What a Distribution Board Is
A distribution board (DB) is an electrical panel that receives power from the main supply and safely distributes it to multiple downstream circuits. It contains protective and control devices such as circuit breakers, RCD/RCBOs, surge protection, and sometimes energy meters. In EV charging projects, the DB is the central point where power is split and protected before feeding one or more chargers.
Common synonyms: consumer unit (UK residential), panelboard (some markets), electrical distribution panel.
Why a DB Matters in EV Charging Installations
The DB is critical because EV charging adds large, continuous loads that must be protected and coordinated properly. A well-designed DB helps:
– Protect people and equipment from faults (short circuit, earth leakage, overload)
– Prevent nuisance trips through correct breaker and RCD selection
– Enable scalable deployments (adding more chargers later)
– Support load management by grouping circuits and measuring site load
– Improve maintainability with clear labeling and isolation points
What’s Inside a Typical DB for EV Charging
A charging-focused DB often includes:
– Main isolator or switch disconnector
– MCBs/MCCBs for each charger feeder
– RCD / RCBO protection (type depends on charger design and local code)
– Surge protection device (SPD) (especially for outdoor/public sites)
– Energy metering (MID where required, or site sub-metering)
– Contactors / relays for control (optional, e.g., emergency stop, load shedding)
– Terminal blocks for neutral and earth bars
– Clear circuit labeling and documentation
DB vs Main Switchboard
In larger commercial sites, the DB is usually downstream of a main switchboard:
– Main switchboard handles the incoming supply and high-level protection
– DBs handle distribution to zones, car parks, or charger groups
Depots and multi-bay installations often use multiple DBs to reduce cable runs and simplify maintenance.
Design Considerations for EV Chargers
DB design for EV charging should account for:
– Continuous load behavior (derating, cable sizing, breaker selection)
– Selectivity/coordination so one fault doesn’t shut down the whole site
– RCD type compatibility (and DC leakage considerations)
– Earthing arrangement (TT/TN systems, local requirements)
– Spare ways for future expansion
– Ingress protection (IP rating) and corrosion resistance for outdoor use
– Integration points for load management (CT clamps, meters, controllers)
Common Pitfalls
– Not allowing enough spare capacity (no room to add chargers later)
– Wrong RCD strategy leading to nuisance tripping or non-compliance
– Poor labeling and documentation → slow fault finding and unsafe servicing
– No SPD in exposed environments → damage from transients
– Undersized enclosures or poor thermal management → overheating
– Incorrect phase balancing in 3-phase systems when many AC chargers are used
Related Terms for Internal Linking
– Electrical panels
– Circuit breaker (MCB/MCCB)
– Residual current device (RCD/RCBO)
– Surge protection device (SPD)
– Earthing (grounding)
– Load management
– Cable sizing