June 2005

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Fully Interoperable Lighting Control
through BAS

Jerry Mills
Easylite Integrated Lighting Systems

General building fluorescent lighting may now be effectively controlled to manage energy and to offer occupant comfort and flexibility. A Boulder Colorado based company, Easylite Integrated Lighting Systems, has developed an integrated ballast and control system that overcomes previous obstacles in implementing scalable, economical general lighting control.

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Historically, lighting control for large commercial spaces lit with fluorescent fixtures has been limited to line voltage relays located at the breaker panel switching large areas on or off based on a time-of-day schedule. These controls offered a reduction in operating hours but provided no ability to tailor light levels to user needs or reduce the building’s lighting power demand.

Dimming of fluorescent fixtures offers peak KW savings, user friendly local adjustment of personal light levels, and automatic light reduction in response to ambient daylight. The use of dimming to control fluorescent fixtures has been primarily applied in presentation areas, conference rooms, and classrooms. The focus has been on aesthetics and scene control, not energy savings. These systems have been expensive to install, difficult to commission, and have not offered convenient interface with the building automation system (BAS).

Controls designed for typical fluorescent dimming systems have been intended for small spaces with few ballasts, have been expensive to install, and have not been scalable. The majority of dimming ballasts offered operate in response to a 0 -10 volt DC signal that drives the lamp output from 10% to 100%. A variable output power supply provides the DC control voltage. This power supply can operate only a limited number of fixtures ( typically 20 to 40) due to power consumption and voltage drop in the control circuit. Addition of any control device within a group of dimmed fixtures requires an additional power supply, limiting flexibility and adding cost. The ballasts, power supplies, dimmers, daylighting controllers, occupancy sensors, and software (if used) are supplied by many vendors, none of whom assume responsibility for the overall “system” function.

Another protocol using a digitally addressable ballasts called DALI has offered the flexibility of using a twisted pair of communication wires, routed with the power wiring, to address and control each ballast in a system. This system provides for global flexibility but requires DALI compatible control components, not provided by the ballast manufacturer and software programming to operate the system. DALI is likewise limited due to requiring a power supply and computer interface module for every 64 ballasts. Installation and commissioning costs are significant and simple modifications require a knowledgeable software technician. DALI is configured as a stand-alone lighting system. Interface with generic BAS is cumbersome and limited.

Reliable Controls The Integrated Lighting System (ILS) created by Easylite is a ballast based system that includes local dimmer/faders, daylight harvesting controls, occupancy sensor controls, stand-alone scheduling software and unlimited flexibility to adapt to any new or existing BAS.

The ballast, offered in T-8 & T5-HO models from 1 to 8 lamps, provides power for all controls in the system without the need for supplemental supplies. All ballasts have integral lamp shut-off via control, eliminating the need for line voltage relays. These ballasts provide dimming using frequency modulation and are parallel circuited with an independent power supply to each lamp.

Power supplied by the ballast is delivered to the analog control loop at 14 volts DC. The controls operate the ballasts from 1.8 volts (full light output) to 8.8 volts (10% of full output), to 10 volts (off). Controls are connected to the ballasts with factory cables pre-terminated with RJ-11 connectors. Due to the continuous delivery of control power from the ballasts through the control loop, controls may be inserted at any point in the ballast chain. All controls are fully compatible and integrated to provide a flexible, adaptable low voltage control system serving from one fixture up to thousands. All this is possible without the need for supplemental power supplies or software input.

Systems using only the analog control loop may use one dimmer/fader controlling up to 250 fixtures, multiple occupancy sensors, and daylighting control using the unique Easylite Daylite Harvester, or all three in concert. The Daylite Harvester is a self contained, ballast powered device, sized for mounting within direct/indirect fixtures and with an un-obtrusive 1” diameter sensor. This device will adjust lamp output to compensate for ambient daylight to maintain working surface light levels within ± 5 footcandles. It may be remotely calibrated from beneath the sensor without need to access the ceiling or fixture.

To schedule fixtures served by the low voltage analog loop described above, there are two options:

contemporary The first is the stand-alone software package that is digitally connected via the standard pre-terminated cabling system to zone controllers. Each controller serves four zones and up to 64 of these controllers may be connected to each software front end. Each zone output of these controllers sends an analog DC voltage signal into the control loop setting the maximum light level for that zone and scheduling light levels by time of day. A standard feature allows input from the building demand meter to be read by the system with peak demand set by zone for reducing peak building KW using the automatic lighting controls. All local controls noted above are available and operational in concert with the software system.

The second option allows any programmable analog output device capable of delivering a 0 – 10 volt DC control signal to be connected to our control loop. These programmable devices are available in many configurations and protocols spanning all major brands of automation systems and including the interoperable protocols of BACnet, Lon-works, and Modbus. In other cases a lighting control loop may be coincident with a VAV zone. The spare analog output capacity provided on many VAV box controllers can then be used to schedule lighting from the central BAS and provide off-hour override with a thermostat mounted switch. With either approach, all scheduling and programming functions may be managed from one BAS with a fully integrated lighting and HVAC system.

Controls integrated with ballasts offer a seamless, single source solution for local dimming and daylighting. Combined with the flexibility to integrate the system with virtually any BAS, and the first cost economy of low voltage plug and play control wiring, this system approach offers a low cost yet flexible solution to general building lighting control.


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