Daylighting Control
Design Guide
Daylighting Control
Design and
Application Guide
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Lighting
Control
Panels
Daylighting
Control
Design Guide
Daylighting benefits
An emerging lighting control method, daylighting control utilizes incoming natural light
to supplement, and at times, supplant artificial
lighting. The benefits of daylighting are
numerous. The U.S. Environmental Protection
Agency has estimated that potential energy
savings can range up to 40%. And because
electrical loads tend to parallel daylight patterns, daylighting control is a natural choice
for load shedding.
Just as importantly, research is beginning to
show that the use of natural light boosts productivity. In studies published in August 1999,
researchers documented higher test scores in grade school students who attended classes
in rooms that received daylight. In another study, research revealed that retail sales in daylit
stores increased as much as 40% when the retail space was illuminated with daylight.
Other benefits include:
• peak demand reduction
• energy conservation
• physiological and psychological benefits
• higher leasing rates for commercial buildings
• lower tenant vacancy rates
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Daylighting Control
Design Guide
Daylighting control
Types of control
Both indoor and outdoor lighting can be controlled by light
level control systems, and generally, two types of control are
involved:
• ON/OFF switching control (also called “stepped” dimming)
• Dimming control
While ON/OFF control is an effective tool for both indoor
and outdoor lights, dimming control is usually used only with
indoor lighting. ON/OFF control uses light level data to
determine whether lights should be switched on or off. In
contrast, dimming systems use the data to determine the amount of artificial light that is
needed to supplement the available natural light by raising or lowering light levels to the
desired light level.
For daylighting control, products are usually found in two configurations:
Control systems include controller modules and an external photocell as well as
other options or components such as
power supplies and other control devices.
Usually, facilities with more complex
applications that require more extensive
control capabilities will find that control
systems are more appropriate. These
products can be used to control multiple
zones of lighting independently, and have
numerous adjustable settings to tailor
control more closely to users’ needs.
Stand-alone products, on the other hand,
are self-contained units that operate independently. Facility managers, building
owners or tenants that have a smaller
facility with simpler control needs may
find that a stand-alone controller is perfectly adequate.
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LCD Control Module
Dimming Ballasts and Fixtures
LCD-103
Fade
Rate
Ramp
Rate
Min.
Voltage
4
6
Dimming
Response 1
1
0
Offset 1
6
Dimming
Response 2
3
1
0
Zone 2
Zone 3
5
3
2
1
6
Dimming
Response 3
2
4
Zone 1
4
5
3
2
1
2
ON
Max.
Voltage
4
5
3
2
1
2
Offset 2
3
1
4
0
3
Offset 3
4
Occupancy Sensor
LS-190C
Photocell
Autom.
On/Off switch
Key switch
Timer
Energy management
system
|
Control Interlock
LS-4 Dimming
Wall Switch
At a minimum, a daylighting control system will include
a control module and an external photocell. It may also
include optional devices such as other lighting controls
or switches, such as with the LightSaver LCD dimming
control system.
S
Types of control
products
Daylighting controls are either “closed loop” or “open loop” systems. Closed loop systems
consider the illuminated environment – indoor light as well as outdoor light – in determining
how to adjust artificial lighting. Based on the feedback from the controlled area, these controllers will adjust lighting output. Open loop systems, on the other hand, measure incoming
daylight and make lighting adjustments based on the estimated daylight contribution.
D
Basic control
technologies
Stand-alone daylighting
controls incorporate both
the control module and
the photocell within one
self-contained unit.
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Daylighting Control
Design Guide
Overview of process
In a daylighting project, the entire process may involve individuals as diverse as building
owners, property managers, facility managers, lighting designers, electrical contractors,
project engineers, architects, and energy managers in different stages. These include:
Preliminary assessment
• Is daylighting a feasible control strategy?
• Are there any energy code provisions that either require daylighting controls in certain
spaces, or treat their use favorably?
Development of viable daylighting design
• Which control technology is right for your application?
• Should you use multiple lighting control zones? If so, how do you define them?
Implementation
• Are there any special considerations in the installation process?
Commissioning
• What sort of follow-up is necessary?
Each stage offers different issues that will affect the selection and success of the daylighting control chosen.
After briefly considering these issues, this guide will offer some application examples that
illustrate the different types of light level control, the control technologies, and the various
design and implementation issues.
The Watt Stopper’s application experts are available for design support and assistance during any phase of a lighting control project. They are ready to help with
light level, occupancy sensor, lighting control panel, or any lighting control
design question. Call The Watt Stopper’s technical support at 800-879-8585.
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Daylighting Control
Design Guide
Preliminary assessment
Preliminary
planning
When beginning to consider whether daylighting is a feasible control strategy, the first
question to be answered is:
• Does this facility receive enough daylight to supplement and/or replace artificial lighting?
Initially, this may require simply assessing the building’s architectural features:
• Are there a lot of windows?
• Does the building contain any skylights?
• Are there any atriums?
Further analysis may take into consideration many of the variables that influence daylight:
the time of day and year, the location (longitude and latitude), and other environmental conditions. Other external factors come into play as well, such as climate, building and window
placement. In assessing daylight availability, designers may use specific tools to identify daylight levels (some examples include Desktop Radiance, daylighting design software
currently in development by Lawrence Berkeley National Laboratory, and SkyCalc, distributed by Pacific Gas & Electric).
Another threshold question may be:
• Are there any regulatory provisions that require or promote
the use of daylighting controls?
Some jurisdictions, such as California, have specific energy code
provisions that deal with daylighting controls. For instance,
California’s Title 24 requires that spaces more than 250 square
feet that receive adequate natural light must have controls that reduce the artificial lighting
by at least 50%. ASHRAE 90.1, a standard adopted by a number of jurisdictions, also
includes provisions about daylighting control.
Daylighting
design
In the process of developing the best daylighting system for a specific application, the project team will want to consider many important factors:
• types of daylighting systems
-- dimming or switching
-- control system or stand-alone controller
• setting up control zones
• integration with other controls (i.e., occupancy sensors, lighting control panels)
• integration with building elements (new construction or retrofit)
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Daylighting Control
Design Guide
Developing a daylighting control design
Selecting a control
technology
When selecting a type of daylighting system, designers will be choosing from two main
types of systems: dimming systems, which raise and lower light levels in response to control
signals, or switching, which turn controlled lights on or off in response to those signals. The
following table offers a quick summary of the respective advantages and disadvantages
when deciding between dimming and ON/OFF switching controls.
Dimming
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Switching
• Ideal in new construction settings
with dimming ballasts
• Ideal in retrofit applications with
non-dimming ballasts
• Greater user acceptance because light
level changes are subtle
• Less user acceptance because
light level changes are more
abrupt
• Generally more expensive daylighting
control technology (when including
the cost of dimming ballasts)
• Less expensive than dimming
• Ideal in applications where occupants
are engaged in small motion activities
(sitting, reading, typing)
• Ideal for applications where occupants are engaged in large motion
activities (walking or moving
about) because more abrupt light
level changes are less distracting
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Daylighting Control
Design Guide
Control systems vs. stand-alone controllers
Control
systems
The following table offers a quick summary of the respective advantages and disadvantages
when deciding between control systems and stand-alone units.
Systems
• Multiple adjustable settings
• Basic adjustable settings
• Easier to calibrate during set-up and
in future because mounted in panel
• More difficult to calibrate during setup and in future (installed in ceiling)
• More expensive
• Less expensive
• Capable of controlling multiple lighting zones
• Capable of controlling only a single
lighting zone
• Generally open loop systems
• Generally closed loop systems
• Manual dimming capabilities possible
with dimming systems
• Automatic dimming capabilities only
• Ideal in large rooms or facilities
where daylight levels might vary from
one location to another (i.e., classrooms, open office areas, warehouses,
cafeterias)
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Stand-alone
• Ideal in small rooms or spaces where
daylight contributions are relatively
even or balanced (i.e., enclosed
offices, hallways)
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Daylighting Control
Design Guide
Implementing daylighting controls
Once a control technology has been selected, implementation will begin.
Positioning the
photocell
Control zones
To position the photocell, select a location
where the photocell will receive a representative sampling of the daylight entering the
area. For instance, if the photocell is going
to be placed inside a window where an
awning or overhang extends far out from the
window, try to place the photocell in a position where it will not be excessively shaded
by the awning or overhang. However, the
photocell should not be placed in direct sunlight. Photocells can be positioned either
indoors or outdoors.
Window
LS-190C
Photocell
Zone 1
Zone 2
Zone 3
Control systems offer the capability of multiple control zones. To best utilize multiple control zones in daylighting, we suggest the following guidelines:
• Define zones by the amount of daylight an area receives. For instance, define a single
zone as a row of fixtures nearest to the window since this area will receive more daylight
than other areas of the room. Another zone might be the next two rows of fixtures,
which receive a lesser amount of daylight.
• Define zones by similar occupant activity. For instance, if some occupants of an open
office area use computer terminals frequently, while other occupants are active on the
telephone with minimal computer work, avoid including both groups in the same zone,
since their light level requirements will differ. However, daylighting control zones do not
need to conform exactly to occupancy zones as long as different occupancy zones share
similar light level requirements.
• Try to limit the number of zones if possible. When defining zones, keep in mind that the
more zones exist, the more costly the application will be.
• If the ON/OFF switching strategy is being implemented, use multiple zones to create
“stepped dimming” by switching individual lamps within fixtures on and off. Another way
to achieve stepped dimming is to define zones according to patterns so that light level
changes throughout the room will be more even. This will moderate the potential for
user dissatisfaction over abrupt light level changes.
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Daylighting Control
Design Guide
Commissioning the daylighting controls
Both control systems and stand-alone controllers provide adjustable settings of
different kinds. Once the control product
and all its components are in place, it is
time to adjust the control settings.
2. Set lowest and highest levels
to which lights can dim
1. Sets ramp and fade
speeds for dimming
LightSaver ¤
LCD-103
60
sec.
4
Fade
Rate
60
sec.
4
Ramp
Rate
4
Dimming control
settings
10V
6
Max.
Output
4
4
5
3
4V
0
Min.
Output
5
3
5
3
For dimming controls, this can include the
speed of the fade and ramp rates, the
amount of time it takes for light output to
decrease or increase (the dials labeled # 1
Sets lighting output
to respond in proin the illustration control these settings). To
portion to daylight
Sets starting threshold for
minimize abruptness of light level changes,
level for each zone
dimming for each zone
the fade rate should be set to the slowest
The LCD dimming controller provides adjustable settings
setting, to ensure that a minimum light
located on the front of the module.
level is always maintained. Conversely, the
ramp rate should be set to the fastest setting available to ensure that the required light level
is maintained at all times.
2
1
6
Dimming
Response 1
2
3
1
ON
4
Offset 1
1(800)879-8585
0
2
1
6
Dimming
Response 2
2
1
0
2
1
6
Dimming
Response 3
2
3
1
4
0
Offset 2
3
4
Offset 3
Light output levels can be adjusted with dimming controls. To save energy, by decreasing
the maximum level of light output, controlled lighting can be adjusted to satisfy the design
requirements of the lighting. Furthermore, the lights will operate at the selected output
level unless they are dimmed to a lower level by the daylighting controller. (The dials
labeled # 2 in the illustration above control these settings.)
ON/OFF switching
control settings
Adjustments with switching controls generally involve ON and OFF delays. It is recommended that users set the ON delay on the low side so that lighting will turn on more
quickly when daylight levels are inadequate. The reverse is true with the OFF delay setting.
Here, installers should set the delay
Indicates photolonger, to prevent lamp cycling due to
LCO-101
LightSaver
cell footcandle
Setpoint
passing cloud cover.
Set to delay
range and set®
NOTE: The factory default settings are
the minimum settings on all dials.
Installers will always need to adjust these
settings to reflect the characteristics of a
particular application.
when lights
will turn ON
or OFF after
setpoint light
level is
achieved
x1
x 10
x 100
x 1000
16
8
Sec.
0
24
.4
32
.2
ON Delay
1.5
2
Setpoint
16
+30 +40
24
+20
Min.
32
0
OFF Delay
+0
8
point multiplier
1
+50
%
+70
Deadband
Adjust light level
setpoint values
to turn lights ON
and OFF
1(800)879-8585
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Daylighting Control
Design Guide
Application - Classroom
Application
highlights
•
•
•
•
Control system application
Three-zone daylighting control
Manual dimming
Interface with occupancy sensor
Classrooms are ideal candidates for daylighting control as
they very often have significant access to natural light.
What’s more, the benefits of daylighting may be particularly
pronounced; studies sponsored by the California Board of
Energy Efficiency have indicated that student productivity
and test scores increased when they were in an environment
employing natural light.
Dimming
control
Creating control
zones
Manual control
options
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In determining which type of light level control is most appropriate, designers will take into
consideration the accessibility of ambient daylight. Many classrooms include large windows
that enable incoming daylight to illuminate the room from the sides. This type of lighting
pattern is well suited to multi-zone dimming control. The lights closest to the windows can
be dimmed or even switched off for long periods of time, while lights in other parts of the
room may need to be maintained at a higher output level for more hours. The final result is
a balanced task illumination level.
For multi-zone dimming control, the LCD dimming
control system, with an LCD-103 control module and
an LS-190C photocell, may be an appropriate choice.
The photocell should be positioned in a location
near the classroom windows to measure incoming
daylight. A three-zone application would divide the
classroom according to the light levels found in
three discrete zones of the room, as shown in the
illustration. The fixtures closest to the windows
would comprise zone 1, the fixtures in the center of
the room would make up zone 2, while the fixtures
on the far side of the room would comprise zone 3.
Sunlight entering the room
1
2
}3
Each zone is defined by the numeral to the
right of the row of fixtures.
Because teaching activities may involve a range of tasks, the lighting requirements may
vary substantially. For instance, during presentations or videos, the teacher would want the
room to be darkened completely. During periods when the students are working on drawing or other fine work, the teacher would want the room to be fully illuminated. To achieve
these objectives and override the automatic daylighting control, the teacher can operate the
lighting system in manual mode, utilizing the system’s optional LS-4 Dimming Wall Switch.
Using the override OFF feature would darken the room; conversely, the override ON would
ensure the lights were operating at full output. The manual up/down dimming capability
enables the teacher to attain light levels that accommodate a range of specific activities.
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Daylighting Control
Design Guide
Application - Classroom (cont.)
Integration with
other lighting
controls
To maximize savings, the daylighting control system can be integrated with other control
devices (i.e., occupancy sensors or a building management system) via a control interlock.
In the classroom, for instance, a DT-200 Dual Technology sensor would be suitable. The
occupancy sensor could then be used to turn the controlled lighting off, or to signal the
dimming system to fully dim the lights when no one is in the space. Another common scenario might be the integration of the daylighting system with the facility building
management system. The BMS could be used to turn the daylighting system on and off
according to a pre-set schedule.
LCD Control Module
Dimming Ballasts and Fixtures
LCD-103
Fade
Rate
Ramp
Rate
Min.
Voltage
4
5
3
2
1
6
Dimming
Response 1
0
Offset 1
5
3
6
Dimming
Response 2
1
0
Offset 2
Zone 3
6
Dimming
Response 3
2
3
1
4
0
3
Offset 3
4
Occupancy Sensor
LS-190C
Photocell
Zone 2
5
3
2
1
2
3
4
Zone 1
4
2
1
2
1
ON
Max.
Voltage
4
Autom.
On/Off switch
Key switch
Timer
Energy management
system
|
Control Interlock
LS-4 Dimming
Wall Switch
060.MJ.2
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Daylighting Control
Design Guide
Application - Warehouse
Application
highlights
•
•
•
•
•
Control system application
Multi-zone ON/OFF control
Interface with DM-100 for bi-level HID control
Interface with occupancy sensors
Interface with time clock/building management system
Today, many warehouses, distribution centers, and other
storage facilities utilize skylights, loading docks, and bays
that introduce large amounts of natural light into the facility. Moreover, although many of these facilities are
operated around the clock, they are also intermittently
used. This combination of factors indicates it makes economic sense to implement daylighting controls to take
advantage of the existing natural light.
Certain areas in warehouses receive substantial levels of natural light, such as loading dock
areas with direct light coming in from the sides, and areas below skylights receiving indirect light from above. With these adequate sources of light, daylighting control can be
utilized to eliminate electric lighting specifically where it is not needed. This will enable the
user to customize control to match the light level present in each specific area.
Multi-zone
ON/OFF control
For multi-zone ON/OFF control in a warehouse,
the LCO ON/OFF switching system, with an
LCO-103 control module and an LS-150 series
photocell, would be the recommended choice.
The photocell would be positioned inside the
well of the skylight pointing upward to obtain
the most representative reading of incoming
daylight. For general warehouse use, light levels
in the range of 10-30 footcandles are common.
An LS-156 or LS-157 would be the appropriate
choices for photocell.
Skylights
zone 1
zone 1
zone 1
zone 2
zone 3
As shown in the illustration, control of zone 1,
which consists of the lights closest to the skylights, would involve switching lights off early
in the morning as adequate light became available in those areas. Lights would be switched
back on in the darkening late afternoon or early evening hours.
The lights in zone 2, consisting of alternating fixtures in the rows further from the skylights,
would be switched off during the middle hours of the day when light levels are at their
greatest.
Zone 3 is defined as the remaining fixtures in the rows furthest from the skylights. For zone
3 lighting, ON/OFF control would involve switching lights OFF only for a brief time during
midday as in zone 2. The result in zones 1, 2, and 3 is stepped dimming.
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Daylighting Control
Design Guide
Application - Warehouse (cont.)
Interface with
DM-100 for
HID control
Many warehouses use high intensity discharge (HID) lighting to take advantage of their
greater energy efficiency. However, these lamps are not amenable to traditional ON/OFF
control due to their long restrike period. Instead, high/low control is implemented using
Watt Stopper DM-100 bi-level controllers. After connecting one DM-100 controller to each
HID fixture, the linked HID controllers can be connected with the LCO controller. Then, the
DM-100s will switch HID lights to low light levels when the LCO controller signals that adequate light levels exist.
Skylight
When there is adequate daylight contribution, such as from this skylight, the LCO ON/OFF control system will signal the DM-100 HID controllers to switch the adjacent HID lights to low levels.
Occupancy sensor
interface
Time clock/BMS
interface
060.MJ.2
Another common characteristic of warehouse facilities is the intermittent occupancy of different work spaces. To tailor lighting control more precisely to these usage patterns, the
daylighting system can be supplemented with occupancy sensors. For aisleways, the CX100-3 passive infrared sensor is a suitable choice. In open areas, the CI-200 sensor, with 360°
coverage, would be suggested. The occupancy sensors and daylighting controls can be combined with either HID or fluorescent lighting. In the case of HID lighting, lamps would be
operating on low at all times except when there is no daylight contribution or the controlled
area is occupied. If fluorescent lighting is in use, the combination of occupancy sensors and
daylighting controls will switch controlled lighting off when there is either adequate daylight contribution or the space is vacant.
Often, warehouse facilities utilize time clocks or building management systems for master
control of lighting and other building systems. Daylighting control easily integrates with
these devices. The BMS or time clock would still provide the master ON/OFF control for
lighting, while the LCO controllers could control lights during the intervening hours for
greater energy savings.
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Daylighting Control
Applications
Application - Exterior walkway
Application
highlights
• Outdoor lighting control
• Control system application
• Adjustable deadband capability
A key area of lighting control in commercial buildings
involves the exterior walkways and entryway. While
employee and visitor safety and convenience are the primary concerns, energy savings are also a consideration.
Thus, photo-sensitive control is a suitable strategy, and
the LCE exterior lighting control system would be a convenient choice for ON/OFF control.
Comprised of an LCE-201 control module and an LS-071C
photocell, the LCE control system will control lighting such as parking lot lights or walkway
lights. When the LS-071C photocell detects adequate light levels in the morning, it will signal the LCE control module to switch controlled lights off. Then, in the evening when
daylight levels drop below a user-defined setpoint, the photocell will signal the controller to
turn the lights back on.
060.MJ.2
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Daylighting Control
Design Guide
Application - Corridor
Application
highlights
• ON/OFF switching control
• Stand-alone control
• Integration with other control devices
ON/OFF switching control for indoor lighting is best
suited to areas where the greatest amount of natural light
exists. In many buildings, corridors are ideal locations for
such control, due to their positions around building
perimeters, or around inner courtyards or atriums also
providing abundant natural light. And since they are
areas in which occupants are moving about, abrupt light
level changes that can accompany ON/OFF control will
be less distracting.
The LS-100 provides low cost, stand-alone ON/OFF switching control. Typically, the unit
would be installed in the ceiling, so that the center of the LS-100’s window rests at an 45°
angle from the daylight source. It relies on Watt Stopper power packs to control lighting.
Prior to installation, the contractor should make the necessary adjustments, such as the
time delay, deadband, and sensitivity settings. When daylight contribution reaches the sensitivity setting established by the user, the LS-100 signals the connected power pack(s) to
switch off the controlled lights. Conversely, when the daylight contribution falls below the
threshold value, the LS-100 will signal to switch the lights back on.
Integration
with other
control devices
060.MJ.2
The LS-100 also integrates with other control devices or systems. For instance, in an application such as a hospital or high-rise commercial office building, a single LS-100 can control
lighting in perimeter corridors on multiple floors. If the corridor where the LS-100 is being
used is similar to corridors on other floors (i.e., each floor has a corridor on the same side
of the building that receives similar daylight), interfacing the daylighting controller with a
central lighting control panel will enable the panel to switch lighting in multiple corridors on
or off based on the signal from that individual LS-100.
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