A busway centre feed unit is the electrical point where power is supplied into the middle, or “centre,” of a busway system. A busway, also called a bus duct, is a prefabricated power distribution system made of metal-enclosed conductors that carry electricity to different parts of a building or facility.

In a centre feed arrangement, the incoming electrical supply is connected at a point located somewhere along the length of the busway rather than only at one end. This allows power to flow in both directions from the centre feed point, which can reduce voltage drop, improve efficiency, and make the system more flexible for large installations.

The centre feed unit usually includes connection terminals, protective enclosure, and sometimes isolation or switching devices. It is commonly used in factories, commercial buildings, data centers, and industrial plants where power demand is high and distribution needs to be adaptable.

Its main advantages are easier expansion, better load balancing, and more efficient use of the busway layout. Instead of running long feeder cables from one end, the supply can be introduced closer to the center of the load area.

In simple terms, a busway centre feed unit is the component that injects electrical power into the middle of a busway distribution line, helping distribute electricity evenly to connected loads on both sides.

A centre feed unit has several advantages over an end feed unit.

First, it supplies power from the middle of the distribution run, so the load is shared in both directions. This greatly reduces voltage drop at the far ends of the circuit, which helps equipment receive a more stable and efficient supply.

Second, because current flows only partway in each direction instead of the full length from one end, there is less power loss and less heating in the conductors. This improves overall efficiency and can increase the life of the system.

Third, a centre feed arrangement allows better balancing of heavy loads on long runs. It is especially useful where the load is spread fairly evenly along a busbar or trunking system, since the electrical stress is distributed more uniformly.

Fourth, it can reduce the need for larger cable sizes or additional reinforcing, since the current path is shortened on both sides. This can make installation more economical in some applications.

Finally, centre feeding provides more flexibility in design and expansion, because the supply point can serve loads in both directions without overloading one end of the system.

In short, the main advantages are lower voltage drop, reduced losses, better load distribution, and improved efficiency compared with an end feed unit.

Busway centre feed units are typically used in the middle of a busbar run to supply power from a central point rather than from one end. They are common in large commercial, industrial, and data centre installations where balanced power distribution is important.

They are often found in:

• Data centres, to feed large sections of rack power distribution from a central electrical room
• Manufacturing plants, where busway runs serve multiple machines or production lines
• Warehouses and logistics facilities, for lighting, conveyors, and equipment
• Hospitals and laboratories, where reliable and flexible power distribution is needed
• Large office buildings, malls, and high-rise developments with long busway trunking systems

A centre feed unit is especially useful when the busway extends in two directions from the power source. This reduces voltage drop, improves load balancing, and can make the installation more efficient than feeding from one end only. It is also used when space or layout makes a middle connection more practical than an end connection.

In short, busway centre feed units are typically used wherever a long busway system needs power introduced from the center to serve loads on both sides efficiently and reliably.

To size or select a centre feed unit for a busbar trunking system, first determine the electrical load and installation constraints.

1. Calculate the design current Find the maximum demand current of the system, including diversity, future growth, and any continuous loading. Select a centre feed unit with a continuous current rating equal to or greater than this value.

2. Check the fault level Confirm the prospective short-circuit current at the point of installation. The centre feed unit and associated busbar trunking must have a short-circuit withstand rating and protective device breaking capacity higher than the available fault level.

3. Verify voltage drop Since the feed is in the centre, current flows in both directions, reducing voltage drop compared with end feed. Still, calculate voltage drop for the longest half-run to ensure it remains within permissible limits for the load.

4. Match to the busbar trunking rating The feed unit must be compatible with the busbar system’s phase arrangement, conductor size, insulation class, tap-off provision, and enclosure type. It should not become the limiting component in the system.

5. Consider protection and isolation Select appropriate incomer protection, such as an MCCB or ACB, coordinated with the busbar trunking. Ensure the unit provides safe isolation, earthing, and any required discrimination with downstream devices.

6. Check physical and environmental conditions Confirm space for installation, access for maintenance, cable entry direction, ambient temperature, IP rating, and any corrosion or fire-performance requirements.

7. Allow for expansion If future load increase is expected, choose a centre feed unit with spare capacity or a higher-rated trunking section.

In practice, the unit is selected by current rating, fault withstand, voltage drop, protection coordination, and physical compatibility with the busbar system.

A busway centre feed unit should be installed by a qualified electrician in accordance with the manufacturer’s instructions, applicable electrical codes, and the project drawings. It must be positioned to match the busway system rating, phase arrangement, and load demand. The support structure should be strong, level, and able to carry the unit and connected busway without strain. Adequate clearances must be maintained for access, ventilation, inspection, and future maintenance. All incoming supply cables must be correctly sized, properly terminated, and fitted with suitable protection and isolation devices. Connections should be torque-tightened to the specified value, and all joints, covers, and access panels must be secured. The unit should be correctly earthed, and its enclosure must be protected against moisture, dust, vibration, and physical damage.

Maintenance requirements include regular visual inspections for overheating, discolouration, loose fittings, corrosion, contamination, and signs of arcing or insulation damage. Electrical connections should be periodically checked and re-torqued as recommended by the manufacturer, especially after the initial commissioning period and after any heavy load operation. Ventilation openings and internal compartments should be kept clean and free of dust or debris. Any damaged seals, covers, or insulating parts must be replaced immediately. Protective devices, isolators, and meters should be tested at scheduled intervals to confirm proper operation. Maintenance work must only be carried out after isolating and locking out the supply, proving dead, and following safe working procedures. A maintenance record should be kept to track inspections, defects, repairs, and test results.