Lesson: Lighting Levels & De- Lamping Assessment Estimated Time 90 minutes Lesson Overview Standards: CA Science Investigation & Experimentation: 1.a, b, d & l CCSS Math Quantities: 1, 2, 3; Reasoning with Equations & Inequalities: 3; Modeling with Geometry: 3 CCSS ELA Literacy Language: 6; Writing Standards for Literacy in History/Social Studies, Science, and Technical Subjects: 7 CA Tech. Standards, Energy and Utilities Industry Sector 5.0 Problem Solving and Critical Thinking: 5.1, 5.3; Public Utilities Pathway: D3.1, D3.2; Technical Knowledge and Skills: 10.1 CA Career Technical Education Model Curriculum Standards Foundation Standards Academics: 1.2 Objectives: Students will be able to: Use a light meter to measure the illuminance of classroom lighting Identify de-lamping opportunities and calculate energy savings based on the recommendations. Handouts 4.2.1 IES Recommended Light Levels 4.2.2 Light Meter 4.2.3 De-lamping Worksheet Materials Light meters (one per small group) Additional Resources Lighting Design Lab De-lamping article: http://www.lightingdesignlab.com/articl es/delamping/delamping.htm PG&E tool lending library: http://www.pge.com/mybusiness/edusa fety/training/pec/toolbox/tll/ Illuminating Engineering Society: http://ies.org De-lamping (i.e., the removal of fluorescent lamps from a fixture) is a cost-effective way to save energy while ensuring that adequate lighting still exists. In this lesson, we utilize a light meter to identify opportunities for removing lamps while still maintaining adequate light for the classroom. Through a hands-on assignment, students will conduct an assessment and calculate energy savings based on their recommendations for de-lamping. KEY WORDS De-lamping: removal of one or more fluorescent lamps from a fixture that does not prevent the remaining lamps in the fixture from operating Foot-Candles: a measure of illuminance, one foot-candle equals one lumen per square foot of surface area Illuminance: the amount of light arriving at a surface Light Meter: an instrument used to measure the amount of striking or reflecting from an object Lumen: a measure of light output from a light source Over-Lit: a space that receives more light than is needed Parallel Circuit: a type of wiring where the electric loads, or users of electricity (e.g. light bulbs, electronic equipment, etc.), each run along its own circuit path, thus reducing the disruption of the flow of electricity Series Circuit: a type of wiring where the circuit is similar to a single looping path. When you remove one bulb, all the lights go out Daylighting: the practice of using sunlight to illuminate indoor spaces
PREPARATION Prior to this module, the instructor should review background material on lighting and de-lamping. Read through the handouts and become familiar with using a light meter and IES recommendations. Also, the instructor should have at least one light meter, but preferably one light meter per small group. This may require checking out the light meters 2 weeks in advance. Check your local utility to see if they have a tool lending library. If performing a full audit of the school, the instructor may want to arrange staff or volunteers to accompany small groups as they inventory lighting levels around the campus. SETTING THE STAGE The level and quality of a school's lighting can have a direct impact on learning. When rooms have dull, gray light, it is difficult to see and to learn. The amount of light needed for a task depends on a number of factors, including: The age of the person doing the task. The younger the person, the less light is needed. The speed with which the task is to be done. The slower the task can be done, the less light is needed. The size of the item or the task. The larger the item, the less light is needed. The amount of contrast between the item and the background. The greater the contrast, the less light is needed. Experts have calculated what the lighting levels should be on the work plane for each type of room in a school or business. These levels are specified in building codes that are followed by architects as they design a facility. Typical light levels are specified in Handout 4.2.1. Many of our schools, businesses, and office buildings are over-lit. This means that more light is generated from the lights in the ceiling than is needed for the tasks conducted beneath them. This means that energy is being wasted to produce unnecessary light. There can be a variety of reasons as to why these areas are over-lit, including: Overhead fixtures originally designed for T12 lamps have been retrofitted with T8 lamps, which may have a greater light output. Over the time the space became used in a different manner than which it was originally intended, but the lighting remained the same. Energy was much cheaper a couple of decades ago, so having extra light fixtures didn t hurt the pocketbook like it does today.
Light output from a lamp is measured in lumens. For example, a four foot 32 Watt T8 lamp has a light output of around 3,000 lumens, which is very bright. In contrast, a 100 W incandescent light bulb produces around 1,750 lumens. A lumen is the measure of light output right at the lamp, but for the most part that s not where we need the light to read, write, and do other tasks. Light must first travel from the lamp to a desktop, to the gymnasium floor, or some other surface before it becomes useful to us. There are a number of things that diminish the light as it travels from the lamp to the desktop. Dust in the air, the lamp s fixture, and other obstructions reflect away or diffuse the light. We therefore have another measurement, called illuminance, to tell us how much of the light from the lamp is actually getting to where we want it. Illuminance tells us how well an area is illuminated. Illuminance is measured in foot-candles. One foot-candle equals one lumen hitting one square foot of a surface. We can measure illuminance with a device called a light meter. The light meter can tell you how many foot-candles of light are hitting a desktop, the gym floor, or other surfaces where you need adequate light. The Illuminating Engineering Society (IES) conducts research into appropriate light levels and is a recognized authority on lighting design. The IES has published their findings on recommended light levels required for various tasks. Provide a copy of Handout 4.2.1 to each student in the class. What is the recommended illumination for regular deskwork in a classroom? 30 Foot-candles. If the light meter tells us that there is too much light, we may be able to remove lamps to bring light levels down to the IES recommended levels and save energy. De-lamping is a process of removing one or more fluorescent tubes from a fixture that does not prevent other lamps in the fixture from operating. We typically find two or more lamps in a fixture driven by one ballast. Removing lamps causes no risk to the ballast. However, the remaining lamps will be powered at a higher level. The life of the lamp may be marginally shortened when more than one lamp is removed. It is important to note that before delamping, determine whether lights are wiring in series or in parallel by asking the building maintenance staff. Ballast wiring is either in series or in parallel. Series and parallel are two different ways that circuits can be wired and connected. To simplify, you can think of series wiring as a single looping path, like a string of a Christmas tree light. When you remove one bulb, all the lights go out. This is because when you remove one of the bulbs, you re opening up the circuit and thus disrupting the flow of the electricity. Parallel wiring provides individual connections to all the bulbs so that if one lamp is removed, the current can take an alternative route, and thus does not disrupt the flow of the current. This is analogous to overhead lights in a hallway where the lights are controlled by a switch. Even if one light goes out, the other lights stay on. Most magnetic ballasts (inefficient T12s) are series wired while electronic ballasts (efficient T8s) have both series and parallel wiring. If the ballast wiring is in series, delamping is discouraged,
as it will cause the remaining lamp(s) to flicker, or produce very little light. Delamping is only recommended for ballasts that are wired in parallel. Here are some rules of thumb for de-lamping: De-lamping is best done with T8 lamps, and not T12s. This is because T12s utilize magnetic ballasts, which are wired in series. The removal of one lamp in a series wiring will prevent other lamps in the fixture from operating properly. For T12s, the best thing to do is a retrofit with T8s. Check to see if the T8 lamps electronic ballasts are wired in series or parallel, ideally by asking your school Maintenance and Grounds staff or by removing a bulb, since electronic ballasts can operate on both. If it s series wiring, you have the option of changing the wiring so that it is parallel. Otherwise, delamping is discouraged. Measure light levels at night or with the windows covered. This is to make sure that any delamping will still leave adequate light during darker times of the day or year. Measure light levels throughout the working space and de-lamp only those areas that have light levels higher than levels recommended by the IES. Entryways, hallways, and storage areas do not need the high lighting levels that work areas require. In a classroom or office, the IES considers two, 4-foot T8 lamps for every 64 square feet to be adequate. Do not de-lamp the fixture if in doing so reduces the number of lamps to fewer than two 4-foot lamps for every 64 square feet. ACTIVITY 1: MEASURING CLASSROOM LIGHT LEVELS 1. Turn on all of the overhead lighting and shade the windows (if possible). Have students look around the room. Does the illumination appear to be uniform throughout the entire classroom? Are there areas of the classroom that appear brighter than other areas? 2. Divide the class into their small audit groups. Provide each group with a copy of Handout 4.2.2 How to Use a Light Meter. 3. Next, demonstrate the use of the light meter to the class, having students refer to Handout 4.2.2 as you set up the meter. Place the meter on a desk just underneath a ceiling light fixture and turn it on (do not remove the sensor cap just yet). Make sure the meter is set to measure foot-candles from fluorescent lighting in the 0-199.9Fc range. Now remove the sensor cap and take a few steps back to avoid shading the sensor. How many footcandles are there? 4. Now have students refer to Handout 4.2.1. Does the light meter show that it is over-lit, under-lit, or about right? 5. If the overhead lighting is on multiple circuits (switches), turn off one of the circuits and repeat the demonstration. Now what is the meter reading?
6. What other sources of light are there that may add to the illumination of the room? 7. Could the room be re-arranged so that some of the lamps could be turned off? 8. Have students think about other parts of the school, such as classrooms, hallways and other common areas. Are there parts of the school that may be over-lit? 9. Explain to the class that they will now conduct an assessment of the classroom to identify opportunities for de-lamping. First thing students will do is to create an illumination map of the classroom. On the chalkboard, draw a rough floor plan of the classroom, and over it super-impose the banks of fluorescent light fixtures in the ceiling. See example below: 10. Turn all the lights back on. Provide each group with a light meter. Next, assign each group to a region in the room and ask that they take at least 4 readings in that area of the classroom. Remind students to use Handout 4.2.2 to use the meter. Meter readings should be taken at the level where the light is needed, for example, desk level. Upon completion of each reading, have one individual from each group come up to the chalkboard and write down their reading in its proper location on the class map. By the end of this exercise your map should look something like this (but with personalized meter readings):
11. On your map, label each light fixture with it s own number (e.g., #1, #2, etc). Discuss the map with the class. Is the illumination in the classroom generally too high, too low, or just right? Are there opportunities to de-lamp some of the fixtures? 12. How many total lamps could be taken out, and from which fixtures? To calculate the number of lamps that can be removed, divide the measured foot-candles by the number of lamps in the room; this yields illuminance per lamp. Next, refer to Handout 4.2.1 and consider the recommended Illuminance for the space. Dividing the recommended illuminance by the measured foot-candles per lamp gives us the number of bulbs needed to meet the recommended levels. Circle the fixtures on your map that are recommended by the class for de-lamping. Be sure to evenly distribute lamps to be removed to retain consistent lighting. 13. Provide each student with a copy of Handout 4.2.3. Students will use this worksheet and results from the mapping project to calculate the estimated savings based on recommended de-lamping. 14. Upon completion of the assignment, discuss students calculations and recommendations. What are some other savings tips to share with the rest of the class? ACTIVITY 2: SCHOOL LIGHTING LEVELS INVENTORY Activity Inform student groups that they will now conduct a lighting level assessment of the school. Distribute Handout 3.3.4 the Light Levels Inventory. Review the Procedures with students and clarify if needed. Provide each group with a light meter. Next, assign the groups to a different region of the school to conduct light meter readings. Have student groups visit different types of rooms within their region record their readings on the Light Levels Inventory worksheet. Ask groups to return at a certain time to enter their findings into the Energy Audit Reporting tool and to discuss delamping and daylighting opportunities discovered around the school.
Handout 4.2.1 ILLUMINATING ENGINEERING SOCIETY (IES) RECOMMENDED LIGHT LEVELS Name Date 1 1 Table from Illuminating Engineering Society (IES)
Handout 4.2.2 HOW TO USE A LIGHT METER What is a Light Meter For? A light meter measures (in foot-candles of light) the light level of a given area or work surface. It tells how much light is actually reaching the work surface where it is placed and can be used to determine whether there is too much or too little light there. What You Can Do with a Light Meter Measure light levels at different distances from a source to determine appropriate light levels. Measure the light in different areas of the school to find out if they are appropriately lit. Compare light levels for various tasks. In general, less light is needed when the task can be done at a slow rate or does not require accuracy, when the contrast between the item and the background is great, and when the person doing the task is young. How To Use the Light Meter 2 When using the light meter, put the meter at the surface level where the work takes place. For example, in the hallway, meter readings should be taken on the floor because that is where the work (walking) takes place. In the classroom, readings should be taken on the desk because that is where the work takes place. Before getting the lighting level measurements, make sure all the window blinds are closed in the classroom to ensure that we have enough light, even when it s dark out. Important: Keep Light Meter sensor covered until ready to take reading. When taking the light level reading, make sure to stand clear of the sensor or you will affect the light level. First, make sure that the light meter sensor is covered. Check that the Range switch is set to A: 0 to 199.9 Fc (foot-candles), unless you expect a high lighting level of more than 200 Fc. Turn on the Power button. Remove the sensor cover. Read the lighting level. Readings should be taken at the level where the work occurs. Careful not to shade the sensor with your shadow. Care and Storage To replace battery: The battery compartment located on the back lower section of the meter and may be opened with a small coin or screwdriver. Replace the battery with a heavy-duty 9V battery. Properly dispose of the used battery. 2 Image of light meter from Extech
Handout 4.2.2 DE-LAMPING WORKSHEET Date: Room: Surveyor Name(s): Activity: Measure illuminance for your classroom and decide whether the room is over-lit, has appropriate lighting, or is under-lit. If it is over-lit, determine the number of lamps to be removed. To calculate the number of lamps that can be removed, divide the measured foot-candles by the number of lamps in the room; this yields illuminance per lamp. Next, refer to Handout 4.2.1 and determine the recommended Illuminance for the space. Divide the recommended illuminance by the measured foot-candles per lamp to determine the number of bulbs needed to meet the recommended levels. Measured Illuminace (foot-candles) Number of Lamps Illuminance per lamp Recommended Illuminance # of lamps needed # of lamps to be removed A B C = A/B D E = D/C F = B E Ex. 60 fc 24 lamps 2.5 30 12 lamps 12 lamps Record lighting fixtures, wattages, and hours of operation for each light fixture that you recommend for delamping in the chart below, using the Master Lighting Chart as a reference, and then answer the following questions. Lamp Type # of Fixtures # Lamps / fixture Fixture Watts (W) Estimated Operating Hours/wk Energy Used/wk (kwh) Recommended # Lamps Remaining in fixture Delamped Fixture Watts (W) Energy Used/wk (kwh) by Delamped Fixtures A B C D E =(AxCxD)/ 1000 F G = (C/B)*F H = (AxGxD) /1000 48 T8 12 3 73 40 35.04 2 49 23.52
Handout 4.2.2 De-Lamping Calculations 1. How much energy will delamping save per week? kwh 2. How much energy will delamping save per year assuming 36 weeks of annual use? kwh 3. By what percent will energy consumption be reduced from overhead lighting? % 4. What will the energy cost savings be per year? (Use your school s cost per kwh or the SMUD average of $0.12 per kwh) $ 5. How much CO2 will be prevented from entering the atmosphere per year? (SMUD Emissions Factor: 0.66 lbs CO2 per kwh) lbs of CO2 6. What other recommendations do you have to reduce lighting energy consumption in this room? T8 Lighting Chart 3 Lamp Type lamps/ fixture Fixture Watts F24" T8 1 lamp 1 15 F24" T8 2 lamp 2 28 F24" T8 3 lamp 3 41 F24" T8 4 lamp 4 57 F36" T8 1 lamp 1 23 F36" T8 2 lamp 2 42 F36" T8 3 lamp 3 62 F36" T8 4 lamp 4 84 F48" T8 1 lamp 1 25 F48" T8 2 lamp 2 54 F48" T8 3 lamp 3 73 F48" T8 4 lamp 4 94 F96" T8 1 lamp 1 57 F96" T8 2 lamp 2 98 F96" T8 3 lamp 3 167 F96" T8 4 lamp 4 219 T12 Lamps Lamp Type Lamps/fixture Watts per Fixture 24" T12 1 lamp 1 28 24" T12 2 lamp 2 56 24" T12 3 lamp 3 62 24" T12 4 lamp 4 112 36" T12 1 lamp 1 32 36" T12 2 lamp 2 65 36" T12 3 lamp 3 115 36" T12 4 lamp 4 136 48" T12 1 lamp 1 40 48" T12 2 lamp 2 72 48" T12 3 lamp 3 112 48" T12 4 lamp 4 142 72"T12 1 lamp 1 76 72"T12 2 lamp 2 122 72"T12 3 lamp 3 202 72"T12 4 lamp 4 244 96" T12 1 lamp 1 75 96" T12 2 lamp 2 128 96" T12 3 lamp 3 203 96" T12 4 lamp 4 256 34 T12/U-bend/1 lamp 1 34 34 T12/U-bend/ 2 2 66 3 Courtesy of Stan Walerczyk, Generic Best Practices Lighting Report, October 2007