Only connect

The Egan report "Rethinking Construction", called for the increased use of standardised and prefabricated products. Following the report, the DETR commissioned the Building Research Establishment to study the potential for doing so. "Overcoming the barriers to standardised wiring systems" was born, the project aiming to make it easier to use standardised wiring products in construction.

The conventional wiring installation process is time-consuming, costly, and dependent on skilled labour. In addition to the costs of components and labour, there are hidden costs due to the time that a building is unoccupied.

Conventional wiring systems are, to a large extent, manufactured on-site. Standardised wiring systems aim to move the manufacture off-site into a controlled factory environment, often using automated manufacturing techniques. This is more efficient and can produce more reliable products. The combined component and installation costs can be lower with this approach, and installation is much faster.

Modern commercial buildings need data networks for IT, telephony, bems, fire and security, as well as new media such as distributed video. The showcase Integer House, at the BRE Garston site, contains seven networks. A recent high-end housing development in Watford termed 'Internet Homes' provides remote control and monitoring of security systems and household appliances. Such buildings benefit greatly from an integrated approach to wiring.

Data networks are often manufactured on-site. Cable is taken to each point where it is required, cut to length and manually terminated either with RJ45 connectors, by insulation displacement, or other manual methods. It is common practice to install voice and data networks together, taking advantage of the four twisted-pairs in standard cable to provide two voice and two data points for each desk. Further integration with power outlets is less common but also possible.

Standardised wiring systems

The problems of installing conventional wiring can be largely solved by shifting the manufacturing burden off-site and integrating the systems. This can be achieved by replacing the standard components of conventional systems with modular, prefabricated, integrated alternatives. Trunking and conduit can be avoided entirely by using integrated armoured cabling containing shielded wires for a number of networks as well as for power.

Prefabricated wiring components available today include modular cables with standard connectors, T-connectors for branching and switches, photoelectric and PIR controlled switching, integrated outlets for power, data and voice, and busbars.

The busbar is an established modular, prefabricated component that can also be used as trunking for various data networks. However, installing a busbar is more complex than other modular wiring components.

The installation of prefabricated wiring systems is, to a large extent, 'plug and play'. The difficulties associated with installing conventional wiring are mostly avoided, reducing the need for on-site specialists. The connectors used generally prevent incorrect connection of wires.

During specification, the information in computer-generated designs for electrical services, bems, voice and data systems can be used to derive a parts list. Alternatively, it can be used to drive an automated production line producing the required modular components.

Benefits and barriers

The typical project savings from using modular wiring for power over a conventional wiring system have been estimated at 25-50%. This results from a 30% increase in component costs coupled with a 50-70% reduction in labour costs. Because the installation process is so straightforward, programme reduction is typically between 70-90%, which further increases the cost-effectiveness.

So what's stopping more people from using standardised wiring systems? Workshops have identified the main barriers to uptake as a lack of information, inertia from established practice and uncertainty about long-term performance. There is also concern over higher initial hardware costs, long-term availability of replacement components, and the need for more detailed initial design.

New skills may be required to cope with prefabricated components. Conventional thinking is against the replacement of conduit by cable hangers, and there are always worries about the integrity of networks.

The central aim of the BRE project is to find ways to address these barriers. It is clear that some of the most important barriers are lack of information and uncertainty.

The role of standards

There are a large number of standards associated with conventional power wiring systems, from the performance of insulation and electrical properties to the standards for wall sockets and plugs.

The relative novelty of modular wiring systems means that there are currently few standards designed specifically for them. The most important omission from existing Standards is in the area of the connectors for modular wiring.

Conventional systems do not use plug-in components as part of the wiring infrastructure. Appliances use three-pin plugs to attach to wall sockets, but wiring from there to the source uses connections relying on stripped cable and manually tightened joints. Pressure on the wire preserves a safe and permanent connection.

Modular wiring components, by contrast, use specialised plug-in connectors. Some of these are designed for single-phase systems with modest loads, others for three-phase systems with higher currents. The connectors may include a communications bus and other data connections in a unified system.

Currently these connectors are proprietary, and there is little compatibility between different manufacturers. It would be of great benefit to the modular wiring market if there were standards to ensure compatibility between different manufacturers' components. This is happening in almost every other type of prefabricated wiring component.

Standards are being drafted for some types of connector. However, in a technology as new and rapidly evolving as modular wiring, it will be difficult for any standard to ensure compatibility between components, while being general enough to cover all possible connector types.

New standardised wiring systems that are becoming available promise to streamline the installation of power and wiring in buildings, providing clear benefits to clients. Better availability of information, more site experience and the introduction of appropriate standards should help remove the barriers to uptake. When this happens, it is likely that modular, prefabricated, integrated wiring systems will become the norm rather than the exception.