Electronic Design

Integrating Lighting And HVAC Via BACnet

The emergence of BACnet-compatible hardware/software interfaces is driving the convergence of discrete building automation systems, such as HVAC and lighting, into an integrated, facility-wide, energy-management structure that provides management and control of two-thirds of a building's total energy load. (The three-tier load comprises HVAC, lighting, and plug load.) Popular front-end software systems such as Tridium tie it all together through a single, user-friendly window to the integrated energy-management system.

Facility load shedding and demand response programs benefit by transferring part of the HVAC burden to lighting. For example, instead of the lighting load rais ing building temperature by two or three degrees, the combined system can effectively limit that temperature increase to o nly one or two degrees by dimming all of the lights by 10% . Doing so would simultaneously reduce the building's heat level , lower air-conditioning use, and decrease the lighting energy load.

It's economical to install occupancy sensors for lighting controls. Also, many state codes mandate their use in conjunction with utility incentive programs. New BACnet interfaces enable addressable lighting controls to share occupancy data with security, fire, HVAC, and other building automation systems. This not only permits the HVAC system to reduce its load through standard temperature sensing and time scheduling, it also provides further control granularity by allowing programmed set points to be overridden if no occupants are sensed for a user-specified period of time.

TAGS: Components
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