March 21, 2024 – We have used the terms bonding and grounding interchangeably in the CE Code for systems under 1000V for many years; not surprisingly, this causes confusion and a lack of understanding as to the difference between the two.

Grounding is one of the most important aspects of electrical or electronic system design, yet the practice remains largely misunderstood by many engineers and electricians.

Let’s take a closer look at grounding and bonding, and use some examples to help bring clarity to the confusion.

Grounding is the intentional connection to earth (or common reference) through a grounding electrode for the purposes of stabilizing the electrical system and creating a safety ground (which is equipotential to the location of the system).

Bonding is the permanent and continuous conductive path to the source grounding connection, with sufficient ampacity to carry any current imposed upon it back to the source. This facilitates the operation of the protective devices in the circuit and ensures equipotentiality within the system.

(Equipotentiality is the state in which conductive parts are at an equal electrical potential.)

Through these definitions, we can see that two purposes for grounding are to:

• ensure safety of persons and property from electric shock and fire by creating a stabilized system, referenced to the earth, and
• ensure that the system is at the same potential, whether under a fault condition or a lightning strike.

Two purposes of bonding are to:

• protect persons and property from shock or fire by ensuring equipotentiality of the system, and
• provide a path that is sufficient to conduct a potential fault back to its source, thereby facilitating the operation of overcurrent devices.

With these definitions and examples, we begin to understand how grounding and bonding fit within our electrical systems.

But what about this equipotentiality thing I keep talking about, and what does it have to do with grounding or bonding? When we have metallic parts that are not bonded together, there is the possibility of a potential (electrical) difference between two parts.

Think of a receptacle and the two metal connections within. If the Hot side were to energize a piece of metal that had no reference to the source, then it would simply remain energized (potential). Were you to then touch that piece of metal while at the same time touching something that was bonded back to the source, you would be shocked, or possibly even electrocuted.

By bonding the piece of metal, we create a substantially equal electrical potential. This prevents that piece of metal from maintaining an unsafe potential that may injure or kill someone, and facilitates the operation of our overcurrent protective devices should that piece become energized.

When a facility is large, or there are multiple buildings spread over a large area, how do we ensure that the earth upon which this structure(s) is situated is at the same potential as the service feeding the site?

One way is equipotential grounding. Here, we install a grounding electrode connected only to the system bond, which effectively ensures that the earth at the next building (or some far-flung corner of a large facility) is at a substantially equal potential to the main service—wherever it may be.

On a farm, equipotential grounding can help mitigate tingle voltage issues. In the case of a lightning event, it can help dissipate that potential energy over a larger area. In both cases, we are providing a system that helps protect people and property from shock and fire hazards.

In short:

• Bonding is the method
• Equipotentiality is the goal

Now, if we could just change the language within the trade—so that we only speak of grounding when we are actually setting our reference, and everywhere else we speak of bonding (to ground)—we would have a lot more clarity in our discussions.

David Pilon is manager, Electrical Inspections, at Technical Safety Authority, Saskatchewan (TSASK). He also serves as vice-chair of the Canadian Certified Electrical Inspector (CCEI) committee of the International Association of Electrical Inspectors (IAEI), Canadian Section.

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