Busbars—how they work and how they compare to normal cable systems

Traditionally, busbars are the power distribution systems that carry and distribute electricity throughout industrial premises.

In offices, the term “busbar” usually refers to a type of powertrack that’s typically installed within raised access floors and used to supply power to floor boxes beneath desks and workstations.

On this page, we cover underfloor busbars, and explain:

  • how they work
  • how they compare to normal cable distribution systems
  • how they are installed

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What is a busbar?

The type of busbar seen in many offices is a power distribution system. It looks like a metallic track featuring a series of plug sockets that are used to feed the building’s mains power to wherever electricity is needed—whether that’s floor boxes, electrical sockets or other outlets.

Busbars both ground and conduct electricity, to safely distribute electric power throughout premises.

You can find powertrack-style busbars in:

  • offices
  • factories and workshops
  • supermarkets and shopping centres
  • hospitals
  • universities and schools

Overhead busbars fix to ceilings or walls, while underfloor busbars sit inside the cavities in raised access floors.

The term “busbar” can also refer to large uninsulated metallic strips employed in industrial applications to distribute local high-current power. These are used in high-voltage electrical switchyards or in battery banks, for example. To prevent people touching these fatally high-voltage busbars, they are usually placed within an earthed metallic enclosure or high out of reach.

On this page, we focus on the underfloor powertrack type of busbar.

How do busbars work?

Busbars carry power from the transformer to the low-voltage switchgear—in other words, the switches, fuses or circuit breakers that control, protect and isolate the electrical equipment.

In a typical office building, the busbar system is installed under the raised floor. Its feed unit is connected to the building’s mains supply. Rooms can feature several busbars depending on the size of the room to which they are supplying power. The tracks contain strips (often made of copper) with excellent conductivity, housed within metallic trunking.

At each point where the electricity needs to branch off to power the floor boxes or other outlets above, a tap-off unit is connected. The systems tend to be designed to accept tap-off units at certain intervals, so they can be removed or added without the need to isolate the whole system.

This is one of the main advantages that busbars have over normal cable distribution systems. With cabling, you’re restricted to tapping electricity from just one fixed point. Tap-off units allow you to draw power from a number of electrical connections, and vary them as needed.

This image shows a CMD Betatrak busbar installed under a raised floor.

The two white components are the tap-off units, the first of which is connected to a floor grommet.

Why choose busbars over normal cable distribution systems?

Busbars have come to replace cabling as the power distribution system of choice as they have a wide variety of benefits. But what makes them so advantageous, particularly to office-based businesses?



They use space more efficiently

  • Compact, flat modular design means they need less space than traditional cabling
  • Can be installed under raised access floors more easily

They are a cost effective solution to traditional cabling methods and less time-consuming to install

  • Quick and easy manual assembly—powertrack busbar snaps together while tap-off units simply plug in
  • No tools needed

They offer a more flexible range of configurations

  • Configurations to suit most shapes and sizes of buildings and rooms with raised access floors
  • Modular design makes them less costly as they can be moved and reinstalled easily

They are suitable for installations with a high ambient temperature

  • Designed to comply with BS EN 61534 and allow installations to comply with Appendix 8 of the 18th Edition of the Wiring Regulations BS 7671:2018

They can be installed in long runs within the installation

  • Low-voltage drop at full load current distributes power efficiently, with low losses
  • More effective means of power distribution when compared with traditional cabling methods

They require fewer additional components

Powertrack systems don’t have the same reliance on other equipment (such as cable trays etc.) to achieve a compliant installation

How are busbars installed?

Most modular busbar systems follow similar methods of installation. Below, we explain how a CMD Betatrak underfloor busbar would be installed in an office with a raised access floor.

For the best possible layout, we advise arranging the Betatrak busbars in parallel lines, with the feed units facing towards the incoming supply.

Space each length of track no more than five metres apart and no more than 2.5 metres from the nearest wall when using a standard three-metre tap-off to a floor box.

Installing a busbar—step-by-step

This is the standard process for installing CMD’s powertrack busbar. The process for other similar busbar systems might differ slightly.

Before you start

Use a chalk string (or equivalent) to mark out where you intend the track to run. When installing, align the track lengths with the chalk line.

Connecting the feed unit

  1. Unscrew the two fixing screws at the top of the feed unit.
  2. Open the hinged cover and remove the ‘stop end’ from the feed unit by taking out the fixing screw. Make sure the fixing tabs are in position for fixing to the slab.
  3. Check that the label information on the feed unit matches that on the track. Align the dovetails and push firmly down until the track connector engages fully. Note: Do not hammer the connector into the feed unit or otherwise force it in.
  4. Secure the track connector with screw provided.
    1. Position the feed unit and align it and the track length with the marked-out run direction.
    2. Screw down the feed unit and track length.
    3. Connect the cables.
    4. Close the cover.

Note: Tighten the screw terminals for the supply cable to a torque setting of no more than 2.5Nm.

Connecting the track length

  1. Align the dovetails and push firmly down until the track connector engages fully. Make sure to position the plastic clips over the flanges. Note: Do not hammer the connector into the track or otherwise force it in.
  2. Secure the track connector with the screw provided (optional).
  3. Locate the bracket between the coupler and the last socket and screw to the slab.

Fixing the track

  1. Position the intermediate brackets (pre-assembled to track).
  2. Flip down the tabs.
  3. Screw the bracket to the slab.

Fitting the stop end

  1. Fit the ‘stop end’ and secure with a screw (taken from feed unit).
  2. Locate the intermediate bracket between the coupler bracket and last socket then screw to the slab.

Using flexible corners

Flexible corners are made up of:

  • one type 1 feed unit
  • one type 2 feed unit

Secure both feed units to the slab.

Engaging and releasing the tap-off

  1. To engage:
    1. align the tap-off pins with the corresponding socket slots and push down to engage
    2. maintain downward pressure to the front of the tap-off and push back until the button clicks upward to lock
  2. To release:
    1. press the button to disengage
    2. push the plug forward to release

Related content

Floor power—understanding floor boxes, busbars and underfloor accessories

Floor boxes—their features and how they can benefit your business premises