Lightning Protection & Grounding Systems

Equipotential Bonding Bars. Surely you have seen them before but do you know exactly what are they and what are they used for?

Along this post we will talk about this basic and very important piece of the grounding and the bounding system.

Also, we will talk about the importance of grounding and bonding for people and equipment safety, and for lightning protection.

What is an Equipotential Bonding Bar?

The most popular bonding product in use today is the ground bar or bonding bar. The equipotential bonding bars provide a convenient, single-point grounding and bonding location.

It's a metal structure which has a different number of connection possibilities. These bars are normally installed in a registry box, or fixed directly to a wall.

The bars come with holes and bolts where cables are fixed.

Manufacturers normally makes them in metals like copper or stainless steel.

In the market you can find simple equipotential bonding bars but also isolated or built with insulators. Sometimes it is necessary to have a grounding connection collector element, or a grounding connection distributor that remains isolated from the structure on which it is mounted.

What is the main purpose of equipotential bonding and how does it work?

Equipotential bonding is a very important measure for reducing the risk of personal injury (like an electric shock), or of damage to the equipment.

Bonding requires joining together all metalwork and conductive components that are or may be grounded so that it is at the same potential (voltage) everywhere. 

For example, if a component failure occurs, all circuits and conductors in a bonded area will have "the same electrical potential". In this case, a person cannot touch two objects with significantly different potentials. 

Even when connection to a distant earth ground is lost, people are safe from dangerous potential differences. These potential differences can cause injuries or death from electric shock.

What is the difference between grounding and bonding?

The purpose of grounding is “to limit the duration of voltages”. On the other hand, the intention of bonding is “to limit the magnitude of voltages”.

The danger of electric shock due to indirect contact arises from the following voltages which may occur under ground fault conditions in an installation:

  1. 1
    Voltages between exposed conductive materials and other exposed conductive materials.
  2. 2
    Voltages between peripheral conductive materials and other peripheral conductive materials.
  3. 3
    Voltages between exposed conductive materials and peripheral conductive materials.
  4. 4
    Voltages between exposed conductive materials and Earth, or peripheral conductive materials and Earth.

As mentioned before, the purpose of grounding, where used for protective purposes within a building or other facility, is to limit the duration of the voltages in the above examples.

To achieve this, you have the operation of a protective device (such as a fuse or circuit-breaker) under ground fault conditions, which removes the voltages by causing an automatic disconnection of the supply to the faulty circuit.

Without an adequate grounding system in place, the protective device could not operate as required under ground fault conditions. 

In contrast, the purpose of bonding is to limit the magnitude of the voltages in examples 1, 2 and 3 above. This is achieved by electrically connecting (bonding) those conductive parts.

Equipotential bonding is done from the switchboard (also known as the fuse box, breaker box, or distribution board) to incoming water and gas services. 

It is also done in bathrooms where all exposed metal that leaves the bathroom (including metal pipes and the earths of electrical circuits) must be bonded together to ensure that they are always at the same potential. 

Isolated conductive objects (including metal fittings fed by plastic pipe) do not need to be bonded.

The "ying and yang" of an electrical protection system.

Grounding and bonding are an integral part of any modern electrical protection system. 

Furthermore, these systems are crucial in ensuring people safety at home or in a commercial or industrial installations. These systems also provide reliable protection for vital equipment and to minimise interruptions of service and costly down time.

What is lightning equipotential bonding?

The purpose of a lightning protection system is to discharge lightning currents and to distribute them in the ground. 

The way to minimise dangerous potential differences between all electrical equipment in the inner lighting protection zone is to install a low-impedance equipotential bonding network.  

In addition, the integration of the grounding system in the equipotential bonding system does not only ensure low impedance, but also an increased current carrying capability of the equipotential bonding network to be established.

An intermeshed equipotential bonding network can achieve these goals. To this end, all conductive parts of the structure and the internal system are integrated in this network and all metal parts or conductive lines at the boundaries of each LPZ (lightning protection zone) are connected directly or via adequate surge protective devices.

Is grounding and bonding a legal requirement in the United States?

Yes, it is. 

Article 250 is a foundational pillar of the NEC (National Electrical Code). Section 250.4 states the general requirements for grounding and bonding of electrical systems for both grounded and ungrounded systems.

For grounded systems, the NEC requires you to perform all of the following:

One, electrical system grounding.

Two, electrical equipment grounding.

Three, electrical equipment bounding.

Four, bonding of electrically conductive materials.

The NEC requires the same actions  for ungrounded systems, except for electrical system grounding. 

By implementing these NEC requirements, you are creating an effective ground-fault current path, which is the desired end goal.


To sum up, grounding and bonding are not the same thing. However, they do work closely together in a yin and yang relationship to help ensure safety in electrical systems.

The equipotential bonding bar is the ideal solution for shunts or multiple connections to different equipment in the installation of a grounding network.


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