Environmental zoning within buildings was a step forward in ensuring comfort and saving energy. But the greater control and sensitivity of clustering means an even greater flexibility in open-plan spaces
FIRST there was the dumb outstation. Then came intelligent controllers that led to the introduction of master/slave control systems. These enabled control of open areas in order better to manage the demands of occupants and the effects of the weather. The master/slave configuration reduced switching, allowing the intelligent controller to take decisions on behalf of its slave controllers, and ensured uniformity of control throughout a given zoned area. An inherent weakness, however, was its inflexibility.

Take, for example, a zoned area on the south side of a building. The sun travels from the east increasing natural light to the south side of the building, a sensor detects the increased light level and the master controller instructs its slave controllers to switch-off the lights.

This is all well and good if the zoned area covers only that space nearest the windows but if it should stretch to the core of the building, its occupants would be plunged into semi-darkness. This is where clustering can make a difference - independently managing the heating, cooling, ventilation, lighting, and sun blinds within given areas of a building, while maintaining the uniformity of control during specific time or instances.

Cluster effect

The Comforte CX from Priva has programmed control modules that can be clustered together to regulate climate (hvac), lighting and blinds. Clustering is proving particularly profitable in buildings where there is a high level of churn - the movement of people - that involves re-planning work areas that can include the erection or removal of partitioning.

Control units on a Priva BACnet CX network can be programmed as clusters. The control regimes in a cluster work together; for example, with a single room temperature sensor. As a result, various clusters can be used to control temperature, so that the temperature in a given zone is maintained according to an agreed setting, with the lighting and sun blind controls allowed to work independently of each other.Therefore, temperature throughout the zone is maintained at, say, 20˚C, which is regulated not just by the heating and cooling services but by allowing the blinds to be individually controlled to match the movement of the sun. The latter blind control will also effect the lighting system, which, through clustering, has the freedom to switch lights in accordance with actual light levels.

To control air vents, valves and sun blind motors, clustering is based on the control requirement of the individual control units, enabling different characteristics and running times for each.

Clustering parameters are set in the software. Consequently, it is a simple operation to introduce new regimes or alter existing ones. Creating clusters is simply a case of identifying an area and its associated sensors.

The multiple cut and paste facility means that the control parameters for climate, lighting and sun blinds can be quickly, and more securely, engineered throughout the building. Initial programming would be done by the commissioning engineer, but future adjustments can easily be accomplished by the facilities manager.

Control software

It is anticipated that the Energy Performance in Buildings Directive will be the catalyst for increased sun blind installation. Priva says its software developed for sun blind control means that it only requires the date, together with the building's longitude and latitude references, and it will calculate the position of the sun dependent on the time of day and global positioning of the building. This information allows the controller to tilt the blinds for maximum ingress of natural light while curtailing blinding sunlight.

To control external louvred blinds, Priva says it has created anemometer software that measures wind velocity. Should the speed of the wind indicate possible damage to the louvres then the controller will automatically adjust them to the optimum position to safeguard the blinds and the building.

Clustering is not just for new-build, however, Priva products support a range of sensors allowing the concepts of clustering to be included in refurbishment projects. With this in mind, building designers have a genuine reason to include a network of sensors at the design stage. Incorporating sufficient sensors at the building stage does not attract marked additional costs, but they can be the base for precise, effective control through clustering.

And clustering does not mean sacrificing local control. By allowing the Comset CX to take the role of the sensor, the end-user benefits from both sensor and room control, plus it provides local control including temperature adjustment, override facility and a holiday program.