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CATEGORY: Topics » Design
By Craig DiLouie, on September 19, 2011
As demand for lighting controls continues to grow, advanced solutions are becoming increasingly specified while also becoming increasingly sophisticated. This increasing sophistication translates to greater owner benefit but can also pose greater risk of design and installation mistakes.
In a perfect world, designers create clear and detailed lighting control requirements that are easily installed by the installer and the owner. In the real world, however, the owner may not have clear expectations about their lighting. Further, the designer may not provide clear design intent, the installer may make errors and, if anything goes wrong, users will complain.
For the designer, the key is to clearly express the design intent, or the basis of design, so as to provide a common roadmap for the functionality of the lighting control system.
The question is: How?
While there is no standard for communicating design intent, designers have a number of tools at their disposal:
The written lighting control narrative describes the lighting controls, including a sequence of operation, or description of system outputs in response to various inputs. Device settings include occupancy sensor time delay and sensitivity adjustments, integrated dimmer presets, time schedules for relays, and other programming and calibration. Control zoning visually reveals what control devices control what loads. One-line wiring diagrams visually reveal how all of the control devices connect and their relationship to each other. Specifications and cut sheets describe the products used and desired baseline levels of performance. Lighting and electrical panel schedules assign loads to specific dimmers or switches in the panel. And performance testing criteria tell the commissioning authority and electrical contractor how and what to test the system for after installation, and criteria for acceptance.
The written control narrative could be considered most important because it informs everything else, and yet it is often missing in project documents. Going beyond what drawings can communicate, it provides a common guide and reference for the project. Specifically, it can be used to support contract document and specification preparation, provide clear direction during bidding to contractors and manufacturers, give the commissioning authority criteria for testing and accepting the control system, and tell the owner how their control system operates.
Designers benefit by accessing a common roadmap describing the lighting control system’s intended functionality, which increases the likelihood of satisfying the owner. Contractors and manufacturers have clear direction for bidding. Installers are less likely to commit costly errors. The commissioning authority knows what to test, how to test it, and criteria for acceptance. And the owner is more likely to receive a quality product, increasing the likelihood of acceptance.
 (Click on the image to enlarge for easier viewing; enlarged image will appear in a new window; click the back button to return to the article.) Problems and fixes matrix illustrating the relative degree of difficulty (and expense) of correcting problems during construction, and whether a controls narrative would likely make an impact on avoiding these problems. Image courtesy of The Weidt Group. This type of documentation may become common in the future as commercial building model energy codes address documentation and commissioning. ASHRAE/IES 90.1-2010 requires the following documentation be delivered to the owner within 90 days after acceptance of the control system: record drawings of the actual installation, submittal data for all controls, recommended schedule for inspection and recalibration, and a complete control narrative showing “how each lighting control system is intended to operate, including recommended settings.”
A basic control narrative might include at least two main elements. First, a general description of the project goals and delivered control strategies deployed to satisfy these goals. Second, a description of the control system and sequence of operations for each space type. The document may change or be fleshed out over time as the project moves from the pre-design (programming) to design (schematic design, design development, construction documentation) to construction and occupancy and operations, with changes reviewed and approved at each step.
 (Click to download as XLS file.) Example of a matrix approach to creating a control narrative. The matrix identifies spaces or space types and control strategies implemented within each; on the far right, number codes reference the wiring diagrams and a detailed sequence of operations for each space or space type. Here is an example of very general project goals, including relevant codes, for a new office building:
“The lighting controls must meet the mandatory control requirements as defined in the ASHRAE/IES 90.1-2007 energy standard. Select control strategies implemented by the lighting systems go beyond these requirements to support LEED certification.”
Ideally, the owner will provide clear direction to inform the project goals. Following is a general description of the control strategies used in the project. Here’s an example:
“The interior lighting controls will enact two primary strategies intended to minimize energy consumption: 1) automatic shutoff via occupancy sensors in small, enclosed spaces and via a timeclock-based low-voltage control system in larger, open spaces, and 2) daylight harvesting in all spaces receiving high, consistent levels of daylight contribution, notably the main lobby and private and open office spaces. In certain spaces lacking daylight and where personal safety is an issue, such as corridors illuminated by electric lighting, select lights will remain ON at all times during normal hours of occupancy. In presentation spaces, notably the meeting and training rooms, flexibility will be provided to enable users to select preset light levels. Lighting controls will also turn exterior lighting ON/OFF using a photocell/timeclock based on curfew (grounds lighting) or dusk-to-dawn operation (security lighting).”
Following the project description is a lighting control system description, including a sequence of operations—a description of what the controls in each space do in response to inputs such as occupancy, time events or daylight levels.
This could take the form of a written description produced in a simple and consistent format; a matrix providing an at-a-glance view for each space type or each individual space (room numbers pulled from the drawings), an approach well suited to complex projects.
Back to our example, we will be deploying manual-ON, timeclock-OFF for general lighting in the open office spaces in our office building, and daylight harvesting dimming in perimeter zones receiving sufficient levels of daylight. The control narrative for the manual-ON and timeclock-OFF switching controls (code 2 under the “sequence of operations” column on the matrix) might read (adapted from the Department of Energy’s Commercial Lighting Solutions webtool):
“ON/OFF control of the general lighting in each open office area will be controlled by a combination of manual wall switches and timeclock schedule functionality residing in a low-voltage relay panel-based control system.
“Users entering the space at the start of business hours will turn the general lighting ON by control zone, with each zone being within 2,500 sq.ft. in area or per the local energy codes.
“At 6:00 PM, the control system will blink several times, warning users that the lights will turn OFF in five minutes. At 6:05 PM, the control system will turn the general lighting OFF. Users working afterhours may keep the lights ON, or turn the lights back ON, by toggling the manual wall switches, which function as a 120-minute override for the timeclock automatic shutoff system.
“After 120 minutes, the system will blink the lights again, and sweep them OFF five minutes later unless the override is again activated.”
Using this basis, we might add even more information—the more detail, the better:
“The control system shall be programmable at a microprocessor-based central processing unit (CPU). The system shall provide weekly routine and annual holiday scheduling and automatically adjust for leap year and daylight savings time. Each program shall not exceed 25,000 sq.ft. or one floor, whichever is smaller. The control system shall have 10-year nonvolatile memory that stores all schedules. The system shall be able to reboot the program and reset the time schedule and current time, without errors, following power outages up to 14 days in duration. The system shall export lighting energy consumption reports by space and zone. The control system shall operate independently of but be capable of communicating with the building automation system, if present.”
From there, we could also add performance testing and criteria for acceptance. For the above low-voltage relay control system, this might include ensuring that the general lighting in each zone turns OFF at the scheduled time, the sweep is properly preceded by a blink or other warning, and the overrides are properly zoned and working.
Finally, we could add references to other pertinent documents, such as wiring diagrams, control zoning and equipment specifications and cut sheets.
Producing a written controls narrative entails more effort at the front end, but can deliver strong project benefits. By providing clear expectations for lighting control system functionality, designers will more likely deliver a quality product, contractors will more likely provide an error-free installation and properly calibrate and program the system, the owner will more likely properly maintain it, and users will more likely accept it.
By Lighting Controls Association, on June 8, 2011
In May 2011, Correctional News published “Lighting Controls Provide Green Benefits” by Joshua Slobin, which describes the energy-saving and resulting sustainability benefits of advanced lighting controls.
“Lighting control systems, based on a variety of technologies, have been proven to reduce lighting energy consumption in commercial and industrial buildings by up to 70 percent. These solutions can automatically turn off lights when they are not needed, optimize light levels to suit worker needs, reduce overall demand for lighting energy, and provide facility managers with system-wide lighting management.”
Get the full story here.
By Lighting Controls Association, on May 26, 2011
 Buildings Magazine recently published an article about advanced lighting control, featuring interviews with a number of experts, including Tom Hinds of Lutron and Scott Jordan of Schneider Electric.
Many precision controls can be integrated into your existing building automation system. Coordinate them with occupancy sensors to make sure empty rooms aren’t wasting energy, or add daylight sensors to balance artificial light with natural light. Having such precise control provides you with an easy way to tailor lighting to everyone’s specific needs while still cutting energy consumption.
Check it out here.
By Craig DiLouie, on June 23, 2010
The U.S. Department of Energy (DOE) has unveiled the Commercial Lighting Solutions for Office webtool. Available free at www.lightingsolutions.energy.gov, CLS for Office provides customizable lighting and control templates enabling building owners to generate more than 30% lighting energy savings compared to office buildings complying with prevailing energy codes.
Why is this big news?
The Federal stimulus targeted $5 billion to upgrade Federal buildings, with an estimated $1 billion being spent on lighting. The CLS for Office webtool was fast-tracked by DOE to support Federal facility managers who will be looking for solutions. Meanwhile, the Energy Policy Act of 2005 requires all new nonresidential Federal buildings to exceed ASHRAE 90.1-2004 by 30%.
Green construction is growing from about 10% of the current commercial building market to 20-2% by 2013, or $96-$140 billion, according to McGraw-Hill. Public construction at state and local levels benefits from Federal stimulus money as well, and more than 30 states, 35 counties and 135 cities now have laws and policies requiring or encouraging the use of LEED in public construction. These jurisdictions may begin adopting green construction codes based on standards such as ASHRAE’s new Standard 189.1, published in January.
LEED 2009 requires the building to achieve 10% lower energy consumption than ASHRAE 90.1-2007, and assigns LEED points towards different levels of certification based on going above and beyond. The ASHRAE 189.1 green construction code caps maximum allowable lighting power density at 90% of 90.1-2007.
Saving energy is easy. One could find some light fixtures with the highest efficiency possible, for example—say, some industrial open-bottomed strips with T5 or T8 lamps, install them in an open office, and dramatically reduce energy use. The only problem would be the people working in that office would hate being in the space, as that type of light fixture, while highly efficient, is also a “glare bomb” at typical office mounting heights. The employees would come to work wearing baseball caps—or not at all.
Saving energy while providing good lighting quality is hard, particularly when tasked to save lighting energy compared to a building already complying with ASHRAE 90.1-2004. In fact, it is arguable that only design leaders in the field can do it well.
To take on this problem, the Department of Energy launched the Commercial Lighting Solutions (CLS) program at www.lightingsolutions.energy.gov. CLS is a webtool that allows people to customize lighting templates designed to produce 30+% energy savings compared to ASHRAE 90.1-2004, while also providing good lighting, in different building types. The tool includes extensive lighting control templates developed by the author in collaboration with the Lighting Controls Association.
Following the CLS for Retail webtool, which launched at last year’s LIGHTFAIR, CLS for Office launched at LIGHTFAIR 2010 in May.
Here’s how it works.
The user provides information about the building, such as location, operating hours and prevailing energy code. Next, the user selects a typical office space within the building, including private office, open plan, open plan perimeter, corridor, conference room and reception area, and enters information about it, such as total area, ceiling height and whether there is daylight present. If daylight enters the space, additional information is requested, including shading, presence of light shelves, orientation, etc.
The webtool takes this information and produces several lighting options, called lighting vignettes. Suppose we want to meet certain energy-saving and lighting quality goals in the renovation of a series of private offices. After entering some information, we are given a choice of direct/indirect pendant light fixtures or recessed lensed, with lighting power densities (W/sq.ft.) up to 35% lower than the maximum allowed by ASHRAE 90.1-2004/2007 using the Space by Space Method. All lighting vignettes were designed by lighting design firm Horton Lees Brogden.
After selecting the lighting vignette, control options are presented. The control options were developed in an exhaustive process involving members of the Lighting Controls Association and its parent, the NEMA Lighting Controls Section. Due to the multitude of control choices, the user is given a general performance spec and clearly expressed design intent based on their control choices.
In the case of private offices, for example, the user can choose a manual-ON occupancy sensor with either bilevel switching or manual dimming and a photosensor for daylight harvesting.
With both the lighting and control options selected, total energy savings is shown at the bottom. The user can now download an energy summary, implementation instructions for the different spaces/lighting templates, and a light fixture schedule. For the lighting, the implementation instructions include sample lighting layout, light levels, contrast ratios, color rendering, how to integrate the electric lighting with the daylighting and notes on maintenance.
For the controls, the implementation instructions include a strategy description, color-coded control zone drawing revealing the strategy at a glance, performance specifications and notes on maintenance and commissioning.
Using the CLS for Office webtool, construction professionals can achieve lighting designs that maximize both energy efficiency and lighting quality. It’s available free here: www.lightingsolutions.energy.gov.
By Craig DiLouie, on May 12, 2008
 The NEMA Premium Ballast special mark distinguishes the ballast as the highest-performing electronic ballast on the market. The National Electrical Manufacturers Association (NEMA) launched the Premium Ballast program to identify the industry’s most efficient fluorescent fixed-output and dimmable electronic T8 ballasts, thereby providing a mechanism for market recognition and specification of these products.
Ballasts qualifying as NEMA Premium Ballasts are recognizable via a special mark on the label distinguishing these products as the most efficient T8 ballasts on the market.
As of the time of publication, Advance, OSRAM SYLVANIA, Universal Lighting Technologies and GE have achieved NEMA Premium Ballast certification for their high-efficiency products. (September 2008 update: Robertson Worldwide has achived NEMA Premium Ballast certification for its high-efficiency products as well.)
In the past several years, ballast manufacturers have begun offering high-efficiency electronic ballasts that provide the same light output as a standard electronic ballast but do so more efficiently, reducing lighting power by another 2-5W, typically 3W.
However, this definition of “high efficiency” is informal: Some manufacturers have used it to describe the most efficient products, others to describe all electronic ballasts. Lack of recognition and a slightly higher cost have inhibited market adoption, frustrating manufacturers, which worked together through NEMA to overcome these barriers.
The Consortium for Energy Efficiency (CEE) had worked with NEMA to develop a definition of high-efficiency T8 ballasts—using a metric called ballast efficacy factor (BEF), expressed as ballast factor ÷ input watts x 100—which became adopted as NEMA Standard BL 2-2007 covering electronic ballasts for use with 4-ft. T8 lamps. This standard became the threshold to qualify for designation as a NEMA Premium Ballast.
It is believed this will promote the most efficient ballast options to end-users and utility rebate program generic specs, creating pull-through in the marketplace, as occurred earlier with the NEMA Premium program for electric motors. More than 25 utilities, for example, use CEE minimum performance levels in their incentive programs.
High-efficiency T8 electronic ballasts include instant-start, programmed-start and dimmable models; can be specified as low (<0.86), normal (0.86-1) and high (>1) ballast factor; are available with universal voltage; can be specified for operation of one, two, three or four lamps; and may include value-added features such as anti-striation and anti-arcing. They have no limitations compared to standard electronic ballasts.
High-efficiency ballasts can cost 10-20% more than standard electronic ballasts while producing an additional 5-7% energy savings in typical projects (see Table 1).
 Table 1. High-efficiency electronic ballasts can save an additional two to five watts per ballast, depending on the number of lamps. Source: OSRAM SYLVANIA. In an installation with two-ballasted four-lamp fluorescent fixtures on 10×10 centers (100 sq.ft. area), using high-efficiency ballasts can add about $0.03-$0.06 per sq.ft. to the cost of the project—while reducing annual operating costs by about $0.04 per sq.ft., based on an assumption of savings of $2 per ballast (or $1 per lamp) per year.
NEMA advises this simple language for specification for new light fixtures: “Luminaire shall contain a NEMA Premium electronic ballast (do not substitute).” For retrofit or spot replacement, specify: “Ballast shall be a NEMA Premium electronic ballast (do not substitute).” Then specify the starting method, number of lamps and ballast factor.
While the program currently only covers electronic ballasts operating 4-ft. T8 lamps, the NEMA Premium Ballast program may expand in the future to include T4, T5 and HID ballasts and possibly also LED drivers and power supplies.
For more information about the NEMA Premium Ballast program and to access a list of qualifying ballast models, click here (PDF).
By Craig DiLouie, on June 13, 2007
While automatic shutoff of general lighting, required by prevailing energy codes, has received a significant amount of attention by the lighting specification community, bi-level switching is another frequent code requirement that can play an important role in energy conservation.
While energy savings with bi-level switching can be less than automated control strategies due to reliance on human initiative, it is a simple, durable switching strategy, with no special user training or maintenance to maintain its functionality.
In this special report by the Lighting Controls Association, we will describe bi-level switching code requirements, its role in the Commercial Buildings Deduction, methods and equipment, and the results of a study of typical energy savings achievable with bi-level switching in popular applications.
Bi-Level Switching and IECC
While ASHRAE/IESNA 90.1 is the national energy standard, many states have adopted an alternative—the International Energy Conservation Code (IECC) developed by the International Code Council (ICC), a membership association dedicated to building safety and fire prevention. The IECC is a model energy code that covers lighting in addition to other energy-using building systems. States have adopted various versions of the IECC, including the 2000 version (with 2001 supplement), 2003 version (with 2004 supplement), and 2006 version (with 2007 supplement), with the 2003 version being the most prevalent. The 2003 and 2006 versions of the IECC, covered in this report, require bi-level switching in interior spaces.
A number of states have developed state-specific codes that may or may not also require bi-level switching. For example, California’s Title 24 energy code requires bi-level switching in interior spaces.
Below is a table that reflects state-by-state adoption of IECC as of April 8, 2007. Confirm your state’s status by clicking here and scrolling down to the commercial code section of the page. Note that the 2003 and 2006 versions of IECC reference ASHRAE 90.1 as an alternative standard. ASHRAE 90.1 versions up to 2004 do not require bi-level switching in interior spaces.
IECC requires at least one manual control for lighting in all interior spaces enclosed by ceiling-height partitions, with few exceptions. If the space …
* has more than one light fixture
* is not controlled by an occupancy sensor
* is not a corridor, storeroom, restroom or public lobby
* has a lighting power density (lighting W/sq.ft.) >0.6W/sq.ft.
* is not a guestroom/sleeping unit
… then it must have bi-level switching. IECC defines bi-level switching as providing occupants the ability to reduce lighting load in a reasonably uniform pattern by at least 50%, and recognizes four methods (see “Methods of Bi-Level Switching” below).
Bi-level Switching and the Commercial Buildings Deduction
The Commercial Buildings Deduction created by the Energy Policy Act of 2005 established the Interim Lighting Rule, which enables an accelerated tax deduction of $0.30-$0.60/sq.ft. proportional to lighting power density savings of 25-40% below ASHRAE 90.1-2001.
There are several other requirements, one of which is bi-level switching must be installed in all occupancies except hotel and motel guest rooms, store rooms, restrooms and public lobbies.
Methods of Bi-level Switching
IECC recognizes four methods of light level reduction control:
* Controlling all lamps or fixtures (e.g., dimming or light level switching)
* Dual switching alternate rows, fixtures or lamps
* Switching middle lamp independent of outer lamps (3-lamp fixtures)
* Switching each fixture or each lamp
Suitable solutions include dimming controls, manual switches and daylighting controls. Other methods are acceptable if approved by the authority having jurisdiction.
Below is an example of the dimmer control option:
Another option for controlling all lamps and fixtures is to use step-dimming or light level switching ballasts, which provide a uniform change in illumination in the space. For example, a light level switching ballast incorporates two hot power leads for control with two standard switches or relays; switching one lead on provides 50% power while having both switches on provides 100% power. Alternatively, if only one switch is available or desired, the light level switching ballast can provide 100% power when the switch is first turned on and 50% after toggling down and back up.
Below is an example of bi-level switching based on separately circuiting and switching alternate fixtures:
Below is an example of bi-level switching based on separately circuiting and switching alternate lamps (a/b).
Another approach based on lamps would be multi-level switching, which enables three levels of light output and power input using three-lamp fixtures: all lamps OFF (0% light output), one lamp on in each fixture (33%), two lamps on in each fixture (66%), and all lamps ON (100%). Multi-level switching provides greater flexibility than bi-level switching and poses a less abrupt change in light level when automatic control is used. Greater granularity is possible depending on the lighting equipment and need.
Note that the term “bi-level switching” often refers to both bi-level and multi-level switching strategies.
Study of Bi-Level Switching Use and Energy Savings
In May 2002, “Lighting Controls Effectiveness Assessment: Final Report on Bi-Level Lighting Study” was published by the California Public Utilities Commission (CPUC), prepared by ADM Associates for Heschong Mahone Group, project managers for the Southern California Edison Company on behalf of the CPUC.
This is one of only a few field studies that have actually examined the use and utility of bi-level switching as a means to reduce energy costs. Two specific goals of the study were:
* Study how occupants used manual bi-level switching controls, including behaviors that reduced savings potential; and
* Estimate energy and demand savings.
The researchers measured data for bi-level switching applications in 256 open and private office, retail and classroom spaces in 79 buildings. The fixtures contained three lamps that were switched in a multi-level switching scheme, providing four lighting states: all lamps OFF, 1/3 lamps operating, 2/3 lamps operating and all lamps ON.
Table 2 below shows the breakdown of use of different bi-level switching conditions (high-wattage or 2/3 lamps switch only ON, low-wattage or 1/3 lamps switch only ON, or both switches ON or OFF).
 Table 2. Use of bi-level switching conditions at 3PM on weekdays by space type. Source: ADM Associates ADM Associates discovered that private offices demonstrated the highest level of energy savings derived from using bi-level switching at 21.6% (with bi-level energy savings defined as occurring at 1/3 or 2/3 power). Open offices came in second at 16.0%, followed by retail at 14.8% and classrooms at 8.3%.
One of the factors of bi-level switching use that was studied was daylight contribution. Use of bi-level switching and subsequent energy savings in open offices and retail spaces showed a positive correlation with daylight availability. Private offices did not show a positive correlation. Classrooms did, but demonstrated the opposite of researcher expectations: Classrooms with the lowest amount of daylight also had the lowest level of use of lighting.
In the end, the study demonstrated that manual bi-level switching results in energy savings, which could be increased with occupant education, and with the limitations on the use of only one switch offset by the simplicity and economy of the approach.
By Craig DiLouie, on November 14, 2004
Originally published November 2004; revised May 2009
Indoor spaces with high ceilings, such as factories, warehouses, big box retail stores, gymnasiums and all-purpose rooms are often lighted by probe-start metal halide lighting systems. At higher ceiling heights, 350W and 400W units are common.
Probe-start metal halide lamps are compact, rugged, powerful light sources, well suited for illuminating large spaces with a crisp, white light. These systems are able to operate reliably in a wide range of ambient temperatures, with numerous fixtures specially designed to operate in demanding environments such as hazardous locations.
Probe-start metal halide lighting presents a number of disadvantages, however. These systems are not easily dimmable, experience color shift over time, and require four minutes to start and about 10 minutes for re-strike after shutoff. Most significantly, service life, light output and efficacy severely degrade over time. These systems are often deployed in basic-grade spun-aluminum dome fixtures, which present a typical 75% efficiency—meaning 25% of the light produced remains trapped in the light fixture. As a result of its lumen maintenance and typical fixture efficiencies, this standard metal halide system appears low-cost but in fact is not very economical relative to the best alternatives, as either more fixtures, or higher-wattage fixtures, are required to provide desired maintained light levels.
The inefficiency of these fixtures, in fact, led to a prohibition on manufacturing probe-start fixtures that do not meet a certain ballast efficacy standard, as mandated by the Energy Independence and Security Act of 2007, virtually eliminating probe-start magnetic-ballasted fixtures starting in 2009.
Advancements in lamp and ballast technology have resulted in two alternatives to this basic system that can significantly reduce energy consumption while providing other benefits. The first alternative is fluorescent T8 or T5HO hi-bay fixtures, which can replace probe-start metal halide fixtures in retrofit or new construction for energy savings up to about 50%. The second alternative is pulse-start metal halide lamp-ballast systems, which can provide up to 25% energy cost savings in existing applications and up to 30% in capital and operating costs in new construction.
 Galt High School upgraded its metal halide fixtures with T5HO linear fixtures, reducing energy consumption by nearly 50%. Photo courtesy of Sacramento Municipal Utility District.
Hi-Bay Lighting
In the lighting industry, one may hear the terms “high-bay” (also “hi-bay”) and “low-bay” (also “lo-bay”) lighting.
In the construction of some types of industrial facilities, a skeletal framework is used, which forms an interior subspace called a “bay,” which in turn marks the space as “high bay” or “low bay.”
An older definition designated hi-bay to mean >25 ft. off the floor, medium-bay to mean 15-25 ft., and lo-bay to mean <15 ft. Some manufacturers define hi-bay as being over 15 ft. or 20 ft. off the floor. IESNA categorizes spaces as either hi-bay (>25 ft.) or lo-bay (<25 ft.).
The terms hi-bay and lo-bay also refer to fixtures designed for these applications, although it is not uncommon to see hi-bay fixtures in lo-bay applications, and vice versa.
Fluorescent Fixtures
Fluorescent fixtures for high-ceiling applications offer single- or multi-point pendant mounting for retrofit or construction alternative to HID fixtures such as probe-start metal halide. Manufacturers include Lithonia, Holophane, Columbia Lighting, Cooper Lighting, Day-Brite, HE Williams, MetalOptics, Amerillum, Orion, Simkar, Intrepid, 1st Source Lighting, Ruud Lighting, Stonco, Guth Lighting, Hubbell and others.
- These fixtures may house 4, 6 or other number of lamps.
- The lamps are typically T8 or T5HO, although compact fluorescent models are available.
- Optics are available with narrow and wide distributions. Wide distributions are best for lower mounting heights and general lighting areas, while narrow distributions are best for aisle and similar applications. Some fixtures offer a degree of uplight as well as direct downlight.
- Some models are available that can operate in demanding environments.
- Models are available that offer emergency ballasting options.
 Photo courtesy of OSRAM SYLVANIA. T5HO Systems
T5HO lamps are about 5/8 in. in diameter, about 40% of the size of T12 lamps, and therefore enable better photo-optic control of the light produced by the fixture, increasing efficiency and providing uniform distribution of light output. T5HO lamps used for hi-ceiling lighting applications are typically 4-ft. 54W lamps. Because T5HO lamps are built to metric dimensions, a 4-ft. lamp is actually 45.8 in. long, a little shorter than T8 and T12 lamps.
Initial rated light output is based on peak output at an ambient temperature of 35°C (95°F), whereas T8 and T12 lamps are based on 25°C (77°F). Amalgam lamps extend reliability of light output across a wider temperature range between cold and hot. T5HO lamps operate on programmed-start or instant-start electronic ballasts; universal-voltage (120-277V and 347-480V) ballast, dimming ballasts and four-lamp ballasts are available. T5HO lamps are not interchangeable with T8, T12 and T5 lamps.
There are two recent developments of interest. First, 49-51W T5HO lamps are now available that can replace 54W lamps for energy savings and a boost in efficacy with no loss of light output. Second, amalgam T5 VHO lamps are now available. These lamps produce 7,200 lumens of initial light output, reaching 80% of light output about three minutes after startup. Using amalgam technology, light output is above 90% from 65°F to 170°F. Dimming, however, may not be recommended.
 Using amalgam technology, light output is above 90% from 65°F to 170°F for this T5 VHO lamp. Graphic courtesy of Philips Lighting. T8 Systems
Fluorescent fixtures for high-ceiling lighting applications often include “Super T8” lighting systems. Super T8 lamps are 32W lamps that provide 3,100+ initial lumens instead of the 2,850 offered by standard 32W T8 lamps, and 95% lumen maintenance at 40% of rated service life. Examples include Philips Advantage, Sylvania Xtreme XPS and GE’s High Lumen Eco. Super T8 lamps can be operated on programmed-start or instant-start ballasts. For hi-bay lighting, they are often paired with high-ballast-factor ballasts (1.15-1.18 BF) to maximize system light output. For example, a system consisting of six 3,100-lumen T8 lamps operating on 1.18 BF ballasts produces nearly 22,000 lumens, still about a third less than a 6-lamp T5HO system but somewhat more than a 4-lamp T5HO system.
Note that amalgam T8 VHO lamps are now available that produce light output above 90% from 50°F to 160°F (10°C to 70°C). This lamp produces the same light output as the T5 VHO, but offers lower wattage, higher effiacy, shorter rated life, and ability to dim down to 20%. See the below table for a comparison.
|
T5 VHO amalgam |
T8 VHO amalgam |
| Watts |
95 |
84 |
| Initial lumens |
7,200 |
7,200 |
| Mean lumens |
6,480 |
6480 (3500K and 4100K); 6,550 (5000K) |
| Efficacy |
76 |
86 |
| CRI |
85 |
85 (3500K/4100K); 82 (5000K) |
| CCT |
3500K, 4100K |
3500K, 4100K |
| Life @ 12 hrs/st on PS ballast |
35,000 |
25,000 |
| Light output >90% |
65°-170°F |
50°-160°F |
T5HO Versus T8
You may hear recommendations to use T8 fixtures for a better quality of light and less glare at fixture heights <20 ft., T5HO fixtures for quality light output and higher fixture efficiency at >20 ft., and either between 18 and 25 ft. However, while T5HO may produce “glare bombs” at lower mounting heights, both T8 and T5HO fixtures can be used in both hi- and lo-bay applications, depending on the application, and if correctly applied.
Otherwise, a T5HO system is not as efficacious as T8 lamps, but produces more light output for the same number of lamps. With more light produced from a smaller diameter lamp, T5HO lamps are much brighter than T8 lamps, which can become a lighting quality factor.
T5HO lamp operation is optimized at a higher ambient temperature than T8s; another thing to watch out for with T8s is high-BF ballasts, which produce more heat. This may make T5HO systems more desirable in industrial spaces with higher ambient temperatures at the fixture mounting height. Note that ambient temperature is less a function of heat around the fixture as it is heat within the fixture’s lamp compartment; for best results, specify fixtures with a good temperature design.
A final consideration is maintenance. To get the highest amount of light output from a T8 fixture, Super T8 lamps should be specified, but the owner must continue to order this lamp type to maintain lighting performance. The maintenance department should not be permitted to substitute cheaper and lower-lumen 32W T8 lamps, particularly if these standard T8 lamps are used in a connected office. Conversely, if Super T8 lamps are used in a connected office, then this can be seen as a maintenance advantage for using them in a hi-ceiling application in the same building or campus.
 In this school gymnasium, 400W metal halide fixtures (left) were changed over to F32T8 hi-bay fixtures (right) on a one-for-one replacement basis, increasing light levels from 30 to 50 fc and CRI from 65 to 85 while reducing wattage per fixture from 450W to 224W. Photos courtesy of Acuity Brands Lighting. Lumen Maintenance
A 400W probe-start metal halide fixture, with a ballast factor of 1.0, produces 36,000 initial lumens. A 6-lamp Super T8 fluorescent fixture, with a ballast factor of 1.18, produces about 21,950 initial lumens. How can this fluorescent fixture replace the metal halide fixture to generate 52% energy savings and still produce comparable light levels?
The answer is lumen maintenance. In review, lumen maintenance is an expression of the fraction of initial light output that is produced by a light source over time—typically at 40% of lamp life, which provides mean lumens. This determines the design light level.
Probe-start metal halide lamps experience a higher level of lumen depreciation than T5HO and T8 lamps. For example, a 400W metal halide lamp can lose 35% of its light output at 40% of life, while a T5HO or T8 lamp will lose only 5-6%. As a result, a 6-lamp Super T8 lamp-ballast system produces 11% fewer mean lumens for 52% less energy.
| System |
Initial Lumens* |
Mean Lumens @ 40% Lamp Life** |
Relative Mean Lumen Output |
| 400W Probe-Start Metal Halide |
36,000 |
23,500 |
100% |
| 400W Pulse-Start Metal Halide |
42,000 |
32,800 (magnetic ballast); 36,000 (electronic ballast) |
140%; 153% |
| 4-Lamp T5HO Fluorescent |
20,000 |
19,000 |
81% |
| 6-Lamp T5HO Fluorescent |
30,000 |
28,500 |
121% |
| 6-Lamp Super T8 Fluorescent |
21,948 |
20,851 |
89% |
**Fluorescent lamp lumens are based on optical temperatures; adjust as needed.
**Note that pulse-start system light output declines at a significantly sharper rate than fluorescent after 40% of lamp life. To further the comparison, consider researching and comparing these numbers at end of lamp life rather than at the mean. Data source: Advance.
Wattages
This article focuses on comparing a standard probe-start metal halide lamp-ballast system with relevant T5HO and Super T8 lighting systems. Note that when comparing wattages to do so based on system wattage (lamp/ballast) rather than solely on lamp wattage. A “400W metal halide” system, accounting for ballast losses, draws 458W, not 400W. Similarly, a 6-lamp T5HO system draws 324W based solely on lamp wattage but 351W when these lamps operate on necessary ballasts. Comparing system wattages can be important when determining cost savings resulting from a lighting retrofit, but in new construction, efficacy, covered on the next page, is often considered more important.
| System |
Total Lamp Watts |
Total System Watts |
Relative System Wattage |
| 400W Probe-Start Metal Halide |
400W |
458W |
100% |
| 400W Pulse-Start Metal Halide |
400W |
452W (magnetic ballast); 425W (electronic ballast) |
99%; 93% |
| 4-Lamp T5HO Fluorescent |
216W |
234W |
51% |
| 6-Lamp T5HO Fluorescent |
324W |
351W |
77% |
| 6-Lamp Super T8 Fluorescent |
192W |
222W |
48% |
Data source: Advance.
Efficacy
Efficacy, in review, is an expression of relative lamp efficiency. Expressed in lumens of light output per watt of electrical input, this useful metric is similar to “miles per gallon.” As lumen output decreases over time, efficacy decreases because wattage says the same.
400W probe-start metal halide has an initial lamp-ballast system efficacy of 79 lumens/W. Although well below the efficacy of Super T8 with its efficacy of 99 lumens/W, it is only 7% less efficacious than T5HO with its efficacy of 85 lumens/W. However, initial efficacy is virtually meaningless because efficacy changes during operation. At 40% of lamp life, considered the design average, the efficacy of a 400W probe-start lamp-ballast system drops 40% to 51 lumens/W, while T5HO and Super T8 efficacies drop 5% to 81 lumens/W and 94 lumens/W respectively.
| System |
Initial Efficacy (lumens/W) |
Mean Efficacy @ 40% Lamp Life |
Relative Mean Efficacy |
| 400W Probe-Start Metal Halide |
79 |
51 |
100% |
| 400W Pulse-Start Metal Halide |
93 (magnetic ballast); 99 (electronic ballast) |
73; 85 |
143%; 167% |
| 4-Lamp T5HO Fluorescent |
85 |
81 |
159% |
| 6-Lamp T5HO Fluorescent |
85 |
81 |
159% |
| 6-Lamp Super T8 Fluorescent |
99 |
94 |
184% |
Data source: Advance.
Fixture-Based Efficacy
Fluorescent and metal halide lighting systems operate as the light-producing component within a light fixture. The light output and efficacy numbers previously discussed, therefore, must account for the impact of the fixture.
Many probe-start metal halide light fixtures found in the field offer low efficiencies of about 75%, while the best T5HO and T8 (and HID) hi-bay fixtures offer efficiencies as high as 91-92%. (For best results when choosing fluorescent, select fixtures with optics that are specifically designed for the specific lamp type, whether it be T5HO or T8.)
When one considers the impact of fixture optics, the basic-grade 400W probe-start metal halide fixture produces the lowest amount of maintained light output of all the options, and has a maintained efficacy of less than half the Super T8 option.
| System |
Fixture Efficiency |
Fixture Mean Lumens @ 40% Lamp Life |
Relative Mean Lumen Output |
Fixture Mean Efficacy (lumens/W) |
Relative Fixture Efficacy |
| 400W Probe-Start Metal Halide, basic-grade dome |
75% |
17,625 |
100% |
39 |
100% |
| 400W Probe-Start Metal Halide, high-performance dome |
92% |
21,620 |
123% |
47 |
121% |
| 400W Pulse-Start Metal Halide, high-performance dome |
92% |
30,176 (magnetic ballast); 33,120 (electronic ballast) |
171%; 188% |
67; 78 |
172%; 200% |
| 4-Lamp T5HO Fluorescent, high-performance reflector |
92% |
17,480 |
99% |
75 |
192% |
| 6-Lamp T5HO Fluorescent, high-performance reflector |
92% |
26,220 |
149% |
75 |
192% |
| 6-Lamp Super T8 Fluorescent, high-performance reflector |
91% |
18,974 |
108% |
85 |
218% |
Source of fixture efficiency numbers: Lighting Wizards, Inc.
Controls Flexibility
Probe-start metal halide lamps take 4 minutes to start and 10 minutes to restart after being turned off and then shortly after turned on again. Pulse-start lamps take 2 minutes to achieve full brightness on a magnetic ballast and less than 1 minute on an electronic ballast, while taking 4 minutes to hot re-strike. Because of safety concerns, HID systems are not compatible with switching controls such as occupancy sensors.
 Hi-bay occupancy sensor. Photo courtesy of Leviton. Fluorescent systems, however, start almost instantly, opening up significant controls possibilities. Line-voltage occupancy sensors have significantly reduced their installed cost, making it economical to install one sensor per fixture for intermittently occupied spaces. (This type of strategy, for example, can be used to satisfy the Commercial Buildings Deduction’s bi-level switching requirement.) Fluorescent systems are also relatively easy and inexpensive to dim, enabling daylight harvesting with skylights or flexible light level selection in all-purpose spaces. These opportunities further extend the potential for energy cost savings.
Lamp Life
In review, the rated service life of gaseous discharge lamps is an average. At rated life, half of a large population of lamps is expected to fail, distributed according to the lamp’s mortality curve. Lamp life is particularly important in hi-bay applications because the fixtures can be difficult to reach for maintenance.
At first glance, probe-start metal halide appears to offer very good service life compared to fluorescents. However, service life is rated based on the anticipated switching cycle, or “hours/start,” as the frequency of switching lamps on and off significantly impacts service life. Fluorescent lamps are typically rated based on 3 hours/start, while metal halide lamps are typically rated based on 10 hours/start. Fluorescent service life improves on an apples-to-apples basis of 10-hour switching cycles. At 10 hours/start, Super T8 leads the pack with a 28,000-hour service life compared to 24,000 hours for T5HO and 20,000 hours for probe-start.
Note, however, that fluorescent lighting enables the introduction of occupancy sensors, which may switch the lamps more frequently and thereby reduce lamp life. For these applications, programmed-start ballasts can be specified to optimize lamp life.
| System |
Rated Service Life @ 10 Hours/Start (hours) |
Relative Service Life |
| 250W Probe-Start Metal Halide |
15,000 |
75% |
| 250W Pulse-Start Metal Halide |
20,000 |
100% |
| 400W Probe-Start Metal Halide |
20,000* |
100% |
| 400W Pulse-Start Metal Halide |
20,000 |
100% |
| 4-Lamp T5HO Fluorescent (Programmed Start Ballast) |
24,000** |
120% |
| 6-Lamp T5HO Fluorescent (Programmed Start Ballast) |
24,000** |
120% |
| 6-Lamp Super T8 Fluorescent (Instant Start Ballast) |
28,000 |
140% |
*OSRAM SYLVANIA has introduced a 250W pulse-start metal halide lamp rated to 20,000 hours.
**Philips Lighting has re-rated its T5HO lamps with programmed-start ballasts to 25,000 hours at 3/hours/start, which would increase for 10 hours/start.
Data source: Advance, with notations by Lighting Wizards.
Color Temperature
In review, color temperature indicates the color appearance of a light source and the light it emits. For general lighting in many industrial spaces and warehouses, 4000K is considered suitable. In big box retail stores, color temperature is typically on the warmer side of neutral-white (3000-3500K), but can vary based on preference.
Typical probe-start metal halide lamps provide a 3000-4000K color temperature. As metal halide lamps age, however, chemical changes occur in the lamp which can cause a shift in color temperature of 200-600K over time. If group relamping (replacement of all lamps in a system at periodic intervals) does not occur, replacement lamps mingling with older lamps can result in noticeable poor lamp-to-lamp color consistency over time; some lamps may appear white while others may appear bluish, pink or purple. Additionally, when metal halide lamps are dimmed, they may shift to a higher color temperature, from white to blue-green; when a clear lamp is dimmed to 50% of rated power, color temperature can increase by 1500K, according to the Lighting Research Center.
HID lamps can experience a color shift during dimming and also a reduction in color rendering ability. Metal halide lamps are most susceptible to changes in lamp color characteristics.
T8 and T5HO experience negligible color shift during operation (although dimming may make the lamps appear uniformly cooler) and therefore maintain consistent color lamp to lamp. These lamps also offer a broader color temperature range from a neutral-white range up to a very cool 5000K.
| Probe-Start Metal Halide |
3000-4000K |
| Pulse-Start Metal Halide |
3600-4000K |
| Ceramic Pulse-Start Metal Halide |
3000-4200K |
| T5HO Fluorescent |
3000-5000K |
| Super T8 Fluorescent |
3000-5000K |
Data source: Advance.
Color Rendering
In review, color rendering, expressed on the Color Rendering Index (CRI), is the ability of a light source to make colors in the space appear “natural.” According to IESNA, in a manufacturing space, an >80 CRI rating may be suitable, although a CRI >90 may be desirable for tasks where matching or distinguishing colors is critical. In a warehouse, a CRI of at least 60 is suitable, with a CRI of at least 80 desirable where color is important. In big box retail stores and supermarkets, light sources should have a >80 CRI.
T5HO and T8 lamps provide 82-85 CRI compared to 65 for probe-start metal halide lamps. (Note that metal halide lamps may suffer a reduction in CRI when dimming; for example, when a clear metal halide lamp is dimmed to 50% of rated power, the CRI value may decline from 65 to 45.) To achieve a 90+ CRI, some fluorescent models are available but the higher color rendering is achieved at the expense of light output, disqualifying these lamps for many hi-bay applications. Other choices include daylight, ceramic metal halide and incandescent, although incandescent is generally undesirable due to its short service life and very low efficacy.
| Probe-Start Metal Halide |
65 CRI |
| Pulse-Start Metal Halide |
65 CRI (clear); 70 CRI (coated) |
| Ceramic Pulse-Start Metal Halide |
80-90+ CRI |
| T5HO Fluorescent |
82-85 CRI |
| Super T8 Fluorescent |
85 CRI |
Data source: Advance.
 Photo courtesy of Lithonia Lighting. Lighting Quality and Aesthetics
Lighting quality and aesthetic issues that are important to consider include color, glare, shadows, uplight, uniformity, vertical distribution and fixture appearance.
Metal halide lamps are point sources, while fluorescent lamps are linear sources. As a result, fluorescent fixtures are less likely to present “glare bombs” than metal halide fixtures, while increasing vertical light levels and providing softer light distribution, which minimizes shadows. However, whether metal halide or fluorescent is used, these aspects are highly dependent on good fixture design. On the other hand, metal halide hi-bay fixtures with clear prismatic domes are often seen in big box retail stores, selected partly for their aesthetic appearance and ability to provide dramatic highlights and a uniform uplight pattern on the ceiling. Wherever metal halide is selected, pulse-start metal halide should be considered.
Hi-bay fixtures with linear sources can improve vertical footcandles, important in applications such as big box retail, warehouses and some sports facilities.
Maintenance
Fluorescent hi-bays often present 4-6 times more lamps to maintain, with the primary cost-adder being labor. As lamps fail, fixtures exhibit lamp outages, which can affect space appearance, not to mention produce less light. Typically, a lift or similar mechanism will be required, as pole changers do not work with linear fluorescent lamps.
On the other hand, if a metal halide lamp fails, a significant space will not have a sufficient light level. With fluorescent fixtures, when a lamp fails, the space will still receive light from the remaining lamps. Similarly, fixtures usually contain more than one ballast, so if one ballast fails, the other may continue operating. Lamp life with fluorescent systems can be maximized with programmed-start ballasts, especially important if occupancy sensors are present which can result in frequent switching. If maintenance is an extremely critical issue, consider induction lamps, which can provide up to a 100,000-hour rated lamp life and retained performance in extremely cold conditions, albeit for a much higher installed cost.
Another maintenance issue is lamp replacement when Super T8 lamps are used. It is critical for maintenance personnel to replace Super T8 lamps with Super T8 lamps and not standard 32W T8 lamps because this will result in a reduction in light levels.
Disadvantages of Fluorescent
Fluorescent fixtures are not for all hi-ceiling lighting applications:
* Extreme mounting heights, which may lend themselves better to 1000W metal halide lamps.
* Unconditioned spaces with wide temperature ranges.
* Severe environments such as hazardous locations, corrosive environments, etc. for which a suitable fluorescent fixture is not available.
* Environments where the aesthetic of a dome-shaped fixture is desired; for these spaces, one can still consider domes fitted with compact fluorescent lamps.
* Spaces where a retrofit or upgrade alternative is not economical. In a retrofit, this will depend on product purchasing, installation labor and local energy costs. In a new construction project, note that a good fluorescent hi-bay fixture costs more to install than a basic-grade hi-bay metal halide fixture, but these initial cost savings are wiped out within months due to higher operating costs.
As always in lighting, the choice of the best system will often depend not just on the economics of initial and operating cost, but also on environmental considerations and what level of performance the owner is looking for from their lighting system.
 Utility Con Edison’s Astoria, NY 320,000-sq.ft. distribution warehouse. Con Ed wanted to streamline the lighting system in its Astoria, NY 320,000-sq.ft. distribution warehouse, improve efficiency and lighting quality, and integrate a sensor to control vacant areas and aisles, thereby adding to operating cost savings. Con Edison replaced the entire lighting system (left) with T5HO fixtures operating on programmed-start electronic ballasts and controlled by occupancy sensors (right). Photos courtesy of OSRAM SYLVANIA. Lighting Controls
Hi-bay fluorescent lighting enables owners to take advantage of all the control systems already enjoyed in office settings—scheduling, daylight harvesting, bi-level switching, occupancy sensors and dimming.
Automatic Shutoff
Fluorescent lighting starts almost instantly and therefore is highly compatible with automatic switching strategies such as automatic shutoff using occupancy sensors or control panels with time clocks.
Occupancy Sensors
Besides scheduling, occupancy sensors represent a major controls opportunity that can be used to maximize energy savings during a fluorescent upgrade, particularly in warehouses and similar spaces that are often under-occupied.
Line-voltage occupancy sensors have slashed the cost of occupancy-sensing by about two-thirds, according to Platts/McGraw-Hill, making it economical to consider installing a sensor for each fixture in intermittently, infrequently occupied areas. The sensor is installed directly onto the fluorescent fixture or electrical junction boxes. Occupancy sensors are available with lenses specifically designed for hi-bay applications, providing reliable coverage from a range of mounting heights, and some are available with narrow-view lenses for warehouse aisles. When using occupancy sensors, which can result in frequent switching, consider programmed-start ballasts to maximize lamp life.
Dimming
Fluorescent dimming can be accomplished in two ways. First, fixtures can be wired with multiple circuits to vary light levels, enabling bi-level or multi-level switching. Unlike hi-lo HID ballasts, energy savings proportional to light output reduction. Second, the fixtures can be equipped with dimming ballasts for continuous dimming. Unlike HID dimming, the lamps can be dimmed to 10-20%. Both bi-level switching and continuous dimming can be instituted to generate energy savings resulting from occupancy-sensing (with occupancy sensors), scheduled demand reduction (with a scheduling device such as a control panel with a time clock), and/or daylight harvesting (with a photosensor). Bi-level switching and continuous dimming also enable flexibility to adjust light levels for multiple uses of a space.
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