Earthing and Bonding for EV Chargers

In recent years, Ireland's electric vehicle charging capacity has experienced exponential growth. Approximately 80% of EV charging activities within the state occur at home, emphasizing the imperative for homeowners to be well-versed in proper installation procedures and associated safety protocols.

At Wattcharger, we take pride in providing comprehensive information on sustainable technologies. With various programs in place, an increasing number of households are opting for home charging infrastructure. However, as we delve into the subject, it becomes evident that a home charging setup involves more complexity than meets the eye.

While "bonding" may not be frequently used, it represents a critical aspect of EV installation. Intended to mitigate the risks of electric shocks and fires, bonding involves employing a connective bonding connector on all exposed metallic items. Ensuring proper bonding on conductive objects like pipes and wires neutralizes the impact of renegade electricity. Additionally, earth rods serve as a primary means to responsibly eliminate any potentially harmful elements.

Similar to many other appliances, EV chargers bear a substantial electrical load. Without adherence to proper bonding practices, this load may inadvertently transfer to conducive elements within households. Consequently, the use of bonding connectors can significantly reduce the power load, mitigating the potential for harmful shocks.

When deciding to install an electric vehicle charger, the inclusion of proper earthing and bonding apparatus is imperative. To guarantee this, a certified electrician must take the lead. This ensures that your system complies with regulations and can divert potential shock threats away from areas where harm could occur.

Today, we will delve into the concepts of bonding and earthing, exploring their safety implications. Ensuring adherence to both practices will contribute to the best possible home EV charging experience.

Earthing and Bonding Features in the EV Charger System


At its most basic level, an EV charger serves as interface equipment connecting an electric vehicle's battery to an electricity source, facilitating the drawing of power to recharge the battery. EV chargers typically utilize either Alternating Current (AC) or Direct Current (DC) output technology. While DC is generally more potent, both output types can generate hazardous currents if power management is inadequate.

Given that EV chargers introduce an additional load to a property's existing capacity, it is crucial to ensure the current system can accommodate the incremental demand. Failure to assess the output capabilities of your home could lead to severe consequences. Therefore, employing a qualified installer becomes imperative.

Even with properly installed EV chargers, the potential for dangerous voltage exists, especially when the energy output surpasses the system's capacity. However, using earth rods allows the redirection of this hazardous flow away from exposed conductors, guiding it into the earth.

This precautionary measure, known as Earthing, involves diverting excess energy into the ground using earth rods. Within the realm of EV earthing, distinctions arise. TN-C-S signifies an earthing system where a single source of supply is connected to the earth at one or more points, with the N denoting the presence of a protective conductor at other exposed conductive parts of the installation. The C-S letters imply that the protective and neutral conductors are connected in the supply, and the TN-C-S supply source is integrated into the supply rather than the installation.

Protective multiple earthing (PME) aims to connect the conductor to the earth at multiple points, both in the supply and the source itself. This configuration provides multiple low-resistance points for diverting possibly dangerous excess power away from conductive elements into the ground. The excess power is then directed to long copper Earth Rods, which disperse it into the Earth, where it is absorbed and neutralized. The electrical shedding for earthing occurs in the consumer unit, also known as the "fuse box," serving as the control center for the electrical system and managing the distribution of both usable and expelled energy.

While sharing some broad similarities, bonding provides a different method of protecting homes against dangerous electrical surges. Particularly relevant in older homes, bonding safeguards against electrical faults that could energize metallic objects, making them "live." This practice involves "leveling" the electrical potential of various conductors, ensuring no dangerous current exists attempting to spread.

Equipotential bonding seeks to maintain a balance between exposed and extraneous conductors, preventing internal faults from jumping to other exposed elements. For example, equipotential bonding on a faulty dishwasher prevents touch voltage from reaching the outer surface, averting potential dangers. The purpose of the bonding system is to contain stray electrical currents that can cause voltage differences between two conductors. In the case of EV chargers, these stray currents can lead to internal wire corrosion, potentially damaging or rendering the entire charger unusable.

Earth Bonding for EV Charging Points


Whenever a new electrical demand is introduced to your system, it is essential to implement proper earthing and bonding measures. This applies to EVs as well, and compliance with legal requirements mandates the incorporation of earthing and bonding as integral components of the installation process.

If the home features metal pipes, it is advisable to run yellow and green bonding cable clamps from the charger back to the consumer unit. These clamps should connect to a main earthing terminal at the consumer unit, preventing faults from traveling up the pipes and ensuring automatic and reliable shedding of potential issues.

In certain scenarios, EV chargers may not be directly connected to the fuse box to mitigate the harmful effects of excess energy. Instead, these models typically rely on an earth electrode. Earth electrodes, usually copper or steel rods, extend directly from the EV charger.

The charge can travel from the charger's earthing terminal to the earth electrode through clamps, commonly known as earthing conductors. It is crucial to set these clamps to carry a maximum electrical current to the earthing electrode if necessary.

During the installation of these conductors, it is imperative not to use material compositions such as aluminum and copper that may corrode each other. Corrosion can hinder the charger's earthing ability, potentially leading to electrical fires. Therefore, careful consideration of material compatibility is essential to ensure the effective functioning and safety of the EV charger's earthing system.

Installation and Protection for Electric Vehicle Chargers


When the decision is made to install an electric vehicle charger on your property, two crucial considerations are bonding and earthing. To initiate the process, the homeowner must notify the Distribution Network Operator (DNO) of their intent to install a new connection to the local LV network. For points with maximum loads exceeding 60A, DNO approval is mandatory before commencing any work.

Due to the high currents drawn by EV chargers over extended periods, the proper implementation of bonding, earthing, and other protective measures is imperative, leading to the mandated use of Residual Current Devices (RCDs).

Residual Current Devices (RCDs) measure the current between an in-use circuit and a neutral wire. Any deviations between the two can result in a harmful rogue current, capable of passing through a person. Upon detecting a fault, RCDs cut the flow to the neutral wire, redirecting the electrical flow toward the earthing terminal. Among the various RCD types, Type A RCDs are the most common, handling currents of up to 6mA and effectively managing sinusoidal residual currents and pulsating direct currents.

Bonding is crucial to ensure that all parts of the electrical system are equipped to carry an equal load. This involves bonding conductors to metal, preventing the concentration of electric force in one place. During installation, the installer will inspect the home's pipes for existing bonding connectors and install new ones if necessary.

In addition to preventing dangerous electricity flows, RCDs offer protection against electrical arcing, leading to dangerously high temperatures, and water ingress, which has the potential to severely damage the electrical system.

For TN-C-S earthing configurations, a 16mm copper conductor connects the conductor to the EV's main earthing terminal. Ensuring the compatibility of materials used is of utmost importance. The earth rod, typically extending 2-3 meters into the ground, is a critical component of this configuration.

Some EV chargers like The Zappi may come with a protective earthed neutral (PEN) conductor, combining the functions of providing both neutral and protective earth conductors. PENs can either be separated from the line conductors or combined with a multi-core cable consisting of several conductors.

Rules and Regulations for EV Charger Earthing and Bonding


It is essential to comply with a set of rules and regulations when addressing matters of earthing and bonding for your EV charger system.

The Institute for Engineering and Technology outlined its Requirements for Electrical Installations (IET Wiring Regulations, 18th Edition) in 2020. This regulatory framework aims to enhance safety measures regarding the wiring of EV chargers, introducing the concept of a "TT Island." According to this practice, all exposed and extraneous conductive materials must be connected to a common earth electrode. By incorporating the earth fault loop in both the source and installation electrodes, the system ensures that the earth fault current remains below a threatening level. The use of an RCD is integral to this process.

In the T-C-NS earthing system, protective conductors may need to carry "neutral diverted currents." Using Steel Wired Armor (SWA) cables as the sole means to offset energy can be hazardous, as they might become overheated. It is advised against relying on SWAs as the primary protective bonding connector, as they can dangerously overheat without an additional non-conductive element in the bonding setup.

The IET's Standard BS 7671 mandates proper bonding of all gas and water pipes. Due to their metallic properties, these pipes can become overheated and charged when encountering a wayward electric current. However, the rule does not apply to plastic piping arrangements. Homeowners should inspect gas meters for a yellow or green cable attached to a nearby copper rod to ensure proper bonding. This check should be performed in other "hot zones" on the property, such as near the water heater and under the kitchen sink.

Verification of the existence of bonding connectors is necessary before any work commences. If none are identified by the licensed electrical installer, they must be installed, typically incurring an additional cost.

Earthing and bonding are integral components of the EV charging strategy, though not always apparent. Despite their technical nature, these technologies play a crucial role in safely offloading dangerous currents and electrical faults.

At Wattcharger, we believe in providing comprehensive information about exciting renewable technologies, including the technical aspects of earthing and bonding. If you are considering installing your own EV charger or want to learn more, feel free to reach out to our expert team using the tool below.


Blog Author: Adrian Dorney