Home Service Grounding Electrodes
- Aluminum has a tendency to corrode and should not be used in ground wires unless they are insulated. Moisture and mineral salts from masonry are common causes of corrosion to uninsulated aluminum. It is also a poorer conductor than copper. Aluminum wires in grounding systems are not permitted in Canada.
- Since grounding electrodes are not insulated, they can never be made of aluminum.
- If more than one electrode is present, they must be connected to each other with a bonding jumper.
Common Types of Grounding Electrodes Grounding Rods
- Rust at the rod’s top. Grounding rods have a corrosion-resistant coating but are usually made of steel or iron and are vulnerable to rusting at any location that the rod is cut.
- Most rods have an etched label on their top. If this label is missing it is likely that the rod has been cut.
Inspectors should bear in mind that utility companies sometimes allow ground rods to be shortened. A qualified electrician can test whether a shortened rod is an adequate grounding electrode.
If accessible, inspectors should check the condition of the clamp that connects the grounding rod to the ground wire. Clamps should be made of bronze or copper and be tightly fastened. Requirements for rod length, thickness, and protective coating are addressed in the 2006 International Residential Code (IRC) as follows:
- Electrodes of pipe or conduit shall be not smaller than trade size ¾ (metric designator 21) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
- Electrodes of rods of iron or steel shall be at least 5/8 inch (15.9 mm) in diameter. Stainless steel rods less than 5/8 inch (15.9mm) in diameter, nonferrous rods or their equivalent shall be listed and shall be not less than 1⁄2 inch (12.7mm) in diameter.
- Although the 2006 IRC does not mention whether the rod may be driven at an angle, the 1998 California Electrical Code allows for a maximum oblique angle of 45 degrees from the vertical.
- An electrician can install two grounding rods if necessary. They should be at least 6 feet apart from one another.
- In Canada, grounding rods should be 10 feet long and two are required.
Concrete-Encased Electrodes (Ufer Grounds)
- Ground wires should be firmly attached to water pipes close to the point of entry to the building. A ground wire that is loosely tied around a pipe is inadequate.
- Gas pipes should never be used as grounding conductors. They usually are made of plastic at the exterior of the home and carry flammable gases that may ignite if exposed to electrical current.
The 2006 IRC states the following about water pipe electrodes:
A metal underground water pipe that is in direct contact with the earth for 10 feet (3048 mm) or more, including any well casing effectively bonded to the pipe and that is electrically continuous by bonding around insulating joints or insulating pipe to the points of connection of the grounding electrode conductor and the bonding conductors, shall be considered as a grounding electrode. Interior metal water piping located more than 5 feet (1524 mm) from the entrance to the building shall not be used as part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.