A supplemental grounding electrode is a grounding electrode used to "back-up" a metal water pipe grounding electrode.

Question

Quizplus · Accepted Answer

A supplemental grounding electrode may be required by the National Electrical Code (NEC) to provide additional grounding for a building or structure. If a metal water pipe is used as the grounding electrode, a supplemental grounding electrode can be installed to provide a redundant grounding path in case the water pipe fails or is no longer used as a grounding electrode. This can include installation of a ground rod, plate or other type of grounding electrode.

A Supplemental Grounding Electrode Is a Grounding Electrode Used to "Back-Up