The Lighting/BAS Convergence, Cont’d.
For most buildings, it will be a question not of if, but when.
June 1, 2013
Both new and existing building projects should have lighting control provided, either as part of a standalone system or, ideally, integrated as part of the BAS. But we often find that there are many reasons automated lighting control is not provided, ranging from simple economics to frustration with the programming and support of these systems. But recent and upcoming code changes are going to make this a requirement, so it is important to be up to speed on what is involved with the design and use of lighting control.
There are several basics to lighting control in a commercial building. These include:
- Occupancy/Vacancy Control.Turning off lights when space is not occupied. This can be achieved through the use of motion sen-sors, time clocks, or from a BAS schedule. Generally, private offices, classrooms, conference rooms, etc. will get occupancy or vacancy sensors, while public areas and open offices ideally will be scheduled from the BAS in coordination with HVAC.
- Daylight Harvesting. Adjusting light levels when daylight is available.
- Bi-Level Switching. The ability to control lighting using either dimming or several levels to allow the occupant to adjust light levels to their needs.
- Exterior Lighting. Bringing exterior lights and signs off during the day as well as at other selected times.
- Special Areas. Control of special areas including classrooms, conference rooms, lecture halls, and boardrooms. This often includes integrated control of lights, blinds, AV equipment, etc.
We prefer to use a lighting control architecture that is highly distributed and readily integrated. These systems generally have a controller that is mounted in the zone, often in a junction box or directly to a fixture. This controller is capable of doing local control functions (occupancy/vacancy control, daylight harvesting, bi-level control), as well as time of day scheduling and status through the BAS integration. Options for connecting include wired, wireless, and power-line carrier. Most of these systems will readily integrate using open protocols such as BACnet.
The current codes in place in most states have limited requirements for lighting control, which applies primarily to new construction. As states change their energy codes to follow ASHRAE 90.1 2010 (or equal), the requirements for lighting control are going to become more stringent. There are added requirements for automatic shutoff, daylight harvesting, and occupancy sensing, as well as the control of exterior lights and even those in parking garages. Other requirements include control of plug loads as well. What is most interesting about the code changes is when it is mandated. Changing as little as 10% of lights and ballasts will now require adherence to areas of the code related to automatic shutoff. This is going to drive the need for fairly sophisticated lighting control in new projects and at least basic lighting control for existing buildings.
The Energy Information Administration estimates that lighting accounts for 21% of energy use in commercial buildings. Providing effective control can provide an important tool in improving energy efficiency, and it will soon (if not already) be required in your state energy code. Look to make lighting control part of an integrated system as part of the BAS for improved coordination, support, and efficiency.
Paul has worked on a series of ASHRAE projects including BACnet committee and “Guideline 13 – Specifying DDC Controls.” The formation of Building Intelligence Group allowed him to provide assistance to owners with the planning, design, and development of Intelligent Building Systems.