INTRODUCTION
TO LIGHTING CONTROLS
Introduction:
Lighting controls play a critical role in electric lighting systems,
providing the function of:
In recent decades,
technological development has increasingly automated these functions and
allowed integration of devices into larger, more flexible systems. The
result is significantly expanding energy-saving opportunities,
flexibility, reliability and interoperability between devices from
different manufacturers.
The Lighting
Control System: Lighting control systems contain three
components linked by communication wiring, which is used to transmit
control signals, and power wiring, which supplies power.
|
Component |
Sensing Device → |
Logic
Circuit → |
Power
Controller |
|
Function |
Provides
information to logic circuit |
Decides
whether to supply lighting, and how much |
Changes the
output of the lighting system |
We can therefore view a lighting control system or device as an
apparatus that 1) receives information, 2) decides what to do with that
information, and 3) changes the operation of the lighting system. In
other words, we can look at lighting control devices based on inputs and
outputs. Below are three examples.
|
Control |
Input
|
Decision-making |
Output
|
|
Occupancy
sensor |
Sensor detects
presence or absence or people |
Decide whether
to turn on or shut off lights |
Sends signal
to relay, which closes or opens circuit |
|
Control
station and dimming panel |
User presses
button to recall preset scene |
Control
station recalls scene from memory and sends signal to dimmer at
dimming panel |
Dimmer adjusts
light output to desired level |
|
Dimmable
ballast |
Controller
provides signal to dim |
Ballast is
instructed to dim, and by how much |
Ballast alters
the current to the lamps, dimming them |
Below is an example of a robust lighting control system with a control
station, occupancy sensor, photosensor and time switch or centralized
switching system providing a variety of inputs to the master lighting
controller. The lighting controller can be a switching panel, dimming
panel or both linked together. The controller in turn controls the
lighting load with a variety of outputs based on decisions made by the
logic circuits. Since different control strategies may have overlapping
device requirements, control synergies can be gained by building a
system of simple components.
Purpose of
Lighting Controls: In many applications, the overall purpose of
the lighting control system is to eliminate waste while providing a
productive visual environment. This entails:
-
Providing the
right amount of light
-
Providing that
light where it’s needed
-
Providing that
light when it’s needed
The Right Amount
of Light … Control systems provide the right amount of light. This
lighting decision is based on the type of tasks being performed in the
space. Lighting controls support this goal in two ways.
Lighting controls
provide flexibility in adapting the lighting system to different uses.
For example, a school auditorium, which is home to a diverse range of
activities, would need different light levels for these activities.
Lighting controls
provide the ability for users to adjust light levels based on changing
needs or individual preference, either through dimming or through bi- or
multi-level switching. Dimming provides the greatest amount of
flexibility in light level adjustment.
By enabling the
lighting system to deliver the right amount of light to the task, the
control system can eliminate energy waste while providing a productive
visual environment.
… Where It’s
Needed … Lighting controls support the lighting system putting
light where it’s needed. This entails establishing control zones, which
is a light fixture or group of fixtures controlled simultaneously as a
single entity by a single controller. Zones are typically established
based on types of tasks to be lighted, lighting schedules, types of
lighting systems, architectural finishes/furnishings, and daylight
availability.
The greater the resolution of the control zones—that is, the smaller
they are—the greater the precision the control system can provide. For
example, a control system can turn the lights on automatically when a
person enters a building during non-operating hours. Only the areas to
be used should be lighted, however, and not the entire floor. A zone can
also be as small as single ballast or light fixture, which enables the
greatest amount of control resolution. For example, each user in an open
office can be given capability via PC or handheld remote to dim his or
her own lighting to personal preference.
Generally, the smaller
the control zone, the greater the control resolution and potential
utility cost savings and the greater the opportunity to enable the
lighting system to support visual needs.
… And When It’s
Needed: An effective control system ensures that the lighting
system operates—and consumes energy which costs the owner money—only
when it’s needed. Determining when the lighting system should be
operating depends on how the space is occupied. This will entail whether
a time-based or a threshold event should be the deciding factor in
whether the lights should be turned on or shut off.
If occupancy is
predictable, a time-based strategy can be considered. For example, a
switching system can be scheduled to automatically shut off the lights
by area, by floor or in an entire building if a building’s occupancy is
predictable.
If occupancy is not
predictable, a threshold-event-based strategy can be considered. For
example, occupancy sensors can be used to automatically turn on and shut
off lights in areas depending on whether the sensor detects the presence
or absence of people in the monitored area.
By ensuring the
lighting system provides light only when it’s needed, the control system
can significantly reduce wasted energy and generate utility cost savings
for the owner.
Energy Management:
Advanced lighting control devices and systems can be used to reduce
ongoing costs for the owner and thereby increase profitability and
competitiveness. According to the New Buildings Institute, lighting
controls can reduce lighting energy consumption by 50% in existing
buildings and by at least 35% in new construction.
-
Lighting energy:
Controls can reduce the amount of power drawn by the lighting system
during operation and also the number of operating hours, thereby
reducing utility energy charges.
-
Lighting demand:
Controls can reduce the amount of power drawn by the lighting
system, reducing utility demand charges—particularly during peak
demand periods, when demand charges are highest.
These cost savings can
produce a short payback and a high rate of return for the investment in
the new controls. In new construction, the rate of return is often
higher because only the premium, not the total installed cost, will be
recouped before positive cash flow is realized.
Visual Needs:
The project may be driven by business benefits other than energy savings
by providing increased performance and flexibility:
-
Adapt the lighting
for multiple uses of a space, such as a conference room or
gymnasium.
-
Adapt the lighting
to evolving space needs resulting from employee churn and office
strategies such as hoteling and hot-desking.
-
Mood-setting for
restaurants and similar applications.
-
Increasing worker
satisfaction by providing personal control of their lighting systems
in office and other environments.
-
Enhanced
aesthetics and image, greater space marketability, and pollution
prevention.
These business
benefits are often more difficult to calculate than energy savings, but
tangibly contribute to the bottom line.
Studies, for example,
have shown that personal lighting control can increase worker
satisfaction, a major contributor to productivity, while providing
energy savings. According to the Building Owners and Managers
Association (BOMA), energy costs run about $2/sq.ft. in a typical
commercial building while worker salaries and benefits can run to
$130/sq.ft. or more. While reducing energy costs by a large percentage
can be profitable, increasing productivity by even a very small
percentage can be much more profitable.
Defining the
Application Goals: The first step in determining the right
control strategy is to thoroughly define and understand the application
goals.
|
|
2003
Ducker Research/ Watt Stopper Lighting Automation Study
|
2004-2005 ZING Communications/ LCA Dimming Study
|
2005
Square D Bulls Eye Study |
|
Methodology |
Telephone
interviews of 158 facility managers, electrical engineers and
architects |
Email survey
to 4,317 lighting designers, architects, engineers, distributors
and contractors with 6.7% response |
Direct mail
survey |
|
Study Focus |
Automatic
Switching |
Dimming |
Lighting
Controls |
|
Research
Question |
What are the
top five factors driving the use of automatic lighting controls? |
What are the
top five reasons for specifying dimming systems? |
What are the
most important benefits of lighting control? |
|
Average
Respondent Answer |
1. Increasing
energy savings
2. Complying
with owner requests
3. Compliance
with state and national energy codes
4. Providing
occupant control capability
5. Obtaining
utility rebates and incentives |
1. Ability to
light space for different uses (flexibility)
2. Client
request
3. Energy
savings
4. Add value
to the design
5. Mood
setting |
1. Reduce
energy costs
2. Worker
safety
3. Occupant
convenience
4. Prolong
equipment life
5. Meet state
energy codes |
Switching or Dimming? The first primary decision after defining
the load and the application goals is whether to switch or dim the load.
Switching and dimming are stand-alone strategies but are often used in
the same facility, and may be integrated in the same control system.
|
Method |
Switching |
Dimming |
|
Primary Use |
Energy
management |
Visual needs |
|
Basic Function |
Turn lights on
or off |
Change light
output with smooth transitions between light levels |
|
Benefits |
Utility cost
savings |
Occupant
satisfaction, flexibility, utility cost savings |
|
Advantages |
Relatively
inexpensive and simple to commission |
Can set light
output at any level within available range, greater user
acceptance due to smooth transitions between light levels
|
|
Disadvantages |
Lower user
acceptance in occupied spaces with stationary tasks due to
abrupt, noticeable changes in light level |
Higher
installed cost, and can require more sophisticated commissioning |
Local or Central Control? The next step is to determine the
amount of local vs. central control that is needed from the lighting
control system.
|
Control Method |
|
Divide the
building into series of control zones, each zone constituting a
lighting load controlled by a single controller |
|
Localized |
Centralized |
|
Each zone
operated by its own point of control independently of other
zones |
All zones
operated by single point of control |
|
Lower cost,
less sophisticated commissioning |
Greater
capabilities, flexibility, potential cost savings |
|
The control
scheme can be designed with local systems and a centralized
system working together as layers. Both local and centralized
systems can be integrated into building automation systems for
control of lighting and HVAC. |
What Degree of Automation Is Required? Manual lighting controls
range from a single switch to a bank of switches and dimmers that are
actuated by toggles, rotary knobs, push buttons, remote control, and
other means. Manual controls can be cost-effective options for
small-scale situations. However, as the size of the lighting system
grows, manual controls lose their cost-effectiveness. In addition,
manual controls often waste energy because the decision to shut off the
lights when they are not needed is based entirely on human initiative.
|
Method
|
Strategy |
Manual
vs. Automatic |
|
Switching
|
Occupancy
sensors |
Turn the
lights on or off automatically based on whether
space is occupied |
|
Scheduled
automatic shut-off at end of workday switching panels,
time-clocks or building automation system |
Turn selected
lights on or off automatically based on
schedule when space is predictably unoccupied |
|
Scheduled
automatic shut-off of select loads (bi-level switching) during
peak demand periods, time-clocks or building automation system
|
Turn off one
or two lamps in each fixture or checkerboard fixtures
automatically for load shedding during peak demand
periods |
|
Bi-level
switching using wall switches controlling lighting system
layered as two separate circuits |
Turn selected
circuit on and off manually to achieve ON, 50%
light level, and OFF |
|
Multilevel
switching using photosensor and low-voltage relay |
Turn the
lights off automatically based on available
ambient daylight |
|
Dimming
|
Dimming
control of smaller loads using wall-box and remote dimmers
|
Adjust light
output manually based on space need or personal
preference |
|
Dimming
control of larger loads using control stations and dimming
panels |
Adjust light
output manually based on space need or personal
preference |
|
Daylight
harvesting using photosensor, controller and dimmable ballast
|
Adjust light
output automatically to maintain target light
level as daylight enters space |
|
Adaptive
compensation using dimming panels and scheduling device such as
time-clock |
Adjust light
output automatically to provide lower light
levels at night based on studies about human lighting
preferences |
|
Peak shaving
and load shedding using dimming panels and scheduling or control
device |
Adjust light
output automatically during peak demand periods
and/or manually based on utility request to
curtail load |
Example Strategies: Below are six sample strategies defined
according to whether they are dimming or switching, local or
centralized, and manual or automatic.
What Degree of Control Accuracy Is Required? A key step in
designing a lighting control system is to determine the degree of
control over the lighting system, which means breaking the load up into
zones. A control zone is a fixture or group of fixtures controlled
simultaneously as a single entity by a single controller. Zones are
typically established based on types of tasks to be lighted, lighting
schedules, types of lighting systems, architectural finishes/furnishings
and daylight availability. Establishing smaller zones increases control
accuracy and flexibility but also increases cost.
See also:
Occupancy Sensors
Intelligent Control Panels
|
