For many building tenants, wiring is frequently not the first aspect of building controls or building energy management system (BEMS) that comes to mind. However, wiring is not only a crucial element of cost; it also provides power to the BEMS as well as transporting the vital data on energy use. Wiring is certainly a subject that should be given priority by systems installers. Like all aspects of building services, controls are increasingly under scrutiny for ways to find cost-savings. This is of particular concern for installers at the value-engineering stage who are looking for savings while retaining their margins. A well selected wiring solution does offer cost savings and faster installation, saving on the bottom line for those pricing a project. Wiring also has implications for how a BEMS functions; including what types of components can be used in the control system, so it is also something that specifiers need to think about too, for both new-build and refurbishment projects. As buildings and building services equipment continue to advance, the functionality of today’s buildings are also becoming more complex. The necessity for detailed reporting on building performance means that collecting and delivering that data is vital.Communications networks are used extensively in building management systems at the automation and management levels. These are often known as the primary levels of a BEMS network. Devices further down the network, at the device level, such as sensors, and I/O modules including indicators and actuators, would traditionally require separate wiring runs to link them to primary level. This means that if a project plan includes a high number of these devices spread over a wide area, then the wiring costs using the traditional approach could be high. This may result in modifications to the design of the system, with field devices omitted because it is considered too costly to include them. So the BEMS cannot offer the functionality that the designer initially had in mind. However, advancements in wiring technologies and techniques overthrow this problem. For example, a 2-wire bus system (e.g. Dupline) can link field devices together, without the requirement to connect each separate sensor or actuator back to the primary level of the building management system. Essentially, this creates decentralised sensors and I/O modules, giving much greater flexibility on the distribution of devices without the costs of extra wiring. There are also sensors for CO2, temperature and humidity that can now be powered from the bus. This further reduces the need for wiring to power the devices. Also, a 2-wire bus cable can be run from sensor to sensor, collecting all the measured values. Each sensor does not have to be individually wired back to the main controller. The flexibility of this approach is such that it can even be used to add to traditionally-wired building management systems, to help reduce the cost of updating an existing BEMS without the need for disruptive rewiring work. Although wiring may be something of a specialised subject, careful attention to what type of wiring is used can support better outcomes for building users. It can enhance the performance of other areas of the building services. For example, when considering underfloor heating in commercial applications i.e. schools and hospitals, there may be a number of sensors involved in the control system. With the ‘traditional’ wiring method, the sensors will have to be individually wired back to the main controller, adding to costs. It’s highly likely that as a result the number of sensors will be restricted due to costs. Adopting a 2-wire system will go a long way to removing this issue, allowing use of more sensors and creating a superior-controlled underfloor system. There is no doubt that this will create a more sophisticated indoor environment for the building occupiers. Smarter wiring strategies that save on capital expenditure mean that managers of smaller buildings can access the sort of control capabilities and useful data on energy use that would otherwise only be available to those investing in larger-scale BEMS. So, small retail outlets can track energy use as well as being able to easily and automatically extend the time when lighting is on for late-openings. As building management systems continue to advance they will be expected to perform more complex tasks, wiring is a key element that is not worth overlooking by specifiers and installers alike.
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