Faster by bus?

Busbar trunking provides a quick and easy way to tackle even the largest installations. A single run of busbar trunking can replace several runs of cable, along with their associated trays, bringing big savings in installation time and therefore labour costs. These savings can easily add to more than the additional capital costs of busbar trunking over cable, leaving any contractors that use it with a clear extra profit.

Although busbar trunking is not suitable for all applications, where it can be used its speed of installation and flexibility can bring great benefits to both contractor and user.

Installation issues
Cabling large buildings presents some real challenges to the installer, such as the need to terminate multiple cables in switchboards. These must be drilled on site, taking care to ensure accurate positioning of entry holes.

There is also the risk of swarf falling into the electrical connections, causing short circuits. Any errors here could delay the project's completion and cause additional costs to the contractor.

Depending on the power requirements, the switchboards may need to be large to accommodate heavy gauge cables, which are hard to handle and bend into place. This all takes up valuable space within the building.

Cable ladders will need to be installed to support the cable during installation as well as circuit-protective conductors. These may need a dedicated group to set up. The cables must then be tidied, glanded into the switchboard and terminated.

In contrast, a single run of busbar trunking can replace several runs of cable and trays. Busbar trunking is simple and fast to put up, with all connections and terminations being completed by simple bolted connections.

Installation time is also saved by the use of factory-built joints that change the direction of the busbar run. U-turns, 90° bends and T-pieces are all simply slotted into place, cutting the need to bend steel-armoured cable around corners. These also take up minimal space compared to cable.

Busbar trunking also needs fewer fixings than the equivalent length of cable, giving cost and time savings on items such as cable trays, junction boxes and fixings.

Cost issues
Most cost savings come from the far lower labour costs, due to the reduced time spent on site. This is the key benefit of busbar trunking to contractors.

Shorter lead times mean that a more attractive quote can be offered to customers, increasing the chances of winning new business. This can make a firm more competitive than other companies looking to pick up the same work. Also, with many project lead times becoming shorter, busbar trunking may be the only option to meet very tight timetables.

Rapid installation also means that there is more time available – getting off the site quicker means that there is time to fit in more work or to win new contracts, helping increase profits and expand business more quickly.

Busbar trunking also gives less scope for error because it is factory-built and fully tested before it gets to the site. Together with its easy installation, this reduces the chance of errors creeping in when it is being installed. With cable, errors are often found at the testing stage, incurring further work, time and cost to correct them.

However, there are some applications that busbar trunking can't be used for. These are mainly older buildings with odd-shaped rooms that would need many small linking pieces of busbar to change direction many times. This would probably not make the system cost-effective.

As a rule of thumb, when an installation involves fewer than four connections or tap-off outlets, a conventional cabling installation would be better.

Length for length, the price of busbar trunking is higher than for cable. Yet, busbar trunking gives such a saving in labour that the overall cost of the project using busbar trunking should work out cheaper than one using cable.

For example, if a job involves a lighting run 20 m long, with luminaires every 2 m, based on an average installation time per metre, with labour cost at £10/h and using typical 2000 prices for materials, the two methods compare as shown in table one.

These results show that busbar trunking can offer an overall cost saving of £141.60. In addition, it offers 28·19 free labour hours. This time can be used to start work on the next project, improving cash flow.

Used in the right way and for the right applications, busbar trunking offers big advantages. Not only is it easy and quick to install, but customers like it too. Its flexibility is a big selling point, one that can be used to help win contracts.

Typical applications
Busbar trunking is used in a wide variety of applications in many different types of building. The main applications include retail premises, offices, warehouses and factories; with large uncluttered areas and straight walls, such sites are ideal for busbar trunking.

There are real benefits of busbar trunking to the user too. Warehouse operators find it useful for its adaptability; for instance when a new racking system necessitates moving the luminaires to provide a new lighting scheme.

Factories also often need to install new machines and reorganise production lines, and busbar trunking is ideal for such situations. For heavy power distribution, busbar trunking is often used to provide a connection between a transformer and switchboard and in three-phase supplies it can handle currents of 5 kA.

Retail outlets find the flexibility of tap-off units useful when they need to rearrange the positions of lights, counters and tills. Using busbar trunking, it is not necessary to call in electricians every time changes are made to the store layout, giving more flexibility and reducing the time needed to make changes.

Typical applications include:

• small and medium-sized factories, such as machining, assembly and moulding plants;
  
• electrical generation facilities, petrochemicals industries and oil and gas platforms;
  
• retail buildings, such as supermarkets, shopping malls, do-it-yourself centres and garden centres;
  
• storage buildings, such as warehouses, distribution centres and agricultural buildings;
  
• workshops, for instance garages, textile workshops and repair facilities;
  
• leisure facilities;
  
• university and college buildings, in areas such as technical schools and laboratories;
  
• hospitals;
  
• hotels;
  
• apartment blocks.

Specification process
With busbar trunking it is easier to design a distribution system because there is no need to know the final distribution load layout. It is only necessary to know the characteristics of the source of supply and the loads themselves.

It is just as easy to estimate lengths for either busbar trunking or cable, but for labour costs, it is easier to make estimates for busbar trunking because the tasks needed to install it are better defined.

Another thing to keep in mind is discrimination. This can be difficult to achieve if the busbar trunking and circuit-breakers are sourced from different manufacturers. The best way to avoid this is to purchase from a manufacturer that can supply both.

Busbar trunking can make everyone a winner – it keeps the customer happy by giving a quick installation and helps increase the contractor's profit. So contractors working on larger projects: don't always automatically think of cable when specifying for a contract, consider busbar trunking – it could be the difference between winning and losing the job.