Here are some quick tips for inspecting rod and pipe electrodes. As a home inspector college (internachi.edu), we continually review and revise our curriculum. And we’ve updated some training content within the free, online How to Perform Residential Electrical Inspections Course with the following inspection tips that you might be interested in using during your next home inspection:
- Rod and pipe electrodes must be at least 8 feet in length to be considered a grounding electrode.
- Grounding electrodes of pipe or conduit must be at least 3/4-inch (metric designator 21) and, if made of iron or steel, must have its outer surface galvanized or metal-coated for corrosion protection.
- Rod-type grounding electrodes of stainless steel and copper or zinc-coated steel must be at least 5/8-inch in diameter unless listed.
- The rod and pipe electrodes must be installed so that at least 8 feet of length is in direct contact with soil. They should be driven at least 8 feet into the ground. They could be driven at an angle not to exceed 45 degrees from vertical or buried in a trench at least 30 inches deep.
- The upper end of the electrode should be flush with the ground or just below ground level so that the end and attachment are protected from damage.
Pipe electrodes are rarely used today. The most common electrode is a listed 5/8-inch (15.9 mm) copper-coated steel rod.
If a micrometer or similar device is not available, a home inspector shouldn’t guess on the rod diameter. If visible, you may be able to confirm by looking at the listing marks which may indicate that the rod complies with the diameter requirements of the National Electric Code (NEC). Listing agencies CSA, ETL, MET, and UL, will mark rods that are greater than ½ inch in diameter and that have the correct minimum amount of coating.
Image: The Home Depot, 6258 8-foot grounding rod.
The listing mark must be stamped in the top foot of the rod. If you’re inspecting a new home under construction, you may want to ask the contractor to leave a shovel full of dirt away from the rod with the listed marking showing. This is one way to check the rod
According to the Home Inspection Standards of Practice, a home inspector is required to inspect the service grounding.
You may be interested in watching a recent InterNACHI Webinar on the ICC residential code flashcards.
Reference: 2018 IRC E3608.1.4 and NEC 250.52(A)(5).