National Electrical Installation Standards

Standards as High as Your Own

Monday, April 26, 2021



I appreciate your forum. My question is if a THHN copper conductor is used for a Grounding Electrode Conductor, does it need to be installed in one of the wiring methods from Chapter 3 as addressed in Section 300.3(A) since THHN is specified in Table 310.104(A)?

Dale Earixson



Hi Dale,

Thanks for the question. First, the conductor in question is a grounding electrode conductor, which does not carry current in normal operation. Article 310 would not need to be applied. Section 300.3(A) explains that single conductors specified in 310.104(A) shall only be installed where part of a recognized wiring method in Chapter 3. Again this applies to general wiring and wiring methods. Article 250 contains the specific rules related to installation of grounding electrode conductors. See Section 250.64(A) through (A) through (F). According to Section 250.62 the grounding electrode conductor can be solid, stranded, insulated covered or bare.  If a conduit is used to contain a grounding electrode conductor, it is typically for physical protection as may be required by 250.64(B). Section 250.64(B)(2) indicates the types of conduit or tubing that that shall be used for protecting sizes  6 AWG and larger, and Section 250.64(B)(3) indicates the types of conduit or tubing that shall be used for protection of sizes smaller than 6 AWG. Hope this is helpful.

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