The evolution of lighting systems in industrial applications
- Learn where and what to look for when defining the criteria for a new lighting system design.
- Understand how lighting system design has evolved in industrial applications.
- Think beyond energy audits by using the audit to design and implement lighting systems to provide both greater safety and cost savings.
Just 10 years ago, engineers were able to reuse lighting fixture types for new designs without considerations as to their performance. The fixtures were typically consistent from project to project and, depending on the environment where they were being installed, there was a fixture type that was consistent with every application. As many of these fixtures are reaching their end of useful life, they are being replaced by new technologies, such as LEDs, due to their increased energy efficiency. This is evident at most sites where the same high-bay, high-intensity discharge (HID) fixtures were used for 25 years. The same can be said for fixtures in general office areas or electrical rooms.
Lighting systems have changed dramatically in the past 5 years. With the rapid evolution of fixture technologies, such as LED, manufacturers are innovating every day with new products that offer better performance. Due to this rapid evolution, designing lighting systems requires staying current with codes and standards. It also requires staying well-versed in the latest offerings by light fixture manufacturers, to be sure the most recent product information and model numbers, or the products best suited for the application, are installed.
Codes, standards, and guidelines
As the world moves toward greater energy efficiency, codes are being changed and owners are challenging their consultants to design smart, energy-efficient systems that require less maintenance. As such, the first and most important step to designing a successful lighting system is to involve both the owners and the end users
Either ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings or the International Energy Conservation Code (IECC) will determine the energy efficiency measures that will need to be implemented. However, some jurisdictions adopt more stringent guidelines than these documents. For instance, some state-driven guidelines, such as Title 24 in California, have influenced changes to the IECC and ASHRAE 90.1. Additionally, some locations in Massachusetts have adopted the Stretch Energy Code, which uses the IECC as a baseline and defines areas that are required to be designed in more energy-efficient measures.
To illustrate the ever-changing landscape of energy code adoption, a graphic released in June 2018 from the Massachusetts Department of Energy Resources(DOER) shows that 241 municipalities have adopted the Stretch Energy Code out of a total of 315 municipalities. This number is up from 186 municipalities in 2016. With 55 communities adding the stretch code as a requirement over the course of about 18 months, it is easy to understand why staying current with local energy codes is a must.
Both the IECC and ASHRAE 90.1 define the lighting-power density (LPD) or lighting-power allowance, which is measured in watts per square foot, or watts per square meter, respectively. The IECC defines these values in Tables C405.4.2(1) and C405.4.2(2) and ASHRAE 90.1 defines these values in Tables 9.5.1 and 9.6.1. The calculation for LPD can be calculated in two ways, either the space-by-space method or the building area method. It is up to the discretion of the designer.
The IECC and ASHRAE 90.1 also define requirements for lighting controls. ASHRAE 90.1 does so by defining the criteria for bilevel lighting control, automatic daylight-responsive controls, vacancy sensors, and timers in Section 9.4.1, and by listing the requirements by space in the same 9.5.1 and 9.6.1 tables. The IECC defines lighting controls in Section C405.2.
Because there are many options for including emergency lighting integral to light fixtures, NFPA 101: Life Safety Code includes the requirements for these emergency lighting systems. For the purposes of LED lighting system design, this code provides criteria for the required illumination along the egress path. NFPA 70: National Electrical Code (NEC) and other applicable codes used to classify spaces within a facility where work is being completed also should be referenced.
For instance, NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities should be researched to properly classify locations where fixtures will be installed within wastewater-treatment facilities. These facilities have many locations that are rated Class I, Division 1, which require the fixture types to be rated as explosion-proof. Additionally, there are many chemicals or gases that require fixtures to be corrosion-resistant. These are either byproducts of the wastewater-treatment process, or materials used throughout the process. Special attention should be made to the materials the fixtures are made of to ensure a long-lasting, and properly operating, fixture.
After all these codes have been researched, a final resource is the Illuminating Engineering Society (IES) Lighting Handbook. This is a comprehensive reference guide for designing lighting. The document is not a code book; it is a helpful resource to define design criteria and conduct lighting calculations. Referencing the IES Lighting Handbook, along with owner standards (if available), is a great way to develop the design criteria for footcandle requirements for differing space types. In Chapters 21 through 37, the IES Lighting Handbook breaks down area types and provides recommendations for these values. Many industrial owners are not aware of the IES Lighting Handbook, and as consultants, it is good practice to define the footcandle values for different spaces based on use and then discuss them with the owner.
Light-loss factor (LLF) is another element that affects lighting calculations. As stated in the IES Lighting Handbook, Section 10.7.1, LLFs "adjust lighting calculations from laboratory to field conditions … and are divided into recoverable and nonrecoverable factors."
Nonrecoverable factors for LLF, such as ambient temperatures and voltage-to-luminaire factors, are those that are not able to be controlled by the end user through maintenance, whereas recoverable factors can be affected by maintenance. Chapter 10.7 of The IES Lighting Handbook should be referenced for all these factors.
Many of these factors cannot be determined, and for these instances, they should still be included in the overall calculation of the LLF and considered to be a value of 1. The LLF is the product of all these factors defined in chapter 10.7, and for the sake of this calculation, there are two factors that should never be ignored. These two factors are lamp lumen depreciation (LLD) and luminaire dirt depreciation (LDD). Both LLD and LDD factors are easily definable by the designer. The LLD can be found in almost all fixture specification sheets, and the LDD should be determined by the designer based on the type of area (using the tables in chapter 10.7).
The final elements for consideration are the uniformity ratios. Maximum-to-minimum and average-to-minimum footcandle ratios are important elements in providing uniform lighting designs. Just as important as providing enough light, a nonuniform lighting design can cause one’s eyes to not properly focus. For that reason, the IES Lighting Handbook defines ratios in the same tables found in Chapters 21 through 37 based on the task level and location.
For instance, a laboratory would require more strict requirements for uniformity than a warehouse due to the precise nature of the work being completed in the laboratory. Additionally, an indoor gymnasium would require more strict requirements for uniformity than an office area due to the speed of action in the space.
Choosing fixture types
The goal of selecting the right fixture type for the application is to ensure that the proper illuminance is obtained, while also maximizing energy efficiency and ensuring visual comfort for the occupants. Because the individual diodes that make up the array of the LED fixtures can be arranged in practically any orientation, the distribution of LEDs is more precise than that of HID and fluorescent fixtures.
By assessing the environment where the light fixtures are being installed, the mounting type (pendant, surface, recessed, wall, etc.) and the approximate installation height, a preliminary lighting fixture schedule can be constructed. Choosing the right fixture type for the environment is very important because owners expect their newly installed LED lighting system to be virtually maintenance-free for 10 years.
When working in an existing facility, careful consideration should be given to the site and condition of the existing fixtures. For instance, if there are signs of corrosion or deterioration in a locker room or bathroom, perhaps these areas warrant a fixture with a wet application versus a damp application. If working in an area such as a maintenance garage, fixtures installed 15 ft or higher above the finished floor are typically considered high-bay light fixtures. A light fixture installation in a corrosive environment with the possibility of explosive gases is shown in Figure 1. The final item to pay attention to with regard to choosing your LED fixture is color temperature, and matching color temperatures throughout a facility is a wise practice.
Once these considerations are satisfied, including a strong review of codes and references, it is then time to design lighting layouts and determine the best light fixture selection for each space. Once the preliminary fixture schedule is completed, contacting the local electrical utility may help identify additional funding in the form of rebates for the owner. Many utilities now have a separate division that will work with consultants during the design phase to develop equipment schedules that qualify for rebates.
Lighting calculations can be done either by hand or by using computer software. Hand calculations are done using the lumen or zonal cavity method, which relies on ratios to calculate the light levels. The method essentially takes the entire lumens in a room and divides it over the area of the space. It is often advantageous to do a few lighting calculations by hand to learn the process; however, with the advancements in software and the complexity of some lighting systems, using a computer software program, such as AGi32 or Visual Lighting 2017, is recommended. Additionally, there is an Autodesk Revit add-in application called ElumTools, which uses the same engine as AGi32. ElumTools is able to produce real-time results in a rendering within the Revit model, as shown in Figure 2. It can be extremely helpful when designing a model to have the calculations updating with every movement of the fixture. It also is helpful when demonstrating the design to the owner.
Still, there are some basic principles to follow when using the lighting software to design a lighting layout. In the simplest form (a rectangular-shaped room), the fixtures should be distance "X" away from the wall and spaced distance "2X" from between one another. Using this method, or the recommended spacing criteria sometimes found on manufacturers’ fixture specification sheets, lighting calculations should start off with a uniform distribution.
From there, quantity can be adjusted, or perhaps an increasing or decreasing in the lumen output of the chosen fixture type. Similar to the ElumTools rendering, Visual Lighting, AGi32, and ElumTools in a 2-D view are also able to show contour lines or different colors of footcandle levels as demonstrated in Figure 3. Uniform contour lines will produce uniform ratios, and the contour lines can be used to identify dark areas and provide ways to adjust the lighting layout. Before printing calculations and sending them for review, it is good practice to check and make sure the LLF is included. The LLF can have large impacts on the calculation output, and it can be frustrating to produce the perfect lighting calculation only to realize the LLF was still inadvertently set at a 1 value.
LEDs have opened the doors for controls to become more useful in industrial applications. A high-bay application that once used HID fixtures (i.e., metal halide) can now achieve the same results with LED fixtures (i.e., illuminance levels) while reducing energy consumption. Instead of these fixtures remaining on 24/7, or during the entire shift of a working day (which is common practice with HID fixtures due to the period required for cool down and warmup when switching on/off), they can now be controlled via an occupancy sensor to either dim to a determined light level, or shut off entirely.
As referenced above, the IECC and ASHRAE 90.1, along with local codes, govern the required controls; however, many industrial installations may be exempt from them due to possible safety concerns. In spaces where safety issues are not a concern, such as administration areas or office spaces, they will require many of the controls that are defined in the IECC and ASHRAE 90.1. Areas such as assembly lines, where there may be a potential hazard to personnel if lights were suddenly shut off or dimmed by an occupancy sensor, require additional attention and should be discussed with the owner. Other areas may not be allowed to have only automatic controls, such as electrical rooms, per NEC, Article 110.26(D). For these types of areas, automatic controls with a bypass switch could be considered. If the owner would like to install lighting controls in these areas, the engineer should recommend a written safety procedure be established for when work is done in these areas.
Additionally, if the owner would like to install an advanced lighting control system that can be controlled remotely by its onsite energy manager, the engineer could recommend a procedure similar to lockout-tagout for when maintenance is done to the electrical distribution equipment. Lockout-tagout is a safety procedure to ensure that certain machines are shut down and not able to be started up again before the needed maintenance or repair work. This would protect against a situation where the lights are automatically controlled.
When a lighting design is finalized in accordance with all the codes and owner requirements, the U.S. Department of Energy’s COMcheck provides a final assessment of the proposed lighting system. Although not a requirement for all projects, users of COMcheck can input the lighting fixture types and overall building areas (either by using the room-by-room method or total building area method) and define the area types.
A report is then generated with a checklist (see Figure 4). The report determines how efficient the design is in relation to the code, and the checklist allows the engineer to go through control items required by code. The figure illustrates an example where the interior lighting met code better than 67% of what was required for energy efficiency. The figure also includes several checklist items that are often requirements of industrial clients.
Audits lead to efficient, safe lighting designs
Consultants often are tasked with providing energy audits for owners, and these audits can eventually become design projects. As part of these audits, taking inventory of light fixtures requires the auditors to be diligent with detailed note-taking. Proper preparation to document orientation and layout, fixture types, the condition of the conduit system, controls, and existing footcandle measurements are essential items to provide the owner an accurate assessment of their entire lighting system. These audits items can also provide the proper recommendations for upgrades. Audits not only help provide the owner with a clear picture of their lighting system, theyalso can turn into full-scale design projects that will benefit the owner with cost savings and improved safety.
Over the past several years, CDM Smith has provided both audit services and new lighting systems designs with LEDs for various types of owners. Often the scope of work from the owner, or recommendation from a previous audit report, is to provide a one-for-one replacement of existing fixtures with LEDs. The one-for-one replacement method is typically completed by comparing the lumen output of the existing fixture and then matching it with a new fixture with a similar lumen output. While this method does reduce the energy used, it does not consider existing conditions and several other factors that could lead to increased energy savings and improved lighting conditions.
Unfortunately, upgrades to LEDs as part of either a retrofit program or energy-conservation measure are completed with little consideration to the existing footcandle levels and infrastructure condition. Paying attention to both items is key to ensuring that what is installed will maintain proper operation for the life of the fixture. Examining the infrastructure condition also can help reveal conditions that were not expected.
For instance, a room with light fixtures rated for a dry environment may be connected to a conduit system showing signs of corrosion. The designer should then consider the possible reasons for the corrosion, if it is an anomaly, and whether to install a corrosion-resistant fixture instead. The evaluation of existing footcandle measurements allows the designer to use more recent guidelines or updated owner standards. This evaluation may also help further reduce energy usage if the space is overlit or, if the space is underlit, provide proper illumination for that space.
The final item to examine is the existing layout. Because LEDs can be arranged in countless array patterns, the distribution of light is much more precise. There may be more lumen-output options in a single-fixture footprint, which means a one-to-one replacement of a 2×4-ft fluorescent fixture to a 2×4-ft LED based on lumen output may not provide the owner with the best value or most energy savings.
LED fixtures often provide several options for lumen output on a fixture type, similar to how a 2×4-ft fluorescent fixture can be found to have two, three, four, or even six lamps. The difference that has been revealed through completing various scenarios of lighting calculations is, that with the right LED fixture, a similar footcandle average can be achieved with fewer light fixtures installed in the existing fixture locations. Where this has been the case, reductions of up to 50% of the fixtures in a space has been typically realized.
The same success has been seen in high-bay applications where an existing configuration of 50 metal-halide fixtures were replaced with an installation of 30 LED fixtures, all while providing the owners with better lighting conditions after the installation. In all these scenarios, the new LEDs were installed using existing conduit and wiring. Because existing fixture layouts were used where fixtures were no longer needed, the boxes were covered and became junction boxes.
This technique maximizes payback for the new lighting system. Figure 5 is an example of a new LED calculation using an existing high-intensity discharge (HID) fixture layout. The sample lighting calculation used Visual Lighting 2017 and shows the reduction of light fixtures when replacing HID fixtures with LEDs-all while reducing the power density, increasing the footcandle average, and producing a more uniform lighting design.
For these reasons, it is recommended that owners include complete lighting calculations in the assessment of their existing lighting system. The rapid change in lighting technology means that engineers need to be confident in using the new fixtures, and calculations are one way to provide this assurance. While the upfront engineering cost is increased, the evaluation of a whole lighting system has multiple benefits. These calculations may lead to the reduction of hundreds, or even thousands, of fixtures on large projects. It is important to provide adequate footcandle levels when lighting conditions are being evaluated. The ultimate goal of the improvements are to address any conditions that are hazardous to staff while maximizing energy savings through the improvements.
Jeff Donaldson is a senior electrical engineer at CDM Smith. He has more than 10 years of experience working in the power electrical engineering field providing design engineering and construction observation of electrical systems for municipal, industrial, and private clients.
Michael Stevens is a technical writer and editor with CDM Smith and has been supporting technical submittals and deliverables across multiple engineering disciplines for more than 20 years.