This article is about NEC Article 110.6 conductor sizes calculation.
Conductor Sizes Calculation (NEC 110.6)
The size of a conductor, also known as its cross-sectional area, is an important factor in determining its electrical performance. In general, the larger the cross-sectional area of a conductor, the lower its resistance will be and the more electrical current it will be able to carry.
The size of a conductor is typically expressed in terms of its American Wire Gauge (AWG) size, which is a standard system for denoting the diameter of a conductor. The smaller the AWG size, the larger the conductor’s cross-sectional area and the more electrical current it can carry.
For example, a conductor with an AWG size of 8 has a larger cross-sectional area than a conductor with an AWG size of 10. The appropriate size of a conductor depends on the specific electrical application and the required current-carrying capacity.
NEC Article 110.6 Main Points to Remember
According to the National Electrical Code (NEC), the size of copper, aluminum, or copper-clad aluminum conductors is expressed using the American Wire Gauge (AWG) system for sizes up to 4/0 AWG. The size of a conductor is expressed as XX AWG, with XX being the size of the wire.
For example, a conductor that was previously expressed as No. 12 before the 2002 edition would be expressed as 12 AWG. Conductors larger than 4/0 AWG are sized in circular mils, starting at 250,000 circular mils. Prior to the 1990 edition, a conductor with a size of 250,000 circular mils was labeled 250 MCM, with the term “MCM” defined as 1000 circular mils. However, beginning in the 1990 edition, the notation was changed to 250kcmil to align with the accepted convention that “k” indicates 1000. Both UL standards and IEEE standards also use the notation kcmil instead of MCM.
Conductor Size Calculation Example:
To determine the circular mil area of an 8 AWG solid conductor with a diameter of 0.1285 inches, you can follow these steps:
- Convert the diameter of the conductor from inches to mils by multiplying it by 1000: 0.1285 inches * 1000 = 128.5 mils.
- Square the diameter in mils to find the circular mil area: 128.5 mils * 128.5 mils = 16,512.25 circular mils.
- Round off the result to the nearest whole number: 16,512.25 circular mils = 16,510 circular mils.
- Note that this calculation is for a solid conductor. If the conductor is stranded, you will need to multiply the circular mil area of each strand by the number of strands to determine the total circular mil area of the conductor.
According to Table 8 in Chapter 9 of the National Electrical Code (NEC), the rounded value of 16,510 circular mils represents the circular mil area for one solid conductor.
