The evolution of lighting systems in industrial applications

As lighting designers, it is key to stay current, to design systems using the latest technologies, and to educate industrial facility owners—all while striving to exceed the latest energy codes.

08/24/2018


Learning Objectives

  • 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

Figure 1: Installation of light fixtures is shown in a corrosive environment requiring Class 1, Division 1-rated light fixtures. All graphics courtesy: CDM Smith 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.

Figure 2: ElumTools provides lighting calculations and renderings within Autodesk Revit.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.

Figure 3: This sample lighting calculation using Visual Lighting 2017 shows footcandle contours of a uniform lighting design using linear LEDs.Light factors

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.


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