All questions and answers are based on the 2017 NEC.
Q. If more than one electrode is available, what does the Code allow for connecting one grounding electrode to another electrode?
A. Grounding electrode conductors (GECs). GECs and bonding jumpers are permitted to terminate and use the following to extend the connection to another electrode(s) [250.68(C)]:
(1) Interior metal water piping that’s electrically continuous with a metal underground water pipe electrode and is located not more than 5 ft from the point of entrance to the building can be used to extend the connection to electrodes. Interior metal water piping located more than 5 ft from the point of entrance to the building isn’t permitted to be used as a conductor to interconnect electrodes of the grounding electrode system (Fig. 1).
(2) The metal structural frame of a building can be used as a conductor to interconnect electrodes that are part of the grounding electrode system, or as a grounding electrode conductor. Hold‑down bolts securing the structural steel column to a concrete‑encased electrode [250.52(A)(3)] can connect the metal structural frame of a building to the concrete‑encased grounding electrode. The hold‑down bolts must be connected to the concrete‑encased electrode by welding, exothermic welding, the usual steel tie wires, or other approved means (Fig 2).
(3) A rebar‑type concrete‑encased electrode [250.52(A)(3)] with an additional rebar section to an accessible location above the concrete, where not in contact with the earth or subject to corrosion, can be used for the connection of the grounding electrode conductors and bonding jumpers.
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