Taking control with KNX

Published:  12 August, 2008

The benefits of integrated systems — Paul Murphy.

Paul Murphy explores the many benefits of the KNX standard for building automation — and includes a look at some major projects, including Terminal 5 at Heathrow Airport.

Responsibility for the energy used in their buildings has come to the top of the agenda for commercial building managers and owners. This is in part the result of the certification that came into force from April 2008 — Energy Performance Certificates (EPCs) and Display Energy Certificates (DECs). The pressure is now on to make continuous energy savings through effective building management.

Systems that track the energy performance of a building in real time can identify all areas where there is need for improvement, allowing the owner (occupier) to take steps to further improve energy efficiency, how to find the best building-management system and how to fine the most effective long-term solution to controlling energy usage are the challenges. In short, what is the most effective way of achieving A-rated commercial buildings on a continuous basis?

The KNX Standard (formerly EIB) is a system for building and home-automated control that is fully compliant with EN50090, the European standard for building and home electronic systems. Major commercial building owners are rapidly accepting it as a technology to achieve maximum energy efficiency. It has a number of advantages over alternative solutions. For example, at a time when BEMSs are expected to be even more widely employed, it has the ability to be integrated with any type of BEMS thanks to its open protocol OPC Gateway. Once this integration has been achieved, the other advantages of KNX come into play to bring local and zonal control to every area of a building.

The over-riding advantage of KNX is that it provides a holistic approach to efficient energy usage. It is not limited to lighting or heating or metering or appliances or audio-visual any other specific function. The KNX platform has been adopted by many and highly respected major manufacturers with a vast choice of products covering all these product lines. In the longer term, this is also important to building owners, as any installation is future proofed. Choose a proprietary protocol from a single manufacturer or integrator and you are beholden to that company and its technology, and this could be problematic during the lifecycle of a development. With KNX, if a certain product is no longer available, there will be an alternative.

As KNX covers such a diversity of applications using one standard, cabling network can be much simpler. A single twisted-pair cable can often suffice, with multiple elements operating together on a single network. KNX-controlled devices are generally based around the standard green KNX bus cable (i.e. twisted pair) but can be run across radio bus (wireless), Ethernet (structured cabling), fibre optic and, occasionally, power line.

A number of manufacturers have also developed ‘gateways’ to other control protocols, such as DALI (Digital Addressable Lighting Intelligence). These simple devices are used to expand the capability of KNX control systems to provide the complete solution for a building. KNX has also worked closely with management-level protocols such as BACnet to enable a close co-operation between these two standards when the project requires additional integration.

Consultants, specifiers and end users looking for an open solution for building control applications are increasingly considering KNX and recognising the drawbacks of proprietary solutions or various hardware-based controls.

What also helps maintain KNX’s position is that every KNX-compliant piece of equipment has been fully tested and certified to this stringent standard by an independent regulatory body. It is only at this point that it can carry the KNX logo, as controlled by the international KNX Association of Brussels. There can be total confidence in reliability and interoperability, whatever KNX devices are chosen.

A growing number of integrators have joined KNX UK to share their experiences, help promote the KNX standard and assist consultants and building owners achieve the optimum solution for their building. They can get involved at the drawing stage of any project, liaise with the client and install a KNX infrastructure that can be developed as the building itself develops or its use and occupants change.

The pressure on energy management makes it vitally important to make the most effective use of energy. For instance, a lighting-control system can be simply configured to turn lights on only when someone is present in the room; it can also monitor daylight levels to dim or turn lights off when enough ambient light is present. This is a very simple example of preserving energy, but drive through any town centre or industrial estate at night and you will realise an awful lot of energy can be saved by such simple measures.

Effective lighting control can result in highly significant energy savings. If it is integrated with the control of shutters and blinds, solar panels, façade management and effective monitoring, there are potentially massive savings. The beauty of KNX is the ability to seamlessly add more energy-saving functions that work the background and go largely unnoticed. What is more, KNX is distributed technology so in the event of failure of one element of building services, the rest carry on regardless.

KNX is accepted throughout the world from China to the United States as well as Australia and the Middle East. It has also been dubbed ‘Europe’s best kept secret’, so advanced are many of our neighbours in embracing its capabilities. It is even taught in schools in Germany! The UK is now also embracing KNX in many landmark developments and refurbishments, including Terminal 5 at Heathrow Airport, the British Library, the Passport Office and Bridgewater Place in Leeds.

Among major projects in the UK that have exploited the capabilities of the KNX standard for building automation are Terminal 5 at Heathrow Airport (below) and the Liverpool office of the Passport Service (left).

At Terminal 5, KNX technology is helping to manage the lighting systems and provide passengers with a well-lit environment in many areas — including the rail terminus, the main concourse building and the TTS passenger link, which provides access between the main concourse building and the buildings used for boarding. It also provides lighting to the multi-storey car park and the energy centre, which supplies heating and chilled water to T5. Lighting is also being supplied to the air traffic control tower.

To provide the level of control required by BAA, a lighting-control system was designed and installed. Whilst it has not been developed to communicate directly with building-management systems, KNX’s open-platform technology allows it to be incorporated into the T5 building-management system.

Using this gateway, staff can now monitor the lighting systems throughout the terminal and quickly identify any faults through the central building-management system, including the precise location of a fault. This will help ensure that all areas of the terminal are constantly well lit and easy to maintain. As well as the mains lighting, monitoring capabilities have also been provided for escalators, travelators, low-voltage supplies, life-safety equipment and toilets for the disabled.

KNX and the lighting system had to be integrated into the rail station’s supervisory control and data acquisition (SCADA) building-management system, which provides reporting for station staff. As the system is fully automated, lights will turn off as staff leave rooms, helping reduce energy consumption and costs. The system can also monitor emergency-lighting circuits.

As the train station has been designed to let in as much natural light as possible, it was also important that the system had daylight-saving capabilities.

The lighting system responds to external weather conditions so artificial light can be adjusted in response to natural light entering the station and the interchange. In all, over 400 KNX actuators to control the lighting in the terminal have been installed. Push-button interfaces provide localised manual control of the lighting system in some areas and over-ride automated lighting controls in the concourse area. Late at night and early in the morning, when the airport is less busy, the lighting system will automatically reduce illumination levels. If passengers arrive from a night flight, for example, the lighting system can be over-ridden to illuminate the concourse area, switching on only the lighting required to guide passengers to baggage and customs areas.

One of the intelligent lighting systems offered by Electrak, a member of KNX UK, has been utilised in the Passport Office in Liverpool. It was specified to optimise energy performance and, particularly, to adjust the level of artificial lighting in the occupied spaces as the Sun passes across the complex, mainly glazed structure. The project team decided to install the Electrak KNX lighting power distribution and control system as six separate lines to zone the three floors of the property. In addition to the automatic daylight dimming, the installation uses movement sensors in many of the occupied spaces.

The property has been designed with sustainability in mind and to make the best use of the energy consumed through its designs. The project team particularly wanted to take account of the building’s curved shape and large glazed area with its high natural light levels. A lighting-control system was therefore required that would respond to changing conditions. There were also many partitioned areas where movement sensors were applicable.

The KNX installation features a stand-alone building-management system and a series of remote lighting control modules. There are also line couplers in the service risers and large quantities of KNX busbar trunking installed within the ceiling.

Paul Murphy is a systems integrator with KNX UK.



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