Building automation systems (BAS) provide automatic control of electrical loads, such as HVAC, lighting and electric motors, and functions not related to energy management, such as security and fire safety systems. Energy management systems (EMS) provide automatic control of electrical loads to manage energy consumption either as a stand-alone system or as part of a BAS.
While EMS may be capable of provide automatic switching of large blocks of lighting loads, only a fraction of installed EMS actually control lighting, according to the U.S. Department of Energy (2003). EMS that control HVAC are installed in about 5.6% of commercial buildings representing 24% of commercial floorspace—most commonly >100,000 sq.ft. office and education buildings—while EMS that control lighting are installed in 1.3% of buildings covering 7.4% of floorspace.
One reason for this may be traditional fragmentation of the construction process, with lighting control specified by electrical engineers (Division 16) separately from EMS specified by mechanical engineers (Division 15). But this is changing due to rising energy costs and the proliferation of energy codes requiring that interior lighting be turned off when it’s not being used.
When designing a new building, the are basically two choices:
• specify lighting, HVAC and other systems as stand-alone control systems; or
• specify a single whole-building system that provides all desired functionality.
The whole-building approach has a distinct advantage in that the building operator theoretically can control the entire building’s electrical loads from a single workstation, and not have to learn and use multiple software programs.
The disadvantage is traditional EMS do not work well with advanced lighting control inputs and strategies such as daylighting control, occupancy sensing, architectural dimming and networked digital switches.
As a result, EMS manufacturers have been looking to lighting management system (LMS) manufacturers to provide lighting solutions that can be integrated into their solutions using an open communication protocol such as ASHRAE’s BACnet and Echelon’s LonWorks. These protocols allow a higher level of system integration without the need for gateway devices.
While protocols enable lighting control points to be mapped to the EMS and then controlled and monitored from the EMS workstation, they currently do not allow programming of advanced lighting control functions at the workstation. Taking BACnet as an example, the current objects do not include dawn/dusk scheduling events, architectural dimming, blink warnings before shutoff, and other functions. As a result, until BACnet begins covering these functions, most BACnet-based LMS control functions must be programmed at the LMS control panel.
In some buildings, it may be desirable to attempt to leverage the investment in lighting controls into automation of other building systems. Below the LMS level, occupancy sensors and power packs can be specified with an isolated relay for control of and interfacing with additional loads such as HVAC and security. At the LMS level, lighting control panels are available with outputs that can handle lighting and also HVAC, service water heater and motor loads, thereby satisfying many of the functions required in ASHRAE 90.1 Section 6.4, such as automatic shutoff of HVAC (22.214.171.124.1) and dampers (126.96.36.199.3).
In an existing building in which we want to install an LMS, legacy EMS going back as early as the 1960s may be encountered, creating special integration challenges. Options include:
• invest in newer EMS with greater capabilities and install with the LMS, enabling the possibility of a single user interface; or
• specify a gateway that enables the legacy EMS and LMS to communicate but typically be operated via multiple user interfaces.
The general trend in building controls is automation. Within the lighting segment, control functions are becoming increasingly able to be integrated with each other, with EMS and with lighting equipment such as light fixtures. As integration intensifies, in some cases it may make design and specification easier, but in others, it may in turn require integration of the design process—closer collaboration among the project’s designers and contractors. Successful integration of an EMS and LMS requires careful and early coordination among the electrical and mechanical engineers, contractors and the building owner to properly estimate the required labor, produce a successful design, and properly install and commission the building’s control system.