b. In cable, such as nonmetallic sheathed cable, ground conductors can be built-in (Figure 2-8).
Request cable with a ground conductor if you need a ground conductor. You do not need to worry about
the size of the ground conductor in cable. However, when you pull conductors in conduit, you must
select the proper size of ground conductor.
Figure 2-8. Cable with built-in ground conductor
c. The size of electrical conductors is expressed in American wire gauge (AWG). The gauge
refers to the diameter of the conductor. In house (interior) wiring, the minimum size conductor allowed
is No. 14 AWG. Using the AWG designation, the smaller the number, the larger the size or diameter of
the conductor. For example, a No. 8 AWG conductor is larger in diameter than a No. 10 AWG
conductor. Once the AWG size reaches 4/0 (spoken as 4 aught), the next larger conductor is 250
thousand circular mills (kcmil). At this point, the AWG designation reverses and the larger the number,
the larger the conductor.
NOTE: If the exact amperage is not shown in the appropriate table, always go to the next larger
size conductor for safety.
d. Use Table 2-2, page 2-5, and Table 2-3, page 2-8, to see the difference in conductor size
between a current-carrying conductor and a ground conductor. A No. 8 moisture-resistant, thermal-
plastic copper conductor can carry 40 amperes (Table 2-3); however, a ground conductor for a 40-
ampere circuit must be No. 10 copper (Table 2-2). In large cables and conduit where individual
conductors are used, the ground conductor or conductors are smaller than the current-carrying
conductors.
2-7
EN5144
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