Busbar trunking (also called busbar trunking system or busduct) is a modular electrical distribution system that uses enclosed busbars within a protective housing to efficiently distribute power across a building or site. In EV charging infrastructure, busbar trunking is often used in car parks, parking garages, depots, and commercial sites to feed multiple chargers along a route, reducing cabling, enabling easier expansion, and improving installation speed.
What Is Busbar Trunking?
Busbar trunking is an enclosed conductor system designed to carry high currents over distance and provide multiple tap-off points for loads. A typical system includes:
– Enclosed busbar sections (straight lengths and elbows)
– Insulated conductors (copper or aluminum) inside a metal housing
– Joint kits and mechanical supports
– Tap-off units or connection boxes to feed branch circuits
– Earthing/grounding conductor and protective enclosure
– Ratings for current, short-circuit withstand, and IP protection
Instead of running many individual cables from a distribution board to each charger, a busbar trunk runs through the area and chargers are connected via tap-offs.
Why Busbar Trunking Matters in EV Charging
EV charging rollouts often grow over time, with more bays added each year. Busbar trunking supports scalability and clean site design, especially in parking structures.
It matters because it:
– Reduces cable volume and installation complexity
– Speeds up deployment in long corridors and multi-level car parks
– Enables easy expansion by adding tap-off units for new chargers
– Provides predictable voltage drop performance over long runs
– Improves maintainability with clearer distribution architecture
– Supports high-current distribution for multi-charger sites and depots
For sites planning additional charger provision, busbar trunking can be a future-proof backbone.
How Busbar Trunking Is Used in Charging Installations
A common EV charging design looks like this:
– Main switchboard supplies the busbar trunking with a protected feeder
– Trunking runs along the parking area or structure (ceiling or wall mounted)
– Tap-off boxes connect at planned intervals for chargers or charger groups
– Each charger (or group) has its own protective devices (breaker, RCD) downstream
– Load management may cap the total demand to match available import capacity
Busbar trunking can support both AC charging distribution and, in some designs, centralized power cabinets feeding multiple points.
Typical Use Cases
– Multi-storey car parks where chargers are spread across long distances
– Business parks and outdoor car parks with many bays in a row
– Fleet depots and bus depots with repeatable bay layouts
– Warehouses and logistics hubs adding chargers in phases
– Sites requiring clean, maintainable electrical distribution with easy future expansion
Key Benefits of Busbar Trunking
– Faster installation compared to running many long cable routes
– Modular expansion with tap-off units for new chargers
– Cleaner, less congested cable management in parking structures
– Strong current-carrying capability and good thermal performance
– Predictable distribution and easier fault isolation by sections
– Reduced downtime when expanding sites (add tap-offs without re-pulling cables)
Limitations to Consider
– Higher upfront cost than cables for small or low-density installations
– Requires careful engineering for short-circuit withstand and protection coordination
– Physical routing constraints (clearances, fire barriers, aesthetics)
– Joint quality and torque control are critical for long-term reliability
– Tap-off spacing must be planned; changes later can require new sections
– Local code requirements for fire rating, support spacing, and IP protection must be met
Related Glossary Terms
Busbar
Switchboard
Distribution Board
Branch Circuit
Protection Coordination
Breaking Capacity (kA Rating)
Available Import Capacity
Voltage Drop
Charging Site Design
Additional Charger Provision