What BS 7671 requires
BS 7671 Section 537.4 covers emergency switching: the means by which a circuit or section of an installation can be rapidly disconnected in response to a danger that has arisen or is anticipated. The requirements are framed in general terms and apply to any installation — but their application to EV charging installations deserves specific consideration, because the hazards associated with EV charging differ in important ways from those of conventional electrical loads.
BS 7671 requires that every means of emergency switching be clearly identifiable, readily accessible, and capable of cutting off the electrical supply to all live conductors — including the neutral in a TT installation, where the neutral cannot be treated as being at earth potential. This last point is frequently overlooked: a switching device that opens only the line conductors in a TT-earthed charging installation may leave the neutral conductor live following a fault, which is not an acceptable emergency condition.
The standard also requires that the emergency switching device be positioned where the operator has a clear view of the equipment it controls, or where there is no risk that the equipment could be inadvertently re-energised while hazardous conditions exist. For a multi-bay charging forecourt, a single emergency switch serving the whole installation should generally be positioned at a point from which the entire charging area is visible.
The IET Code of Practice — practical interpretation
The IET Code of Practice for EV Charging Equipment Installation (5th edition) elaborates on the BS 7671 requirements in the specific context of EV charging. It recommends that emergency switching be provided for all EV charging installations — not just those where it would be mandated by BS 7671 — reflecting the specific risks of the charging environment: the possibility of a vehicle battery entering thermal runaway during charging, the potential for fire in an enclosed parking structure, and the need for emergency services to be able to rapidly disconnect charging supply without specialist knowledge of the installation.
For public-accessible installations, the Code recommends that emergency switching devices be of a type and in a location accessible to members of the public — clearly labelled, at an accessible height, and of sufficient ingress protection (IP rating) for the installation environment. A mushroom-head emergency stop button behind a locked electrical panel does not fulfil this requirement.
Fire authority guidance and the implications of EV fires
The National Fire Chiefs Council and local fire authorities have published guidance addressing the specific challenges of EV battery fires. RC59, developed with input from the fire services, addresses EV fire risk management in the context of car parks and charging infrastructure, and its recommendations inform how emergency switching should be approached for larger installations.
The key concern is thermal runaway — an exothermic chemical reaction within a lithium-ion battery cell that, once initiated, propagates through adjacent cells and cannot be suppressed by conventional fire suppression. An EV fire can take many hours or days to fully extinguish, with repeated re-ignition possible as the battery continues to release energy. Disconnecting the charging supply does not stop a battery fire that has already started, but it removes the ongoing electrical energy input that could escalate the event, and it is a precaution that fire crews will routinely want to take on arrival.
For enclosed car parks and multi-storey structures, the fire authority guidance increasingly points toward automatic disconnection of EV charging supply on fire alarm activation — removing the need for manual emergency switching as a first response and ensuring the charging circuits are de-energised before fire crews enter the building. This integration with the fire alarm system requires coordination at the design stage between the electrical engineer and the fire system designer, and should be confirmed with the relevant fire authority before the installation is designed.
Common design errors
Three recurring errors appear in emergency switching provision for EV charging installations. First, the emergency switching device is specified to open line conductors only — creating a false sense of security in TT installations where the neutral remains live. Second, the device is positioned inside a locked enclosure or meter cabinet, inaccessible to users or emergency services. Third, the device is specified to serve individual charge points rather than a grouped circuit arrangement, leading to installations where twelve individual emergency buttons are needed where one appropriately positioned switch would serve the entire forecourt.
These are not trivial omissions. Inspection and certification under BS 7671 should identify them — but the appropriate point to address them is at the design stage, where corrections can be made without cost or delay.