What Does BS7671 Amendment 1 Mean for Installers & Charging Point Manufacturers?
By Martyn Berry, Independent Consultant - Solar PV, Storage & EV Charging
Over the last three years I’ve worked with many charging point manufacturers and installers to help improve installation quality and compliance through installer training, including many sessions together with the team at Replenishh. A common experience for me at each training session were the groans, huffs and scowls across the room when we got to the topic of earthing arrangements for EV charging points.
Since the arrival of the BS7671 18th Edition, the majority of EV charging points have required the installation of a TT earth electrode in order to be compliant with regulation 722.411.4.1. This regulation sets out that where the charging point is installed outdoors or the vehicle charging will take place outdoors, PME (TN-C-S) earthing shall not be used as the means of earthing.
Installing a TT electrode creates a variety of practical and safety complications, including hitting a buried service, the potential need to dig up a customer’s new expensive driveway and achieving a good impedance value that will enable reliable charging (some vehicles require no greater than 150Ω in order to accept charge). The risk of simultaneous contact with nearby equipment on PME must be considered. There are also circumstances where, due to the proximity of the new earth electrode to buried metalwork connected to the PME earthing system, the electrode actually makes the situation worse. And that’s before we consider the time and additional cost on the job for the electrician.
Last autumn the IET and BSI announced they would be fast tracking an amendment to respond to the advancing technology in the EV charging sector, resulting in an updated section 722. This was out for industry review in October last year and resulted in the BS7671 Amendment 1 which was officially published on Monday 3rd February 2020.
So, what does Amendment 1 say and how will charging point installations change?
There are various smaller changes in wording and technical requirements of section 722, but the key aspect is a series of updates to the earthing requirements for charging points. The indents within 722.411.4.1 have been updated and re-written with some clearer wording. Indent (iii) has been adjusted so it now only applies to three-phase installations. There are two new indents: (iv) covering single phase applications and (v) referencing alternative devices offering equivalent safety to those mentioned in (iii) & (iv). The ball is clearly in the court of the equipment manufacturers to design compliant solutions into their products and take the complications of earth electrodes away from the installer.
Let me go into a little more detail about the requirements. For indent (iii) there must be a device which monitors the voltage between the circuit protective conductor and charging equipment and Earth, and isolates the supply to the charging equipment in the event of the voltage difference rising above 70V. The Earth could be obtained via an earth electrode or a reference earth derived from a three-phase system.
Indent (iv) requires single-phase equipment to monitor for voltage deviations on the supply network. Voltage rises above 253V or below 207V can indicate loss of PEN conductor (aligned with the European harmonised voltage limits of 230V +/- 10%).
Indent (v) offers the scope for other innovative solutions that may be available to offer the same level of safety to those offered by (iii) & (iv). This is a great opportunity for charging equipment manufacturers to innovate. Yet at the same time you have to question how the industry will assess these alternative methods to confirm whether they match or exceed the level of safety of those already proposed in the regulations.
Finally, Note 6 reminds us of another issue. A TT electrode installed without sufficient separation from buried metalwork connected to the PME earthing system may not be an appropriate solution. This reads very much like a note that will disappear in the next amendment once the manufacturers have caught up with the options for integrating the functionality from indents (iii) or (iv) into their equipment. At that point you can imagine the option to use TT being removed for all but the most exceptional cases.
In both (iii) and (iv) the charging point must pro-actively trip off within five seconds of the voltage deviation, disconnecting the EV from the supply on all conductors, including earth. Since voltages on the network constantly fluctuate, the trip time must be set to a few seconds to allow for these variations on the network, only tripping off if the voltage excursion persists for more than four seconds. Reset must be prevented until voltage readings return to the required range.
Matt:E RCBO connection units
There are already a few manufacturers ready to offer products that enable compliance with Amendment 1. The leader in the space is Matt:E with their O-PEN products, now available from Replenishh. Matt:E offer both three-phase and single-phase products that will comply with Amendment 1. It’s worth noting that these are connection units that are installed between the supply and the charging point and can be added to any charging point product to achieve compliance.
Options are limited for charging points that offer a complete solution in a single enclosure. However, we can expect to see products compliant with (iii), (iv) or (v) becoming widespread on the market over the coming months, particularly for single phase domestic installations. I would also expect that the home grown, UK-based manufacturers will provide solutions first, before the international players - just because they are closer to the needs of the market. For example, EO Charging have a solution in development that we can expect to see later this year for single phase installation.
In summary, Amendment 1 is good news for the EV charging sector. It gives manufacturers clear regulations that will allow installers to use their products and remove the need for the troublesome earth electrodes. Having said that, there will still be occasions when making the installation TT is the best approach. If this is the case electrodes are not the only option. Increasingly installers are working with alternatives such as the Conducrete disk. Installer feedback is that these are easier to work with than driving electrodes and can achieve better impedance readings.
As for accessing the document, the good news is that Amendment 1 is free to view on the IET website here and can be purchased in a printable format for £5 from the IET Academy. The next thing to look out for is the fourth edition of the IET code of practice for Electric Vehicle charging; a new edition is being published to align with Amendment 1. Check here for further details.