a.   Table 2-2, shows the minimum size ground conductor that can be used for grounding equipment or raceways. Each ground conductor in the table has the capacity to safely carry the current required to blow a fuse or trip a circuit breaker (Figure 2-7).

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.

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.

d.   Use Table 2-2, andTable 2-3, 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.