BS 7671 Section 722 Is Quietly Redesigning Your Car Parks: How EV Wiring Rules Are Shaping Real-World Projects

There is a persistent misconception in commercial property and construction circles that EV charging is primarily a procurement decision — choose a charger brand, choose a number of bays, install, done. The reality, for anyone who has actually delivered a compliant EV charging installation in the UK, is considerably more involved, and the source of that complexity has a specific name: Section 722 of BS 7671.

What Section 722 actually requires

Section 722 sits within Part 7 of BS 7671, the part of the wiring regulations dealing with "Special Installations or Locations" — environments where the general rules in Parts 1–6 need modification or addition because of specific additional hazards. EV charging earns its place in Part 7 because of a genuinely distinct set of risks that don't arise in most other electrical installations.

The most significant of these concerns earthing. The majority of UK domestic and many commercial supplies use PME (Protective Multiple Earthing, also called TN-C-S) earthing arrangements, where the neutral and earth conductors are combined for part of their run. This is normally safe and standard practice. It becomes a specific hazard in the context of EV charging because if the combined neutral-earth (PEN) conductor suffers an open-circuit fault, the body of a vehicle being charged could become live — and anyone touching the vehicle while it remains connected to the network could receive a fatal shock.

Regulation 722.411.4.1 addresses this directly: a PME earthing facility cannot be used as the means of earthing for an EV charge point's protective conductor unless one of four specific alternative protective measures is applied. These range from connecting the installation's main earthing terminal to an independent earth electrode, to using a device that detects an open-circuit PEN fault and disconnects the charging point within five seconds.

RCD selection — a more complex question than it appears

The second area where Section 722 imposes genuinely specific requirements concerns residual current device (RCD) selection, and it's an area where misunderstanding is common even among experienced installers.

EV charging circuits can carry DC residual currents — a consequence of the power electronics inside most EV charging equipment. A standard Type AC RCD is not capable of reliably detecting DC residual current, and worse, the presence of DC current can actually "blind" certain RCD types upstream, preventing them from operating correctly even for faults they would normally detect. Regulation 722.531.3.101 addresses this by requiring each charge point to be protected by an RCD of Type A, Type F, or Type B, each rated at no more than 30mA.

Getting RCD selection wrong on an EV installation is one of the more common compliance failures identified in the sector, precisely because it requires understanding a fault mechanism — DC blinding of upstream protection — that doesn't arise in conventional domestic or commercial electrical work.

Dedicated circuits and load management

Section 722 also requires, with limited exceptions, that EV charging equipment be supplied by its own dedicated final circuit — charging points cannot simply be looped together on a shared radial circuit the way some other equipment can. This has direct implications for car park and building electrical design: the number of dedicated circuits required scales with the number of charge points, which in turn has implications for distribution board capacity, cable routing, and the overall electrical infrastructure needed to support a given number of bays.

This is where the regulation intersects directly with practical capacity planning. A site with genuine ambitions to support a meaningful number of EV bays needs either substantial spare electrical capacity or a load management strategy — dynamically sharing available capacity across multiple charge points rather than provisioning each one for simultaneous full-rate charging. Without that strategy, the dedicated circuit requirement alone can force expensive supply upgrades that a more considered design could have avoided or deferred.

Where Approved Document S fits in

Section 722 governs how an EV charge point must be wired once it exists. A separate piece of regulation — Approved Document S, part of the Building Regulations — governs whether and where charging infrastructure provision must exist in new buildings in the first place.

Part S requires what's commonly called "passive provision" in much new residential and non-residential construction: even where an EV charge point isn't being installed immediately, the building must include the necessary ducting, cable routes, and electrical capacity to allow one to be added later without disruptive retrofit works. This is a deliberate policy response to the well-documented cost differential between EV-ready new build and EV retrofit — provisioning the infrastructure during initial construction is consistently and substantially cheaper than adding it after the fact.

The design implications that follow

Taken together, Section 722 and Part S have a cumulative effect that goes well beyond "charger procurement." They are pushing EV charging considerations into the structural and electrical concept of car parks, podium decks, and risers at a stage of design where it used to be entirely absent.

Concretely, this means:

• Cable route planning for dedicated circuits needs to happen alongside structural design, not after it — particularly in multi-storey or podium car parks where riser space and route geometry are genuinely constrained.
• Earthing system design needs to account for PME restrictions from the earliest concept stage, particularly on sites where outdoor charging is intended and the existing supply arrangement is PME-based, which is the majority case in the UK.
• Distribution board and supply capacity sizing needs to reflect a realistic forecast of future EV demand, not just the bays being fitted out immediately — because Part S passive provision requirements exist precisely to avoid the alternative, which is expensive retrofit later.
• Load management strategy should be decided at design stage, because it directly affects how much spare distribution capacity is actually required, and therefore how much of the site's electrical infrastructure budget needs to go toward EV provision versus other uses.

None of this is exotic engineering. It's well-documented, well-understood regulation that has been in force for several years. What's striking is how often it still gets treated as a late-stage installation detail rather than a design input — and how consistently that produces avoidable cost and delay on projects where EV charging was assumed to be simple right up until someone actually had to wire it.