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Fifth Edition of the IET Code of Practice for Electric Vehicle Charging Equipment Installation

There have been a number of changes in the EV charging installation sector since the publication of the Fourth Edition of the IET Code of Practice for Electric Vehicle Charging Equipment Installation in 2020, which have prompted calls from the industry for updates to the publication.

The guidance has been updated and expanded primarily as a result of:

  • introduction of new legislation;
  • availability of new guidance on fire safety and accessibility of charging points;
  • increased roll-out of Mode 4 (rapid charging) points;
  • removal of indent (i) to Regulation 722.411.4.1 in BS 7671:2018+A2:2022;
  • change of focus on related industry vocational qualifications; and
  • completion of vehicle-to-grid (V2G) trials, along with innovations making vehicle-to-home (V2H) applications more likely.

The Fifth Edition of the IET Code of Practice for Electric Vehicle Charging Equipment Installation is now available. Technical Author Graham Kenyon provides some insight into what we can expect of the new publication.

The Electric Vehicles (Smart Charge Points) Regulations 2021

The Electric Vehicles (Smart Charge Points) Regulations 2021 came into force in Great Britain in June 2022, and apply to private charging points rated at not more than 50 kW, installed after 30 June 2022. The legislation requires charging points to include:

  • inter-operable smart functionality to enable integration of the charging equipment to integrate with the smart grid for load curtailment (dropping maximum output of the charger) and demand side response services
  • pre-set default charging times for off-peak usage (with a suitable user override)
  • cyber-security, and
  • minimum safety provisions.

Further guidance on the Regulations can be found on the Office for Product Safety and Standards website: https://www.gov.uk/guidance/regulations-electric-vehicle-smart-charge-points

Part S of the Building Regulations in England

Part S of the Building Regulations came into force in England on 15 June 2022 and relates to EV charging point provision associated with dwellings and residential buildings and certain non-residential premises. The legislation mandates charging equipment to be at least Mode 3, with a power capability of at least 7 kW, with a universal outlet, supplied by a dedicated circuit, and mandates the equipment to be installed according to BS 7671 and the IET Code of Practice for Electric Vehicle Charging Equipment Installation.

Installation of telecommunications and auxiliary cabling

One impact of the Electric Vehicles (Smart Charge Points) Regulations 2021 for installers is the increased requirement for communications interfaces and, where applicable, control and monitoring. As a result, guidance on communications and integration has been expanded in the Fifth Edition of the Code of Practice, and now includes guidance on telecommunications and auxiliary (control and monitoring) cabling installation according to BS 7671, BS 6701 and BS EN 50174 series. Cabling for Ethernet, ANSI/TIA/EIC-485-A (commonly known as ‘RS 485’) and control and monitoring auxiliary purposes are considered.

Guidance is provided on selection of appropriate cabling, and installation practices for telecommunications cabling inside and outside buildings.

Location and accessibility of charging points

The guidance on location and accessibility of charging points has been updated to take account of new standard PAS 1899:2022 Electric vehicles - Accessible EV charging points - Specification and the requirements of the Scotland Building Standards Division technical handbooks that came into force in June 2023.

Installers are also advised to consider RISCAuthority RC59 Recommendations for fire safety when charging electric vehicles when considering the location of charging points.

Vehicle as storage

Section 10 of the Code of Practice, which looks at vehicle as storage, has been updated to reflect guidance on the latest BS 7671 requirements for prosumer’s electrical installations and includes guidance on V2H integration for installations operating in island mode, when the grid supply is disconnected.

Inspection and testing

Section 9 on inspection and testing has additional guidance for:

  • earth electrode resistance measurement;
  • RCD testing; and
  • use of vehicle simulators for carrying out tests at socket-outlets or tethered cable vehicle connectors on the vehicle side of charging equipment.

The Code of Practice also provides advice on testing of RCD-DDs to BS IEC 62955. BS 7671 does not require tests of RDC-DDs to be conducted, however, tests could be carried out for fault-finding purposes, or functional testing if recommended by the manufacturer of the RDC-DD or electric vehicle charging equipment. Although, it should be noted that the test parameters in RCD test instruments or multifunction testers to BS EN IEC 61557 series Electrical safety in low voltage distribution systems up to 1 000 V AC and 1 500 V DC. Equipment for testing, measuring or monitoring of protective measures are not always suitable for RDC-DDs.

Installation of earth electrodes

Clearer guidance is provided for good practice in the installation of earth electrodes in accordance with BS 7671 and BS 7430.

Calculations for steel wire armoured (SWA) cables where the armour is used as the circuit protective conductor (cpc)

A new appendix has been included to help designers consider the reactance of steel wire armoured cables on the earth fault loop impedance calculations where the armour is used as a cpc (with or without an additional copper conductor in parallel). This can also be used by those carrying out inspection and testing, in cases where loop impedances are to be determined at least in part by calculation.

Appendix 4 to BS 7671 tells us that reactive effects need not be considered where the cross-sectional area (csa) of cables does not exceed 16 mm2. However, where SWA cables are used, the csa of the armour usually exceeds 16 mm2. For example, with BS 5467 cables, the gross csa of the armour exceeds 16 mm2 for all:

  • three-, four- and five-core multicore cables with conductor csa at least 1.5 mm2; and
  • two-core cables with conductor csa of at least 2.5 mm2.

What is the effect of not taking cable reactance into account for SWA cables? As we can see from Table 1, (Z1+Z2) taking into account reactance is between 4 % and 9 % greater than (R1+R2), and this might be significant for long runs where overcurrent protective devices provide automatic disconnection of supply. In addition, with larger supplies required for commercial sites and Mode 4 (DC rapid charging) electric vehicle charging equipment installations, it may be necessary to take into account the reactance of the loop impedance at the feeder pillar or distribution board, which will have a further impact.

Table 1 Comparison of loop impedance contribution of SWA cables to BS 5467, where the armour is used as cpc, with and without consideration of reactance

Conductor csa (mm2)

Loop impedance contribution per metre at 70 °C (mΩ/m)

2-core

3-core

4-core

5-core

(Z1+Z2)

(R1+R2)

(Z1+Z2)

(R1+R2)

(Z1+Z2)

(R1+R2)

(Z1+Z2)

(R1+R2)

1.5

28.3

27.0

27.3

26.2

26.4

25.3

25.6

24.6

2.5

20.8

19.7

19.9

18.9

19.2

18.3

18.1

17.2

4.0

16.2

15.2

15.6

14.7

14.7

13.9

13.9

13.1

6.0

13.1

12.3

12.7

11.9

9.50

8.96

8.96

8.47

10

10.3

9.55

7.59

7.10

7.19

6.73

6.78

6.36

16

6.37

5.91

6.10

5.67

5.57

5.18

4.35

4.08

25

5.19

4.79

3.98

3.69

3.71

3.45

3.31

3.08

35

3.61

3.32

3.47

3.20

3.20

2.96

2.80

2.59

50

3.17

2.91

2.91

2.67

2.24

2.06

1.97

1.81

 

NOTE: (Z1+Z2) is the loop impedance taking into account reactance. (R1+R2) is the loop impedance not taking into account reactance.

Depth of buried cables and height of overhead cables

With the exception of the Streetworks UK guidelines relating to cabling buried under the highway, there is currently no easy-use reference for the minimum depth of buried cables, and minimum height of overhead cables. It has been recognized that EV charging equipment is now starting to be installed in a variety of different types of premises, some having more onerous requirements. Appendix K to the Fifth Edition of the Code of Practice provides a ‘one-stop-shop’ for designers and installers to easily see how minimum depth and height requirements may change, when providing charging points in, say, agricultural premises or caravan sites.

Other guidance for designers

For each of the use-case classifications (domestic, on-street, and commercial and industrial) there is updated guidance on determining adequacy of supply and maximum demand. The guidance takes into account load curtailment (where used), and also helps designers understand the difference between the maximum demand values required for:

  • the maximum demand required by the electricity supplier (DNO);
  • sizing switchgear assemblies and distribution arrangements; and
  • selection of final circuit wiring systems and suitable conductor cross-sectional area.

There is also guidance on determining whether vehicles on charge are considered indoors or outdoors for the purposes of Regulation 722.411.4.1 in commercial and industrial applications. This is not always straightforward in buildings with parking on multiple levels (see Figure 1).

Figure 1 Examples of vehicle spaces considered to be indoors or outdoors for the purposes of Regulation 722.411.4.1 (from the 5th Edition of the IET Code of Practice for Electric Vehicle Charging Equipment Installation)

Conclusion

The Fifth Edition of the IET Code of Practice for Electric Vehicle Charging Equipment Installation contains a number of timely updates, so that industry can be kept up-to-speed with the rapidly changing landscape in this field which is of key importance to the UK Government’s approach to reducing the UK’s carbon emissions. The Fifth Edition includes updates to cover technological developments, industry practices, and legislative frameworks, since the previous edition.

About the author

Graham Kenyon is a Chartered Engineer, and Managing Director of consultancy G Kenyon Technology Ltd. Graham Chairs:

  • the joint IET/BSI Committee JPEL/64, responsible for BS 7671;
  • the IET Wiring Regulations Policy Committee; and
  • the IET Committee developing the IET Standard for open-PEN disconnection devices (OPDDs), which will shortly be available for public consultation.

He is the technical author of a number of IET guidance publications including the IET Code of Practice for EV Charging Equipment Installations, the Second Edition of the IET Code of Practice for Grid-Connected Solar PV Installations (2022), and the latest editions of IET Guidance Notes 3, 5 and 6.