Charging towards high standards
The installation of electric vehicle supply equipment is nothing new, but the issue of protective devices can still cause some debate. Here, our guest expert focuses on RCD protection for Mode 3 charging and looks at whether integrated devices comply with the current regulations
What are the RCD requirements for the different charging modes?
Mode 1 and Mode 2 charging utilises BS 1363 socket-outlets, with a type A RCD required. Mode 3 charging is provided by a dedicated circuit, typically single-phase 7kW or three-phase 22 kW. This is the most common type of electric vehicle (EV) charger installed in domestic/household premises.
Mode 4 charging is provided by a dedicated AC supply circuit to the EV supply equipment (EVSE). The EVSE uses switch mode power supplies (SMPS) to convert the AC to DC which is used on the output circuit; Mode 4 charging is typically used for publicly available fast charging 50 kW to 350 kW.
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, as referred to in Note 2 to Regulation 722.531.3.101 of BS 7671:2018+A2:2022.
For Mode 4 charging, RCDs may be required for the AC supply circuit, e.g. if it is a TT system or where disconnection times cannot be met using circuit-breakers. However, RCDs are not required on the DC side as this protection is provided by the manufacturer of the EVSE.
“Compliance with standards is voluntary but it can help to demonstrate conformity with the relevant legislation – this is known as presumption of conformity”
What are the standards and regulations for EVSE?
In order for electrical equipment to be sold in the UK, the electrical equipment must conform to the Electrical Equipment (Safety) Regulations 2016, the Electromagnetic Compatibility Regulations 2016 (as amended) and other relevant legislation.
The Electric Vehicles (Smart Charge Points) Regulations 2021 also apply to Mode 3 EVSE. These are statutory regulations and must be adhered to by manufacturers of EVSE.
Compliance with standards is voluntary but it can help to demonstrate conformity with the relevant legislation – this is known as presumption of conformity.
The series of standards for the design and performance requirements for EV conductive charging equipment is the BS EN IEC 61851/BS EN 61851 series. Section 722 of BS 7671:2018+A2:2022 provides requirements for the installation of EVSE, in addition to the general requirements.
What are the RCD requirements in BS 7671 for EVSE?
Regulation 722.531.3.101 of BS 7671 states that unless the circuit is supplied using the protective measure of electrical separation, each charging point incorporating a socket-outlet or vehicle connector complying with the BS EN 62196 series is to 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. The RCD is also required to disconnect all live conductors.
The definition of an EV charging point in BS 7671 is “the point where the electric vehicle is connected to the fixed installation”. This means that the requirement for RCD protection applies to the socket-outlet or connector and not the circuit supplying the EVSE. A note clarifies that the point is the socket-outlet supplying the EV, or a connector where the charging cable is not part of the EVSE.
There may be other reasons why RCD protection is required to protect the final circuit, such as where a TT earthing system is used, or cables are buried in walls at a depth of less than 50mm or where high earth fault loop impedances require an RCD to achieve fault protection.
What type of RCD is required?
EVSE are likely to produce DC residual currents during operation, due to the design of the electronic equipment for the charging circuit within the EVSE.
The DC residual currents will be superimposed on the AC waveform which will affect the operation of RCDs. The type of RCD required depends on the protection against DC residual currents installed in the EVSE.
Where no protection against DC residual current is provided in the EVSE, Regulation 722.531.3.101 of BS 7671 requires a Type B RCD to be installed.
Where protection against DC residual current is provided in the EVSE, a Type A or Type F RCD can be used. This is typically provided by a Type A RCD 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.
BS EN 62955:2018 provides requirements for RDC-DD to be used for Mode 3 charging of EVs. RDC-DDs are a detection device for DC residual current which do not incorporate a mechanical switching device. Switching is provided by an external device, such as a contactor which is switched by the RDC-DD.
It is also important to consider any RCDs installed upstream as they could also be blinded by DC residual currents. The hierarchy of RCDs with respect to DC residual current should be observed. For example, a Type AC RCD cannot be installed upstream of a Type A RCD.
The BEAMA guide, Selection and application of RCDs, provides useful information, as does its separate publication, RCD selection for protection of electric vehicle charging installations. Links to both can be found in this article.
As with all electrical equipment, account should be taken of the EVSE manufacturer’s instructions.
Can I use an EVSE with an integrated RCD?
Some manufacturers state that EVSE contain integrated RCDs. The question is often asked if the RCD protecting the final circuit can be omitted and the RCD in the EVSE used to provide additional protection for the EVSE. After all, the requirement for RCD protection is for the socket-outlet, and not the final circuit. BS 7671 does not dictate the location for the RCD, with Regulation 722.531.3.101 stating that “except where provided by the EV charging equipment”, protection against DC fault currents shall be provided by a Type B RCD or a Type A or Type F in conjunction with an RDC-DD. So it is clear that it IS acceptable to locate an RCD within the EVSE.
This Regulation also states that RCDs shall comply with one of the following standards:
BS EN 61008-1
BS EN 61009-1
BS EN 60947-2
BS EN 62423.
If the RCD included in the EVSE complies with one of these standards, then it could be used as additional protection for the EV charging point without the need for additional RCD protection upstream.
Often RCDs built in to EVSE integrated into the printed circuit board (PCB) do not fully conform to any of the standards required by Regulation 722.531.3.101 of BS 7671 or Clause 8.5 of BS EN IEC 61851-1:2019.
What is an integrated RCD?
In simple terms, an integrated RCD is an electronic device controlled by an algorithm programmed to operate in a similar way to how a traditional RCD operates according to the relevant product standards.
Some EVSE incorporate a residual direct current protective device (RDC-PD), a protective device with integrated AC, pulsating DC and 6 mA DC detection, evaluation, and mechanical switching in one unit.
The requirements for RDC-PDs are provided in Annex O (normative) of BS IEC 62955:2018. It is stated that that the requirements and test of IEC 61008-1 concerning RDC-PD integrated in RCCB function, and IEC 61009-1 concerning RDC-PD integrated in RCBO function apply as relevant. With the exception of a couple of clauses modified by BS IEC 62955, RDC-PDs must conform to all the requirements of either IEC 61008 or IEC 61009.
An RCD-DD/RDC-PD is not one of those cited in Regulation 722.531.3.101, which leaves the installer in a difficult position. BS 7671 and BS EN IEC 61851 mandate that 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.
Can I install equipment which does not comply with any British Standards?
Yes, but any intended departure requires special consideration by the designer of the installation in consultation with the client and other interested parties.
It is important to note that the resulting degree of safety of the installation shall be not less than that obtained by compliance with the BS 7671, Regulation 120.3 refers. Any departures along with the justification must be recorded on the electrical certification.
Regulation 122.1.2 states that where there are no applicable standards, the item of equipment concerned shall be selected by a special agreement between the person specifying the installation and the installer. This route requires careful consideration as it could result in liabilities at a future date.
Regulation 133.5 provides requirements for new materials and inventions, and Regulation 133.1.3 provides requirements for equipment which does not comply with any British or Harmonised Standard or used outside the scope of its standard.
Again, the resulting degree of safety of the installation shall be not less than that obtained by compliance with BS 7671, and the chances of the EVSE manufacturer putting this clearly in writing is unlikely.
Regulation 722.411.4.1 of BS 7671 recognises that equipment can be used which is not covered by a British or Harmonised Standard, in this case, open PEN detection devices. It is required that the equipment meets the requirements of statutory legislation, the Electrical Equipment (Safety) Regulations 2016 (as amended), the Electromagnetic Compatibility Regulations 2016 (as amended) and other relevant legislation, and the equipment has either a CE, UKCA or UKNI mark and a declaration of conformity (DOC).
The DOC is to be appended to the certification for initial verification and where this is satisfied, it is NOT considered to be a departure from BS 7671.
What is a DOC?
When installing any item of electrical equipment, it is important the manufacturer supplies a DOC, which is a mandatory document provided by manufacturers to declare their products comply with the law.
The CE, UKCA or UKNI mark accompanied by the DOC document confirms that the manufacturer takes full responsibility for the products compliance with the applicable laws. The DOC is usually available on the manufacturer’s website or available on request. The DOC will specify the relevant regulations and standards to which the product conforms.
“When installing any item of electrical equipment, it is important the manufacturer supplies a DOC, which is a mandatory document provided by manufacturers to declare their products comply with the law”
What if the manufacturer states an RCD is not required?
Be wary of claims by manufacturers that an external RCD is not required for EVSE.
Some manufacturers of EVSE declare on their website that the equipment does feature an integrated RCD which operates ‘similar’ to a traditional RCD complying with BS EN 61008 or BS EN 61009. However, if the RCD is integrated into the circuit board, it will not be compliant with the RCD product standards.
When inspectors of competent person schemes carry out their audits, they will be looking for compliance with BS 7671 and will expect to see an external RCD installed.
In summary
Regulation 722.531.3.101 of BS 7671 requires RCDs to protect the charging point, i.e. the socket-outlet or connector and not necessarily the circuit supplying it.
The RCD can be installed at the distribution board or within the EVSE.
RCD functionality built into circuit boards does not conform to the relevant product standards required by BS 7671 or BS EN IEC 61851-1:2019.
RCDs shall disconnect all live conductors and comply with one of the following standards: BS EN 61008-1, BS EN 61009-1, BS EN 60947-2 or BS EN 62423.
For Mode 3 charging, a Type A or Type F RCD is required where protection against DC residual currents in the form of an RDC-DD is provided within the EVSE.
Where the EVSE does not incorporate such protection, a Type B RCD is required. When installing EVSE, account should be taken of manufacturer’s instructions.
Sweden bans EV chargers with integrated RCDs
Swedish authorities have recently placed a sales ban on a manufacturer of EV charge points. One of the issues raised is regarding the use of integrated electronic RCDs. The manufacturer has provided a robust response and maintains that its products are safe and it is a matter of correct documentation. Read more at bit.ly/EV-response
Further reading
Lists of standards that businesses can use to show their products, services or processes comply with essential requirements of legislation
Guidance on the selection and application of the range of RCDs now available, enabling conformity with Amendment 2 to BS 7671.
The effects of DC fault currents on RCDs, the different types of Residual Direct Current Detecting Devices (RDC-DDs) and their testing.
In addition to Bob Cairney and Stuart McKelvie of SELECT, I would like to thank the following for their contributions to this article: Mark Coles, Leon Markwell and Craig O’Neill (IET), Joe Cannon and John Peckham (IET volunteers), Darren Crannis, Curtis Jones and Gary Parker (ECA), Frank Bertie (NAPIT), Gary Gundry (technical consultant), Peter Monfort (Arena Training).
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