lighting i_lighting your way course transcript

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Lighting I: Lighting Your Way Course Transcript

Slide 1 Welcome to the course Lighting Your Way: Four Principles for Efficiency. Slide 2 This course is intended to be easy to use. You will encounter a few different screen types. Some screens will auto-advance, and others will require you to take action to proceed. Please take a few moments to familiarize yourself with the course layout, including the various tabs or virtual buttons you should access and explore. When you are ready, click the next button to continue. Slide 3 At the completion of this course, you will be able to:

• List the four principles for efficient lighting design. • Discuss the importance of recommended light levels. • Identify the four basic lamp families. • List a variety of opportunities to improve energy efficiency through upgrades in lighting

and controls. Slide 4 Lighting is considered a “quick hit” by many building owners and managers looking to save energy and reduce costs. To meet European building standards for energy consumption, lighting efficiency is a key area of attention. According to the National Lighting Bureau’s 2003 study, only 17 percent of US commercial buildings built before 1980 have retrofitted their lighting systems. That means more than 2.2 million US buildings could benefit just by updating their lighting systems! It is important to note, however, that these figures also have some significant exclusions; the report did not include shopping centers, strip malls, or industrial facilities. Throughout the world, lighting offers opportunities to reduce consumption while maintaining comfort and style.


Slide 5 How much energy is used for lighting? Here are some common commercial building types and the percentage of the facility’s total energy usage consumed by lighting. It can be as much as 37 percent. Slide 5 There are four principles of efficient lighting:

• Determine how much light is needed, the appropriate quality, and where is it needed—amount, quality, and distribution. This will vary with the space’s orientation and availability of daylight, the tasks and activities performed in the space, and the ages and visual comfort requirements of the occupants of the space.

• Use efficient luminaires designed to satisfy these criteria. The luminaire includes the lamp and its housing, along with other components such as reflectors and diffusers.

• Use lighting controls to automate the amount, distribution, and scheduling for the luminaires.

• Lastly, commission the lighting system to ensure proper operation and maintain the system through periodic audits and maintenance.

Slide 6 Lastly, commission the lighting system to ensure proper operation and maintain the system through periodic audits and maintenance. Slide 6 There are four principles of efficient lighting:

• Determine how much light is needed, the appropriate quality, and where is it needed—amount, quality, and distribution. This will vary with the space’s orientation and availability of daylight, the tasks and activities performed in the space, and the ages and visual comfort requirements of the occupants of the space.

• Use efficient luminaires designed to satisfy these criteria. The luminaire includes the lamp and its housing, along with other components such as reflectors and diffusers.

• Use lighting controls to automate the amount, distribution, and scheduling for the luminaires.

Lastly, commission the lighting system to ensure proper operation and maintain the system through periodic audits and maintenance. Slide 7 Whether new construction or retrofit, determining the appropriate amount, quality, and distribution of light is the first step in providing an efficient lighting system. Over-lighting can be as detrimental to safety, productivity, and visual comfort as under-lighting. Slide 8 How do we measure light? We measure the power of light in lumens, and we measure illuminance in lumens per unit area.

• The SI unit of illuminance is lux, and is equal to one lumen spread evenly over one square meter.


• The US customary unit for illuminance is the footcandle, or fc, and is equal to one lumen spread evenly over one square foot.

• Illuminance is a measure of light density. It is measured with a calibrated light meter. Lux or footcandle recommendations are meant as a guideline for lighting density, not as the only criteria for appropriate lighting. Equally important criteria are uniformity, object reflectivity, and glare. Slide 9 Natural light levels vary tremendously, from the dim light of the moon to the intense light of a sunny day. Lighting requirements based on artificial light have a narrower range. The values shown are general recommendations for illuminance, in lux and footcandles.

Slide 10 Some questions to ask when faced with a lighting project: How much light do I need?

• Appropriate amounts of light based on tasks and environment are published by lighting engineering societies or government agencies and can vary by country or region. Examples of these are the EN standards in Europe, the Illuminating Engineering Society of North Americas, or IESNA, Handbook and Australia and New Zealand’s Standard AS1680.

Where do I need the light?

• Again, the reference for this will vary depending on your country.


• Some applications, such as a classroom whiteboard, require light to be distributed on a vertical surface, as opposed to reading a magazine, which may require light to be distributed on a horizontal or angled surface.

• Distribution can also describe the uniformity of light required for a particular task or application. Uniform lighting is desirable in classrooms, offices, and parking lots, but to create drama and draw an occupant’s attention to an object or area of interest, uneven light levels provide a “cue” to the human brain that says “look at me!”

What quality of light do I need?

• Color temperature in Kelvin (K) indicates the “warmth” or “coolness” of a light source. • CRI (1-100 scale) is a measurement of how “true” colors appear under a particular light

source using the standard incandescent light bulb as the standard at 100. What is the age of the user?

• Another factor to consider is the age of the occupants or users of the space. The older the user, the more light that is required to achieve the same visual acuity as a younger individual.

Slide 11 Color temperature is an indication of the hue of a specific type of light source. Higher temperatures indicate whiter, "cooler" colors, while lower temperatures indicate yellower, "warmer" colors. Notice the difference in these two scenes, lit with sources of different color temperature. This chart shows you some examples of common light sources on a scale of color temperatures.

Halogen 3150°k

Daylight 5100°k

Metal Halide 5000°k

Cool White Fluorescent

4100°k Warm White Fluorescent

2900°k

High Pressure Sodium 1700°k

Incandescent 2700°k

Slide 12 The color rendering index (CRI) is a measure from 0 to 100 of how faithfully the light source illuminates colors when compared to an incandescent source. Here you see the same scene, illuminated by different light sources. To effectively compare the CRI of different light sources, the color temperature, or K, should be the same. A source with a low color rendering index will tend to make colors look unnatural. In some environments, like car parking lots, that might be okay. But in environments where seeing colors correctly is important, this would have a big impact on the choice of the light source.


Slide 13 Raw light output, or lamp lumens for any light source will depreciate over time, as the lamp ages. In other words, older lamps typically produce less light than brand new ones. We already saw that a lumen is the measurement of light emitted from a source. Lamp manufacturers publish intial lumens and mean lumens, based on “lumen maintenance,” the percent of lumens remaining at mid life. These data vary with the light source and will be discussed in more detail in the second class in this series: Defining Light. Slide 14 In addition to lamp lumen depreciation, there are other effects over time on the luminaire operating system and environment that can reduce light levels. Light Loss Factors that an expert will consider include:

• Room surface depreciation • Luminaire surface depreciation • Luminaire Ambient Temperature (LAT) • Ballast Factor (BF) • Voltage Variation (VV)

Room Surface Depreciation Accounts for the changes in reflectivity of room surfaces as they age. Luminaire Surface Depreciation Accounts for loss of fixture light output due to luminaire reflector or lens deterioration. Some conditions that influence this light loss factor are dirt accumulation or UV damage. Luminaire Ambient Temperature (LAT) The temperature in which a luminaire is operated is often different than the temperature in which the luminaire was tested. These temperature differences can increase or decrease the light output of the fixture. Ballast Factor (BF) This is a multiplier which takes into account the differences between “real life” operation, and component testing, which happens under controlled laboratory conditions. Ballast factor specifically addresses potential losses when using a specific ballast/lamp combination. We'll learn more about ballasts later in the class. Voltage Variation (VV) Voltage fluctuations can cause a luminaire to burn more or less brightly and can affect ballast and lamp life. Slide 15 Here are some general guidelines for good lighting:

• Give what is needed, not what is asked for. • Use your region’s official guidelines and recommended practices, and consult local codes. • Increase levels for workers over the age of 40 or dark room surfaces.

Industrial applications have seen greater emphasis on increasing maintained light levels over system life. This provides increased safety for hazardous environments.


Commercial light levels have been dropping over the decades. Much of this change has been driven by computer-use. Lower ambient levels of 300 or 400 lux, equal to 30 to 40 fc respectively, are common in today’s computer-based office, as compared to 1000 lux, equal to 100 fc, which was the norm in the 1970s; or to 700 lux equal to 70 fc, which was the norm in the 1980s. Slide 16 Not all the required lighting has to come from ceiling mounted luminaires. Click each area of the office space to learn more.

• For horizontal surfaces, general room lighting can be supplemented by task lighting mounted close to task level. This can be more efficient because it applies the lighting where it is most required, rather than illuminating the whole space to the same degree.

• In environments where there is intensive use of visual display terminals, there is often a preference for lower ambient light levels.

• Lighting vertical room surfaces eliminates the “cave” effect, visually raising the ceiling and creating a more “open”, vibrant space.

• Examples of vertical task surfaces are shelving, white boards and retail displays. Slide 17 There are, of course, many other factors to consider when planning lighting or a lighting retrofit for any type of facility:

• Safety and security: Is additional lighting needed to address unique safety or security concerns?

• Worker performance: Studies have shown that people feel better and perform better under white light compared to yellow or orange light. In a facility where, for example, a decision between a more efficient High Pressure Sodium system and a more “worker-friendly” fluorescent or metal halide system needs to be made, where does worker performance or comfort fit into your calculations? Is it measurable?

• System Maintenance/Life Cycle: How difficult or time-consuming is it to change out lamps? Would you consider paying more for a system that required less maintenance?

• Environmental Factors: Do the products under consideration require recycling at end of life? What provisions are in place in your region for recycling?

• Economic Considerations: Both initial cost and life cycle cost need to be considered. • Regulatory Compliance: Does the lighting system under consideration meet all of your

region’s regulations? For example, does your region require RoHS compliance? • Professional Standards: In addition to meeting light level standards as determined by the

authority with jurisdiction in your region, are there other recommendations, possibly set forth by an industry organization, specific to the type of facility you are lighting? For example, automobile manufacturers have recommendations for different light levels depending on the vehicle paint color, which are not part of the IES recommended practices.

Slide 18 Think about the lighting in your facility. If you have access to a light meter, take a few readings, but be careful where you take the measurements, because the recommendations are based on task, as opposed to overall or general ambient light levels in the room. You can download some examples of lighting standards for offices from the Attachments tab. How do the levels you’ve measured for your facility compare with the standards for your region?


Slide 19 The second principle is to select efficient luminaires. The “luminaire” is the light source in a fixture, and includes all of the auxiliary gear that helps it do its job. Reflectors, diffusers, current regulating devices, and mounting hardware are all part of the luminaire. Think of the luminaire as a car and the lamp as its engine. Choosing an appropriate luminaire, placing it correctly, and controlling it are the foundation of any lighting project. In a quality lighting design, luminaires are part of a system that delivers an appropriate amount of light where and when it is needed, without over- or under-illuminating or lighting unoccupied spaces. Slide 20 For new construction and remodeling projects that affect 50 percent or more of the designed space, using efficient luminaires, for example, lamps, fixtures, and ballasts, is no longer optional in many parts of the world. Although the codes and standards rarely exclude inefficient technologies, they have become impractical for a code compliant strategy that still meets recommended light levels. Slide 21 Today, lighting energy codes and standards often are based on lighting power density (LPD), or watts per unit area. Maximum lighting power density can be based on building type and footprint, or the individual spaces within a building. EN15193 calls for lighting power density of office spaces in European buildings to be from 15 to 25 watts per square meter, and specifies benchmarks for lighting power density in three grades. One star represents basic fulfillment of requirements, two stars represent good fulfillment of requirements, and three stars represent comprehensive fulfillment of requirements. In the US, the ANSI/IES/ASHRAE 90.1 standard calls for LPDs from 1.1 to 1.3 watts per square foot, depending on the tasks performed in the office. Generally, in an office building, corridors, conference rooms, and restrooms would each have a prescribed maximum lighting power density, based on that particular space. Hospitals, schools, and industrial spaces will have their own standards. Specific standards will vary by country and global region. You can see some more examples of recommended lighting levels and LPD in a space in a downloadable file available on the Attachments tab. Slide 22 The basic light source family members include: incandescent, low-pressure discharge, high-intensity discharge, and Light Emitting Diode (LED). Incandescent lamps have a tungsten filament, and are resistive in nature, which produces mostly heat. They are available in various shapes. The “A” shape is the familiar elongated globe. Reflector bulbs have a reflective coating inside the bulb, to direct the light. PAR bulbs, or parabolic aluminized reflector bulbs, direct the light more precisely. Halogen lamps are a type of incandescent lamp. Many countries are progressively outlawing incandescent lamps due to their poor energy efficiency.


Gas discharge lamps work by sending an electrical discharge through an ionized gas. Examples of these lamps where the gas is under low pressure include fluorescent and low pressure sodium. Fluorescent lamps include the long tubes often used for office lighting and also compact fluorescent lamps. You may have seen low-pressure sodium lamps in street lighting or in parking lots. It is one of the most efficient lamps, but it gives a yellow light, which means it can’t be used for most applications High-intensity discharge lamps are a family that includes mercury vapor lamps, metal halide lamps, and high pressure sodium lamps. These lamps have a wide range of applications, and are often found where high levels of light are required over a large area. Mercury vapor lamps are virtually obsolete, and have been replaced by metal halide lamps. The light output of both these types of lamps tends to decline significantly over time. Light-emitting diodes, or LEDs, are a newer form of lighting which you may have seen on exit signs or traffic control signals, but are becoming increasingly available for interior and exterior commercial and residential lighting in retrofit and new construction products.

Slide 23 The choice of the right lamps will depend on factors such as the color rendering index and temperature that we saw in our earlier discussion. It will also depend on factors such as:

• Lamp life • Efficacy • Cost • Suitability for the operating conditions

Let’s look at some of those now. Click each factor to learn more.


Published Lamp Life Some lamps last longer than others. Lamp testing begins with 100 lamps. Incandescent lamps are burned continuously, which means that field performance will always be shorter if cycled on and off. Fluorescent lamps are cycled off for 20 minutes every three hours, which means that field performance will usually be longer in a commercial application, where 12 hour cycles are common. High pressure sodium and metal halide lamps have a longer, more realistic 10 hour cycle, but are tested with magnetic ballasts, not indicating the extended life obtained with today’s electronic ballasts. Rather than published hourly life, consumers and facility owners are concerned about calendar life. A control strategy that regulates the length and frequency of lighting cycles increases lamp calendar life and improves energy savings by eliminating wasted burning hours. Lastly, because lamp life is determined when the 50th lamp burns out, theoretically half of the lamps produced will burn out before their rated life is reached, and half the lamps will exceed their rated life. LED Life The industry ideal for LED luminaires is 70 percent lumen maintenance at 50,000 hours. Since LEDs do not fail catastrophically, they might continue to perform at diminishing levels for up to 100,000 hours, but 30 percent lumen depreciation is considered the end of useful life. This ideal can only be achieved with high-quality components and adequate heat dissipation. The popularity of LEDs has resulted in a plethora of inferior products. Always choose LED products tested to the Illuminating Engineering Society’s LM-80 standard. Because the standard was initiated in 2009, there are no LED luminaires that have burned long enough to ensure the test’s accuracy, but LM-80 testing is one way to screen for manufacturers that are committed to quality products, and willing to back them up. Lamp Efficacy At the heart of energy efficient lighting performance is the concept of efficacy. Lumens are used when discussing the total light output from an omnidirectional source, such as fluorescent. Efficacy is the ratio of lumens per watt, analogous to miles per gallon to describe fuel efficiency. Lamps with high efficacy help us to lower lighting power density (LPD), while lamps with low efficacy generally increase LPD. In most of the world, you will see lumens per watt abbreviated as lm/W. In the US you may see LPW.


Slide 24 Let’s see how some different factors might influence the choice of a lamp. The initial price and lifetime of the lamps are factors with a direct bearing on cost. Here’s an example based on US dollars, but it holds true in other countries as well. Costs are in kilo-lumens or per thousand lumens of light output. Initial cost shows incandescent as the clear winner—far lower cost than the alternatives. Slide 25 Life cycle costs show a different story. Efficacy is a measure of the efficiency of the light source. How much light does it generate per watt of power consumed? This impacts the lifecycle cost of the lighting system. Lamps that are cheap to buy may ultimately be expensive if they use a lot of electricity and need frequent replacement. Slide 26 Finally, the operating conditions can have an impact. There are a variety of environmental conditions that affect the life and output of different lamp and luminaire types. Among them: dirt, heat and cold, vibration, corrosive atmospheres, underground burial, lamp position or orientation, and on-off cycling. Slide 27 Let’s look at some of the most common opportunities for improving the efficiency of lamps, which include:

• Incandescent upgrades • Fluorescent upgrades • HID upgrades

To learn about the lamp families and the advantages and disadvantages in more detail in each case, see Lighting 3 – Basic Lamp Families. Slide 25 Life cycle costs show a different story. Efficacy is a measure of the efficiency of the light source. How much light does it generate per watt of power consumed? This impacts the lifecycle cost of the lighting system. Lamps that are cheap to buy may ultimately be expensive if they use a lot of electricity and need frequent replacement. Slide 26 Finally, the operating conditions can have an impact. There are a variety of environmental conditions that affect the life and output of different lamp and luminaire types. Among them: dirt, heat and cold, vibration, corrosive atmospheres, underground burial, lamp position or orientation, and on-off cycling.


Slide 27 Let’s look at some of the most common opportunities for improving the efficiency of lamps, which include:

• Incandescent upgrades • Fluorescent upgrades • HID upgrades

To learn about the lamp families and the advantages and disadvantages in more detail in each case, see Lighting 3 – Basic Lamp Families. Slide 28 Incandescent lamps, which include halogen lamps, are comparatively inefficient. Halogen lamps are more efficient than incandescent, but they still generate a lot of heat and not a lot of light when compared to their power consumption. Where a 100 CRI dimmable light source is required, low voltage halogen can be applied sparingly. Instant on and inexpensive dimming are practical features that add to halogen lamp utility with control systems, and lengthen their life. Compact fluorescent lamps are a possible alternative to incandescent lamps. Here we see an example in dollars. In real situations you may encounter different prices, but the same general principles will still apply. This table illustrates the potential savings from just one lamp. Although the CFL may cost over five times more initially, it lasts ten times as long and pays for itself in just a few months. Caution should be exercised when selecting retrofit “screw-in” replacement options for “A” lamps. Operating position is critical, and enclosing these units (such as in a recessed downlight) will often cause them to overheat and greatly shorten the manufacturer’s estimated lamp life. In addition, screw-in retrofits that can easily be returned to their “A” lamp configuration generally do not comply with energy saving code regulations. This phenomenon is called “snap-back”. Retrofit options that utilize “pin-based” compact fluorescent lamps are a better option and will ensure that a less efficient lamp cannot be installed at end of life.


Slide 29 While they are a considerable cost upgrade, code requirements for reduced lighting power density in retail environments have made low-wattage ceramic metal halide the technology of choice to replace directional halogen sources. Improved CRI, 3–4 times the life of halogen, and wattage reductions greater than 50 percent are significant advantages over halogen. Directional LED sources that replace multi-faceted reflector (MR) and parabolic aluminized reflector (PAR) halogen sources cost more than metal halide, but don't require expensive lamp changes over their 50,000-hour useful life. Instant on and practical dimming options are LED features, not available with metal halide, that help simulate halogen performance and facilitate control strategies. Slide 30 Fluorescent lamps come in different shapes and sizes. You may hear lamps referred to as T8, or T12. What does that mean? It is based on the diameter of the lamp in eighths of an inch. So a T8 lamp is 1 inch in diameter, equivalent to 2.54cm. T12 lamps are fatter and T5 lamps are thinner. Compared with incandescent lamps, fluorescent lamps use less power for the same amount of light and generally last longer, but they are bulkier, more complex, and require recycling because they contain mercury. Generally speaking, the thinner the lamp, the more efficient it is. T12 lamps are big, old, and inefficient, so if you see them, they may represent a good opportunity to upgrade to newer fluorescent lamps. T8 lamps are often chosen because they have the same length and pins, so they can fit in the same fixtures, although new ballasts may be required. Some other lamps may not be the same size. The final choice of replacement with T8, T5, or even thinner lamps will depend on factors such as ambient temperature, existing fixtures, and willingness to replace fixtures if necessary.


Slide 31 HID lamps have similar efficacy to fluorescent lamps, and much better efficacy than incandescent lamps. The color of the lamps and the effect on color rendering varies depending on which type is selected. Older HID lamps may have poorer efficiency, which would make them candidates for upgrading to newer lamps that produce more light per watt. In a factory or warehouse, if you look up and see large round lamps, it’s worth checking how old the installation is. If it is more than 10 years old, it may be a candidate for upgrade. Most importantly, newer technology gives us much higher maintained light levels throughout the lamps life cycle. One disadvantage of HID lamps is that the cold start-up time typically takes 2–10 minutes, and restarting, referred to as a hot restrike, after a shutdown or power interruption takes 7–15 minutes. This means they are not suitable for applications where they need to be turned off frequently. Most importantly, if power is lost, then restored, a backup emergency lighting system is required, so as not to keep people in the dark for an additional 10 minutes after power is restored, waiting for a hot restrike. Another issue is that the color of metal halide lamps shifts as they age and when they are dimmed. In addition, metal halide units produce high levels of UV (ultraviolet) radiation that must be shielded by glass in the lamp or fixture, or the outer jacket. Another hazard is arc tube rupture, which produces hot glass that can cause fires and injuries. This is prevented by using a protected arc tube or an appropriately enclosed fixture, which may be required by the local electrical code. This is an important retrofit issue, since older, non-lensed fixtures will accept non-protected lamps, and it is the responsibility of the installer to take the appropriate precautions. Because of these issues, plus energy efficiency, linear fluorescent lamp usage in warehouse and manufacturing applications has dramatically increased. Slide 32 Let’s turn our attention to the fixtures themselves: The fixture is what holds the light source and its power connections. The design of the fixture influences efficiency because it impacts how the light is dispersed from the lamp. Manufacturer’s specification sheets publish the results of luminaire testing and include “Total Luminaire Efficiency”. Efficiency is the percentage of luminaire lumens relative to bare lamp lumens. The amount of light emitted by the luminaire will always be less than published light output for the lamp. An example of high luminaire efficiency may be a keyless porcelain socket with an “A” lamp. This luminaire could be considered 100 percent efficient, as all of the lamp lumens “escape” from the fixture, but what drawbacks does this high efficiency produce? High efficiency often translates as “glare” in the installed environment. It is critical to observe a luminaire “in action” to properly evaluate the light output and visual comfort.


Slide 33 Finally, let’s consider ballasts. A ballast is required by all the gas discharge lamps we have mentioned so far, including fluorescent lamps and HID lamps. It usually does three things:

• Gets the lamp ready to start by warming up the electrodes • Starts the lamp by injecting a high voltage to initiate the gas discharge • Regulates the current and voltage to the required level until the lamp is turned off

There are various types of ballast, used according to how fast the lamp has to start, and how often it is switched off and on each day. If there is a need to dim the lights, a special type of ballast is required. In fluorescent ballast systems, the main efficiency opportunity is changing from magnetic to electronic ballasts. Magnetic ballasts are an older technology and not as efficient as electronic ballasts. The newer electronic ballasts significantly outperform the older magnetic ballasts. However the lamp and ballast need to be considered together when efficiency improvements are made.

Slide 34 You now know that the type of light source makes an enormous difference in energy usage. Incandescent light bulbs have an efficiency of 5 percent as compared to fluorescent lights with an efficiency of 45 percent. Clearly you will save money every time you replace an incandescent lamp with a fluorescent lamp. However, all lights of the same type are not the same in terms of efficiency. With discharge lamps such as fluorescent and HID, the type of ballast and design of the fixture is very important.


So what type of savings can you get when you put efficient lamps, ballasts and fixtures together? Let’s see two examples. Slide 35 This case study is based on a manufacturer that sought a retrofit lighting solution that would result in significant annual energy savings for the company and to research any tax breaks that may come with the installation. The existing manufacturing facility was lit with 534 high-pressure sodium fixtures. This application was retrofitted with T8 lamps and electronic ballasts. This generated 51 percent annual energy savings of US$55,600, and the company qualified for a tax deduction of US$58,000. Even though there was 40 percent less light, surveys showed that the workers thought that the light level was increased. One reason is that human physiology is affected by whiter light, resulting in greater visual acuity and depth of field. This can be perceived as more light. Slide 36 Here’s another example, implemented at 18 Schneider Electric facilities in North America. Over 10,500 new light fixtures were installed resulting in more than a 50 percent reduction of electrical consumption in some facilities, increasing light quality and reducing heat output. This action alone has resulted in over US$1.1 million per year in electrical savings and tax benefits of over US$300,000. Increasing lighting efficiency is one of the fastest ways to decrease energy costs. Slide 37 The third principle is efficient control. A high efficacy fluorescent lamp still wastes energy if it is left on when it is not required. Let's look at some opportunities, which include:

• Switches • Occupancy sensors • Timers • Keycard controls • Scheduling • Centralized control • Dimmers • Daylight harvesting • Twilight switch

Slide 38 The simplest lighting control device is the on/off switch! Unfortunately, they rely on people to use them. Automatic control of lighting is more reliable. One simple solution is occupancy sensors, also called movement sensors or presence detectors. These devices detect motion or heat when a person is in the space and turn lights on automatically. After a period where no occupancy is detected, the lights are turned off. They can be mounted on walls or ceilings. Wall-mounted presence detectors are ideal for situations where


occupancy is variable in relatively small spaces, such as individual offices, classrooms, storage cupboards, and restrooms. Ceiling-mounted occupancy sensors can be useful in larger conference rooms, open-plan offices, or warehouses where occupancy sensors can be used aisle by aisle, to only illuminate the areas that are in use. Slide 39 Timer switches are another simple solution. Here, the person initiates turning the light on, and it turns off automatically after a certain period. These are suitable where occupancy is variable and typically for only short periods, such as corridors and restrooms. Slide 40 Keycard controls are a popular solution for hotel rooms. The lights and other electrical sockets in the room are controlled by a master switch near the door. The user has to place their keycard in the receptacle for the electricity in the room to be enabled. When the user leaves the room, he takes the keycard with him, and the lights and sockets are turned off. This avoids the waste associated with hotel guests leaving lights and TVs on when they are not in their rooms. Slide 41 Scheduling can be used to provide time-based control for a space. It can be implemented by room-level controllers, or by programmable breakers at the switchboard, by dedicated lighting control solutions based on networks such as DALI or KNX, or by a full building automation system. Scheduling ensures that lights are turned on before occupants are expected to arrive, and turned off after they leave. In spaces where occupancy sensors are impractical but there are clearly defined times of use, this can make large savings on wasted energy. Slide 42 Dedicated lighting control solutions and building automation systems also allow centralized control that’s not automated. From a control panel an operator can turn on lights in any part of the building, and turn them off again later. That can be useful for security, and for efficient lighting control in sites where the occupancy times are variable and can’t be scheduled. The operator can turn off all lights in the building when the last person signs out, without having to walk around and do it manually. Slide 43 A dimmer is a device used to vary the level of lighting from one level of output to another. Dimming is used when the maximum light output from the lighting is not required at all times. That can be useful in auditoriums and meeting rooms, for comfort and ambience as well as efficiency. Not all dimmers and light sources operate effectively from 0–100 percent, but often a specific range of output can be regulated. They can be manually or automatically controlled as part of a daylight harvesting strategy. Additionally, not all light sources can be dimmed, and some sources might be costly and impractical to dim. Slide 44 Daylight harvesting applies when the space is partially lit with natural light through windows or skylights. A photo-electric sensor is used to detect the level of light in the space. If the light level exceeds requirements, lamps are dimmed until the desired level is obtained. Normally this requires the lights to be electrically organized on separate circuits, so that the lamps that are nearest the window are dimmed the most or turned off entirely, while lamps that are within the body of the room remain on.


Some movement sensors are combined with photo-electric sensors to combine the benefits of both technologies in one product. As the sensor detects occupancy, it also checks the light level before turning on the lights.

Outdoor light

Internal dimming

Lux level Lighting

Slide 45 A similar solution to daylight harvesting is the twilight switch, often applied to exterior lighting. The sensor detects the outside light levels and switches on when the light is not sufficient, off when the light increases. This saves energy by ensuring those lights are not on in the day when they are not required, and improves comfort and security because people do not have to find a switch in the darkness. However it may not be optimal if the lights are not required the whole time from dusk until dawn. In such a case, a combination of twilight sensing and a timer, other scheduler, or movement detector would be more efficient. Retrofit of lighting control solutions can be made more complicated by the existing wiring of the plant. If many lights are on the same circuit, it may not be possible to control the desired zones. Slide 46 Lamps with a long start and restrike time, such as the HID lamp family, are not suitable for lighting control applications that save energy by turning lights off and on frequently. Sensors are available for HID systems to reduce light levels to 50% when areas are unoccupied, so they can


be rapidly ramped up without any strike time. However fluorescent lights would be more appropriate. Doesn’t turning lamps off and on frequently shorten their life? Yes, increased switching will shorten the overall lifetime of the lamp in operating hours. However, it usually increases the total calendar life, and the energy savings can often considerably outweigh the lamp costs. Slide 47 To estimate the savings from a lighting retrofit, we need the following information: First we need to estimate the existing operating hours of the system. We may be able to get this from the operating schedule of the building, but this is not always reliable, unless there is some way to confirm that the lights are reliably turned off when the building is unoccupied. A simple way to check is with a lighting logger. This is a temporary device that can be mounted on the ceiling of the room. It records motion in the space and whether the lights are off or on. Here we see an example output. We can see that on Tuesday, the lights stayed on all night, even though no-one was present. We can also see significant period during Thursday where lights were on but no occupancy was sensed. Based on this type of data, we can reach conclusions about the true operating hours that exist today, and what might be achievable with lighting control. Measuring the actual lighting level and comparing it to the required level will allow us to determine if the space is over illuminated, and estimate the potential savings from de-lamping. Finally, auditing the existing lighting system for the rating and total number of lamps and ballasts will allow us to calculate the total consumption of the lighting system today, and how much it might be reduced with new lamps and ballasts. You can learn more about the calculations used to estimate the savings in other classes in our lighting series. For now, note that each of these factors is interrelated. For example, if actions are taken to remove lamps or retrofit new, more efficient lamps, that has to be taken into account when calculating the impact of lighting control. At the new efficiency level, it may take a long time for an occupancy sensor to pay for itself.


Saturday Lit

Slide 48 Another factor that can be taken into account in the calculations is the impact that lighting has on heating and cooling. Lights generate heat, so they help to warm a space during the winter, but tend to increase the cooling requirements during the summer. When efficiency is improved, those impacts are reduced: less warming in winter, less cooling need in summer. You may think that over a period of a year, those two factors would balance out. This is not necessarily the case. Some climates are biased towards greater heating or cooling needs. Secondly, heating often relies on gas, while cooling relies on electricity and can be much more expensive. Thirdly, many buildings contain so many heat sources such as people, equipment, and lights, that they require cooling all year round. Slide 49 Congratulations! You have completed your first energy efficient lighting project. All of the luminaires and controls have been installed and energy bills should be reduced, right? The job is not completed until the systems have been commissioned and a plan formulated for continued maintenance. This is the fourth principle for efficient lighting.

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One of the most common reasons that building owners do not realize the predicted savings is that they or the building occupants do not understand the system. How many times is an occupancy sensor disabled by a building occupant because it turns the lights off when they are in the space? How often is a time clock over-ridden for a unique, one-time circumstance and never reset? Slide 50 Part of the overall project is the commissioning of the system. This simply means that all equipment is calibrated and functioning as the system was intended. This prevents user tampering due to distracting light changes during business hours. Here’s an example: It’s a beautiful summer’s day and the office building is flooded with natural sunlight. A cloud momentarily passes over the sun and all of the office fixtures suddenly turn to full on. The sun emerges at full brightness 20 seconds later, and the office lights quickly turn off or dim down. This sudden and drastic change in artificial light can prove distracting in an office environment and may result in a user taking action to disable the system. Proper commissioning would calculate a time delay to accommodate such common occurrences and would incorporate a gradual ramp up/ramp down of the light levels so as not to be a distraction to workers. Slide 51 Keeping lamps and fixtures clean and replacing burned-out lamps are important tasks to maintain the efficiency of an installation. However, maintenance effort can be costly, so using it wisely will help to manage the operating expenses. One potential method is group relamping. We already heard that lamps have an average rated life, and also lose efficacy over time. Knowing the average rated life means you can calculate, on average, how many lamps in your installation will require replacement each year. Number of Annual Replacements = Number of fixtures × Lamps per fixture × Operating hours / Average rated lamp life. Consider a building with 2,000 fixtures, each containing three lamps, that is open from 7 am–7 pm, Monday–Friday. The average rated lamp life is given as 25,000 hours. Operating hours = 12 hours per day × 5 days per week × 52 weeks per year = 3,120 hours. Number of annual replacements = 2,000 x 3 x 3120 / 25,000 = 749 replacements per year. Slide 52 It can be quite costly in terms of effort if each time an individual lamp burns out, the maintenance staff are called out to replace it, because each replacement requires the staff to locate the fixture, gain access, remove the lamp, fit the new one, and dispose of the old one correctly. The overhead of effort in each replacement is quite high. Also, older lamps that have declined in efficacy will be consuming energy in your installation and not providing much light. An alternative is group relamping.


Slide 53 A group relamping strategy does not wait for lamps to burn out before replacing them. Instead, all the lamps are replaced at one time, when they have reached some percentage of their rated life. 70 percent is recommended by the United States Environmental Protection Agency. This reduces the loss of light due to lamp failure, and the time, effort and complaints associated with spot replacement of lamps. The few lamps that fail between group relamping cycles can be spot-replaced as needed. Here is how to calculate the group relamping interval: Group relamping interval = Average rated lamp life × Threshold percentage / Annual operating hours = 25,000 × 70% / 3,120 = 5.6 years


Slide 54 Okay, let’s round that down to five years. Based on a five-year relamping interval, on average, you will be replacing 6,000 lamps / 5 years = 1,200 lamps per year. Let’s see what difference that makes to the maintenance budget. These figures for material and labor cost are taken from a US Environmental Protection Agency study of lighting maintenance published in 1995. Current values are likely higher, but the same principles apply. Labor per lamp is much higher for spot relamping because of the effort to organize and perform individual lamp replacements. Group relamping costs less per lamp because many lamps are replaced at one time. This example shows group relamping has the potential to reduce the maintenance effort in this case by 65 percent. Group relamping is also an opportune time to clean luminaire reflectors and lenses, which will help maximize light output and improve their appearance. Slide 55 Today, we explored the four principles for efficient lighting design:

• Determine how much light is needed • Use efficient luminaires • Use lighting controls • Commission the system to ensure proper automation

We discussed required lighting levels as a factor in evaluating over-illumination. We identified the basic lamp families, and listed opportunities to upgrade lamps, ballasts and fixtures. We saw a variety of possibilities for improving efficiency with lighting control. We looked at the impact of


lighting upgrades on HVAC, and ended by exploring the benefits of group relamping as a way to reduce maintenance effort. By familiarizing ourselves with these items, we can now begin to look at the lighting in our buildings in an informed way. By taking the necessary steps to increase the lighting efficiency in our buildings we can quickly decrease the related energy costs. To learn more about efficient lighting practices, please consider participating in the other courses in our Lighting series. Slide 56 Thank you for participating in this course.

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