Article by LearningLounge.com/eve Technical Lead - Gary Gundry MIET
During the production of EVE, our award winning electric vehicle charging course, we explored and demonstrated many alternative ways for connecting an EV charging point circuit to existing installations. In domestic installations, one solution may be to use an existing split load board, as long as the appropriate type of RCD could be used.
It therefore piqued our interest to hear in conversation with installers and manufacturers, that there were cases where installations had been criticised during an audit for installing an EV Circuit on a split load board.
And the reason given
“The EV charging point circuit must be protected by its own RCD”.
WHAT! Fortunately as I have some knowledge of the history of the regs I was able to provide some support, and it’s all to do with how the requirements have changed over the years - which really does reinforce how keeping well up to date on the changes, by either reading the book from cover to cover, or doing detailed and engaging training courses, is an important part of being not only a professional electrician, but also those that audit them.
Here’s the important detail:
See how the requirements (and regulation numbers) for RCD protection have changed over the years.
1. EXTRACT from Amd 3 of BS 7671:2008(2015) - 17th Edition.
722.531.2 RCDs
722.531.2.101 Every charging point shall be protected individually by an RCD having the characteristics
specified in Regulation 415.1.1. The RCD shall disconnect all live conductors, including the neutral.
2. EXTRACT from BS 7671:2018 - 18th Edition
722.531.2 RCDs
722.531.2.101 Except for circuits using the protective measure of electrical separation, each charging point shall be protected by its own RCD of at least Type A, having a rated residual operating current not exceeding 30 mA.
3. EXTRACT from Amd 1 of BS 7671:2018(2020) - 18th Edition
722.531.3 Residual current devices (RCDs)
722.531.3.1 RCDs shall disconnect all live conductors.
722.531.3.101 Unless supplied by a circuit using the protective measure of electrical separation, each charging point incorporating a socket-outlet or vehicle connector complying with the BS EN 62196 series shall be protected by an RCD having a rated residual operating current not exceeding 30 mA.
So with Amendment One of the 18th Edition it looked possible to install an EV circuit off a split load CU.
Now, since 28 March 2022, we have Amd 2 of BS 7671, and 'individually' is back!
4. Amd 2 BS 7671:2018+A2:2022 - 18th Edition (Brown in colour to match the book)
722.531.3.101
Unless supplied by a circuit using the protective measure of electrical separation, each charging
point incorporating a socket-outlet or vehicle connector complying with the BS EN 62196 series shall be protected
individually by an RCD of Type A, Type F or Type B and having a rated residual operating current not exceeding
30 mA.
Except where provided by the EV charging equipment, protection against DC fault currents shall be provided by:
(i) an RCD Type B, or
(ii) an RCD Type A or Type F in conjunction with a residual direct current detecting device (RDC-DD)
complying with BS IEC 62955 as appropriate to the nature of the residual and superimposed currents and
recommendation of the manufacturer of the charging equipment.
RCDs shall comply with one of the following standards: BS EN 61008-1, BS EN 61009-1, BS EN 60947-2 or
BS EN 62423.
NOTE 1: Types of RCD are described in Regulation 531.3.3 in respect of their behaviour when exposed to DC components and
frequencies.
NOTE 2: Requirements for the selection and erection of RCDs in the case of supplies using DC vehicle connectors according
to the BS EN 62196 series are under consideration.
NOTE 3: An RCD Type A or Type F in conjunction with an RDC-DD can be arranged with the RDC-DD inside the EV charging
equipment and the Type A or Type F RCD upstream in either the charging equipment or the installation.
So this latest change was to the take onboard the general requirements! For instance, Regulation 531.3.2 states that '... in order to avoid unwanted tripping by protective conductor currents and/or earth leakage currents, the accumulation of such currents downstream of the RCD shall be not more than 30 % of the rated residual operating current ...' That's 9 mA on a 30 mA device; so with some vehicles known to reach or exceed these values, unwanted tripping could be an issue - especially where other protective conductor currents of other circuits add to this value!
From
I hope this helps you with any challenges you may face during any work related EV installation audits.
Even if you are already an EV installer course such as EVE will be an important part of keeping you up to date, and will also reinforce knowledge you already have.
You can check out the course on www.learninglounge.com/eve
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Gary Gundry - technical presenter
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