The 2026 National Electrical Code defines an equipment grounding conductor (EGC) as “A conductive path(s) that provides an effective ground-fault current path and connects normally non–current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.”

The EGC performs three important functions in the electrical safety system. The first is grounding. EGCs are intended to act as a conductive path that connects equipment to ground (the earth). The second function is bonding, and the third is to perform as an effective ground-fault path.

Section 250.118 provides the conductive materials and wiring methods that can be used as EGCs with feeders and branch circuits, which includes many more than just wire-type conductors. Section 250.118 provides a list of recognized EGCs that must be run with the circuit conductors. EGCs can be in various forms and are required to be any one or a combination of several types.

Electrical conduit and tubing are acceptable as EGCs according to 250.118. They are generally suitable as EGCs without a wire-type conductor being installed. Proper supports for wiring methods are directly related to maintaining the integrity of the effective ground-fault current path. Good workmanship is essential when installing EGCs of any type and form. 

Section 110.12 addresses mechanical execution of the work and requires electrical conductors and equipment to be installed in a professional and skillful manner. This general requirement also applies to EGCs installed with feeders and branch circuits. Where the wiring method, such as rigid metal conduit or electrical metallic tubing, is installed and serves as the required EGC, the installation must meet the provisions in 110.12.

Metallic tubing and conduit are suitable as EGCs, but it is important to consider the installations’ length. Long runs can affect EGC performance and overcurrent protective device (OCPD) operation. 

Often, wire-type EGCs are installed with feeders and branch circuits. Sections 300.3(B) and 250.134(2) provide important information about installing EGCs. One of the most important considerations is to keep the EGC as close to its associated ungrounded circuit conductors as possible. This keeps the impedance values at a minimum during normal operation and ground-fault conditions. 

Section 300.3(B) requires all conductors of the circuit, including any grounded conductor or EGC, to be run in the same raceway, cable or trench. When the circuit’s EGC is rigid metal conduit, intermediate metal conduit, electrical metallic tubing or any of the other raceway types mentioned in 250.118, the EGC is automatically run with the circuit conductors and is integral to the wiring method. Terminations of wire-type EGCs must be made up tight. Terminal lugs and equipment generally provide torque values for installers to attain the correct tightness of wire-type conductors. It is important not to under- or over-tighten electrical connections, so manufacturers provide specific torque values.

Sizing requirements for wire-type EGCs are found in 250.122 and Table 250.122 of the NEC. The minimum sizes provided in Table 250.122 are related to the conductor’s short time withstanding capabilities. 

An important note following Table 250.122 provides an appropriate reference to 250.4. This indicates the minimum size required for wire-type EGCs could be larger than the sizes provided in the table. The conductor sizes in Table 250.122 offer an approximate relation to the size of the OCPD given in the table. 

The I2t values (short-time rating or withstand rating) of the EGC sizes are generally between 13 and 28 times their nominal continuous rating based on 1A for every 42.25 circular mils of conductor. This value was used to develop the five-second withstand rating for insulated conductors. Using this formula, a five-second rating can be established for insulated conductors covered in the NEC. This proven conductor withstand formula was developed through extensive testing and data collection by the Insulated Cable Engineers Association (ICEA). The value of 42.25 circular mils is applicable to insulated conductors. The value is 29.1 circular mils for uninsulated conductors based on the findings of the ICEA. See the informational note following 240.4. 

Five seconds is a long time for any OCPD to open. Overcurrent protection typically operates in a few cycles or fractions of a cycle. The faster the OCPD operates, the more fault current the insulated conductor can safely carry without degradation or annealing. There are factors such as voltage drop and higher amounts of fault current in systems that could result in the EGC sizes in Table 250.122 being insufficient, in which case increased sizing is warranted.