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Commissioning Lighting Control Systems for Daylighting Applications

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					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.

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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
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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 Site Architecture Design Factors
• • • • • • • • • • • • • • • • • Building orientation • Adjacent buildings or natural features Glazing characteristics Interior lightshelf Exterior lightshelf Ceiling tile reflectance Interior colors

Interior Design Lighting Design

Mechanical Design Occupant Task Solar/Weather

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 Age IES task type Computer use Time of year Time of day • • •

Previous office environment Paper tasks Cloud cover

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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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 Manual Dimming Daylight Dimming Occ Sensor On/Off Occ Sensor Off Only Schedule Override On/Off

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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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
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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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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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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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Room 223, Relay 211 Circuit Amps and Global FC
3 8000.0 7000.0 6000.0 2 Circuit Amps 5000.0 1.5 4000.0 3000.0 1 2000.0 0.5 1000.0 0 9:30 0.0 13:30 Global FC

2.5

10:00

10:30

11:00

11:30 Date / Time

12:00

12:30

13:00

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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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 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.

Distributed Architecture Control Systems Analog and Digital

BAS Integration

Open-loop and Closed-loop 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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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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