Lighting commissioning: Highlighting code compliance

ASHRAE Standard 90.1 provides guidelines for designing lighting and lighting control systems. Commissioning these lighting systems is a key requirement of the 2010 edition of the code.

01/16/2014


Figure 1: This shows a typical computer classroom’s light and receptacle control detail. For the sequence of operation: lights shall be automatic on at 50% or manual on at 100%; 50% of plug loads shall be automatic on; automatic off for lights, plug loadsThe 2010 edition of ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings has significant lighting and control additions that require moderate ramifications from lighting designers and building owners. ASHRAE Standard 90.1 2010 Section nine (9) requires smaller renovation projects to be code compliant, and defines how to light and how much lighting is automatically controlled. Additionally, there are requirements for receptacle control and the testing of lighting systems’ installed operation.

Although ASHRAE 90.1-2010 is designed to reduce the power consumption of lighting systems while not compromising security or safety, the building owner and operations personnel must be provided with the proper design and be properly educated on the design intent. In certain instances, the control strategy may also have to be modified to suit the needs of building operations personnel. If the controls are not understood or do not function properly once a building is “turned over” or the renovated areas are occupied, there is little chance the projected energy savings can be realized.

The following summarizes how the 2010 energy code addresses potential issues.

Application

The 2010 energy code applies to all new construction and to any new retrofit project that involves revising more than 10% (previously 50%) of the lighting systems. This should increase the number of renovation projects that will be required to comply with the 2010 code and hopefully provide a boost in overall energy savings.

Lighting controls

Automatic lighting shutoff is required in every space as part of the 2010 code. Previously, that rule had applied only to buildings that were over 5,000 sq ft. When some people think of automatic lighting, they think of lights that come on as they enter a room. However, the 2010 energy code is concerned with addressing both turning the lights on for safety and security, and also turning them off when the space is unoccupied—seemingly a “no-brainer” when it comes to conserving energy.

Although ASHRAE 90.1-2010 does not limit the designer by detailing exactly how to satisfy the requirement, there are many ways that it can be met. One method is to have the lighting control system provide a scheduled shutoff or time-of-day function to turn the lights out. Another would be to use occupancy sensors that provide a timed delay of 30 minutes before the lights go out. More sophisticated facilities could have the building management system control lighting zones in accordance with the user’s operating times. It’s important to also keep in mind that a single zone programmed area, according to the code, cannot exceed 25,000 sq ft or encompass more than one floor.

The term “all spaces” in the 2010 code replaces the previous “enclosed spaces.” This broadens the area where additional controls are needed. Designers no longer need to worry about whether an area qualifies as enclosed space or not; the space will have a control device for lighting. Of course, a manual on switch qualifies as controlled, but now if the control is automatic, then the lighting must be wired so that no more than half (50% power) of the general lighting will turn on. The occupant needs to manually flip the switch to energize the remaining lights, thereby illuminating the space 100%. It should be noted that this does not apply to public corridors, stairwells, restrooms, primary building entrances, or spaces where a manual on would endanger the safety or security of the space or building occupants.

Space lighting controls have a requirement for automatic shutoff within 30 minutes after all the occupants have left the space. The 2010 energy code has been expanded from the previous group of classrooms, conference/meeting rooms, and employee lunch/break rooms to include new areas such as lecture halls, training rooms, storage and large supply rooms, copy/printing rooms, smaller offices, restrooms, dressing rooms, and locker or fitting rooms. Occupancy sensors or time switches must be used to comply with the code, and they must be configured for automatic on (50%) or manual on to be valid.

Figure 2: In this typical computer classroom, occupancy sensors shall be provided with a handheld remote-control adjusting device. Courtesy: Peter Basso Associates

ASHRAE 90.1-2010 seems to embrace the multilevel lighting scenario, giving the user increased flexibility in choice of brightness within the space. Light level reduction is another way to reduce energy within a building. If the tasks being performed can be accomplished with lower lighting levels, less power used translates directly into energy, and ultimately dollars, saved. The 2010 code asks that provisions be made to reduce the connected power level by 30% to 70%, in addition to turning the lights off completely. Even receptacles are being addressed: 50% of the receptacles in private offices, open offices, and computer classrooms shall be automatically turned off.

Daylighting

In an additional effort to reduce power consumed by lighting, the 2010 code has included automatic daylighting controls for enclosed spaces with side-lighting (natural light) having areas greater than 250 sq ft. By way of comparison, that area is the equivalent of a 5-ft-tall by 50-ft-long window. Also, if the enclosed space has a skylight or rooftop monitor having a daylighting area greater than or equal to 900 sq ft, the day lighting controls must be incorporated into the design.

These spaces have a large glass-to-floor area ratio, and in many cases the sun may outshine the artificial lighting. As the natural light increases, the artificial light can be reduced, thereby saving energy. More efficient systems can perform this task without the occupants even realizing that the artificial lighting is being adjusted. The 2010 code recommends that the control system fluctuate between 50% and 70% with another control step no greater than 35% of the fully connected load. For those familiar with the U.S. Green Building Council LEED rating system, the term daylight harvesting comes to mind when discussing this type of lighting control.

Parking garage and exterior lighting

Parking garage lighting and exterior lighting are also addressed in the 2010 code. The parking garage lighting has taken on some of the requirements for interior lighting with automatic shutoff, reduced light levels, and lighting in naturally lit zones. The automatic shutoff has to reduce power consumption by at least 30% when no activity occurs for 30 minutes. For exterior lighting, Standard 90.1-2007 has provisions to ensure proper shutoff during sufficient daylight. The 2010 version has more stringent requirements to ensure the lights are off during the day and are operating at a reduced level at night for increased energy savings.

Commissioning

The automatic controls with occupancy sensors, timers, dimming controls, and day-lit zone controls are useless if they do not function as the design intended. For this reason, ASHRAE 90.1-2010 requires these systems to be commissioned. A third-party commissioning authority, who is not involved in the design or construction, is required to verify that the lighting controls are adjusted, programmed, and functioning in accordance with the design and the manufacturer’s installation instructions. The commissioning authority also must submit documentation certifying that the lighting systems are in compliance with or exceed the performance requirements. The certification needs to be specific enough to verify conformance to the authority having jurisdiction.

ASHRAE 90.1-2010 for lighting systems incorporates a significant amount of changes to lighting design, maintenance, and operation. Lighting systems for new or renovated spaces must incorporate automatic shutoff and reduced lighting power levels at initial automatic on in an effort to reduce energy consumption, creating a stable conservation of energy for owners. Requiring the systems to be commissioned is the best way to ensure that they operate as intended and that the energy-savings strategies have the best chance of realizing actual reduced energy consumption.


Phillip S. Allen has been a practicing professional engineer for more than 24 years. Over the past several years, Allen has played a vital role in commissioning building lighting systems and design review for not only code compliance but for functionality and adherence to the owners performance requirements.



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