Electrical contractors and end-user call it by different names; a Spec Sheet, a Specification Sheet, or a Cut Sheet, but it all means the same thing. Theses are documents that “should” provide all the specification, performance, safety and regulatory information about a specific LED lighting fixture product.
The problem is that some companies either by negligence or by design do not provide all the information a contractor or end-user needs to properly evaluate a product. So what is a LED lighting fixture spec sheet and what should it contain?
The LED luminaire specification sheet contains a great deal of information typically packed into two pages. The information can be roughly categorized as electrical/safety, physical and performance data and warranty.
Electrical/Safety: The basic electrical information includes voltage, current, wattage, input frequency and power factor. Safety certifications, which vary by testing laboratory and global region, include UL/ETL/CSA/NOM/CE. These marks indicate the product has been tested and found to comply with applicable safety standards. The product should be rated for moisture conditions found in its intended application (dry, damp, wet). Various other ratings may apply based on the type of luminaire and the application. Two examples are ingress protection (IP) and insulation contact (IC) rating.
The IP rating is a code consisting of two numbers. The first number indicates how well protected the luminaire is against solids such as dust, from 0 meaning it’s not protected up to 6 meaning it’s dust-tight. The second how protected it is against liquids, from 0 meaning it’s not protected up to 8 meaning it can be submerged. The IC rating applies to recessed luminaires. IC-rated luminaires are installed where they will come into contact with insulation. Non-IC luminaires cannot be installed in contact with insulation and must have a minimum spacing from it.
This includes the product’s physical dimensions and weight, typically supported by drawings.
This information includes:
Light output, in lumens. Light output is measured using methodology published in the Illuminating Engineering Society’s (IES) LM-79 standard. LM-79 objectively captures 11 performance aspects, including light output, luminaire efficacy, chromaticity (from which color rendering index is derived), and correlated color temperature. All LED products should be tested in accordance with LM-79; detailed test results may be available from the manufacturer upon request.
In addition to basic light output, the spec sheet may include information indicating luminous intensity at all viewing angles. This is important information because it reveals the luminaire’s pattern of light, which can be analyzed to determine its impact on light levels, uniformity and potential glare. A luminaire has a vertical axis, an imaginary line running through its center from nadir (0°, directly below it) up to 180°, directly above it. Using this axis, measurements of light intensity, measured in candelas (cd), can be taken at any angle of elevation from 0° to 180°, called vertical viewing angles. The luminaire also has a horizontal axis crossing the vertical axis from 90° to 270°. Measurements may also be taken at an angle parallel to the lamp axis (0°) and perpendicular to the axis (90°), called horizontal viewing angles. The result is a “blob” of light that is based on the luminaire light source and optics.
The above is depicted visually as a graphic called the candela distribution curve and as a series of data called the candela chart. Many manufacturers offer the data as a downloadable electronic file. Because these files are based on a standard format created by the IES, they’re typically called IES files.
Indoor direct luminaire spec sheets may also include spacing criterion based on the luminaire’s light emission pattern. This is the maximum distance that the luminaires may be spaced while ensuring uniform illumination of the workplane. For outdoor luminaires, the manufacturer may publish a Backlight/Uplight/Glare (BUG) rating. The BUG rating indicates suitable applications (lighting zones) for certain outdoor luminaires based on the IES/International Dark Sky Model Lighting Ordinance. Efficacy, expressed as lumens of light output per watt of electrical input, an indicator of efficiency similar to the miles-per-gallon vehicle metric.
Correlated color temperature (CCT), measured in kelvins (K), which indicates whether the light source is warm-, neutral- or cool-white in visual appearance.
Color rendering index (CRI), which indicates the quality of the color rendering, with a score >80 considered “good” and >90 considered “very good.”
Alternately or in addition to CRI, some manufacturers may display color quality metrics in accordance with the relatively new IES TM-30 method. This includes the Fidelity Index ratings (Rf), similar to CRI but based on 99 color samples instead of 8-14. It also includes Gamut Index (Rg), which reveals average color saturation. Additional graphics may be provided that indicate relative saturation and desaturation of individual colors.
Life, measured in hours at a given L value. A service life of 50,000 hours at L85, for example, means an average product is projected to produce 85% of its initial light output upon 50,000 hours of operation. Life is typically projected based on information derived from testing in accordance with the IES LM-80 standard. This standard prescribes a testing method for LED-based packages, arrays and modules up to 10,000 hours. This information is then applied to a luminaire using the IES TM-21 method and manufacturer methods and data to derive a service life estimate. Detailed backup information may be available from the manufacturer upon request. If you know how to decipher it, the luminaire specification sheet opens up an enormous amount of information you can use to evaluate, discuss, compare, install and predict the performance of luminaires. It is certainly the contractors friend.
Lumight provides very complete specification sheets and has staff available by phone or email to clarify any questions you may have.