Equipment grounding systems, which consist of interconnected networks of equipment grounding conductors, are used to perform the following functions:

1. Limit the hazard to personnel (shock voltage) from the noncurrent-carrying metal parts of equipment raceways and other conductor enclosures in case of ground faults, and

2. Safely conduct ground-fault current at sufficient magnitude for fast operation of the circuit overcurrent protection devices.

To ensure the performance of the above functions, equipment grounding conductors are required to:

1. Be permanent and continuous per NEC Sections 250-51, 250-75, 250-76, 250-77, 250-91, 300-10 and 300-12;

2. Have ample capacity to safely conduct ground-fault current likely to be imposed on them per NEC Table 250-94, Table 250-95, and Section 250-79(d) and (e); and

3. Have impedance sufficiently low to limit the voltage to ground to a safe magnitude and to facilitate the operation of the circuit overcurrent protection devices per NEC Sections 300-3(b) and 250-57(b).

1 See Appendix D, Reference Matrix.

4.4 BONDING

Caution shall be taken to ensure that the main bonding jumper and equipment bonding jumper are sized and selected correctly. Bonding completes the grounding circuit so that it is continuous. If a ground fault occurs, the fault current will flow and open the overcurrent protection devices. The means of bonding shall provide the following to ensure the grounding system is intact:

1. Provide a permanent connection,

2. Provide a positive continuity at all times, and

3. Provide ampacity to conduct fault current.

See Figure 4-1 on the proper grounding of electrical systems.

Figure 4-1. Circuit and system grounding consists of earth grounding the electrical system at the supply transformer and the line side of the service equipment. Equipment grounding and bonding is accomplished by connecting all metal enclosures and raceways together with the grounding conductors.