Illuminating the Art of Integrating BAS and Lighting Systems
Facility owners have more options now than ever when it comes to making decisions about the integration of their lighting systems with their building automation systems. "Motion sensors, for example, can control security, HVAC and lighting," says Spectrum Engineers' Joseph M. "Jody" Good, III, LC, IESNA, IALD.
Facility owners have more options now than ever when it comes to making decisions about the integration of their lighting systems with their building automation systems.
"Motion sensors, for example, can control security, HVAC and lighting," says Spectrum Engineers' Joseph M. "Jody" Good, III, LC, IESNA, IALD. That said, Good, past president of the National Council on Qualifications for the Lighting Professions (NCQLP) and the Illuminating Engineering Society of North America (IES), reminds us that some owners may not want such a significant unification of technologies, but rather something simpler, such as central control of HVAC and local control of lighting.
"This approach has been the norm for quite a few years, but it resulted in needless HVAC activity because multiple systems were included on the same controls," he says.
But there is an alternative: "Today, more integrated control is possible with common devices accessible to most owners," says Good.
Several approaches are available, each with a variety of benefits. That said, the challenge is gaining the desired level of unification once lighting design is completed.
For example, simple on/off control can be interfaced with sophisticated dimming and time-schedule schemes by using standalone lighting control systems (LCS) to fully integrate building management and control systems (BMCS). The broader issue is that such integration may not be necessary as most BMCS can handle such a function. Next, the designer must choose a control strategy based on light levels, time schedules or both. The good news is that occupancy sensors or override switches can easily serve as inputs to give building operators flexibility.
Specifically, using light-level sensors as BMCS inputs and incorporating BMCS time schedules allow building and grounds lighting to be staged to turn on automatically.
Time schedules, on the other hand, can be employed to bracket on/off light-level control, allowing late-night shut-off/early morning turn-on to coincide with building occupancies.
Most BMCS have sufficient spare inputs and outputs to implement this type of control. In fact, in most cases, the on/off operation from the BMCS can control lighting relays or contactors directly without requiring additional hardware or software.
A BMCS can also control fluorescent dimming directly, making the following possible:
Levels can be maintained at various operator-adjustable set points by using the analog input and output capability of the BMCS to measure light level and by modulating dimming ballasts.
Different light levels can be programmed into the BMCS to control lighting based upon time of day and by using the time schedule feature.
If a dedicated low-voltage LCS is desired, interface with the BMCS can occur at many different levels. The simplest form of integration is via a hardwired interface in which the BMCS acts as a remote switch to the LCS. Such a configuration enables the following features:
The LCS can be programmed to control one or more relays or dimming outputs to change a lighting pattern, scene or light level whenever it senses the dry-contact output from the BMCS.
The building operator can attach time schedules, light level algorithms or manual overrides to the BMCS output.
Of course, much higher levels of integration are possible, but it will require a gateway interface that uses a standard building automation protocol such as BACnet or LonWorks. Such schemes allow the BMCS operator access to LCS "soft-wire" programming, time scheduling and relay monitoring. That said, the designer should be aware that building occupancy schedules, overrides and security interfaces can be integrated as well.
The BMCS and LCS must also be fully investigated to ensure they are truly compatible with the chosen automation protocol. Each should provide full compliance with the protocol's standard.
Futhermore, designers should absolutely understand what the owner really wants. For example, the owner may say he or she wants the integration of the LCS with the BMCS when, in reality, all they want is the ability to control the LCS from the BMCS workstation. To do so, simply add the LCS operating program to the BMCS.
This method eliminates the need for a hardware or software interface if both are tied to the same network.
While integration of lighting and BAS is just plain common sense, it's still a luxury most owners opt against. But that may soon change. Parties responsible for the creation of building and energy codes are quickly recognizing unification of technologies, including the integration of lighting systems, and making integration a part of building standards.
Mr. Good sums up the situation well: "Recent revisions to energy codes acknowledge and encourage steps toward integration and may soon require integration in the interest of energy efficiency."