Lighting Controls

A good lighting control design gives you both flexibility and economy. It allows a variety of lighting levels and lighting patterns while conserving energy and money. Energy-efficient lighting control strategies can reduce consumption over uncontrolled installations by up to 60 percent without reducing lighting effectiveness. Money is saved by reduced energy use, reduced air-conditioning costs due to less heat from lights, longer lamp and ballast life due to lower operating temperatures and lower energy output, and lower labor costs due to control automation. In order to meet building code energy budget requirements, it is frequently necessary to employ energy-saving lighting controls that dim or shut off fixtures.

Lighting controls include all the ways that lighting systems can be operated, including both automatic and manual controls. You can help conserve energy by using occupancy sensors and automatic daylight compensation controls where appropriate. Dimming, stepped switching, and programmable controls are sometimes recognized for credits from utility companies. Control systems decisions are made at the same time as the lighting is designed, to assure that controls are appropriate to the light source and that the system arrangement and accessories are coordinated with the control scheme.

Light zones are defined to accommodate the scheduling and functions of various spaces. Ambient, task, and accent lighting are considered in laying out the zones. Each zone should be separately circuited, and each task light should have its own switch. Traffic patterns are analyzed, and an on/off switch is located at every entrance. Convenient, easily accessible lighting controls encourage the use of all possible lighting combinations. The extra initial expense of extra switches and extra cable is made up in energy cost savings. The result is good illumination where needed, and no wasted energy where a lower light level will serve just as well.

When you are designing a complex multiuse space, like a hotel banquet room, it is essential to talk to the people who use the space daily to discover how the space is used. Audiovisual technicians and banquet crews, for example, will be aware of common problems. Often controls are located in places that are hard to reach during an event, or where you can't see the result of an adjustment in lighting level while you are making it.

The minimum number of lighting control points required by code is one per 40.5 square meters (450 square ft), plus one control point per task or group of tasks located in the space. Automatic controls are more effective than manual controls that depend on one person to select lighting levels for others, especially in open office spaces. Interior and exterior lighting systems in buildings larger than 465 square meters (5000 square ft) must have an automatic shut-off control, except for emergency and exit lighting.

The designer of the lighting control system selects the number of lighting elements to be switched together and establishes the number of control levels. Switching off entire fluorescent fixtures results in abrupt changes in light levels in a space. An option is to switch ballasts to allow four different light levels to be produced by a single three-lamp fluorescent fixture with a two-lamp ballast and a one-lamp ballast. Maximum illumination is produced when all three lamps are on. With just the two-lamp ballast on, lighting is at two-thirds. With only the one-lamp ballast, you get one-third of the fixture's output, and with all lamps off, no light at all. Switching ballasts allows light reduction in small steps at low cost.

Fluorescent lamps can be dimmed down to around 40 percent of their output without reduction in efficiency, even with conventional ballasts. A continuous fluorescent dimming from 10 percent to 100 percent is possible with special individual magnetic silicon-controlled rectifier (SCR) dimming ballasts, with triac dimmers, or with electronic ballasts. New high-efficiency electronic ballasts allow for linear fluorescent lamps to be dimmed from 100 percent down to 1 percent. Compact fluorescent lamps can now be dimmed from 100 percent down to 5 percent.

Manual lighting controls generally give employees a sense of control, leading to a feeling of satisfaction and increased productivity. Manual systems can also be wasteful of energy, as people tend to leave lights on at the maximum level even when daylight is sufficient or when leaving the room for an extended period. Manual dimmers in multioccupant spaces lead to personal dissatisfaction and friction. With remote-control dimming systems, occupants can adjust the lighting fixtures closest to their workstations without disturbing other employees, which can help them reduce glare on computer screens.

Static automatic lighting controls can be set for time schedules where there are regularly scheduled periods when task lighting is not required, such as coffee and lunch breaks, cleaning periods, shift changes, and unoccupied periods. Programmed time controls save between 10 and 20 percent of energy use. The payback period for the installation of these controls ranges from one to five years. A relatively simple programmable controller can be substituted for a wall switch. More sophisticated units allow remote control of loads and circuits on a preprogrammed time basis. With tight programming, the system can save up to half over uncontrolled installations. Because they do not detect actual space use patterns, they must have an override for special conditions such as dark, rainy days and evenings when people need to work late.

Dynamic automatic lighting control initiation uses an information feedback loop to respond to actual conditions that are indicated by sensors. Dynamic control systems consist of a programmable controller and field sensors plus wiring. Some systems use high-frequency signals impressed on the power wiring system to transmit control signals in a power line carrier (PLC) system. Completely wireless systems use radio frequencies and wireless transmitters and receivers.

You can change seamlessly from daytime to nighttime lighting environments with a dimming controls system. Dimming also increases the lamp life for incandescent lighting. When specifying a lighting controls system, you need to consider whether the system is flexible enough to expand for unanticipated needs. A reliable controls system manufacturer must be available to modify and adjust the system during the development and implementation of a project. The cost of lighting controls is always a consideration, with features balanced against competitive systems' costs. Lighting controls should be compatible with other related equip ment, such as theatrical or themed entertainment industry standards.

Some lighting controls allow the user to create and recall custom preset scenes for common room activities. These systems are practical for restaurants, conference and meeting rooms, offices, hotel rooms, and homes. Scenes are set by adjusting a light or group of lights controlled together within a room or space for a specific activity. You can switch between scenes at the touch of a button.

Wireless lighting control systems for conference and meeting rooms give a presenter control of lights, motorized window shades, and projection screens at the touch of a button. Some wireless systems use a radio frequency tabletop transmitter that can be located anywhere inside a room. By pressing buttons on the transmitter, radio frequency signals are sent to controllers housed in the ceiling. These controllers then send signals to dimming ballasts to adjust the light levels, and also to optional motorized window shades and projection screens or other audiovisual equipment. Some systems offer control by simple slide dimmers, and are designed for use in classrooms and lecture halls, where presenters may not be as familiar with complex audiovisual equipment.

Simplicity of setup and use is also important. Walking into a conference room and not being able to turn on or control the lights is really an unnecessary challenge. Too many options can be a bad thing. Sophisticated engineering that will allow a system to do almost anything, while still making it all easy to understand and intuitive to use, has eluded most major manufacturers.

Occupancy Sensors

Between 9:00 a.m. and 5:00 p.m., offices in commercial spaces are occupied only one-third to two-thirds of the time, due to coffee breaks, conferences, work assignments, illness, vacations, and different work locations. Occupancy sensors can turn office lights off, or dim them to corridor lighting levels, after the space has been vacant for 10 minutes. Occupancy sensors can also turn off fan-coil air units, air conditioners, and fans. Relighting may be instantaneous, delayed, or manually operated by the occupant.

Passive infrared (IR) occupancy sensors react to the motion of a heat source within their range. The IR sensor creates a pattern of beams, and reacts when a heat source, such as a person, moves from one beam to another. These IR sensors don't react to stationary heat sources. Small movements that don't cross to another beam may not be detected, and the lighting may shut off if a person just sits quietly. Very slow movements may not trigger the sensor. The IR sensor must have the heat source within its line of view, so heat sources blocked by furniture are not detected. If not carefully selected and located, the IR sensors may have dead spots in their detection patterns.

Ultrasonic occupancy sensors (Fig. 34-2) emit energy at between 25 and 40 kHz, well above the human hearing range. The waves of energy reflect and rereflect throughout the space in a pattern monitored by the sensor. The sensor detects any movement disturbing the pattern. Unlike IR systems, ultrasonic systems don't require a direct line of sight to the movement. They detect small movements, which means that curtains, or even air movement, can trigger action, and they must be frequently adjusted to reduce sensitivity to avoid false sensing. However, decreased sensitivity also decreases coverage.

Hybrid dual technology occupancy sensors use both IR and ultrasonic detectors for turning lights on. Once on, a reaction in either sensor keeps the lights on. Sophisticated electronic circuitry learns the space's occupancy pattern, and is programmed to react accordingly.

Occupancy sensors work best in individual rooms and workspaces. You can use wall-mounted sensors in any small office where there is direct line of sight between the sensor and the occupant. Private offices often use ultrasonic wall mounted occupancy sensors that are turned on manually, set for maximum sensitivity and ten-minute delay. Manual-on operation prevents lights from turning on unnecessarily when triggered by corridor activity, day-

light, brief occupancy, or when a task light is sufficient. The sensors may be wall or ceiling mounted, or placed in wall-outlet boxes in a combined sensor/wall switch configuration. The system should be tested before final installation. An IR detector can cover from 23 to 93 square meters (250-1000 square ft), and can save enough energy to pay for itself in six months to three years.

The Audubon Society Headquarters in New York, designed by the Croxton Collaborative, installed motion sensors to detect the presence of persons in a room, and to turn the lights off after a specified number of minutes without activity. The system produced an immediate 30 percent reduction in energy consumption and reduced the lighting-produced cooling load.

For open offices, ultrasonic ceiling mounted occupancy sensors are set to maximum sensitivity with a 15-minute time delay so that they will detect a single, quiet worker. In spaces with vertical files, partitions, or any other objects that create barriers higher than four feet, the standard coverage area given in manufacturer's literature may be too generous, and you may need more closely spaced sensors. Verify sensor spacing directly with the sensor manufacturer.

Some ceiling mounted ultrasonic sensors are specifically designed for linear corridor distribution. They are usually set to maximum sensitivity and 15-minute time delay. The narrow linear distribution patterns increase sensitivity at a distance, turning lights on well before a person reaches an unlighted area.

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