Gary Alder, CEng MIET – BMBJV, Electrical Lead at Tideway, looks at why it is so important to undertake a proper site survey prior to installing EV charging stations.
In 2020, the National Grid stated that if every vehicle went electric overnight, there will be an increase of 10% to the nation’s overall load consumption. This was caveated with a requirement that load management would need to be in place, but what other considerations need to be made for EV charger installations?
Start with a survey
The key place to start is always the survey of a property or site. UK power networks have right of refusal for car charging installations. Applications, where increasing an installation over the 60A maximum demand threshold, are required in advance of completing any installations works. Even where 60A maximum demand is not exceeded, approval is still required and can be completed within a notification period of 28 days post-installation. The application form will require information about the installation, such as installation incoming fuse details, voltage measurements and more. It is very worthwhile to ensure a thorough inspection in advance of quoting and completing installations, including verifying the condition of the consumer unit, protective devices, main bonding conductors – all day-to-day activities that electricians undertake anyway.
One of the major considerations will be the earthing system of the UKPN supply into the property. It is worth noting that within UK power networks earthing specification EDS006 B.4 states for all TN-S supplies to be considered TNC-S, due to concentric cables being utilised within UKPN’s network, not just the visible supply head in the property. The next consideration would be the type of car and mode of charging that’s required. Typically, we expect to see a battery or hybrid car, but it’s always worth checking manufacturer’s guidance and instructions if any specifics are required. Dedicated circuits are a must, as mode 1 type of charging (utilisation of a non-dedicated circuit and socket outlet) is all but outlawed. Most chargers will operate in the 7.4kW load range with a mode 3 type of charging installation giving roughly a three to six-hour charge.
What other loads are in the property?
As mentioned previously, National Grid anticipates that most installations will utilise a form of load management. Whilst being a requirement for the office of low emission vehicles (OLEV) to provide energy management when receiving grants for installations, there is yet to be a formal requirement to do so. Some EV charger manufacturers already include current transformers, providing the ability to stop the car charging during the utilisation of large loads within a property, such as an electric shower or oven. An alternative is load management distribution equipment (as seen in Garo distributon units, for example), which provides the same principle. Selection of protective devices is always a key component to the installation.
At the site survey stage, you may note that an existing AC residual current device is present, which won’t provide adequate protection for the new circuit you’re about to add, requiring the additional cost of an A type or B type device. We then come back to the issue of earthing. Considerations should include assessing other circuits in the proximity of the charger and where the electric vehicle may be parking. You should also complete a simultaneous contact assessment. There are ways of solving such issues, by utilising equipment such as isolating transformers. However, these can be quite clunky bits of kit that the consumer may be reluctant to have in the property. Most installations currently are utilising the O-PEN devices (under BS60255-1 for current sensing relays) to measure voltage disturbances between line and neutral.
Consider surge protection
Where supplied from Henley blocks, due to some of the constraints listed previously, it is also worth considering a surge protection device, as it could be defined as a separate installation, as per the definition in BS7671. The key considerations all lead to one point: no two installations are the same. As such, a thorough site survey can ensure you’re well prepared for any eventuality.
