculation programs available for download that allows you to plug in the variables and the program does the calculations automatically. I have one for AWG sizes that makes life easier when 50 or 100 calculations have to be done in short order. Its a real PITA entering all those numbers by hand on a hand calculator each time. Especially if you only change one variable each time.

Trouble is the inspecting authority wants detailed plans before construction starts and if the percentage loss is calculated as 3.01% its a reject. They do not care if the next size up drops the loss to 1.9% or 2.1%

True, but that is a sort of limit you (and the rest of us) have to work to. If it takes going up a cable size to meet the specified requirements of a bid or tender then you have to do it unless you are allowed to submit a design variation (which is more trouble than its worth, ESPECIALLY if you are trying to win a contract or tender).

On the plus side the wiring costs shouldn't increase significantly by just going up a cable size, and it gives the customer some additional load expansion room.

If price is really an issue then you could look at American cable where you may find a closer match (ie- may only need to go up half a size), but you have said that this is not an option. This will involve more design work (which someone has to pay for) and will likely not be a possible suitable fix if you are limited to a certain standard (like European wire and fittings). Custom manufacture of cable is an unlikely possibility due to cost, necessary cable length to make worthwhile and need for cable testing to approved standards ($$$$).

Cable temperature rating and de-rating factors (ambient temperature, installation environment, etc) will primarily effect cable current rating, so by the time you size a cable to comply with you 3% volt drop limits you will likely find that the cable complies with the current handling capacity requirements (possibly by more than 1 or 2 cable sizes).

but that is a sort of limit you (and the rest of us) have to work to.

Oh yes, I am aware of that fact. What really puzzles me is that the current limit is so different for what is essentially the same cross section wire. NEC says I can run 15 amps with a #14AWG wire. Going to one of the links you sent tells me a #14 wire is good for 32 amps chassis wiring and only 5.9 amps for power transmission. Nowher is insulation temp rating indicated. You do not use bare wire for chassis wiring so I cannot assume this is for bare conductors. One table I did find says a 2.5mm2 wire is good for 16Amps. But the conversion siize table in the linked website says a 2.5mm wire is very close to a #10 AWG wire size. What gives?

With such conflicting data I don't know what to trust.

Again it comes down to standards and derating factors. For example (from the general cable databook), to AS/NZS wiring standards, 2.5mm2 PVC insulated single core building (conduit) wire has the following current ratings under certain installation conditions

- 25A when installed in non-metallic wiring enclosure as a single phase circuit (2 wires running togeather in same conduit)

- 23A when installed in non-metallic wiring enclosure as a three phase circuit (3 wires running togeather in same conduit)

- 36A when buried in duct (single phase circuit)

- 31A when buried in duct (three phase circuit)

- 14A when duct completely surrounded by thermal insulation (single phase circuit)

- 14A when duct completely surrounded by thermal insulation (three phase circuit)

Although standards differ from country to country the current rating is roughly the same, it's the derating values and type cable insulation that cause the current rating to vary by so much.

Stick with the relevant IEC standard ratings if that is what you have been asked to specify to. Although you can get most of this information off the European standard relevant manufacturer websites and cable datasheets, it helps to also have the relevant IEC wiring standard and regulations which clearly cover this sort of thing.

Have a look at the following links as they contain much more information including derating tables and formulas that should answer your questions.

http://www.olex.co.nz/Redirect/redirect.aspx?file=Section-Two-eda6ac7b-d64a-4018-8d74-06503640c2d7.pdf

http://www.olex.co.nz/Redirect/redirect.aspx?file=Section-Three26-bcaae3d7-527c-4b7a-87be-8ac961773e9a.pdf

http://www.olex.co.nz/Products/Low-Voltage.html

Thanks for those links. It explains a lot. By looking at the various ampacities for same size wire I now realize what derating was originally intended for some of the tables I found online.

Sadly this critical information was often not included in the tables I found and downloaded. For example the #14 Ga wire rating for 15 Amp applies when cable is entirely suprroundd by full insulation. That makes sense in a house where walls and ceiling is insulated with batts.

It also explains why the ABYC standard ampacity for #14 Ga wire is so much high even if same wire insulation type is used. Boats typically has wiring mounted on a surface, not imbedded in an insulating wall. I do not recall seeing a caution note in the ABYC manual reminding installers to derate a single branch circuit if the wire is placed inside an insulated overhead.

The marine standards manual does include a derating when multiple conductors are bundled, but fails to mention that insulation style and type must also be given consideration. It makes me wonder why these US marine standards are so poorly worded?

On the plus side the wiring costs shouldn't increase significantly by just going up a cable size, and it gives the customer some additional load expansion room.

Its a domino effect. To begin with the circuits involved are branch circuits to point of use by a single device. Changing the device would involve a whole new engineering review with attendant ECN approvals.

Secondly its a steel vessel. Wires are run in conduit. NEC and other electrical authorities specify allowable wire fill for a given conduit size. If you increase the wire diameter to deal with the up-sizing problem you must now also increase the conduit sizing to comply with the fill rules. . . . BUT .. bigger conduits often bring other problems such as larger bending radius, no room in the available space behind joinery and what have you.

As for 'additional load expansion' not likely for individual items like bilge pumps. That is one critical circuit you must never touch or tap into. Same goes for other critical ship safety circuits. If the owner decided to modify it later on he now has to contend with the insurance company and their surveyors. Not a pleasant experience.

As global trade patterns shift, I suspect this kind of standards conflict will be seen more and more often.

Some American companies also have weird sales department rules. I called up one manufacturer to get product specifications. They would not talk to me. Insisted I give them a postal code number. So I did and three days later some guy from Montreal calls me. I explain what I wanted and he asks me where would the product be delivered to. I tell him. He chokes because it's outside his sales territory. No way is he going to give away a sale to some other guy. Then he asks me where I am located. When he finds out I am on the other side of the continent he wants to know why I am calling him. I explain the batteries would be installed in a boat built in China and at that point he totally lost interest and hung up.

The punch line to this comedy of errors. The owner of the boat who I was working for lived less than 100 miles from the factory. Go figure. America is not geared up for global trade. BTW we were talking about a $8,000 - $10,000 battery installation.

America is not geared up for global trade

In many cases (but not all) that is true. Seems hard to believe if you are used to dealing in places like Europe or where your small country imports and exports large quantities (like New Zealand) and you haven't experienced it first hand.

Suggest a U.S. wire supplier as sole source (Which is actually true). If they insist on a metric equivalent, then tell them it will have to be special ordered.

Thanks Ronseto and Wareagle; but going with an American supplier just isn't viable. I am designing for a client that is having a boat built overseas. Lloyds is the certifying standard body and the country in which the boat is built requires Lloyds standard must be used. Lloyds insist metric sizes must be specified.

In case you haven't noticed yacht building in America is practically at a standstill. For that matter so is ship building except for military contracts. The major building activity is now in the middle east and to a lesser extent far east. Even that is slowing down since most of the yacht buyers in the past were American.

The rest of the world is metric. So naturally designs must also be done in metric. Especially when the yard workers do not even read or write english. Some of them do not even read or write; period. But they can recognize a mm size number and compare it to what is on a wire spool. If they look the same it must be the same.

Its a new world out there.

If there is no exact equivalent for AWG, then the wire will have to be special drawn to the MM equivalent or else go to a bigger size.

Its a new world out there.

Yep - and its high time America thought about joining it.

Very intersting thread by the way - hope you find what you are looking for.

Yep - and its high time America thought about joining it.

Gasp! but it wasn't invented here so how could it be any good?

This thread does illustrate the problems with diverse standards developed locally to deal with what is rapidly becoming a common global issue. Everybody seem to think their standard is better or their unique situation requires an exception or special addendum in the standards.

Lloyds has been the global benchmark for almost two centuries. But they are tough standards and many people feel "too tough", so they come up with lesser standards to the point we now have a 'no standard' standard which is reflected in increasing accidents and mishaps. All in the name of increasing profits and lowering costs.

We had a discussion thread a while back started by ronseto about why go metric? Well this may help explain why it makes sense for everyone to go with one common standard.

I arrived at those websites three different times by different routes of links. Just try and follow the process and you will see what I mean.

You end up with a nonsense answer that is not usable. For one specific 10A load circuit where I must keep voltage drop under 3% I end up calculating a #8 AWG size as being required. My actual drop is 2.64% but the wire size is half way between a 6mm and a 10 mm metric wire size. And the tables do not tell you what is a commercial size that is available. Going to a 10mm wire nearly doubles the cost and greatly increases the physical size. Customer aint going to like that. Not to mention which if you also follow the NEC for conduit wire fill going to such a large wire increases the required conduit size to ridiculous proportions. No inspector will accept cramming a conduit beyond what the tables allow.

Would this help? It appears that cable is manufactured in the sizes indicated below. What you have to find out is; What size cables are available in Europe? Choose the cable closest to your requirement from what is available. Your client will have to make the decision as to the way to go, either a standard size or a special size.

Recommendations for maximum current for cables:

Ron what is the distinguishing difference between power distribution and Equipment cables. Is it a question of allowing greater voltage drop in power distribution? Or does the table assume power distribution somehow can allow greater wire temp and thus more current in same diameter wire? Or is it a question of a different kind of insulation?

Go to MWS Wire Industries. You can down load a rather extensive wire data that cross references the data you appear to need.

The issue I have to contend with appears to be more related to the specific standards body ( Lloyds) and how they arrive at their conclusions.

For instance they insist on using the entire lenght of the hull as the typical branch circuit lenght. In many cases this does not make sense since the power source and the end use equipment is located in the same engine room and in close proximity. They do say it is up to the builder to justify going with a smaller wire gauge than what Lloyds calculate. Furthermore Lloyds apparently want to use the fuse rating as the load current value in the formula rather than the actual max load current. Manufacturers tend to double the value of the running curent then rounding up to next closest standard value. Example a bilge pump is rated for 7.5 amps running current but has a 15 Amp fuse. Lloyds now wants to calculate wire size based on the lenght of the whole boat at double the actual current value. They require the maximum voltage drop to be 3%, not 3.01% What happens is you end up having to run #8 Ga wire for a pump that could be powered by a #16 Ga wire if it is less than 10 feet from the battery. As it happens I normally work in AWG wire size so when I get a wire gage calculated I now have to find the next size larger in metric. To refine the numbers I should now backtrack and calculate the actual Vdrop for that metric size. Most times the drop is well under 3% sometimes even under 2% so then I try the next standard size down to see if it meets Lloyds criteria. This makes for a very time consuming effort. And there is no extra pay for doing this.

I have a nice program that is set up for AWG sizing but it doesn't work for metric. I was hoping to find something equivalent that worked for metric sizes. I'm now into day three of what I had hoped would be a half day effort.

I have a nice program that is set up for AWG sizing but it doesn't work for metric. I was hoping to find something equivalent that worked for metric sizes.

Can you use a spreadsheet? Put all your calculations in based on wire cross sectional area, then change the size of the wire. Should be simple if you can assume a particular temperature. If you want it to also calculate the temperature based on the current flow, that's more complicated. Perhaps you could assume some worst-case high temperature, and then when you are done sizing, double-check to make sure the wire doesn't get that hot?

That is what I have been doing. But spread sheets do not contain look up tables like I need. It would take longer to make such a thing than doing it with a hand calculator. Because every AWG and metric size falls in between each step to next size. Sometimes you round up other times round down.

Once I get a size in AWG, from the spread sheet, then I cross reference to metric and then go back and redo the whole calculation all over again. Royal PITA

I tried to do it just in metric but lack enough familiarity with the sizes to get a feel for it. Ended up starting my guesstimates over about three times per circuit.

When I discovered that their dictated formula also screwed up with my schematic layout and placement of cabinets . . . . . that did it. Took a break and went to bash around a couple of chainsaws I am fixing. Some jerk had glued the case halves together. I ended up using a 4 ton hydra press to pull it apart. Piece of cake compared to this Standards calculations stuff.

I ended up doing a classic CYA. Appended a note saying builder could substitute with justificaation such as measured load current or actual wire distance being less than the calculation guesstimates. Now some poor sod in the yard will have to do the calcs all over again.

MWS appear to be dealing primarily in enamelled magnet wire. This is not suitable for power distribution.

I hope these helps

http://www.onlineconversion.com/gauge_wire.htm

http://www.google.com.au/search?hl=en&source=hp&q=wire+gauge+conversion&meta=&aq=1&oq=wire+g

Yes Thanks! the second link did provide something useful. In addition to doing a mathematical conversion - which gave me weird sizes like 67.13mm2 - I finally found a listing that correlated this to the nearest normal available size. No point in specifying something that is unobtainable.

A big Thank You to all my overseas friends like Jack of all Trades in NZ, Capblanc in Spain, Moe in Denmark and the several other contributors who all provided useful links to stuff I now have filed away. Some was more useful than other. It proved to be an education as well as a reality check. I am even more disillusioned with the ABYC spec than I was before. AFAIC its woefully inadequate. Some of the back ground white papers provided by cable manufactures gave me a better insight into why and how wires are derated than ABYC ever did. And I even taught the course once.

You should see our main electrical wiring standard AS/NZS3000, it had so many problems we had revert to the previous version until the current version was fixed with an amendment (an astonishing 44 page of revisions later).

Additionally (due to a crossover of at least two standards versions in both Australasia and Europe) we had a choice of up to three valid colours for phase (both single and the three phases) and 3 for Neutral (both single phase and a different one for three phase + neutral). In one case the phase colour was also the same as the neutral colour.

A discussion with one of the top men at our local regulating authority resulted in the comment "just use whatever colour you like as long as the earth wire is green/yellow). OOOOk Mr Regulator.