WIRE TABLES
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Re: WIRE TABLES
According to the handbook, Chapter 9, at the end ot table 8 is a note:
The 2002 NEC specifically requires that insulated conductors be marked with their sizes and that the sizes be expressed in either AWG or circular mil area. No exceptions. The wires can also be marked with square millimeters, but AWG or KCM is required. (I got lazy and didn't quote it exactly).
The conversion between CM and square mm is also given in this example.
STeve
According to the handbook, Chapter 9, at the end ot table 8 is a note:
The 2002 NEC specifically requires that insulated conductors be marked with their sizes and that the sizes be expressed in either AWG or circular mil area. No exceptions. The wires can also be marked with square millimeters, but AWG or KCM is required. (I got lazy and didn't quote it exactly).
The conversion between CM and square mm is also given in this example.
STeve
bphgravity
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Re: WIRE TABLES
I overheard a conversation recently on this very topic. Considering the NEC is an "International Code", I too believe the metric values for wire size should be added next to the AWG and kcmil numbers.
Here's a cross-reference (AWG to mm^2)
I overheard a conversation recently on this very topic. Considering the NEC is an "International Code", I too believe the metric values for wire size should be added next to the AWG and kcmil numbers.
Here's a cross-reference (AWG to mm^2)
Re: WIRE TABLES
AWG of soild wire is based on the 39th root of 92 or a multiplying factor of 1.1229322 between sizes. 4/0 is 0.460 and 36 is 0.005 inch diameter. The 92 is .46 divide by .005. The circular mils is the diameter of the wire in one thousands of an inch squared. A circular mil is the area of a wire 0.001 in diameter. A size 36 wire is 5 mils in diamter or 5x5=25 circular mils. If you have a metric wire you can measure the diameter in mils and then square it to get circular mils. If the wire is stranded measure the diameter of one strand , square it, then multiply that result by the number of strands to get the circular mils. A wire with 7 strands and each strand 0.020 diameter is 7x20x20=2800 circular mils. This would fall between a 15awg (3260 cm) and a 16 awg (2580 cm). One square inch is 1,273,239 circular mills. There are about 1974 cm (1973.525) in one square mm.
AWG of soild wire is based on the 39th root of 92 or a multiplying factor of 1.1229322 between sizes. 4/0 is 0.460 and 36 is 0.005 inch diameter. The 92 is .46 divide by .005. The circular mils is the diameter of the wire in one thousands of an inch squared. A circular mil is the area of a wire 0.001 in diameter. A size 36 wire is 5 mils in diamter or 5x5=25 circular mils. If you have a metric wire you can measure the diameter in mils and then square it to get circular mils. If the wire is stranded measure the diameter of one strand , square it, then multiply that result by the number of strands to get the circular mils. A wire with 7 strands and each strand 0.020 diameter is 7x20x20=2800 circular mils. This would fall between a 15awg (3260 cm) and a 16 awg (2580 cm). One square inch is 1,273,239 circular mills. There are about 1974 cm (1973.525) in one square mm.
Re: WIRE TABLES
There is an added difficulty here: Much (most?) metric cable is designed for 70C, not 60C or 75C like the AWG cables. 90C cable exist in both systems.
With a little work, you can work out tables but of course your tables will not be official.
An alternative solution is to use the tables from some metric code, e.g. the British. (Keep in mind that it's probably a bad idea to mix ampacities and derating factors from different codes.)
Bryan kindly posted a link to a conversion table. Please note that the values have been rounded to the nearest existing size. In this case, the AWG/KCMIL sizes have been rounded to the nearest larger metric size.
[ June 25, 2004, 09:39 AM: Message edited by: c-h ]
There is an added difficulty here: Much (most?) metric cable is designed for 70C, not 60C or 75C like the AWG cables. 90C cable exist in both systems.
With a little work, you can work out tables but of course your tables will not be official.
An alternative solution is to use the tables from some metric code, e.g. the British. (Keep in mind that it's probably a bad idea to mix ampacities and derating factors from different codes.)
Bryan kindly posted a link to a conversion table. Please note that the values have been rounded to the nearest existing size. In this case, the AWG/KCMIL sizes have been rounded to the nearest larger metric size.
[ June 25, 2004, 09:39 AM: Message edited by: c-h ]
Re: WIRE TABLES
I would not use ampacity tables from other countries. Many of those are much more generous than the NEC. For example, the canadian electric code rates #8 wire as good for 55A at 60 deg, while the NEC only allows 40A. You would be better off using the NEC and rounding down to the next wire size, or maybe even interpolating between two sizes.
STeve
[ June 25, 2004, 10:03 AM: Message edited by: steve66 ]
I would not use ampacity tables from other countries. Many of those are much more generous than the NEC. For example, the canadian electric code rates #8 wire as good for 55A at 60 deg, while the NEC only allows 40A. You would be better off using the NEC and rounding down to the next wire size, or maybe even interpolating between two sizes.
STeve
[ June 25, 2004, 10:03 AM: Message edited by: steve66 ]
jafro
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- Fort Saskatchewan, Alberta, Canada
Re: WIRE TABLES
- Location
- Illinois
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- retired electrician
Re: WIRE TABLES
jafro,
The NEC is used in many countries. About 15 years ago we did a plant for a company from Japan. Their electrical engineer had a copy of the NEC in Japanese.
Don
jafro,
The NEC is used in many countries. About 15 years ago we did a plant for a company from Japan. Their electrical engineer had a copy of the NEC in Japanese.
Don
bphgravity
Senior Member
- Location
- Florida
Re: WIRE TABLES
According to UL, two documents serve as the basis for electrical wiring in 90% of the world. The NEC and the IEC.
Besides, what would "International Electrical Code Series" be on the front cover for?
The NEC is in use in all 50 states in the United States. Countries that have formally adopted the NEC include Mexico, Costa Rica, Venezuela, Columbia and the Philippines. Many countries in South America use the Code, and it has been translated into Spanish, Korean and Japanese.
According to UL, two documents serve as the basis for electrical wiring in 90% of the world. The NEC and the IEC.
Besides, what would "International Electrical Code Series" be on the front cover for?
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