Installing an electric vehicle charger is usually straightforward, but the earthing arrangement at your home must be checked before work begins. This is particularly important in Redhill, Reigate, Merstham, Earlswood, Meadvale, Nutfield and Salfords, where many properties have a PME supply.
You may be told that your charger needs an earth rod, a PEN fault detection device, or a dedicated protective device. This does not necessarily mean there is anything wrong with your home’s electrics. It usually means the installation needs an additional safety measure because of the way the electricity supply is earthed.
If you are arranging EV charger installation Surrey, the correct solution depends on your property, the charger selected and where the charging point will be installed.
What is PME earthing?
PME stands for Protective Multiple Earthing. It is the earthing arrangement normally associated with a TN-C-S electricity supply.
Most UK homes use a PME/TN-C-S supply, including the majority of properties in Redhill and Reigate. Some homes instead have a TN-S supply, while others have a TT earthing arrangement. These systems can look similar to a homeowner, but they behave differently during certain electrical faults.
With a PME supply, the electricity network uses a combined protective earth and neutral conductor, known as a PEN conductor, for part of the supply route. At the property, the neutral and protective earth are separated at the main earthing terminal.
This arrangement is safe for normal household electrical use. However, a particular risk must be considered when a metal-bodied electric vehicle is connected to an outdoor charge point.
Why can a PME supply affect an outdoor EV charger?
The risk being managed is a broken or disconnected PEN conductor upstream of the property. This is sometimes called an open-PEN or neutral-loss fault.
If this happens, the protective earth at the property can rise to a dangerous voltage relative to the ground outside. If an electric vehicle is connected to a charger at the time, the vehicle body could also become raised to a dangerous voltage.
That creates a potential shock risk for someone standing outdoors and touching the vehicle or charger while also making contact with the ground or another conductive object.
This is why BS 7671 Regulation 722.411.4.1 restricts the use of the PME earthing facility for an outdoor EV charge point unless one of the permitted protective measures is used.
The regulation is not intended to make EV charging unnecessarily complicated. It ensures the charging installation remains safe even if a rare fault occurs on the upstream electricity network.
Does the charger location make a difference?
Yes. A charge point installed inside a garage or integral building may be assessed differently from one mounted outdoors on a driveway wall.
The intended use and layout matter too. For example, a charger inside a garage may still need careful consideration if the vehicle is normally parked outside and the charging cable passes through an opening.
An outdoor charger on a driveway, wall or detached garage is more directly exposed to the situation addressed by Regulation 722.411.4.1. The installer must assess the actual arrangement rather than apply a standard answer to every property.
The main solutions used by electricians
There are several permitted ways to provide the required protection. The two most common approaches for domestic installations are an earth electrode or PEN fault detection.
1. An earth electrode or earth rod
One option is to install an earth electrode, commonly called an earth rod, connected to the property’s main earthing terminal.
For a PME installation, the rod is not simply an isolated earth for the charger. It is part of the wider protective arrangement and must be designed and tested correctly. The electrode must help ensure that the voltage between the main earthing terminal and true Earth remains within the permitted limit during a PEN fault.
The EV circuit also needs appropriate RCD protection. This will normally include a Type A RCD with a residual operating current of no more than 30mA, together with any additional DC leakage protection required by the charger or installation design. Some chargers include suitable RCD and DC protection internally, but this must be confirmed from the manufacturer’s instructions.
An earth rod is a common approach for detached and semi-detached homes with suitable garden or driveway space. It can often be installed in a border or small area of soil with relatively little disruption.
The rod must be positioned carefully. It should be kept clear of gas and water pipes, buried metalwork and other underground services. The electrician will also test the electrode and record the relevant results.
2. Built-in PEN fault detection
Many modern smart chargers include built-in PEN fault or open-PEN detection. Examples available on the UK market include products such as Zappi, Ohme, Hypervolt and Easee, although the exact protection provided can vary between models and versions.
Always check the current manufacturer’s technical documentation rather than relying on the product name alone.
A compliant PEN fault detection device monitors the supply voltage. If the line-to-neutral voltage rises above 253V or falls below 207V, the device identifies a possible neutral or PEN fault and disconnects the vehicle.
The protective system is designed to disconnect the relevant live conductors and protective earth within the required time. It should not automatically reconnect until the supply has returned to safe limits.
This approach can avoid the need for a separate earth rod where the charger’s built-in protection is specifically suitable for the installation and complies with the relevant requirements of BS 7671 Regulation 722.411.4.1.
For example, Zaptec explains its built-in PEN fault protection, while the myenergi Zappi product information describes built-in PEN fault technology and installation without an earth rod.
3. Existing TT earthing arrangements
Some homes already have a TT earthing arrangement, where the installation uses its own earth electrode rather than relying on the supply network’s protective earth.
This does not automatically make EV charger installation simple. TT systems have their own considerations, including:
- Higher earth fault loop impedance
- Greater reliance on RCD protection
- Correct RCD type and selectivity between protective devices
- Electrode resistance limits
- Periodic testing of the earth electrode and associated protective devices
The charger circuit must be designed so that the protective devices disconnect within the required times. An electrician should verify the existing TT arrangement rather than assume it is suitable because an earth rod is already present.
What ADS Electrical checks during an EV charger survey
Before providing a final design for EV charger installation in Surrey, ADS Electrical checks the property-specific details that affect safety, compliance and the practical installation route.
These checks include:
- Whether the earthing system is TN-S, TN-C-S/PME or TT
- Ze and external earth fault loop impedance readings
- The main service fuse rating and available supply capacity
- The condition of the consumer unit and whether spare ways are available
- The length and route of the proposed charger cable
- Whether the charger is on the house, an integral garage, a detached garage or another outbuilding
- Existing metallic services and buried metalwork
- Whether the main earthing terminal or earthing arrangement is shared
- The charger’s RCD, DC leakage and PEN protection features
- The most suitable location for an earth electrode, if one is required
A small separate consumer unit or dedicated RCBO may be used for the EV circuit, depending on the existing installation and the charger manufacturer’s requirements.
Practical advice for homeowners and landlords
Do not accept an EV charger quote that skips the earthing assessment. Before work starts, ask:
- What earthing system does my property have?
- How will the earthing arrangement be verified?
- Does the proposed charger have integral PEN fault protection?
- If not, why is an earth rod or separate PEN protection device being specified?
- Will I receive the Electrical Installation Certificate and test results after commissioning?
- Is RCD protection included, and what type is being used?
- Will the charger be connected to the existing consumer unit or a separate EV consumer unit?
Earthing arrangements can differ between neighbouring properties, even on the same Redhill street. The fact that a neighbour has a charger without an earth rod does not prove that your property can be installed in the same way.
Second-hand or unbranded chargers should also be treated with caution. A low purchase price does not confirm that a charger has suitable PEN fault protection, RCD protection or documentation. Using a “granny charger” through a domestic socket as a workaround does not remove the underlying earthing risk and may not provide a suitable long-term charging solution.
Will an earth rod damage my driveway or garden?
Usually, the installation can be planned to keep disruption low. A rod can often be driven into a garden border, soft ground or a suitable section beside the driveway. The exact method depends on the ground conditions, buried services and the location of the main earthing terminal.
An earth rod does not mean your house is unsafe. It is a standard protective measure used to make certain EV charging installations compliant and safe. The important point is that it must be correctly located, connected, tested and recorded.
For professional advice, arrange an EV charger installation Redhill survey with ADS Electrical. We offer a free site survey and free quotes within 24 hours. As a NICEIC Approved Contractor, ADS Electrical provides installation support from design through to testing, with reliable communication and a 24-month workmanship warranty.
FAQs
What is PME earthing?
PME is Protective Multiple Earthing, normally associated with a TN-C-S electricity supply. It is used by many UK homes, including most properties in the Redhill and Reigate area.
How do I know if my Redhill home is PME?
You should not rely on the appearance of your consumer unit or what a neighbour has installed. An electrician can identify and verify the earthing arrangement through inspection, supply information and electrical testing.
Will I definitely need an earth rod?
No. You may have a TN-S or TT supply, or you may use a suitable charger with compliant built-in PEN fault detection. The correct solution depends on the property and charger.
Does an earth rod mean my electrics are unsafe?
No. An earth rod is often a standard, low-disruption protective measure for an EV installation. It does not automatically indicate a fault with the house.
Does a modern smart charger remove the need for an earth rod?
Sometimes. Many modern chargers include PEN fault detection, but the exact model must be verified. The installer must confirm that the device provides the required protection and is suitable for your earthing arrangement.
Can the earth rod go in my front garden?
Often, yes, if the location is suitable. It must be clear of buried services, gas and water pipes, and other metalwork. The electrode resistance and final installation must also be tested.
Is the earth rod included in the installation quote?
That depends on the survey. A responsible quote should explain whether an earth rod, PEN protection device, separate consumer unit, additional cable work or other measures are required. Installation costs are property-specific, so a site survey is the best way to establish the correct scope.