Reprinted from January 1992 Insights
Forty to sixty percent of the average commercial utility bill is for lighting. That bit of gloomy news for building owners is good news for companies that sell and install devices designed to control lighting and lighting costs. Thanks to the availability of a variety of lighting control options, contractors can take advantage of this potentially lucrative business with a minimum of effort. Convincing a customer to decide on a new or retrofit control installation is made easier because of attractive paybacks that can be projected. These payback projections can be enhanced when tied to utility company rebates and investment programs that encourage these installations. As a result, the customer saves money, relationships are reinforced, and energy waste is curbed as much as possible.
Lighting control methods can be relatively simple to extremely sophisticated – with price tags that escalate with complexity. Among the more common of these methods in use today are: on-off control, occupancy sensors, and light level control.
The simplest of all lighting controls is the use of mechanical or electronic time clocks. Their function is to turn lights on and off at pre-set times of the day. Each time clock can control one or more lighting circuits. The down side to time clock control is lack of flexibility and override capability.
Flexibility can be achieved by interfacing with lighting panels that have either their own time-of-day capability or are controlled from a building automation system. The lighting panel allows multiple lighting circuits to be controlled from one switch or control point on an automation system. These panels also allow flexibility in the assignment of those circuits to various time schedules.
Most lighting panels or automation systems allow for some sort of override function for after hours use and a “flash system” to notify tenants of an impending “lights out” condition. Another way of accomplishing the override is with a SENTRY switch that replaces the normal light switch to provide manual override of the time-of-day function in individual zones and which can be “swept” off from the lighting panel or automation system. A sweep function will reset the lights to an “off” condition periodically during unoccupied hours. These types of systems may also incorporate a remote dial-in function.
The “time-of-day” capability can be especially effective in retail stores and supermarkets. The store could automatically be illuminated at 100% during store hours, reduced to 60% during stocking, then further reduced to 40% illumination for janitorial duties. As a side note, these time-of-day system scan be tied to a security system (like an override) and all the lights can be turned on if the building is burglarized.
Occupancy sensors provide another method of lighting control. These devices will automatically turn lights off after a pre-determined amount of time if there is no one in a given area. There are a number of different types of occupancy sensors on the market today. The most common of these are the infrared and ultrasonic occupancy sensors. The infrared occupancy sensor detects body heat and the ultrasonic type senses a breakup of the ultrasonic signal due to motion. Some occupancy sensors have a wall switch replacement type of detector for easier installation. In all cases, care must be taken in selecting the location, sensitivity and length of time for which these sensors are set, based on the type of sensor and where it is to be used.
Light Level Control
Lighting effectiveness is being built into modern office buildings and shopping malls as more windows and skylights are being used than ever before. To take advantage of this, some lighting control systems allow for a footcandle setpoint and then control the level of lighting required based on a photocell input that senses actual footcandles in a given space. A number of dimming and ballast control systems are available to achieve this type control. Two types of sensors, photo resistive or photo diode, are available as inputs. This method allows the natural lighting in an area to be utilized to its fullest.
Another advantage to this type of control is that various lighting levels can be set based on need. Hallways and open areas would require less light than stores or office areas.
Parking lot and store sign lights can also be controlled. Typically the store lights would come on earlier than the parking lot lights for their advertising effect. The reverse would happen at closing. The store sign lights would go out first to let people know the store is closed. The parking lot lights could remain on long enough to allow store employees to close the store or until the following dawn for security reasons.
Future Trends in Lighting
Higher efficiency lights and new types of reflectors that put more light into the space are the latest in attempts to reduce lighting costs. As control manufacturers study and design new control systems, improved dimming and ballast controls, astronomical time of day control and new strategies in demand control using lighting will be introduced and enhanced. This new lighting technology is continually creating a wide array of innovative products that offer increased savings for customers and, at the same time, provide contractors potentially greater profits.
Between now and the turn of the century, lighting controls could prove to be one of the brightest spots in your business plan.