By: Jerry Durham, JADE Learning.
The terms Grounding and Bonding are found throughout the NEC text, and while they are seemingly interchangeable terms, they are actually two distinct procedures when it comes to the National Electrical Code, as well as the installation of electrical equipment.
The act of “grounding” (versus bonding) is so important, in fact, that the NEC Code-Making-Panel (CMP) had actually proposed to replace the term “grounding” altogether, so as to provide a different term that offered better clarification. Their proposal at that time was to replace the word grounding with the term “earthing”. This proposed change gained a lot of traction, but before the Code’s publication, the proposal was ultimately retracted.
What is grounding exactly? Let’s use the hint provided above, to deduce our answer. Knowing that the NEC Code-Making-Panel was considering replacing this term with the word “earthing”, gives us a very good indication of just what the term is trying to relay to us: to wit, “grounding” means to provide a conductive path for current to flow (in case of a fault condition), from the affected component, to the earth. We can now see why the term “earthing” nearly won the tug-of-war of terminology!
Let’s look at an example of grounding
An electrical panel is installed on the side of a residential dwelling, and there is a copper ground-rod driven into the earth below it. There is a bare, solid, copper No. 6 conductor attached to a lug within this electrical panel, and the other end of that No. 6 conductor is clamped onto the driven rod. This is an example of grounding. We have grounded this metal electrical panel by connecting it to the earth!
That now begs the question, “what is bonding?” Bonding is simply the act of mechanically connecting two or more conductive materials together to establish a conductive path between them. It is possible to “bond” components together without ever grounding them.
Let’s look at this real-world example of bonding
Let’s suppose I have three metal, 4-square junction boxes mounted on a non-conductive wooden wall, spaced 10’ apart. After finding out that we are completely out of EMT (metal thinwall) conduit on our jobsite, I decide to install a 10’ piece of PVC (plastic) conduit between these three metal boxes so that I can complete the job today. I then recall that my employer had specifically told me to bond all 4-square metal junction boxes on this job-site together. Initially, that was to be accomplished by using EMT (metal) conduit between these boxes. But I have changed material with the raceways that I have installed here.
We are aware that the PVC pipe that we have just installed between these boxes, being essentially plastic, is not a conductor, and therefore cannot serve to “bond” these three metal 4-square boxes together. But, if we run a green-colored insulated conductor between the three boxes, utilizing the PVC conduit as a raceway, and we then attach that conductor to the inside wall of each metal box with an approved green bonding screw, we have then successfully “bonded” these three metal boxes together. All of the metal boxes are now bonded together on this job.
So far, so good!
Bonding Vs. Grounding
But alas, we find out we have left out one critical step in our installation. Though we have indeed successfully bonded these three metal boxes together by connecting them all with the green-colored insulated conductor, we have not GROUNDED these three metal boxes. In other words, all of the boxes are connected to one another, but as a system, they are just “floating”; we have not yet introduced a path for current to flow from the metal boxes back to earth!
Understanding that dilemma is the point of this article. We want to help you understand that to “bond” components together, is not to ground them. The two terms are in no way interchangeable. Nor are the life-saving benefits gained from the act of grounding replicated by the mere act of bonding. These are two distinct procedures and both are essential when installing metal electrical enclosures and boxes within any electrical system.
To learn more about grounding and bonding, sign up for a JADE Learning electrical continuing education course.