Tesla Wall Charger with 65m Cable Run

Full Installation Walkthrough

This Tesla Wall Charger installation in the North East presented a significant engineering challenge: a sixty-five metre cable run between the main consumer unit inside the house and the desired charger location on a detached outbuilding at the far end of the property. Long cable runs are one of the most common challenges we face on EV charger installations, particularly in rural and semi-rural properties where the parking area may be some distance from the main electrical supply.

The homeowner had recently taken delivery of a new Tesla and wanted the official Tesla Wall Charger installed at the outbuilding where they normally park. The Tesla Wall Charger is a sleek, purpose-designed unit that integrates seamlessly with Tesla vehicles, automatically detecting the car and beginning the charge without any need to unlock the charger or authenticate through an app. It also works perfectly well with non-Tesla EVs through the standard Type 2 connector.

During the site survey, we measured the cable route from the consumer unit to the proposed charger location and calculated that the total run would be approximately sixty-five metres, accounting for the route through the house, underground across the garden, and along the outbuilding wall to the mounting position. At this distance, voltage drop becomes a critical consideration because the EV charger draws a sustained high current and any excessive voltage drop will reduce the charging power delivered to the vehicle and could trigger the chargers under-voltage protection.

Our engineering calculations determined that standard 6mm cable, which is adequate for most domestic EV charger installations of up to fifteen or twenty metres, would result in an unacceptable voltage drop at sixty-five metres. We therefore specified 10mm SWA cable, which has a significantly lower resistance per metre and keeps the voltage drop within the permissible limits defined by BS 7671 even at the full thirty-two amp charging current over this extended distance.

The cable route was planned in detail before any work commenced. From the consumer unit, the cable runs through the house in surface-mounted trunking to an exit point on the rear wall. It then enters a buried duct that crosses the garden to the outbuilding. We engaged a specialist groundworks contractor to excavate the trench, install the ducting, and backfill with sand and warning tape in accordance with the requirements for buried cables.

The SWA cable was pulled through the duct in a single continuous length to avoid any underground joints, which would represent potential failure points and maintenance difficulties. At each end of the buried section, the cable enters a surface-mounted enclosure where the SWA gland and earth bonding connections are made. These enclosures are weatherproof and provide accessible test points for future maintenance.

At the consumer unit end, the cable is connected to a dedicated forty-amp RCBO in the consumer unit, providing both overcurrent and earth leakage protection for the entire circuit. An isolator is also fitted at the consumer unit to allow the EV charger circuit to be safely disconnected for maintenance without affecting any other circuits in the property.

At the outbuilding end, the cable terminates at a local isolator before connecting to the Tesla Wall Charger. The charger was mounted at the height and position agreed with the homeowner during the site survey, ensuring it would be at a comfortable height for connecting the charging cable and that the cable would reach the vehicle's charge port when parked in the normal position.

The Tesla Wall Charger was commissioned using the Tesla app, which walks through the setup process including Wi-Fi connectivity, power sharing configuration and scheduled charging preferences. The homeowner configured the charger to begin charging automatically after midnight to take advantage of their cheap overnight electricity tariff, ensuring the vehicle is fully charged every morning at the lowest possible cost.

Full circuit testing was carried out on the complete sixty-five metre run, including continuity of protective conductors, insulation resistance, earth fault loop impedance at the charger end, and prospective fault current. All measurements were within the acceptable ranges for the cable specification and protective device rating, confirming that our design calculations were accurate and the installation is safe and compliant.

This project demonstrates that a long cable run does not have to be a barrier to installing an EV charger at your preferred location. With proper engineering calculations, the correct cable specification and professional installation, we can deliver a safe, fully compliant EV charger installation regardless of the distance between your consumer unit and your parking area. At ALPS Electrical, we carry out these calculations as a standard part of every site survey, ensuring that every installation is designed correctly from the outset.