Pick the right protective device for each charger

Every AC charger gets its own dedicated radial with its own protective device. The device must switch all live conductors, be lockable/isolatable, and be labelled ("EV charger" + circuit reference). Typical commercial requirements:

Where an MCB (not an RCBO) is listed, the 30 mA RCD function must come from per-socket RCDs inside the unit - a feature of some models only; confirm on the data sheet before dropping the RCBO. Not accepted: Type AC devices, single-pole switching, shared protection between chargers, or devices rated above the manufacturer's stated maximum.

Type A vs Type B RCDs - and the 6 mA DC rule

EV charging can leak smooth DC fault current, which blinds an ordinary RCD. BS 7671 Section 722 therefore requires each charging point to have both 30 mA RCD protection and protection against DC fault current above 6 mA. That second part can come from:

• RDC-DD built into the charger (most current units, but not all - verify on the data sheet) → a Type A RCD/RCBO upstream is sufficient and is the normal commercial arrangement.
• A Type B RCD at the origin of the circuit → required only where the charger has no built-in DC detection, or on TT systems where the source RCD is specified as Type B (100–300 mA).

Type AC devices are never acceptable for EV circuits. Don't stack a Type B downstream of a Type A - DC blinding works in the other direction; check discrimination with the designer.

Dedicated radials - why there's no diversity on charging

Each charging point is a continuous full-load appliance: a 7 kW socket draws 32 A for hours at a time. BS 7671 Section 722 requires design at full rated current - you cannot apply diversity factors to EV circuits, and chargers must never share a protective device or loop from one unit to the next.

• One radial, one protective device, one cable per charger (per socket on back-to-back posts).
• An EV distribution board (EVDB) close to the chargers keeps radials short and makes future additions cheap.
• If the sums don't fit the supply, the answer is dynamic load management (wired or cloud) or a supply upgrade - never diversity.

Surge protection on EV boards

Since Amendment 2 (2022), BS 7671 expects surge protection in most new installations unless a documented risk assessment says otherwise. For EV work the practical rule: fit a Type 2 SPD in the EVDB or at the origin of the new charging circuits (a Type 1 is also acceptable at the origin on TN-S). Chargers are outdoor electronics on long cable runs - cheap to protect, expensive to replace.

Photograph the SPD with its status window visible for the job's photo record, and note it on the EIC.

Assess maximum demand before you design

Headroom = supply capacity − existing maximum demand. Establish both before placing a single charger:

• Supply capacity: read the cut-out / service fuse rating, or the agreed capacity (kVA) on a CT-metered supply. Never open the cut-out - that's the DNO's.
• Existing demand: half-hourly data from the energy supplier is best; otherwise a logged measurement over a representative week, at the worst season.
• New load: full rating per socket, no diversity - 32 A at 7 kW, 16 A per phase at 11 kW, 32 A per phase at 22 kW - then decide whether dynamic load management brings it inside the headroom.

TN-C-S, TN-S and TT - what changes on site

Touch potential on TT: keep other mains-powered street equipment (lamp columns, powered bollards, gates) at least 2.5 m from the charger unless it shares the same earthing system. This does not apply to TN systems.

Open-PEN protection without an earth rod

On a PME supply, a broken PEN conductor can put mains voltage on everything earthed - including a car on charge outdoors. BS 7671 (722.411.4.1) gives several compliant answers; in practice you'll use one of:

• Built-in open-PEN detection in the charger (voltage-monitoring device to IET 01 / the device standard) - common on current commercial units but not universal. Where the data sheet confirms it, nothing extra to install.
• A separate open-PEN device (OPDD) ahead of a charger that lacks it.
• Convert the circuit to TT with an earth electrode - last resort, brings the TT conditions with it.

Don't double up. If the unit already has O-PEN detection, an extra upstream O-PEN device is unnecessary and can cause commissioning failures. Check the data sheet, then leave it out.

Select and size charger cables

• Type: SWA or an EV-grade composite cable. Twin & Earth is not acceptable for external charger circuits.
• Size: typically 6–16 mm² for single-socket units (25 mm² for twins), driven by load, installation reference method, run length and volt drop - do the calculation, keep it on file.
• Cores: line(s) + neutral + a dedicated CPC core. SWA armour is earthed at the supply end through a proper SWA gland, but the armour can never be the sole CPC.
• Volt drop: long car-park runs are the usual killer - check against the 5% limit at full 32 A load before committing to a route.

Termination, spares and passive circuits

• Leave ≥2 m of cable coiled at every charger position, ready for the unit termination.
• One cable per unit - no loop-in / loop-out between chargers.
• Label every cable at both ends with its circuit reference; fixed, legible, weatherproof.
• Passive (future-use) circuits: terminate into an adaptable box with maintenance-free connectors, label "Passive" with the circuit number, test them, and record them on the draft EIC - untested passive runs get excluded from certification and stall future expansion.

Data cables for load management

• Cloud DLM: no data cabling at all - each charger just needs reliable internet over whichever of Ethernet, Wi-Fi or 4G the unit actually supports (not every model offers all three). Most systems fall back to a safe preset rate if the connection drops - confirm the offline behaviour for the brand.
• Spec (wired): typically 4-core LSZH shielded data cable; screened to 600 V when run alongside LV power. Heavier gauge on runs over ~60 m. 2 m spare both ends. The manufacturer's spec governs - check it before ordering.
• CT limiter: one data cable per charger and per phase, radial only - never daisy-chained.
• Wired DLM: data links the board / controller to every charger - daisy-chained, star-wired or mixed per the manufacturer's topology; keep clusters on different phases on separate data runs.
• Future-proofing: pulling data alongside every power cable today (terminated, labelled "Passive - future load management", on the draft EIC) means moving to wired DLM later needs no re-trenching - or skip it and plan for cloud DLM.

Set up dynamic load management (DLM)

DLM runs a group of chargers inside one supply limit: the system watches demand and de-rates active units in real time so the total never exceeds the limit. Exactly how it behaves is set by the charger brand - typically any mix of 7, 11 and 22 kW AC units from one manufacturer's range can join a group, each keeps charging down to a ~6 A minimum, and below that units queue until capacity frees up. Two ways to build it:

• Limits are per phase - a three-phase group serves 3× the sockets, and three-phase (11 / 22 kW) units are balanced on every phase.
• Set the group limit at commissioning, slightly below the fuse or agreed capacity - never at it. On most systems it stays manually adjustable (on site or remotely) as the site's needs change.
• Many systems also let individual chargers be manually capped - e.g. one unit held at 16 A on a tight corner of the site.
• Sub-main and switchgear are sized to the full group limit - no diversity.

CT-clamp load limiting for tight supplies

A CT clamp on the incoming tails watches whole-site demand; when it approaches the fuse rating the charger de-rates, then ramps back up as demand falls. Set the threshold to sit inside the fuse rating; output typically bottoms out around a ~6 A minimum. Whether a limiter is offered - and which outputs it supports - varies by charger brand and model, so confirm it on the data sheet before quoting one. One dedicated data cable per charger and per phase back to the clamp position - never daisy-chained. For more than a couple of units, a DLM group (wired or cloud) is the better tool.

Bases and ducting that pass first time

• Base: 600 × 600 × 400 mm, C20 concrete or stronger, flat and flush with the finished surface (450 × 450 is often accepted for a single-post unit). One per charger, fully cured before install day - no exceptions.
• Duct: 63 mm twin-wall (63–110 mm for twins), centred through the base and finishing flush; ≥450 mm deep in general areas, ≥600 mm under roadways; bend radius ≥450 mm, entering the base vertically; watertight at every entry.
• Warning tape 150 mm above the duct, plus a pull cord.
• Photograph the bare base before any surface finish is laid - tarmac over it is fine afterwards; block paving is conditional and the fixing risk sits with whoever laid it.

Bay marking and accessible charging (PAS 1899)

• Standard bay 2.4 × 4.8 m, painted "EV only" lettering and a contrasting strip at the open end so drivers stop within cable reach; wheel stops protect the unit.
• PAS 1899:2022 is the accessible-charging spec: wider bays with hatched transfer zones, level ground, clear approach routes, and controls/sockets reachable from a wheelchair (typically 0.75–1.2 m above ground).
• Plan at least some accessible provision on public and workplace sites - grant and planning conditions increasingly expect it, and retrofitting bay layouts is expensive.

Signage, lighting and bays that stay usable

• Signage: an "EV charging only" sign per bay or pair, plus operator and tariff information where the public charges. Fix signs clear of door swings, the hatched transfer zone and the charging lead's reach.
• Enforcement: agree up front who polices the bays and how - parking terms, warnings, fines or barriers. Signage without enforcement means blocked bays within weeks of go-live.
• Lighting: walk the site after dark. You want even light at each charger and along the approach route, no deep shadow between car and socket, and no glare into drivers' eyes. PAS 1899 expects accessible bays to be well lit, and units are commissioned and serviced after dark too.
• Evidence: photograph the signed, lit bays at handover - planning conditions and grant claims increasingly ask for proof.

Get every charger online - or it can't be commissioned

• Mobile (3G/4G): built into most commercial units, zero setup - the default for outdoor positions. Check signal at the actual charger location, not the car park entrance.
• Wi-Fi: 2.4 GHz only on most units - a dedicated 2.4 GHz SSID beats a dual-band network. Private and secured; no captive portals or guest login pages. Watch vendor limits on SSID/password length.
• Ethernet: where the unit has a port (not all do) - shielded Cat5e/Cat6, live before install day, straight to the network; again, no portals.
• Smart-charging regulations assume connectivity: an offline charger fails commissioning outright.

DNO notification and applications

Every chargepoint must be notified to the network operator - it's how the DNO keeps the local network safe as load grows. The route depends on the installation:

• Connect & notify (within 28 days): only when the ENA criteria all hold - a single new unit, cut-out rating known, no looped service, metered supply, and maximum demand stays under the cut-out and under ~60 A (13.8 kVA) per phase.
• Apply first: everything else - multiple chargers, load-managed systems, tight headroom or looped services. The DNO has 10 working days to respond to a notification; larger schemes get a connection offer instead.
• Submissions go through the ENA Connect Direct portal (links below). Since April 2023, demand customers aren't charged for upstream network reinforcement - you pay only for your own connection assets.
• Talk to the DNO early on multi-charger sites: capacity data shapes the whole design.

Certification and a clean photo record

• EIC (with schedules of inspection and test results) for every new circuit - issue a draft covering passive circuits too. Domestic work also needs Part P notification via a competent-person scheme.
• Photograph as you go: cut-out/supply head with ratings legible, protection devices in the board, cable runs and glands, the coiled 2 m spare, and the bare concrete base before surfacing.
• Share before sign-off: if a client, principal contractor or charger supplier has to approve the works, send photos and draft certificates ahead of the visit - surprises on the day become revisits.
• Skipped photos = arguments later: surfacing hides the base, walls hide the cable, and the warranty conversation gets expensive. The record costs minutes.

The 2026 rulebook at a glance

• BS 7671 (18th Edition): Amendment 4 ("Orange Book") was published 15 April 2026; the previous version (…+A2:2022+A3:2024) is withdrawn on 15 October 2026, after which new work certifies to A4. Check which edition your certification software and designs cite. Section 722 is the EV chapter.
• What A4:2026 changed for EV work: Section 722 gains provisions for bidirectional charging (V2G/V2H) and export-capable units; 6 mA DC fault detection for Mode 3 now references RDC-DD to IEC 62955 (not just Type B RCDs); AFDD requirements extend to more premises including EV charging circuits; and a new Chapter 57 covers battery storage that increasingly shares the board with chargers. Schemes also now expect each person doing EV work to hold their own Level 3 qualification.
• IET Code of Practice for EV Charging Equipment Installation, 5th Edition (2023) - the practical companion to Section 722, aligned with ENA G12/4. Covers PAS 1899 accessibility, RC59 fire safety guidance, V2G/prosumer installs, buried-cable depths and telecoms/auxiliary cabling.
• Smart Charge Points Regulations 2021: private chargers up to 50 kW sold since 30 June 2022 must be smart, with default off-peak schedules, randomised delay and security requirements.
• Building Regs Part S (England): new homes and buildings with parking need chargepoints from the outset - at least Mode 3, ≥7 kW, universal socket, on a dedicated circuit.
• Public Charge Point Regulations 2023: consumer duties if your chargers serve the public - see the dedicated guide below.
• PAS 1899:2022: the accessible-charging specification - bay dimensions, clear access zones, charger reach and interface heights.
• Grants: the Workplace Charging Scheme runs until 31 March 2027 - up to £500 per socket (75% of costs, max 40 sockets per applicant) for installs completed from 1 April 2026, via OZEV-authorised installers.

Public charging sites: the consumer-facing rules

The Public Charge Point Regulations 2023 apply to any charger the general public can use - supermarket and destination car parks included. Private workplace and residential chargers are exempt. All the phase-in deadlines have now passed, so a new public site must meet the lot from day one:

• Pricing: the maximum price in p/kWh clearly displayed at the unit, on its screen or in the app before the session starts.
• Contactless payment on every new public charger of 8 kW+ (a shared site terminal is acceptable) - no app or membership barrier for ad-hoc users.
• Free 24/7 staffed helpline, with contact details displayed at the site, plus quarterly performance reporting.
• Open data via OCPI: live status, location, connector type and pricing published in machine-readable form.
• 99% reliability for rapid (50 kW+) networks, measured as an annual average, published and reported to OPSS.
• Roaming: payment through at least one third-party roaming provider (required since Nov 2025); new agreements reported within 28 days.

Enforced by the Office for Product Safety and Standards on behalf of OZEV - compliance notices can block further installs, and fines follow. Flag these duties to clients early: the payment terminal, data feed and helpline contract belong in the quote, not the snag list.

AFDD on EV circuits - decide and record

An AFDD trips on the arc signature of a damaged cable or loose termination - faults an RCD and MCB both miss. BS 7671:2018+A4:2026 extends where arc fault protection is expected, and EV final circuits are squarely in scope for the assessment.

• Mandatory list first: higher-risk residential buildings, HMOs, purpose-built student accommodation and care homes require AFDDs on 32 A socket circuits - an EV radial qualifies. Elsewhere the requirement is a documented judgement, not silence.
• Fitting one: a combined AFDD / RCBO (Type A, 30 mA) in the way feeding the charger keeps board space sane - check coordination with the charger's RDC-DD against the manufacturer's device list.
• Record the decision either way on the EIC / design record: "assessed - required and fitted" or "assessed - not required for this premises type". The written decision is what stands up at inspection.

AFDDs are wider than a plain RCBO and cost real money - decide at design so the board, quote and drawing all agree before fit-off.

CDM, RAMS and the paperwork that opens the site

• CDM 2015 applies to every job, even domestic installs. With more than one contractor on site, a principal designer and principal contractor are appointed and a construction phase plan (CPP) must exist before work starts - a few proportionate pages is fine for a small site.
• Notifiable jobs (30+ working days with 20+ workers at once, or 500+ person-days) also need an F10 notification to HSE before site set-up.
• Welfare from day one (CDM Schedule 2): toilet, washing, drinking water and somewhere to rest and eat: a welfare unit / site cabin on site, or the client's facilities agreed in writing, never assumed. Agree where the cabin, storage container and skip will stand, and which bays or access they take out, before mobilisation.
• RAMS: a site-specific risk assessment and method statement, issued to and accepted by the client or principal contractor before the start date. Name the actual site, tasks, plant and emergency arrangements - recycled generic RAMS are the top reason start dates slip.
• Buried services: utility drawings obtained (a free LSBUD enquiry covers most), the route CAT & Genny scanned and marked, hand-dig within 500 mm of marked services, and dig / isolation / hot-works permits signed before the first trench is cut.
• Public protection: Heras fencing around work areas, open trenches covered or fenced whenever unattended, a signed and lit pedestrian diversion, and banksman control where plant crosses footways.
• Asbestos: in any building built or refurbished before 2000, check the asbestos register / survey before drilling or chasing, and stop if suspect material appears.
• Emergency arrangements: named first aider and kit on site, an extinguisher at the work area, muster point and nearest A&E in the induction.
• Day one: inductions booked and signed, with the paperwork above displayed in the welfare unit.

Set the scale before anything else

Everything measurable - run lengths, lead-reach arcs, true-size chargers and bays, the budget - hangs off the photo scale. Use Set scale, drag along something with a known length (a parking bay ≈ 4.8 m, a door ≈ 0.9 m, a marked dimension on a site plan), type the real length, done. Do it once per photo, first. The readiness score flags any plan still missing its scale.

Routes that measure and price themselves

Pick the right route kind (SWA, duct, trench, tray, trunking, data…) - each carries its own line style, legend entry and spec note. On a scaled photo the length is measured as you draw; snap the ends onto equipment so runs land on the unit or board. Lengths roll into the totals card, and once you've entered rates, the live budget prices trenching, ducting, cabling and reinstatement per metre. Add run notes from the presets ("2 m spare coiled at charger", "Warning tape 150 mm above duct") so the drawing carries the install detail.

Model DLM groups and read the load check

Tag each charger with a DLM group letter (A/B/C) in its properties - any mix of 7, 11 and 22 kW. For wired DLM, place a load management board with the same letter and set its phase and limit; the board panel allocates RCBO ways and warns when sockets would queue. For cloud DLM, switch the group to Cloud in the charger panel and set its limit - no board or data cabling on the plan. The Supply load check card then counts each group at its limit instead of full rate per socket - so you can see exactly how much headroom load management buys before you commit to a supply application.