In this article the team at Kewtech provide best practice advice and guidance on complying with the standards that cover EV charging installations, while offering tips on the right type of equipment to carry out testing and inspection.
British Standard 7671:2018: Amendment 2: 2022, commonly known as the IET Wiring Regulations, is the accepted safety standard for most low voltage electrical installations. Section 722 covers Electric Vehicle Charging Installations.
Where the maximum demand on the installation, with the intended EV charging equipment connected, does not exceed 13.8kVA the Energy Networks Association should be notified. If the total maximum demand on the installation, with the EV charging equipment installed, exceeds 13.8kVA the District Network Operator (DNO) should be consulted before the installation work commences.
DNOs will not usually consent to high current loads, such as EV charging equipment, to be supplied from a βlooped supplyβ. A looped supply is where premises are not directly supplied individually but are shared by looping the DNO supply cable in and out of premises. The DNO should be consulted to verify if there is any restriction on the capacity of their supply.
Insurers may pose additional requirements on their policies for charging equipment installed inside buildings and where vehicles are charged near a building with additional risks such as a building made of combustible materials, extensive glazing and high-risk buildings.
They may refer to a document known as RC59, published by the RiscAuthority. This document can be downloaded for free from the internet. Designers and installers should ask their clients if their insurance company has been consulted for any additional requirements they may wish to impose in respect of the installation of the EV charging equipment.
Circuit protection
EV load currents may be continuous for extended periods of time. Manufacturers of distribution boards and consumer units may place special conditions for continuous extended loading on their equipment for periods longer than 30 minutes or one hour. Data must be obtained for the chosen manufacturerβs equipment to verify any special requirements for continuous loading. BS 7671 refers to this requirement in Regulation 536.4.202 and 134.1.1.
PME earthing systems
An important consideration for EV installations is to verify the earthing system for the installation that the EV charging point is going to be supplied from. Whilst an earthing system may have the appearance of a TN-S system it may not be, due to cable repairs on the DNO network. If the earthing system cannot be verified by enquiry with the DNO it should be considered by default to be TN-C-S (PME).
BS 7671 Regulation 722.411.4.1 forbids the use of PME earthing systems on EV installations unless special methods of protection are applied for vehicles that are intended to be charged outdoors. Regulation 722.411.4.1 provides four alternative measures that may be applied to protect users from PEN failures. Most reputable EV charging equipment manufacturers offer open PEN detection built into their products. Manufacturers should be asked to provide a Declaration of Conformity to ensure the required British Standards stated in 722 are complied with.
Even if the earthing system is TN-S or TT the installation may be connected to an adjacent premises by common bonded gas or water pipework. On a TT earthing system, the consumersβ electrode will need to have a separation distance from adjacent premises having a PME supply with bonded buried pipework. This is needed to prevent impressed voltages appearing on the consumersβ electrode. Different DNOs will specify different distances but this is commonly around 5 metres.
RCD protection
Due to DC currents that may be present in the AC charging supply BS 7671 places special requirements in the selection of RCDs to protect against these DC components preventing the RCD from operating correctly. These can be found in Regulation 722.553.101.
The EV socket must have additional RCD protection and this can either be on the supply to the EV charging equipment or built in to the EV charging equipment. The RCD must either be a 30mA Type B RCD or a 30mA Type A or Type F with RDC-DD DC protection. The selected manufacturer of the EV charging equipment should be asked to provide a Declaration of Conformity specifying compliance with all of the standards listed in Section 722 of BS 7671. RCDs to BS EN 61008 and RCBOs to BS EN 61009 are required to have user test buttons to comply with their respective standards. An indication of non-compliance, or partial compliance with these standards, is the lack of a user test button.
Inspection and testing
Regulation 722.533.101 requires that a new individual final circuit be installed to supply vehicle charging equipment. EV charging equipment cannot be looped together on a radial circuit, see Regulation 722.533.101.
After the installation has been inspected it must be tested to verify if the requirements of BS 7671 Regulation 643.1 have been met. The Kewtech KT66DL Multifunction Tester is able to carry out the full range of the required tests with an instrument that is both convenient and intuitive to use.
Live polarity tests, earth loop impedance tests and RCD tests can be carried out at the socket using test probes with the front fascia of the charging point removed from enclosure. However, this would amount to a breach of Regulation 14 of the Electricity at Work Regulation 1989 (EAWR) which forbids working on, or near, live conductors unless it is unreasonable in all the circumstances.
There is an alternative to live working on or near live conductors and this is to use a special adaptor plugged in to the Mode 3 EV socket and hence comply with Regulation 14 of the EAWR. This adaptor needs to simulate the presence of a vehicle on charge to enable the tests to be performed.
With safety and usersβ convenience in mind Kewtech has produced the KEWEVA universal testing adaptor as a companion to the KT66DL MFT. The KEWEVA will simulate the presence of a vehicle on charge and importantly verifies that the handshake signal between the vehicle and charge point is correct. The KEWEVA can be plugged directly in to a Mode 3 socket on the charging equipment or, where the charging equipment has a tethered cable, into the vehicle end of the charging cable.
The KEWEVA is connected to the KT66DL using the standard 4mm connecting leads and is able to facilitate the testing of both single phase and 3 phase Mode 3 sockets.
When paired with the Kewtech KT66DL the KEWEVA the following tests can safely be performed:
1. Earth loop impedance tests
2. Type B RCD tests
3. Type A RCD tests
4. 6mA RDC-DD tests.
In addition to reducing the shock risk the KEWEVA has the added advantage of not requiring dismantling of the EV charge point, saving testing time or the need to re-test after the EV charging equipment has been re-assembled.
Employers are required to carry out risk assessments and then to produce method statements (RAMS) for work activities under the Management of Health and Safety at Work Regulations 1999. It may be a consideration in the RAMS to use a Kewtech EVA adaptor as a control measure to reduce the risk of electric shock when testing EV charge points and to comply with Regulation 14 of the EAWR.
Visit the Kewtech KEWEVA product information page online here
