/Lounge Blogs/Current Flow/Warning about the use of TT in Amd One!
03, Feb, 2020

Warning about the use of TT in Amd One! This post highlights the most important changes in BS 7671 Amendment 1: 2020 that EV installers will need to consider. As an installer this now includes a warning about the dangers of using a TT system.

If you’re still using TT for EV installations it might be time for a rethink!

Amendment One of the 18th Edition is now available on the IET updates page* and it’s got some shockers! (pardon the pun)

A note warns about the risk of a potential being introduced on a TT earth electrode installed for the charging point, as it may be too close to buried metallic services connected to another TN system.  This is about more than just a simultaneous contact assessment. Its focus is on imported voltages from buried services which you can’t touch as, during an open-circuit on the supply PEN conductor, there can be a rise in potential on any connected electric vehicle – whether it’s being charged or not!

Here are two other key points that will change the way EV charging points are installed.

All EV installations installed after the 31st July 2020 must comply with BS 7671:2018+A1:2020 irrespective of whether it was designed to a previous edition of the regs.  So, if you are installing to an existing design you may have to go back to the drawing board.

The other major additions, with regard to open-circuit PEN conductors, is that there are now five options for installers to consider to overcome the challenges with PME supplies. Three new options, which didn’t exist when the 18th Edition was issued, offer more solutions to enable a wider roll-out of EV charging equipment across the UK. 

Visit http://www.learninglounge.com/eve to check out our Electric Vehicle Online Course. There is currently an early bird pre-release offer and the chance to win a brilliant Metrel MFT MI 3152 worth over £1000!

EVE will be going live soon and will include all of the latest Amendment One requirements, including detailed site surveys, installation design and practical installations including initial verification...all delivered in our highly engaging media rich style!

*To see the standalone free to view document please visit www.theiet.org/updates




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