LED RETROFIT STRATEGIES Common LED Contributing Writer: Suman Parajuli Specs Explained Field Applications Engineer Understanding Common Terms When Selecting an LED Solution and Why These are Important

Total Lumens Lamp Wattage is important because the it burns out – for example a Total Lumens is the total light output of a lower the wattage, the lower the energy bill. may last 4,000 hours. An LED light source given light source and is a measure of the doesn’t burn out, it slowly dims. For an LED, total quantity of light given out by a light System Wattage rated life is the point in time when it’s 30% source. In an omni-directional light source, LED System is the total sum of LED ; 50,000 hours or more depending up to 78% of the light out may be redirected Lamp Watts plus watts used by the LED upon use. with a majority of the redirected light reflected Driver. When comparing a LED lighting back into the luminaire. source to an incumbent lighting source in Maintenance a retrofit, the System Wattage may be the There are two common measures of lumen Understanding lumens will give you the best Wattage of the incumbent lamp plus the maintenance for LED light sources: idea of how much light is produced from a lamp ballast. • LM-80 defines lumen maintenance as lamp. the elapsed operating time at which When planning a retrofit, understanding a specified percentage of the lumen Delivered Lumens System Wattage will provide a more accurate depreciation or lumen output is reached, Delivered Lumens are the total illuminance metric to calculate the time for payback. compared to its initial light output. This delivered directly to the work surface. In is done at the device level. a directed light source such as an LED, Efficacy (LPW) • L70, the point in time at which the LED approximately 80% of the total lumen output Efficacy is a measure of the efficiency of how light source lumen output has reached is delivered with none of the lumens reflected well a light source produces visible light. For 70% of its initial light output, is the back into the luminaire. Therefore, a LED a LED light source, it is the calculated lumens common threshold for recommended light source with a lower rated lumen output output per input (LPW). Commonly, module life. A LED light source typically may deliver the same or more useful light utility companies base rebate eligibility will not burn out. It gradually dims and to a work surface and a traditional lighting for LED retrofits on LPW specifications when it reaches 70%, it is nominally luminaire with a higher rated lumen output. published by the DesignLights Consortium® considered to be at the end of its life. (DLC®), a standards body defining energy Knowing delivered lumens will give you the efficiency lighting metrics agreed upon by Understanding Lumen Maintenance will help best idea of how much light is produced from utility companies and manufacturers. you recognize when it’s time to replace the a luminaire. LED lamp. For consumers, efficacy means the higher Lamp Wattage the value, the more efficient the light source. (CCT) In a light source such as an LED lamp, a Greater efficiency may enable you to save Color Correlated Temperature (CCT) is the Watt is a unit of measure of the amount of energy by dimming lights imperceptibly, indication of the color tint of white light. It is energy it takes per hour to produce a certain space lighting farther apart, or reduce the measured in degrees (K) on a scale amount of light. A higher wattage may number of luminaries installed. from 1,000 to 10,000. Commercial lighting indicate a brighter light or it may indicate a color temperatures typically fall between light using less efficient LED components. Rated Life 2000K and 6500K. Warm White, closer Lamp Wattage is the watts (W) consumed by The Rated Life of an LED light source is the to a more yellow-white incandescent bulb the LED lamp. In a typical LED lamp, watts statistically-determined estimate of median in appearance, is typically in the 2000K – are equated to lumen output: operation life and is dependent upon specific 3000K CCT range. Neutral White, similar • 40W incandescent = 9-4W LED = 380 operating conditions. It’s an indication of how to cool white or bright white common from – 460 lumens long the LED should operate before reaching a fluorescent, is in the 3100K – 4500K CCT • 60W incandescent = 31-15W LED = 70% of its initial brightness. range. And Daylight White, named for its 500-600 lumens near daylight quality, typically falls in a 4600K • 100W incandescent = 13-7W LED = In terms of rated life, LEDs operate differently – 6500K range. 1,700 – 1,800 lumens than traditional light sources. A traditional light source has a rated length of time before LED RETROFIT STRATEGIES

Color Correlated Temperature (CCT) is the indication of the color tint of white light. It is measured in degrees Kelvin (K) on a scale from 1,000 to 10,000.

Color Temperature is important when (PF) Total Harmonic Distortion (THD) choosing the right whiteness of light for a Power factor is an expression of how THD is important to any building. A low particular space. A restaurant might want effectively the LED light source is using THD means a reduction in peak currents, a warmer light to create a cozy space. An electricity. It is the ratio between the Real less heating, and lower losses. THD could office might want a brighter neutral light Power and the Apparent Power and is shown potentially shorten equipment lifespan, to promote productivity. A warehouse or on the Power Factor Triangle. increase power losses on the transmission parking garage might want to use a cooler, line, heat up transformers, and affect more vibrant, daylight white. the performance of the LEDs and other electronics. It’s typically related to Power (CRI) Q, Reactive Factor (PF). Commonly, LED lighting S, Apparent Power Power A Color Rendering Index (CRI) is a 0 specifications will indicate a THD of <20% quantitative measure of the ability of a or greater, which when paired with a Power P, Real Power light source to reveal the colors of various Factor of 0.9 or greater, may qualify the LED objects faithfully in comparison with an ideal lamp for utility rebates. or natural light source. The higher the CRI On the triangle, Real Power is the power value of the light source, the closer colors actually utilized in the LED light and is Ballast Factor will appear as compared to a natural light expressed in Watts. Reactive Power is Ballast factor (BF) is the measured ability of source. CRI is calculated from the differences the unusable or unutilized power, typically a particular ballast to produce light from the in the chromaticities of eight standard color created by capacitive and inductive loads (s) it powers. Ballast factor samples (CIE 1995) when illuminated by caused by circuit operation. Apparent Power is calculated by dividing the lumen output a light source and when illuminated at the is sum of Real Power and Reactive Power. of a lamp-ballast combination by the lumen same correlated color temperature (CCT). output of the same lamp(s) on a reference Commonly in commercial applications for A higher Real Power benefits both the user ballast. A ballast factor of <1 means a LED light sources, a CRI of 80+ is normal. and the utility company. Commonly LED particular fluorescent system will produce LED light sources in particular have a higher lighting specifications will indicate a PF of less light (lumens) than the reference ballast CRI value for R9, or red, color rendering >90% (0.90) or greater, which when paired and a factor of >1 means it will produce making them a desirable light source for retail with a Total Harmonic Distortion of 20% more light. Some linear LED specifications stores and art studio, as red is a common or less, may qualify the LED lamp for utility will indicate the performance of the LED color in the accurate representation of many rebates. lamp when driven by low, nominal, or high fabrics, produce, and skin tones. BF ballasts. Power Factor can maximize the overall

R R R R R R R R current-carrying capacity, improve voltage Ballast Factor, which applies only to 1 2 3 4 5 6 7 8 to the LED array and reduce power losses. installations where an LED lamp is driven

R R R R R R In short, if you see a Power Factor over .9, by the installed ballast, affects the lumen 9 10 11 12 13 14 you’ll have improved efficiency. output, watts consumed, and rated life of the LED. A lamp connected to a LBF ballast will In most cases, natural colors are preferred. consume less power and operate longer, but CRI means, red apples will look red! will output less light. A LED lamp connected to an HBF ballast will put out more light but will consume more power and operate for a shorter period of time. LED RETROFIT STRATEGIES

Beam Angle/Beam Spread LUMINANCE (cd/m2) however, is split into two spherical planes, because of the luminaire’s reflector. The light The beam angle of a LED lamp lets you Vert Angle At 0° Horiz At 45° Horiz At 90° Horiz is blocked by the reflector in the center. know how much area it will illuminate at a PLA14-36W840-U given distance. The lighting industry has 45° 4987 5374 5571 If you look at the luminaire from the side, developed a uniform formula to determine 55° 4416 5121 5409 positioned along the 90-270° axis, a spherical the beam angle. The light output (lumens) is 65° 3692 4738 5095 measured at the center of the beam and then 75° 2873 4219 2929 plane is shown upwards and downwards. light strength (intensity) is measured out from 85° 1950 2016 1147 This means the luminaire distributes light the center until it is 50% of the intensity level evenly. The luminaire’s elongated shape does (as measured in the center). The beam angle not mean the curve is flat or elongated. The is then determined in degrees (see below). When designing a lighting project,it is light distribution is measured from the central The beam spread is the area the light covers important to keep luminance in mind. The point of the luminaire. with at least 10% of the maximum beam brightness the eye perceives at the work angle. This is not typically tested for, but is surface may be less than the lamp specifies; CANDELA PLOT commonly estimated at double the beam an over-lit space uncomfortable and energy angle. inefficient. Angles 10° Candela Plot The Candela plot or chart is an analysis of a LED luminaire’s distribution of light and its impact on lighting levels and potential conditions. IES files are commonly formatted files of data used to simulate the light performance in lighting design software. 1699 Cd Each luminaire and lamp combination has a unique Candela plot or chart. The type of 50% Light Intensity Maximum Light Intensity 50% Light Intensity lamp installation, for example powered by a The Candela Plot aides designers in Beam Angle helps you determine spacing in ballast, driven by a LED driver or connected determining what type of luminaire to use, your lighting plan, avoiding dark spots (cave directly to line voltage will also affect the luminaire placement, spacing, and height in effects) where areas are under lit. specific lamp photometrics. order to deliver sufficient luminance.

Luminance (cd/m2) The Candela distribution curve is a graphical Luminance is a photometric measure of representation of relative light intensity for the luminous intensity per unit area of light a single vertical plane based on candela travelling in a given direction. It describes the readings across the vertical viewing angles amount of light passed through, emitted or (0–180°) for a single horizontal viewing angle. reflected from a particular area and falling For example, in the case of an elongated within a given solid angle. The unit for pendant luminaire with two LED T8 lamps, luminance is candela per square meter (cd/ the two curves will have a different shape. m2), also referred to as a nit. The luminance indicates how much brightness is perceived Looking straight at the luminaire, positioned by an eye looking at the surface of an object along the 0-180° axis, the upward beam is from a particular angle of view. spherical (lower left). The downward beam

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