When installing an EV home charging station, the standard practice used to be to install an earth rod to protect from danger if something goes wrong. In recent years, technology has moved on and earth rods are not always necessary for EV chargers, so let’s take a look at this topic in more depth.
Do you need an earth rod for an EV charger?
An earth rod is no longer required for the installation of an EV charger. If the charger has a built-in earthing system, the need for an external earth rod is eliminated. This shift occurred with the update in the IET wiring regulations in 2020.
However, when your EV charger doesn’t possess built-in earthing, an external earth rod is likely necessary to ensure safe operation. As such, it is essential to understand the specific requirements and capabilities of your chosen EV charger model before installation.
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What is an earth rod?
An earth rod, also known as a ground rod, is a long rod made of conductive material like copper or galvanized steel. It is typically driven deep into the ground to establish an electrical connection with the earth.
The purpose of the earth rod is to provide a pathway for electrical energy to disperse in the event of a fault, like a short circuit or a lightning strike. This process is called “grounding” or “earthing,” and it helps protect people and electrical devices from potentially dangerous electrical surges.
In the context of electrical installations such as EV charging systems, an earth rod is often used to create a safety path for electricity if a fault occurs in the system. This helps prevent any electrical shocks that could occur from touching the equipment when a fault is present.
What is an earth rod used for?
An earth rod is a critical part of the safety measures in an electrical system, protecting both people and equipment from potential electrical hazards. Here are some specifics about what an earth rod is used for:
- Electrical Safety
The primary purpose of an earth rod is to protect people from electric shocks! If a fault occurs in an electrical system (like a short circuit), the earth rod provides a pathway for the electrical energy to disperse into the ground. This reduces the risk of electrical shock when touching the electrical equipment. - Protecting Electrical Equipment
Earth rods can also help prevent damage to electrical appliances and systems from electrical surges. For example, during a lightning strike or power surge, the excess electrical energy is directed safely into the ground via the earth rod, protecting the electrical devices connected to the system. - Stabilising Voltage
Grounding helps stabilise voltage levels in an electrical system. This ensures that they pair chargers with EVs correctly and safely.
What are the earth rod regulations?
The specific regulations for the installation of earth rods in the UK are primarily outlined in the IET Wiring Regulations (BS 7671). These regulations cover a wide range of requirements for electrical installations, including earthing.
The regulations state a number of key points regarding the approach to earth rods:
- Earth rods should be installed in a manner that ensures a good, low-resistance electrical connection with the ground. The specific depth may vary based on soil conditions and moisture levels.
- It is recommended that earth rods be installed vertically. If this isn’t possible, they can be installed at an angle, but this should not be more than 45 degrees from the vertical.
- Earth rods should be made of corrosion-resistant conductive material. Typically, these are made from copper or zinc-coated steel.
- In a TT system, the resistance to earth of the earth rod typically should not exceed 200 ohms. This value ensures prompt operation of circuit protection measures in case of a fault.
What size earth cable do you need for an earth rod?
In the UK, the size of the earth cable used for an earth rod is typically determined by regulations in the BS 7671:2018 IET Wiring Regulations. These regulations consider various factors including the type of earthing system and the size of the main supply.
According to the BS 7671:2018 regulations a typical domestic installation with a TN-S or TN-C-S supply, where the main earthing conductor is connected to the MET (Main Earthing Terminal), a 16mm² copper conductor is often used.
However, when it comes to connecting an earth rod, the minimum size is usually 10mm² for a copper conductor. This could be increased based on the specifics of the installation or local regulations.
How deep should an earth rod be?
Generally, in many cases, earth rods are driven at least 8 feet (approximately 2.4 meters) into the ground but it can vary based on site-specific conditions. British Standard BS 7430 (Code of Practice for protective earthing of electrical installations) provides a general guide on this but doesn’t specify an exact depth. The depth may be determined by the reading on an earth loop impedance tester, with the objective of obtaining a low resistance to earth.
It’s always best to consult with a qualified electrician or an accredited EV charger installer. They can carry out the necessary tests and advise on the correct depth for your specific situation.
Which EV chargers can you install without an earth rod?
Thanks to technology, you now have alternatives to using an earth rod for your EV charger. Most modern EV chargers are designed with a built-in earthing protection mechanism, which can eliminate the need for a separate earth rod.
Some of the latest charging stations even have systems built into the unit that will continuously monitor your electric car’s voltage conditions. Because of this, once the voltage exceeds a certain number, the charge automatically stops operating and will isolate from the EV itself. Even better, it does this even if the charger is off, which means the fault state will remain as it is until you manually reset it. Smart EV chargers will also send diagnostic information about the faults via Wi-Fi.
To find out if your EV charger needs an earth rod, you need to know if it has a PEN conductor or not.
What is a PEN conductor?
A PEN conductor refers to the combined Protective Earth and Neutral conductor used in certain electrical systems, particularly in the UK. The PEN conductor in an EV charger serves the dual purpose of providing both the neutral current return path and the protective earth connection.
When an EV charger is connected to a supply the PEN conductor is responsible for carrying both the neutral current and providing the protective earth connection.
If an EV charger has a PEN conductor it typically does not require an additional earth rod.
The trend now is for companies to develop an “all-in-one” product that already has built-in earthing, which renders the earth rod unnecessary.
The final word on earth rods and EV chargers
Prior to 2020 earth rods were sometimes needed when you bought an EV charger, but that is no longer the case. Thanks to both updated technology and newer regulations, you can now purchase chargers without having to install an earth rod first.
If the EV charger is designed with a PEN conductor and connected to a TN-C-S electrical supply, it typically does not require an additional earth rod. The PEN conductor serves both the neutral and protective earth functions, eliminating the need for a separate grounding rod.
It is critical to check the specifications of the charger you plan to install to determine if it has built-in earthing or not. Speak to the installation company, they will assess the needs of your individual property and offer a proper assessment for safety and peace of mind. They can provide expert guidance tailored to your situation and ensure that the grounding measures are properly implemented for the safe and effective operation of your EV charger.
Safety is paramount when it comes to complex electrical installations such as EV chargers so always get expert guidance to find out if you need an earth rod or not.
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John is the Editor and Spokesperson for Electric Car Guide.
With over 20 years of writing experience, he has written for titles such as City AM, FE News and NerdWallet.com, covering various automotive and personal finance topics.
John’s market commentary has been covered by the likes of The Express, The Independent, Yahoo Finance and The Evening Standard.
