National Conference on Building Commissioning: May 8-10, 2002
Commissioning Lighting Control Systems for Daylighting
Applications
John Phelan PE
Architectural Energy Corporation, Boulder, Colorado
Synopsis
The extensive use of daylighting to meet the ambient illumination requirements is nearly always
a part of “sustainable” building projects, and effective controls for electric lighting systems are
required in order to attain the energy saving benefits of daylighting. At the same time, the entire
daylighting and electric lighting system must be fully accepted by the occupants in order to reach
either the energy or productivity benefits of sustainable design. Daylighting controls are prone
to operational deficiencies because their application is both design and site specific, and because
the technical capabilities of the systems lag far behind those of typical building automation
systems. Commissioning activities during design, construction, and acceptance phases can
ensure that the lighting control systems perform optimally. While the commissioning process for
lighting controls is not fundamentally different than that for any other type of system, this paper
highlights the unique aspects lighting control commissioning for daylighting design applications.
About the Author(s)
John Phelan leads the sustainable design assistance and commissioning business area within
Architectural Energy Corporation. He supervises the integration of sustainable design and
commissioning activities to deliver dynamic high performance buildings.
Mr. Phelan has been involved in the design, construction, and energy efficiency fields for
residential, commercial, industrial, and institutional buildings since 1985. His areas of expertise
include new and existing building commissioning, field monitoring, performance verification,
operational diagnostics, daylighting design, lighting system design and control, evaluation of
mechanical systems, energy simulation for evaluation of sustainable design measures, and
sustainable building rating systems. He was the primary contributor for research sponsored by
the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) to
develop standard guidelines for in-situ field testing of chillers, fans, and pumps for determination
of annual energy performance.
Mr. Phelan’s project experience includes all phases of the design, construction, and occupancy
phases of the building delivery process. His operations and commissioning experience includes
mechanical HVAC, electrical distribution, building automation, lighting control, security and
access, and kitchen equipment systems. Mr. Phelan is a registered professional engineer in the
state of Colorado.
Phelan: Commissioning Lighting Controls for Daylighting Applications
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National Conference on Building Commissioning: May 8-10, 2002
Sustainable Design and Daylighting
The extensive use of daylighting to meet the ambient illumination requirements is nearly always
a part of “sustainable” building projects. The major “sustainable” benefit from daylighting is
from associated energy savings. Direct electrical use reductions from reduced lighting, not
including reductions in the associated mechanical system loads, are verified to result in savings
of as much as 75% of lighting energy. To achieve these objectives, the electric lighting must be
controlled to supplement available daylight, and to provide the design illumination requirements.
Another major benefit attributed to daylighting is the increased productivity of occupants.
Reasons behind increased productivity are an improved sense of “well-being” and reduced
absenteeism related to having a direct visual connection to the outdoors and the natural solar
cycles. Daylighting also creates more dynamic visual environments.
Effective controls for electric lighting systems are required in order to attain the energy saving
benefits of daylighting. At the same time, the entire daylighting and electric lighting system
must be fully accepted by the occupants in order to reach either the energy or productivity
benefits of daylighting. Electric lighting control is one of the most direct and immediate ways
occupants interact with a building. Occupants will often tolerate a less than ideal thermal
environment, but will quickly object to a lighting environment that does not meet their task
requirements.
Case Study #1: Utility Service Center
This project uses exterior light shelves and roof
monitors to provide daylighting deep into the office
space. On/Off lighting controls were installed to
switch rows of lamps off based on ceiling mounted
photosensors. One year after occupancy, the
building manager thought the lighting control
systems were working. The first sensor tested was
covered with electrical tape. Upon removing the
tape, an entire fixture row would cycle on and off at
3 second intervals. The second sensor was disabled
with the factory supplied jumper, and when tested
switched an interior row of fixtures based on
perimeter light levels. Commissioning was not
done at the time of construction.
Daylighting Design Factors
The successful application of daylighting controls relies on many critical factors that are both
design and site specific. Daylighting projects involve a great number of design factors that cross
the disciplines of site planning, architecture, interior design, lighting design, electrical
engineering and mechanical engineering. All of these design factors have to be integrated with
Phelan: Commissioning Lighting Controls for Daylighting Applications
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National Conference on Building Commissioning: May 8-10, 2002
the occupant characteristics, owner operating requirements, task lighting requirements and the
daily and seasonal solar cycles. Table 1 attempts to summarize these design factors. The
commissioning agent is crucial to the success of projects of this type precisely because the
commissioning process is able to bridge all of these disciplines and factors.
Table 1: Daylighting Design Factors
Discipline
Design Factors
Site
•
Building orientation
Architecture
Lighting Design
•
•
•
•
•
•
•
Mechanical Design
•
•
•
•
Building shape, mass
•
Top daylighting
•
Side daylighting
•
Window/wall ratio
•
Cubicle layout
•
Cubicle height
Task / Ambient lighting
• Direct lighting
design
• Lighting zones
Open office
• Task lighting
Enclosed offices
• Lamp and fixture type
Indirect lighting
• Lamp color temperature
Building automation system integration
Occupant
•
Age
•
Previous office environment
Task
•
•
•
•
IES task type
Computer use
Time of year
Time of day
•
Paper tasks
•
Cloud cover
Interior Design
Solar/Weather
•
Adjacent buildings or natural
features
Glazing characteristics
Interior lightshelf
Exterior lightshelf
Ceiling tile reflectance
Interior colors
Commissioning Activities for Lighting Controls
Commissioning activities during design, construction, and acceptance phases can ensure that the
lighting control systems actually work. While the commissioning process for lighting controls is
not fundamentally different than that for any other type of system, this section highlights the
unique aspects lighting control commissioning for daylighting.
Design Phase
Design phase commissioning activities may be more beneficial for daylighting controls than for
other systems. The author has seen many instances where mechanical systems or HVAC
controls have been poorly designed or specified, yet adjustments enabled the systems to function
adequately. Meanwhile, several projects have been encountered where the installed lighting
control systems were not even capable of meeting the operational requirements of the facility.
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National Conference on Building Commissioning: May 8-10, 2002
Owner’s Requirements / Design Intent
Detailed documentation and communication of the owner's requirements and the design intent of
the integrated daylighting, lighting and control systems lay the foundation to successful projects.
Most owners and operations staff are not familiar with daylighting controls, while many are
familiar with more common (non-daylighting) lighting control applications such as occupancy
sensors, lighting relay panels and override buttons. The lighting control system should be
planned from the point of view of the occupant’s interaction with the system. The daylighting
functionality of the control system is an overlay, which is ideally invisible to the user.
The process of thinking through each space type from the occupant’s perspective will often
reveal inadequacies of the system before any design work or documents are issued. For each
space type, the design team needs to decide how the lights are to be turned on and off (manual,
occupancy sensor, time clock, photosensor, etc.) and how daylighting dimming is to be
accomplished (open loop, closed loop, override capability, etc.). A matrix such as the one shown
in Table 2 can be very helpful to help sort out capabilities and space types. After the capabilities
have been determined, a narrative sequence should also be written for each space type.
Table 2: Lighting Control Capabilities by Space Type (Sample School Project)
Space Type
Classroom
Student Work
Area
Commons
Gym
Administration
Corridors
Restrooms
Manual
On/Off
Daylight
On/Off
9
Manual
Dimming
Daylight
Dimming
9
9
9
Occ
Sensor
On/Off
Occ
Sensor
Off Only
9
9
Override
On/Off
9
9
9
9
9
9
9
9
Schedule
9
9
9
9
9
Design Review
The design review commissioning activities need to account for all of the daylighting design
factors specific to the project (see Table 1). This broadens the scope of the design review
beyond that typically included in the commissioning scope. Any of the design factors, if not
consistent with the daylighting concept, can disable the functionality of the system or its
acceptability to the occupants.
Specifications
The specifications for lighting control systems need to fully describe the required functionality of
the system. There appears to be no agreed upon standard for the section number in which to
include low voltage lighting control system requirements, but the section number is less
important than the content. Most electrical engineers or lighting designers will adequately
handle the hardware and wiring requirements of the specs. However, there also needs to be an
explicit “sequence of operations” for the lighting controls. Depending on the selected
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National Conference on Building Commissioning: May 8-10, 2002
manufacturer, this sequence may be implemented via software, but is equally likely to be set up
with hard wiring. The sequence of lighting operation in the specifications is where the critical
details of the owner’s requirements and design intent are first and foremost communicated to the
installing contractors. This includes describing the capabilities and operational narrative of the
system by space type.
Case Study #2: County Office Building
This project uses interior light shelves to project
daylighting deep into the office space. The
daylighting recommendations described the
solar cutoff angle criteria used in the design, and
the hours per year when direct sun could
penetrate the space. The recommendations also
described assumptions for cubicle height and
orientation. The installed arrangement included
workers with no separation from the light
shelves, and extended hours of operation. The
changes in these design factors resulted in
unacceptable glare problems for the occupants.
Division 16 will also require specific commissioning language so that the contracting team
understands the expectations for the commissioning process. The commissioning provider also
needs to verify that any interoperability requirements between lighting, HVAC, and security
systems are defined.
Technology Support
The hardware and software technologies for daylighting control systems are changing rapidly.
The commissioning provider should be capable of informing the design team about the available
marketplace choices. The technology information that is required includes lamps, ballasts, and
luminaires. Very few electrical engineers have designed lighting controls for daylighting
applications. They are likely to be most comfortable with getting support and help from the
manufacturer’s sales representatives, who while very helpful are often not unbiased. Lighting
control technology issues are also discussed at the end of this paper.
Construction Phase
Construction phase commissioning activities for daylighting controls continue with the theme
that earlier involvement of the commissioning provider is key to successful system integration
and performance.
Submittal Review
The submittals are the next opportunity to verify that the proposed system will still meet the
design intent. The capabilities and characteristics of lighting control hardware and software are
Phelan: Commissioning Lighting Controls for Daylighting Applications
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National Conference on Building Commissioning: May 8-10, 2002
very specific to each manufacturer. If the specifications were written around a particular
manufacturer, but include “or equal” clauses, then the engineer and commissioning provider
must carefully verify the capabilities and compatibility of the submitted equipment.
Case Study #3: City Office Building
This project uses two interior light shelves to
project daylighting deep into the office space.
The design-build project did not include detailed
specifications. Perimeter lighting control is
On/Off based on ceiling mounted zone
photosensors. The electrical engineer approved
a lighting control submittal that included On/Off
photosensors that did not have a deadband
function. If these had been installed as shown
on the plans, the indirect lighting would have
caused the sensors to cycle the lights on and off
at the time delay interval.
Scoping Meeting / Lighting Coordination Meeting
The agenda for the commissioning scoping meeting is written to specifically address the lighting
control systems. For daylit buildings, this may affect who needs to attend the scoping meeting,
because the architectural elements of the daylighting system will affect the lighting control
performance. The attendance will also include the electrical engineer, lighting designer and
electrical contractor, who may or may not have attended otherwise (depending on the scope of
commissioned systems).
When the installation time for lighting fixtures and controls approaches, a lighting “pre-work”
meeting should be held. Attendees should include general contractor, electrical contractor,
lighting control equipment supplier, electrical engineer, commissioning provider and owner’s
representative. At this point in construction, everyone has probably forgotten about the design
intent, and is simply moving ahead with a set of construction drawings. This meeting should
review the entire installation, space by space. There are often outstanding variations in how each
party understands the system that can be worked out at this time.
Sensor Location
Control photosensor location is one of the few “levers” available to make the system respond
correctly to available daylight levels. The location needs to account for the control type (open or
closed loop) and be representative of the controlled zone. The daily and seasonal variation in
daylight levels must also be accounted for, although they must generally be estimated based on
available measurements when the system is installed.
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National Conference on Building Commissioning: May 8-10, 2002
Case Study #4: University Technology Classroom Building
This project uses rooftop monitors to create a
light plenum and perforated metal “tiles” to
create a luminous ceiling. Photosensor dimming
controls are located such that they “see” a
section of the north facing interior wall. The
wall area is illuminated approximately 50% by
the indirect light fixtures and 50% from the
daylight ceiling, but will never “see” direct
sunlight. The closed loop control can then
effectively dim the indirect fixtures in response
to varying levels of daylight availability.
Functional Testing
As in HVAC control systems, the functional testing needs to reflect all of the operating modes of
the lighting control system. At this point, the commissioning provider is merely testing whether
the designed functionality of the system is installed, not whether it is performing as intended.
For example, a flashlight can be directed at the photosensor in order to determine whether
dimming occurs and if the zoning of the electric lighting fixtures is correct. This test does not
verify that the system will dim based on available daylight or maintain a target desktop
footcandle requirement.
Sensor Setpoint and Control Adjustments
Once the system and components are verified to function correctly, the sensors need adjustment
and tuning. Each manufacturer has unique setpoint adjustment procedures. In general, the
installation and setup instructions are adequate only for simple and idealized daylighting
scenarios, such as an enclosed office with direct fixtures and a single window. Sensor
adjustments are typically located on the sensor itself, although some systems now allow changes
to be made at wall stations or in software. Physical sensor adjustments include potentiometers,
dipswitches and slide bars. Without lighting control commissioning, this process if often left to
the uninformed owner or electrician to guess at proper light levels and settings.
Acceptance Phase
Acceptance phase commissioning activities for daylighting controls focus first on helping to
ensure occupant acceptance of the lighting control schemes and to verify the performance under
a variety of ambient solar conditions. Occupants will be readily aware of, and will not tolerate,
any shortcoming in the performance of the lighting control system. There is no grace period for
getting them to work after people have moved in. If the control system creates nuisance
problems such as cycling on and off, or if the light levels are too low or high, it is a steep uphill
battle to gain the occupants’ acceptance and confidence. A lighting control system that creates
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National Conference on Building Commissioning: May 8-10, 2002
numerous and vocal complaints will usually be disabled before it has any chance of being
“accepted.”
Occupant Manual
The commissioning provider should create an occupant manual as a part of the training
procedure. The occupant manual is a short and very simple document that describes the
operation of the lighting control system from the user’s perspective. No technical language or
reference to “control strategies” should be included. If possible, this should be on a single page
that can be included in a “move-in” package for each occupant. The occupant manual may need
to stress that people will need an adjustment period to get used to the new lighting environment.
Training
The operations and maintenance training for commissioning will need to be expanded to cover
the hardware and software of the lighting control system. O&M staff should also receive an
introduction to the daylighting design and concepts because it may be important for them to be
able to explain the reasons behind the control schemes as they deal with occupants. There may
be issues as to O&M ownership of lighting control hardware that also interfaces with the HVAC
building automation system (such as occupancy sensors).
Performance Monitoring
Daylit environments dynamically change by season, time of day, and with variable weather
conditions. Performance monitoring is necessary to verify and characterize whether the system
is correctly responding to these dynamic inputs. For one or more representative space types, the
monitoring should include exterior illumination, desktop illumination, lighting circuit current or
power, and lighting fixture light level. Fixture level and circuit level measurements are often
necessary because lighting control circuits and power circuits will be independent. Figure 1
shows the results of monitoring for the daylit computer lab classroom shown in Case Study #4.
The plot shows the dimming of a single circuit in response to global horizontal illumination
levels on a partly cloudy day. Building wide, the monitoring verified 75% savings from the
integrated dimming and occupancy controls compared to a schedule based system.
Design and Operational Requirements for Daylighting Controls
Design Requirements
The integration of architectural daylighting design elements with the electric lighting design is
essential to the success of the lighting controls. The electric lights are intended to balance the
available daylight to create a luminous environment that is dynamic, but not distracting. The
lighting controls are required to respond to both daylight and electric light proportional to their
contribution to workplane illumination.
Simplicity is a second important design criterion. The average building user is accustomed to
simply turning lights on or off. In most cases, a daylighting based lighting control system should
ask no more of the user. Case study #5 describes a project where the complexity of lighting and
controls far exceeded the interests of the occupants.
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National Conference on Building Commissioning: May 8-10, 2002
Room 223, Relay 211 Circuit Amps and Global FC
8000.0
3
7000.0
2.5
6000.0
5000.0
4000.0
1.5
Global FC
Circuit Amps
2
3000.0
1
2000.0
0.5
1000.0
0
9:30
10:00
10:30
11:00
11:30
12:00
12:30
13:00
0.0
13:30
Date / Time
Lighting Circuit Amps
Ambient Footcandles
Figure 1: Performance Monitoring Results for Case Study #4 Classroom
Case Study #5: University Academic Building
This project uses skylights and
suspended ceiling daylight diffusers to
provide uniform classroom daylighting.
The lighting control uses a “scene”
based strategy, with open loop control
based upon four building photosensors.
Electric lighting includes seven different
zones for ambient and task oriented
lighting. The resulting classroom user
has a choice of 16 scene control buttons,
seven manual dimming buttons and a
computer touchscreen interface. The
complexity of the system made it
extremely difficult to commission, and
does not meet the simplicity preferences
of the occupants.
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National Conference on Building Commissioning: May 8-10, 2002
Operational and Technology Factors
This section discusses in more detail some of the operational and technology factors in the
commissioning of lighting / daylighting control systems, but is not an attempt to capture the
status or state of the art in lighting controls.
Dimming and On/Off
Control
Distributed
Architecture Control
Systems
Analog and Digital
BAS Integration
Open-loop and
Closed-loop Control
Photosensors
Dimming fluorescent ballasts are now available with a 0-10 VDC control input
that is compatible with many control systems. The price differential for
dimming ballasts has dropped greatly in the last several years (except for
“architectural” dimming ballasts which dim to 1% output). On/Off controls are
not recommended for any continuously occupied space, especially offices.
Several manufacturers now offer lighting control systems which move away
from the relay panel concept, where all controls are distributed throughout the
facility. This can substantially reduce power wiring costs when compared with
centralized lighting relay panels. The low voltage control wiring also allows
daylighting control zones and power circuiting to be independent.
Several manufacturers now offer lighting control systems with truly digital
capabilities, allowing more sophisticated control and monitoring capabilities.
The DALI standard (Digital Addressable Lighting Interface) is seeing increased
interest as a standard for communicating with individual ballasts.
Many manufacturers allow communication between lighting control systems
and building automation systems through both the BACNET and LonWorks
protocols. In addition, some are capable of simple interfaces through digital
inputs and outputs and 0-10 VDC analog signals.
Both open and closed loop control strategies can be effective, depending on the
application. The choice needs to be thoroughly thought out during design,
because it can greatly affect the number of required photosensors. Closed loop
control can more accurately account for variations within zones. Open loop
control is appropriate for on/off control, or where many zones can be controlled
in a uniform manner.
There is no standard specification information available for photosensors from
the lighting controls industry. Most photosensors are simple photo-resistor
devices that do not accurately measure “footcandle” illumination. They should
be thought of as indicators of lighting level, but not a precision device.
Photosensors have unique spectral response curves, so they do not respond to
electric light and daylight in the same fashion. Photosensors also have unique
spatial response areas, or the three dimensional area that they “see” and respond
to. Finally, photosensors typically have a built in input-output response curve
that is fixed, and can be thought of as the “gain” of the control loop.
Unfortunately, none of the manufacturers supply detailed information on the
spectral response, spatial response, or I-O response for lighting control
photosensors.
As an illustration of the capabilities of typical lighting control systems, consider an analogy with
a common HVAC control loop, a chilled water valve on a chilled water coil. The design
engineer and controls contractor will make equipment selections based upon the coil
characteristics (capacity, pressure drop), valve characteristics (Cv, pressure drop) and actuator
characteristics. The installers will determine a sensor location that serves as an input to the
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National Conference on Building Commissioning: May 8-10, 2002
control loop. Once the system is operating, the control programmer will have the choice of
proportional, proportional integral (PI) or proportional integral derivative (PID) control loops,
with adjustable constants. The combination of setpoint and loop tuning parameter adjustments
provides great flexibility to maintain a stable output based upon the various driving factors (coil
load, water temperature).
The parallel daylighting control system has similar characteristics but much less flexibility. The
electrical engineer and contractor will select equipment based upon the lamp/luminaire/ballast
characteristics and the photosensor that comes from the selected lighting control manufacturer.
Similarly, the installer will typically choose a photosensor location based upon the
manufacturer’s recommendations. Once the system is operating, there are few “levers” available
to ensure the control loop responds correctly. All sensors have an adjustable setpoint. Several
have adjustable “sensitivity”. Some have switches to change from “high” to “low” range. The
lens cover can be changed. Lens covers can be “masked” with tape or pens. The sensor “gain”
can be changed (some in firmware, some in software).
The technical abilities available in an average DDC building automation system are not available
in the most sophisticated lighting control system for daylighting applications. This makes it
essential that any lighting control system for daylighting be subject to a formal commissioning
process. The commissioning process for these systems needs to start early in the design phase,
where critical decisions are made in many disciplines that will affect the ultimate success of the
integrated daylighting and electric lighting systems.
Case Study #6: Corporate Office Building
This project uses a patented miniature optical light shelf, which
fits into the upper glazing similar to a blind. The fixed louvers
provide cutoff angle control and project the incident solar
radiation onto the ceiling and into the office space. The
lighting control system dims the first two rows of fluorescent
fixtures independently, based on ceiling mounted photosensors.
The location of the photosensors, orientation, and the lens type,
were carefully selected because the optical light shelf projects
direct beam daylight across the ceiling. If the sensors “see”
this direct sunlight, the input levels would be high enough to
instantly drive the output to zero.
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