Centralized Dimming Possible with Smart Integration

March 16, 2006

By Craig DiLouie

Fluorescent dimming is often favored when adjustment of light levels is needed to support visual needs, but it is now coming of age for utility cost savings.

Connecting the devices and enabling them to communicate with each other and/or a central control point is the basis for integration. We can choose devices from a single manufacturer that have been tested as a system and usually operate using a proprietary protocol or we can choose devices from different manufacturers, designed to operate on an open protocol, and build a control system from optimal components with competitive pricing. Manufacturers have taken steps to ensure that multivendor dimming systems can be reliably integrated. Ensuring a successful installation, however, requires proper calibration of devices and commissioning of the system - a necessary, but often neglected, final step in integration.

Dimming can be accomplished using several methods. The primary methods used to dim fluorescent ballasts include analog and digital. Analog dimming ballast systems are established and common, while digital systems are emerging. Both enable construction of networks of controls and ballasts wired to local and central control points. Selecting the dimming method is a critical design decision because it affects almost every subsequent design choice.

Analog methods include 0-10VDC, two-wire phase control, three-wire phase control, and wireless infrared. The 0-10VDC method enables the dimming ballast and controller to communicate via low-voltage wires connecting them. Two-wire and three-wire phase control each use line-voltage wires. The primary advantages of 0-10VDC are networking as well as an increasing number of manufacturers offering compatible products; the primary advantage of phase control is installation savings because no dedicated communication wiring is needed.

These methods form the basis of integration - the ballast and controller must use the same method to be interoperable. However, there is currently no industry standard for operation of analog dimming ballasts. As a result, while dimming products using the same method can be interoperable, dimming performance may not be consistent among ballasts made by different manufacturers and across different ballast types. To ensure consistent performance, avoid mixing ballast types and ballasts from different manufacturers in the same dimming system.

Digital methods include Digital Addressable Lighting Interface (DALI) open protocol and proprietary. DALI is the first true open standard available for dimming devices. This offers the possibility of true interchangeability between ballast manufacturers and defines light output for all levels of dimming signals, ensuring consistent dimming performance across all ballasts regardless of type or manufacturer. With DALI, different ballast types can mingle in the same control area and commissioning becomes simplified. Other advantages include greater design flexibility, individual addressing and control of ballasts (zoning at the ballast level), scheduling without an external time clock or control panel, and two-way communication, enabling monitoring. Disadvantages include a higher component cost and greater programming in centralized systems.

Once the dimming system is constructed based on successfully integrated components, it can be integrated with other controls such as photosensors, occupancy sensors, and control panels to expand capabilities. Using simple components, a dimming system can be constructed based on desired level of automation and centralization. Using a low-voltage or Ethernet-based communications network, the lighting system in entire buildings can be controlled from a single PC and local devices.

Other integration opportunities include giving the lighting control system some control over other systems, such as HVAC, and integration into a building automation system (BAS). An example of the former is an occupancy sensor power pack that has a second low-voltage switch for control of and interfacing with HVAC, security, and the BAS. People entering a building after hours, for example, would trigger not only the required lighting, but also HVAC.

An example of the latter is integrating the lighting control system into a BAS by selecting components that use the same protocol. Open protocols include BACnet and LonWorks. If the lighting network is DALI-based or is not compatible with the selected protocol for the BAS, a gateway device can be used to translate between networks that, in effect, speak different languages.

Intelligent lighting is possible using commercially available technologies, sound design decisions, and proper calibration and commissioning. Intelligent lighting can be used to control other building systems, or itself can be integrated into an intelligent building system - allowing flexible, smart building systems that can reduce utility costs, increase capabilities and worker satisfaction, and better serve owner needs.

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