Common Grounding Issues – Part 1

Electrical grounding and bonding are important parts of any electrical 
system. And, they can be somewhat confusing. When it comes to electronic
 equipment, manufacturers often include instructions to protect their 
equipment. But, sometimes it compromises the integrity of the overall 
system. BURNDY, a Hubbell Company

Steve Maurer, IME

Electrical grounding and bonding are important parts of any electrical system. And, they can be somewhat confusing. When it comes to electronic equipment, manufacturers often include instructions to protect their equipment. But, sometimes it compromises the integrity of the overall system.

According to many sources, the regulations on grounding and bonding in Article 250 of the NEC® can be confusing, to say the least. Realizing that, I want to make a disclaimer here. Don't take this information and use it for your electrical grounding bible. My recommendation is that you consult an engineer for complex projects.

Grounding electrodes
Grounding can be divided into two areas or realms:
  • Below-grade or buried, also called earthing.
  • Above-grade grounding.
Below-grade grounding is covered in one section of Article 250. While consisting primarily or even solely of a grounding electrode, there are several schools of thought on what comprises the best electrode. The Code recognizes seven types of electrodes. Five of the most common are:
  • Water pipe, although most authorities don't recommend it as an electrode.
  • Building steel, if it is properly bonded to the concrete foundation with steel rebar. However, building steel is better regarded as a grounding conductor, not an electrode.
  • Ground rings, usually encircling the entire structure.
  • Ground rods, copper-encased steel rods.
  • Ground plates, thin copper plates that are buried at least 30 inches below grade level.
There are others, but these five are the most common. Water pipe as ground is falling out of favor rapidly for several reasons. First, the utility companies often coat metal pipes with a corrosion-resistant coating. This negates the grounding properties of the steel or copper pipe.

Secondly, many are being replaced with nonmetallic materials such as plastic. A third reason is that when used, the connections are often made improperly, many times as code violations. Pipe should be considered more as something that must be bonded, rather than as a grounding electrode.
Grounding rings are gaining popularity with engineers and governing agencies. But, perhaps the most commonly used electrodes are grounding rods. There are several things to consider when using grounding rods.

One final consideration is that the neutral or ungrounded conductor of the system must be bonded to the earth ground, normally by bonding to the cabinet. However, this bonding connection is only to be made at the first disconnect. Downstream cabinets contain derived circuits and the neutral and ground should not be bonded at those locations.


Photo courtesy of BURNDY, a Hubbell Company