Commissioning lighting controls

Indoor lighting is one of the single largest consumers of energy in nonresidential buildings, representing more than one-third of total electricity used. Recognizing its significant effect on energy consumption, the U.S. Green Building Council included requirements for commissioning lighting, including controls in its LEED rating systems.

11/01/2008


Indoor lighting is one of the single largest consumers of energy in nonresidential buildings, representing more than one-third of total electricity used. Recognizing its significant effect on energy consumption, the U.S. Green Building Council included requirements for commissioning lighting, including controls in its LEED rating systems.

 

Other strategic organizations will likely join the call to require commissioning of lighting systems to meet their energy reduction objectives. These organizations include ASHRAE Vision 20/20 , Architecture 2030 Challenge , and the Clinton Climate Initiative .

 

Code requirements driving lighting control design include California's Title 24 multilevel or bilevel switching to decrease lighting power 50% to 70% while maintaining uniformity, and ASHRAE's 90.1-2004 automatic shutoff controls for office spaces greater than 5,000 sq ft. Some state and city codes require occupancy sensors and daylight responsive controls. Most codes require time clocks and/or photocells to turn off lights that are used to illuminate building facades, canopies, parking lots, pedestrian walkways, gardens, and other landscaped areas. With LEED's adoption of the ASHRAE 90.1-2004 energy standard, LEED projects must meet specific lighting control provisions and prescriptive power allowances, and they must include commissioning.

 

Opportunities for the commissioning authority to interact with the design and construction team on lighting include developing the owner's projects requirements and basis of design documents, reviewing drawings and specifications and equipment submittals, verifying equipment installation and start-up, performing or overseeing functional testing, owner training, and warranty review within 10 months of substantial completion.

 

It is difficult to discuss commissioning of lighting controls without some discussion of the impact of design decisions. Some common errors in the design of lighting controls revolve around scheduling. For interior and exterior areas where operation is based on a schedule, it is worth reviewing all operation times with the owner or building manager. Optimally, all surface luminance levels and schedules should be captured in the owner's project requirements. It is important to verify that the time clock has sufficient channels, as some spaces such as loading docks may require the lights to operate independent of the scheduled time that makes sense for other spaces.

 

When a direct digitally controlled (DDC) lighting control system is specified for increased flexibility, the design review should confirm that the sequence of operations includes sufficient detail to allow proper system programming. DDC systems provide greater flexibility than hardwired control systems and can be modified easily, even after installation is complete. However, the commissioning effort needs to match the level of control sophistication.

 

The verification process used should be similar to that required for any HVAC control system; it confirms that all inputs and outputs are functional, that wiring is complete to the end device, and that the end device functions properly. Functional testing must confirm that system programming satisfies the fully developed sequence of operations that should have been incorporated into the plans and specifications. This should include testing the system in all defined modes of operation, including proper operation during and recovery from loss of building power.

 

Occupancy sensors

Occupancy sensors (OS) are increasingly used in lieu of time clocks to better match occupancy patterns. Individual OS even are installed at workstations to control a single light fixture. Each occupancy sensor should be indicated clearly on the drawings, along with which lights are controlled. As architectural finishes are installed, multiple construction site visits may reveal errors in OS locations and save the project time and money. Verifying the location prior to and immediately following installation is a good goal. The OS manufacturer's literature will clearly indicate the optimum placement and sensitivity options and provide opportunity for owner training. The setpoints, sensitivity, and delay are recorded by the installing the contractor's start-up records.

 

Typically, setpoints for sensitivity and time limit are not in the project documents. The commissioning authority must, therefore, be familiar with the equipment and request setpoints and expectations for the operation of the equipment. If nowhere else, this should be documented in the owner's project requirements, pre-functional test document, or functional test document.

 

The affordability and reliability of occupancy sensors have led to their integration into HVAC equipment. Engineers tasked to maximize energy savings using off-the-shelf technology are employing occupancy sensors to communicate with variable air volume boxes and even thermostatically controlled rooftop units. A single or bank of occupancy sensors may be used to turn down ventilation rates when spaces are not fully occupied or to allow the space temperature setpoint to creep up or down a few degrees when spaces are totally unoccupied.

 

Integrate an occupancy sensor into the contacts of the thermostat and you get a rooftop unit that can be scheduled to switch to unoccupied mode immediately at the end of the workday. It is worth mentioning that roughly half of all U.S. commercial floor space is fully or partially cooled through packaged rooftop equipment and controlled by a commercial thermostat (EIA 1998). Although a very elegant detail in the drawings, this application requires atypical wiring, OS sensor tuning, and owner training: a very good casework on the benefits of commissioning.

 

Daylight responsive lighting controls typically require daylight sensors, such as photocells, mounted near the skylight or window. As with OS, these should be clearly indicated on the drawings, indicating the controlled fixtures, and aligned with the recommended placement. For photocells, placement in close proximity to glazing is of special concern and must be carefully coordinated for proper operation. In addition, highly reflective architectural finishes can affect operation. As with an OS, verifying the location prior to and immediately following installation is a good goal and will help catch unseen obstructions from architectural finishes and furniture. The controlled fixtures will be located within the daylit zone. The California Energy Commission and the Oregon Dept. of Energy both provide practical design guidance for selecting the daylit zone.

 

Daylighting controls

According to a recent study by The Heschong Mahone Group and Southern California Edison, daylight responsive controls require commissioning to meet their energy predictions

 

The simplest automated daylight responsive controls turn lights OFF when the daylight levels rise above a minimum threshold. An override switch and some adjustment of the OFF threshold are required to head off combative and annoyed occupants. These should be sufficiently labeled for current and future occupants. A marker, arrow, or other indication of the ON and the OFF threshold should be indicated as clearly as possible. A quantitative value such as foot-candles is recorded in the as-built/project documents.

 

Designers often choose not to turn lights OFF (in response to daylight) in occupied areas. Either the equipment cannot be installed with an appropriate deadband, or it is likely not to be installed with a deadband, leading to cycling of lights ON and OFF and finally the disabling of the OFF function by the annoyed occupants. It is important to emphasize the differences in design and commissioning. The commissioning authority does not “set up” the system, but instead verifies the setup implemented by the contractor according to the designer's setpoints and sequence of operation. Administering sufficient deadbands into the design/settings is a byproduct of competent design, which the commission authority can flag if not indicated clearly in the design documents.

 

A high/low (bilevel) or multilevel scheme uses switching to turn a number of lights OFF in response to daylight while maintaining uniform light distribution in the space. This scheme may be controlled through manual switching or use of photocells. The controls may either turn individual lamps OFF or turn OFF every other fixture. As with ON/OFF control, labeling the manual override, user control of threshold, and owner training is crucial.

 

Another sensor control scheme uses continuous dimming, which linearly reduces the light output of the lamp with increasing daylight levels. If the photosensor is integral to the light fixture, each row of lights may be adjusted as you move away from the daylight source. This typically is done at start-up, and workspace luminance should be recorded by the commissioning agent and compared with the expected results. Alternatively, in a system where fixtures are networked together, a multiplier can be programmed to adjust multiple rows independently based on the input from one photosensor. Owner training can empower the occupants to properly use control features, make adjustments, and understand exactly how their adjustments affect the light source, enabling them to maximize system effectiveness.

 

Lighting manufactures continue to provide new products and, occasionally, user-friendly controls. Current studies, as well as practical field experience, indicate the need for detailed design, proper installation, timely commissioning, ample documentation, and owner training of lighting control systems in order to meet predicted energy savings. These requirements, when combined with the daunting amount of energy consumed in commercial lighting, and the building industry's goal to realize widespread energy reductions, ultimately will lead to more requirements for commissioning of lighting systems in new and existing buildings.

 

 

 

Author Information

Hudson works as a technical consultant within a multidiciplinary team of architects, engineers, planners, and building analyst who share extensive hands-on experience in green building. He manages commissioning, retrocommissioning, and energy audits while supporting design simulation for new construction including energy modeling, daylight modeling, and CFD analysis to assess the effectiveness of specific green building strategies. Riley serves as a project manager and lead electrical engineer for George Butler Assocs. commissioning projects. He has been providing electrical systems start-up and commissioning services for more than 15 years and has specialized in commissioning critical facilities for the past eight years. He has provided educational presentations for Labs 21, 7x24 Exchange, National Assn. of State Facilitators, and the Data Center Journal.



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