What Distribution Boards Are
Distribution boards (DBs) are electrical panels that receive power from an upstream supply (main switchboard or service entrance) and distribute it safely to multiple downstream circuits. They contain protective devices such as circuit breakers, RCD/RCBOs, surge protection, and often metering. In EV charging projects, DBs are the key “hub” that feeds one charger or a group of chargers.
Common names by market: consumer unit (UK residential), electrical panel / panelboard (general), sub-distribution board (commercial).
Why Distribution Boards Matter for EV Charging
EV charging creates sustained, high-current loads and often many parallel circuits. Proper DB design:
– Protects people and equipment from overloads, short circuits, and earth leakage
– Reduces nuisance trips through correct protection coordination
– Enables scalable rollouts (add more bays later without reworking the whole site)
– Simplifies maintenance with clear isolation points and labeling
– Supports load management and energy monitoring for depots and car parks
What You Typically Find Inside a DB
A charging-focused distribution board commonly includes:
– Main isolator / switch disconnector
– MCBs/MCCBs for each charger feeder circuit
– RCD / RCBO protection (type depends on charger design and local rules)
– Surge protection device (SPD) for transient protection
– Energy metering (site sub-metering or compliance metering where needed)
– Neutral and earth bars, terminal blocks
– Optional contactors/relays for emergency stop or load shedding
– Clear circuit labeling and documentation
Types of Distribution Boards in Charging Sites
Different sites use different DB structures:
Single-Charger DB
– Common for small destination/workplace sites
– Simple feeder and protection for one unit
– Often located close to the charger to reduce cable length
Multi-Charger Sub-DB
– Feeds several AC chargers in a car park or depot row
– Designed with spare ways and consistent feeder sizing
– Often integrates metering and a load management controller
Zone-Based DB Architecture
– Larger sites split distribution by zone (garage levels, depot sections)
– Reduces long feeder runs and improves fault isolation
– Helps keep maintenance local and minimizes whole-site outages
Key Design Considerations
Distribution boards for EV charging should be planned as part of the full electrical system:
– Continuous load sizing and derating (EV charging is often sustained)
– Selectivity/coordination so one fault doesn’t drop all chargers
– Phase balancing for three-phase AC networks (avoid overloading one phase)
– Earthing arrangement and local code requirements
– RCD strategy compatible with charger design and DC leakage behavior
– Thermal management inside the enclosure (overheating risk at high duty)
– Correct IP rating and corrosion resistance for outdoor/industrial locations
– Expansion readiness: spare breakers, space, ducts, cable routes
Common Pitfalls
– No spare capacity → expensive rework when expanding bays
– Wrong RCD selection → nuisance tripping or non-compliance
– Missing or undersized SPD → failures after transient events
– Poor labeling/as-builts → slow and risky service work
– Overfilled enclosures → hot spots, reduced reliability
– Ignoring phase balance → uneven loading and unnecessary trips
Related Terms for Internal Linking
– Distribution board (DB)
– Electrical panels
– Circuit breaker (MCB/MCCB)
– Residual current device (RCD/RCBO)
– Surge protection device (SPD)
– Phase balancing
– Load management
– Earthing (grounding)