Module 5 Lighting Calculations
Contents Determining Average Illuminance Average Illuminance Equation The Lumen Method Determining the Illuminance at a Point-Direct Component (Point-by-Point Method) Computer-Aided Lighting Calculations
Determining Average Illuminance The standard lumen method formula is also used to calculate average illuminance levels when the Coefficient of Utilization (CU’s) are taken from a utilization curve.
Average Illuminance Equation Φ(TOTAL) x CU x LLF Awp Ewp General equation for illuminance in space Ewp = average maintained illuminance on the work plane Φ(TOTAL) = total system lamp lumen output CU = coefficient of utilization LLF = light loss factor Awp = area of the work plane
The Lumen Method Means of determining the average workplane illuminance within a space with a given number of luminaires Components Total system lamp lumen output Coefficient of utilization Loss factor determination Calculated illuminance Spacing criteria
Total System Lamp Output Lamp lumen output is the total initial luminous flux that the lamps emit as specified by the manufacturer. Example 1: In an office space 3m x 4.6m with a 2.6m ceiling height, there are 2 recessed fluorescent luminaires. Each luminaire has three (3) 32W 48” T8 fluorescent lamps. Manufacturer’s data shows that the initial lumen output of the lamp is 2900 lumens. What is the total lamp lumen output Φ(TOTAL)? Φ(TOTAL) = 2 luminaires x 3 lamps/luminaire x 2900 lumens/lamp = 17,400 lumens
Coefficient of Utilization (CU) Factors influencing coefficient of utilization: The efficiency of the luminaire The luminaire distribution The geometry of the space The reflectances of the room surface Each luminaire has its own CU table specific to that luminaire’s light distribution and efficiency. CU values are listed in tables for different room geometries and room surface reflectances.
Coefficients of Utilization (CU) Coefficient of utilization is based on room cavity ratio (RCR) RCR is five (5) times the ratio of total vertical surface area to total horizontal surface area within the room cavity, and therefore indicates the relative space proportions. Where, hRC = Room cavity height L = Length of the room W = Width of the room
Coefficients of Utilization (CU) Cavity ratios : Ceiling cavity ratio – is the space between the ceiling and luminaire plane computed using the equation below in relation to room cavity ratio: Floor cavity ratio – is the space between the workplane and the floor computed using the equation below in relation to room cavity ratio:
Coefficients of Utilization (CU) Cross section of a room showing room cavities.
Coefficients of Utilization (CU) For a given room, the cavity ratios are in direct proportion to their respective cavity heights. For the case where the luminaires are mounted on the surface of the ceiling or are recessed into the ceiling, the ceiling cavity ratio is zero. Since the coefficient of utilization is based on the room cavity ratio, it is necessary to treat this cavity as if there were a ceiling surface at the luminaire plane and a floor surface at the workplane level. It is necessary to convert the actual ceiling reflectance into an effective ceiling cavity reflectance (pCC) and the actual floor reflectance must be converted to an effective floor cavity reflectance (pFC).
CU Determination Using Example 1 above, the following steps should be followed in calculating the coefficient of utilization. Step 1. Determine the room cavity ratio using the equation below Room cavity height (hRC) = Luminaire height – Workplane height Assuming a workplane height of 0.76m (typical desk height) hRC = 2. 59 m – 0.76m = 1.83m
CU Determination In this example, the luminaires are recessed in the ceiling so the luminaire height is the as the ceiling height. Computing the room cavity ratio, we have: RCR = 5 x Room cavity height (Length + Width) Length x Width RCR = 5 x 1.83m (3.05m + 4.57m) 3.05m x 4.57m RCR = 5
CU Determination Step 2. Since the Lumen Method considers what occurs only within the room cavity, the ceiling and floor cavities are replaced with their effective reflectances. To find the effective reflectance of a floor or ceiling cavity, find the floor cavity ratio and ceiling cavity ratio using the equations below
CU Determination Step 3. Find the effective cavity reflectances using cavity surface reflectances. The surface that is opposite the opening to the cavity is called the base cavity. The base reflectance, the wall reflectances, and the cavity ratio determine the effective cavity reflectance. Using the IESNA Lighting Handbook, look for the cavity reflectances and cavity ratios. For the ceiling cavity, the base reflectance is the actual ceiling surface reflectance while the floor cavity, the base reflectance is the actual floor surface reflectance.
CU Determination Step 4. Once all room cavity reflectances and the room cavity ratio are known, the CU value can be determined by selecting the appropriate value from the luminaire’s CU table. Continuing with Example 1, the following assumptions are made after consulting the IES Lighting Handbook Table on Effective Reflectances: Effective Ceiling Cavity Reflectance, CC = 0.70 Wall Reflectance, W = 0.50 Effective Floor Cavity Reflectance, FC = 0.20 RCR = 5 (calculated in Step 1)
CU Determination CU = 0.50, which means that 50% of the lumens given off by the lamps reach the workplane and the other 50% are absorbed by the luminaire or the room surfaces and never reach the workplane.
Coefficients of Utilization for Some Luminaire
Light Loss Factor Two types of Light Loss Factor (LLF) Recoverable Non-recoverable Total Light Loss Factor (LLF) is the product of the individual light loss factors, recoverable and non-recoverable
Light Loss Factor Recoverable LLF Lamp Lumen Depreciation (LLD) Lamp Burnout Factor (LBO) Luminaire Dirt Depreciation Factor (LDD) Room Surface Dirt Depreciation Factor (RSDD) Area of workplane (AWP)
Lamp Lumen Depreciation The lamp lumen depreciation factor is the fraction of initial lumens at a specific time during the life of the lamp Lamp lumen depreciation comes from aging and dirt accumulation on lamps, reflectors, lenses and room surfaces. Most lighting designs base calculations on “maintained” as opposed to “initial” lamp lumens
Lamp Burnout Factor If lamps are not replaced immediately after burnout, a lamp burnout factor should be applied to any analysis of the system. Unreplaced burned-out lamps will vary in quantity, depending on the kind of lamps and the relamping program used. This factor is simply the ratio of the number of lamps that would be burning o the total number of lamps in the system.
Room Surface Dirt Depreciation Room Surface Dirt Depreciation Factor (RSDD) is influenced by: The amount of dirt in the environment The room cavity ratio (proportions of the room) Type of lighting equipment used
Room Surface Dirt Depreciation
Luminaire Dirt Depreciation Luminaire Dirt Depreciation Factor (LDD) depends on three (3) aspects of the situation: The amount and type of dirt in the environment (a clean office environment compared to a dirty manufacturing facility) The type of luminaire used The expected cleaning cycle for the equipment
Luminaire Dirt Depreciation
Area of Workplane Is the area of the entire workplane, which is typically the same as the floor area Illuminance will be greatest near the center of the room and slightly less toward the walls for a given uniform layout of luminaires
Light Loss Factor Non-Recoverable LLF Luminaire Ambient Temperature Factor Heat Extraction Thermal Factor Voltage to Luminaire Factor Ballast Factor Ballast Lamp Photometer Factor Equipment operating Factor Lamp Position (Tilt) Factor Luminaire Surface Depreciation Factor
Luminaire Ambient Temperature Variations in temperature, above those normally encountered in interiors, have little effect on the output of incandescent and high intensity discharge (HID) lamps, but can have a significant effect on light output of fluorescent lamps
Heat Extraction Thermal Factor Heat extraction factor is the fractional lumen loss or gain due to airflow Airflow has an effect on lamp temperature and lamp lumens especially those air handling fluorescent luminaires which are integrated with the HVAC system as a means of introducing or removing air from the room
Voltage to Luminaire Factor High or low voltage at the luminaire will affect the lumen output of lamps High voltage condition will increase the lumen output of lamps over their rated output Low voltage condition will reduce the lumen output The rate of change of lumen output with a voltage change varies with each light source, but has the greatest effect on incandescent lamps
Ballast Factor Ballast used for a specific application is usually different from the ballast used to determine the rated lumen output for a lamp Ballast factor corrects this difference to maintain the arc within the lamp Ballast factor is the ratio of the lamp lumens generated on commercial ballasts to those generated on the test quality ballasts . The ballast factor for good quality fluorescent ballast is nominally is 0.95while electronic ballasts can have ballast factors ranging from 0.70 to 1.28
Ballast Lamp Photometer Factor Ballast Lamp Photometer Factor adjusts the lumen output when a different lamp ballast combination is used other than the manufacturer’s set-up Temperature effects within the luminaire may cause the lamp to operate at less than the rated output and should be considered in the determination of the luminaire’s coefficient of utilization
Equipment Operating Factor Effects on the lumen output of lamps caused by the ballast, the lamp operating position and the effect of power reflected from the luminaire back onto the lamp are collectively incorporated into the equipment operating factor
Lamp Position Factor Lumen output is sensitive to the lamp orientation especially for high intensity discharge (HID) lamps when they are tilted from their rated horizontal or vertical position Lamp position factor adjusts the lumen output and is defined as the ratio of luminous flux in the given operating position to that in the test position
Luminaire Surface Depreciation Luminaire surface depreciation results from adverse changes in metal, paint and plastic components that result in permanently reduced light output Luminaire surface depreciation factor adjusts light output to original reflectance
Loss Factor Determination Example 2. LLF Determination Detailed description of the determination of the light loss factors can be found in the IESNA Lighting Handbook. The product of the recoverable factors and the non-recoverable factors will give us the total light loss factor. Recoverable Factors Lamp Lumen Depreciation (LDD) 0.90 Lamp Burnout Factor (LBO) 1.00 Luminaire Dirt Depreciation Factor (LDD) 0.94 Room Surface Dirt Depreciation Factor (RSDD) 0.96
Loss Factor Determination Nonrecoverable Factors Ballast Factor 0.93 Other Non Recoverable Factors 1.00 LLFTOTAL = Recoverable Factors x Nonrecoverable Factors LLFTOTAL = 0.90 x 1.00 x 0.94 x 0.96 x 0.93 x 1.00 LLFTOTAL = 0.75 Total Light Loss Factor (LLF) is 0.75, which means that 25% (100%-75%) of the luminous flux that might otherwise reach the workplane is lost due to ballast factor, dirty luminaires, room surfaces, and aged lamps.
Calculated Illuminance Φ(TOTAL) x CU x LLF Awp Ewp At this point it is possible to calculate the illuminance on the workplane: Ewp = average maintained illuminance on the work plane Φ(TOTAL) = total system lamp lumen output CU = coefficient of utilization LLF = light loss factor Awp = area of the work plane
Calculated Illuminance Substituting all the computed values in Example 1and using the equation for average illuminance on the workplane, we have: EWP = 17,400 lm x 0.50 x 0.75 3.05m x 4.57m = 468 lm/m2 or 486 lux (Maintained) The average initial illuminance on the workplane can be determined by substituting only the non-recoverable light loss factors for the total light loss factor. EWP = 17,400 lm x 0.50 x 0.0.93 3.05m x 4.57m = 581 lm/m2 or 581 lux (Initial)
Calculated Illuminance An average maintained illuminance of 468 lumens per square meter will strike the area covered by the workplane in a completely empty space Some points on the workplane will have an illuminance higher than 468 while others will have an illuminance lower than this value During first time that this system will be turned on, wherein the lamps are new and the surfaces are clean, the average initial illuminance will be greater than the maintained value, which is computed as 582 lumens per square meter (lux)
Calculated Illuminance By rearranging the Lumen Method equation, it is possible to find the number of luminaires required to meet a specific average illuminance level: (lumens/lamp) x (lamps/luminaire) x (no. of luminaires) x CU x LLFTOTAL EWP = AWP AWP x EWP No. of = luminaires (lumens/lamp) x (lamps/luminaires) x CU x LLFTOTAL
Calculated Illuminance Example 2. Find the number of luminaires needed in a room given the following: Room dimensions: 9.15m by 9.15m by 3.5m Target Illuminance: 300 lux average maintained Working Plane Height: 0.76m Luminaire: Recessed round Lamp: 70 watt metal halide, 5600 lumen initial output Reflectances (): Ceiling cavity 0.70 Walls 0.30 Floor Cavity 0.20 Assume LLFTOTAL = 0.75
Calculated Illuminance Step 1. Calculate RCR Using the equation for RCR, we get 3 as the answer. Step 2. Determine Cavity ratios for ceiling and floor Step 3. Obtain Effective Ceiling Cavity Reflectance (CC) using Tables in CU determination for metal halide lamps Step 4. Obtain Effective Floor Cavity Reflectance (FC) using Tables in CU determination for metal halide lamps Step 5. Obtain Coefficient of Utilization (CU) from Manufacturer’s Data The CU based on calculated value of RCR and the given reflectances, we get 0.55 as the answer.
Calculated Illuminance Using the equation below, and substituting all the known values: Number of luminaires = AWP x EWP lumens/lamp x lamps/luminaires x CU x LLFTOTAL Number of luminaires = 9.15m by 9.15m by 3.5m x 300 lux 5600 lumen x 1 x 0.55 x 0.75 Number of luminaires = 10.9 In this example, 12 fixtures can be spaced uniformly in a 3 by 4 pattern. Although 12 is more than the calculated value of 10.9 fixtures, results within a 10% margin is generally acceptable for meeting this target criterion
Spacing Criteria Spacing Criteria is the maximum ratio of spacing to mounting height of the luminaire above the workplane that provides reasonable uniformity of illumination within the space Spacing ratios for specific luminaires are given in the data sheets published by each manufacturer. This number, usually between 0.5 to 1.5, when multiplied with the mounting height, gives the maximum distance that the luminaires maybe separated and provide uniform illuminance on the workplane
Spacing Criteria For luminaires using essentially point sources of light, such as incandescent or HID lamps, the number of luminaires per row should be in proportion to the width-to-length ratio of the room
Spacing Criteria For fluorescent luminaires, it is necessary to first establish the maximum number that can be installed in one row. the maximum number is calculated by subtracting at least 0.3 meter from the room length and then dividing by the length of the luminaire.
Spacing Criteria The exact spacing between rows is calculated by dividing the room width by the number of rows Spacing between luminaires in each row is calculated by dividing the room length by the number of luminaires per row. spacing between the outer luminaires and the adjacent wall is one-half of the luminaire spacing If desks or other work areas are to be located alongside the walls, then the wall-to-luminaires spacing should be reduced to one-third of the luminaire spacing
Illuminance at a Point-Direct Component Examples: What is the illuminance on a wall display from a spotlight aimed at the display? How much light is striking a point on the façade of a building or in a parking lot from a floodlight? Factors to consider Luminous intensity Distance Orientation of the surface
Luminous Intensity Luminous Flux in a certain direction, radiated per unit of solid angle Unit : Candela Symbol : I I = Luminous flux Solid Angle =
Luminous Intensity Rotational symmetrical Light distribution same in all planes Usually Circular or ‘Bowl shaped’ luminaire
Luminous Intensity Planar symmetrical Luminaire distribution is confined to two vertical planes separately Typical distribution for Fluorescent Lamp luminaires and Road Lighting
Luminous Intensity Asymmetrical Asymmetry present in one of the Planes of measurement.
Distance Distance between a surface and the source affects the illuminance (luminous flux per unit of area) striking that surface Surface of a given area that is closer to the source captures a larger portion of the flux in the cone than a surface of the same given area that is further away Considering the luminous intensity as the luminous flux (lumens) leaving a source in a cone traveling in a specific direction, as the area increases the iluminance decreases while the luminous flux remains the same Inverse Square Law states that the cross-sectional area of the cone increases with the square of the distance from the source. Therefore, the illuminance on this surface varies inversely with the square of the distance from the source
Distance P A w Light Source Solid Angle Plane Distance d E = I/ d2 I
Distance Inverse Square Law E = I/ d2 Where: E = Illuminance on the surface I = Luminous intensity of the source in the direction of the surface d = Distance from the source to the surface
Orientation of the Surface Surface orientation is included in the Inverse Square Law by adding a cos term: E = I/ d2 cos is the angle between the light ray coming from the source to the point, and a line that is perpendicular (normal) to the plane or surface on which the illuminance is being measured or calculated
Orientation of the Surface
Illuminance at a Point-Direct Component Example 1. This example will consider the illuminance at a single point on a horizontal surface from a single luminaire straight down. An assumed LLF of 0.85 will be used. D = 2.13 m = 15° LLF = 0.85 I = 2200 candelas The luminous intensity (I) is determined using the photometric data for the specific luminaire used and the angular relationship between the luminaire aiming direction and the direction from the luminaire to the calculation point.
Illuminance at a Point-Direct Component Using the equation; E = I/ d2 x cos x LLFTOTAL E = 2200 cd x cos 15° x 0.85 2.13 m2 E = 398 lux (maintained) This tells us that 398 lux will strike the point in question directly from the luminaire and no reflected light is calculated. The answer is a maintained illuminance level since a light loss factor of 0.85 was included to account for the loss of light over time due to reduced lumen output of the lamp and dirt on the luminaire surfaces.
Illuminance at a Point-Direct Component Example 2. This example will consider the illuminance at a single point on a horizontal surface from two luminaires aimed straight down. An assumed LLF of 0.85 will be used and Luminaire #1 is the same in Example 1. D1 = 2.13m 1 = 15° D2 = 2.29m 2 = 25° 1 = 15° I1 = 2200 cd 2 = 25° I2 = 2000 cd E1 = 398 lux (from previous calculation) E2 = 291 lux (from calculations) ETOTAL = E1 + E2 = 689 lux
Illuminance at a Point-Direct Component Example 3. This example will consider the illuminance at multiple points on a vertical surface from a luminaire aimed at the surface. An assumed LLF of 0.85 will be used. Table 1. Components of Example 3 The luminaire is now aimed at the vertical surface so is no longer measured from straight down, and and are no longer equal. Illuminance is calculated using the same equation as the prior examples.
Illuminance at a Point-Direct Component In Table 1, illuminance at point 2 is greater than at point 1 and illuminance at point 3 is the least. This is because the distance at point 2 is less than point 1 and the angle theta ( ) at point 2 is less than at point 1, despite the fact that the intensity in that direction is less. Similar reasoning can be used with regard to point 3. These two factors cause the illuminance at point 2 to be greater than the illuminance at point 3.
Sample Calculations The calculations presented using various tables and figures are only meant to give the user of this module a general overview of the design of lighting system, showing individual steps from the selection of the recommended luminance level, to the design of lighting layout.
Sample Calculations Sample Calculation 1: The room to be lighted is as follows: Type of building : Commercial Area/activity : Drafting/tracing paper, low contrast Average age of worker : 35 years Demand for speed and/or accuracy : Important Task background reflectance : 75% Size of room : 10.0 by 13.25 meters; 2.91 m ceiling Height of work plane : 0.91 m
Sample Calculations Reflectance factors : Ceiling 80%, walls 50%, and floor 30% Luminaire type : Type 2, IES Lighting Handbook Table ; 300 mm wide with two lamps Lamps : 430 mA, 40 W, 1200 mm, warm white, rapid start tubular fluorescent lamps Atmosphere : Clean Interval between cleaning : 12 months
Sample Calculations Solution: Step 1: Determine the recommended illuminance level: From Illuminance Table (IES Lighting Handbook) , the illuminance category is F. From the IES Lighting Handbook Table, the recommended level is 1000 lux
Sample Calculations Step 2: Draw a cross section of the room and determine cavity heights. Note there is no ceiling cavity.
Sample Calculations Step 3: Calculate the cavity ratios using Equations and indicate dimensions.
Sample Calculations Step 4: Determine the effective floor cavity reflectance (pFC) from IES Lighting Handbook Table. Note that the effective ceiling cavity reflectance is the same as the actual ceiling reflectance.
Sample Calculations Step 5: Determine the coefficient of utilization: It is necessary to interpolate for RCR = 1.75 For luminaire 2, ñCC= 80% and ñW = 50%
Sample Calculations 30% 1.070 (from above) 28% (interpolate) 1.056 20% 1.00 - Multiply by factor 0.9 as per note on IES Lighting Handbook Table for luminaire 2, 300 mm wide using two lamps. Final Coefficient of Utilization (CU) = 0.61 x 1.056 x 0.9 = 0.58
Sample Calculations Step 6: Calculate the light loss factor (LLF): - Ballast factor = 0.95 - LLD from IES Lighting Handbook Table is 84% (use 0.84) - From IES Lighting Handbook Table, luminaire 2 is category V. - LDD is 0.88 - RSDD: the light output is all down (direct distribution) the luminaire is direct. From the graph in IES Lighting Handbook Table , for a clean atmosphere at 12 months, the percent expected dirt depreciation is 12%(use10%) and RSDD is 0.98. LLF = 0.95 x 0.84 x 0.88 x 0.98 = 0.69 (two figure accuracy is acceptable)
Sample Calculations Step 7: Calculate the total initial lamp lumens (TILL) using the equation below:
Sample Calculations Step 8: Calculate the required number of luminaires using equation below. From IES Lighting Handbook Table, the initial lumens are 3175 and there are two lamps per luminaire.
Sample Calculations Step 9: Select a practical layout for the luminaire: - Assume continuous rows are required - Calculate the maximum number per row lengthwise in the room as in figure below for 1200-mm long luminaires.
Sample Calculations - Number of rows required is 52/10 = 5 - Select 5 rows of 10 = 50
Sample Calculations Step 10: Calculate the luminaire spacing using the figure below: Sw = 10/5 = 2.0 m Total length of each row = 10 x 1.2 = 12.0 m
Sample Calculations Step 11: Check the maximum spacing allowed between rows: - From the IES Lighting Handbook Table, for luminaire 2, SC is 1.4 for crosswise spacing. - Maximum spacing = 1.4 x hRC = 1.4 x 2.0 = 2.8 m - 2.0 m is within the limits
Sample Calculations Step 12: Draw plan of the room and indicate the locations of luminaires
Sample Calculations Step 13: Calculate the actual minimum maintained lighting level: (within 4% of target value)
Sample Calculations Step 14: Calculate the unit power density (UPD); From the IES Lighting Handbook table, the power input to the ballast for each luminaire (two 430 mA, 1200 mm lamps) is 95 watts.
Sample Calculations The unit power density (UPD) of 35.85 W/m2 (3.33 watts per square foot) is high. Before the advent of the energy shortage, this value was accepted as normal. Today’s practices, however dictate that the lighting load be kept as low as possible by using energy-saving lamps and ballast. In this example, the designer should start over with F32T8 or F36T8 lamps operated with electronic ballasts and go through the calculations again to reduce the UPD.
Sample Calculations Sample Calculation 2. Illustrations in calculating illumination levels (Lux) on certain lighting layout configurations: Illumination of a conference room with OSRAM DULUX CARRÉ EL/D 2 x 24 W, with two DULUX L 24 W compact fluorescent lamps. Room dimensions: L = 15.00 m (length) W = 8.00 m (width) H = 3.40 m (ceiling-to-floor height) h = 2.55 m (luminaire-to-work plane height)
Sample Calculations Required quality of light: Conference room: Light color ww or nw, Ra group 2A Illuminance E = 300 lux Selected lamp: 2 DULUX L 24 W, Light color LUMILUX Warm (LF 31/830), Ra group 1B, Luminous flux per lamp ƒn= 1800 lumen
Sample Calculations Lighting design data is available in EULUMDAT format for most OSRAM luminaires. EULUMDAT data can be read by a wide range of programs for lighting design, including DIALUX (Version 2.0 and higher), RELUX, SPECTRAL ƒn LUMAGIC and RADEMACHER BELWIN. The table below shows the room utilization factor for numerous combinations of room factors and reflectances (always assuming ideal dispersion). The illuminance E required in a room of area L x W is achieved with n luminaires that have an efficiency çLB and with lamps with a luminous flux .
Sample Calculations Luminaire efficiency and light distribution: OSRAM DULUX CARRÉ EL/D 2 X 24 W Light distribution A40.2 hLB = 0.58 Reflectances: ñ Ceiling = 0.8 ñ Wall = 0.5 ñ Work surface = 0.3 Room utilization factor: From the LiTG Table For A40.2 (Table 1) çR = 0.91
Sample Calculations Calculation: Result: 24 luminaires (ç is rounded up) Recommended arrangement: 3 rows of 8 luminaries
Sample Calculations Sample Calculation 3. Given are the following : Width = 15 m Length = 100 m Ceiling height = 3.5 m Desired Illumination = 400 lux Type of Luminaire = 200mf Downlight w/ 26W TC-D Lamp
Sample Calculations General Information: Project Identification: Shopping Mall Average maintained Illuminance: 400 lux or 400 lux /1lux x 10.76fc = 37.17 fc Lamp data: 26W TC-D (compact fluorescent lamp) Lamp flux: 1800 lumen (as per manufacturer’s data) Luminaire data: Manufacturer: Zumtobel Staff (Fumaco) Model No: Panos HG 2/26W TC-D VVG 200 ñw = 50%
Sample Calculations Selection of Coefficient of Utilization: Step 1: Fill in all information in sketch L (Length) = 100 m W (width) = 15 m h (height) = 3.5 m
Sample Calculations Step 2: Determine Cavity Ratio If from manufacturer’s data, CU table are given based on Room Cavity Ratio
Sample Calculations If from manufacturer's data, CU table are given based on Room Index where:
Sample Calculations Step 3: Obtain effective cavity reflectance: Ceiling : cc = 70% Wall : w = 50% Floor : fc = 20%
Sample Calculations Step 4: Obtain Coefficient of Utilization from manufacturer's data: Based on Fig. 9-28 of IESNA Handbook @ RCR 1.34 @ 70/50/20 reflectance
Sample Calculations by interpolation CU @ 1.34: RCR = 0.64
Sample Calculations Step 5: Compute for the Light Loss Factor (LLF) LLF = Ballast factor x LLD x LDD x RSDD Ballast Factor = 0.95 LLD (as per Figure 6.3 of IESNA Handbook) = Lumen maintenance (LLD) of compact fluorescent lamp double Biax (TC-D) is LLD = 85% LDD under luminaire maintenance category I @ very clean room using Table 6-2 where maintenance frequency is every 12 months LDD = 0.96 Since luminaire is Direct downlight (as per Figure 6.4 of ELI handbook) % Room Surface Dirt Depreciation (RSDDF) is = 12%
Sample Calculations by Interpolation, x = 0.976 (RSDD) LLF = 0.95 x 0.85 x 0.96 x 0.976 LLF = 0.76
Sample Calculations Step 6: Compute for Initial Lamp Lumens (TILL) using equation below:
Sample Calculations Step 7: Calculate the required no. of luminaries using equation below. From table lamp manufacturer’s data, the initial lamp lumens of 26W TC-D lamp = 1,800 lumens
Sample Calculations Step 8: Select a practical lay out for the luminaire. Spacing Criterion, SC = spacing distance/mounting height As per Figure 9-28 of IESNA Handbook, for 8" open reflector using 2-26 CFL, SC = 1.5 Spacing distance = 1.5 x 3.5 m = 5.25 m For this distance, 343 luminaires required to achieve 400 lux illumination cannot be placed for the given area.
Sample Calculations Step 9: Calculate Luminaire Spacing Number of luminaires per row = (15m-5.25m)/5.25 = ~ 2 Number of luminaires per column = 343/2 = 172 luminaires x 5.25 m (spacing) = 903 m which exceeded 150 m. Spacing criterion with this case is not applicable Assuming spacing at end rows = 1 m Number of luminaires/row = 15-2(1)/2 = 6.5 ~ 7 luminaires/row Transverse spacing = 15-2(l)/6= 2.17 m
Sample Calculations Total length at each row = 6 x 2.17 m = 13 m Space at end rows = 15-13/2 = 1 m Number of luminaires/column = 343/7 = 49 luminaires/column Longitudinal spacing = 100-2(1)/48 = 2.04 m Total length at each column = 48 x 2.04 m = 98 m Space at end rows = 100m-98m/2 = 1 m Total luminaires = 7 x 49 = 343 luminaires
Sample Calculations Step 10: Draw plan of the room and indicate the locations of luminaries:
Sample Calculations Step 11: Calculate the actual minimum maintained lighting level: E = 343/343 x 400 lux = 400 lux (within the target value)
Sample Calculations Step 12: Calculate the power density (UPD) or connected load. From manufacturers data, the power consumption of 2 x 26W TC-D lamp using conventional ballast = 90watts, in using electronic ballast = 70 watts
Sample Calculations Sample Calculation 4. Given the following data: Width = 15 m Length = 100 m Ceiling height = 3.5 m Desired Illumination = 400 lux Type of Luminaire = 200mf Downlight w/ 26W TC-D Lamp Luminaire : 8" Downlight with 70W Metal Halide Lamp Lamp Flux : 6600 lumens (from manufacturer’s data) from Table (Figure 9-28) of IESNA handbook CU of metal halide downlight #10 @ 70/50/20 reflectance & RCR of 1.34
Sample Calculations Compute for the Light Loss Factor (LLF) LLF = Ballast factor x LLD x LDD x RSDD Ballast factor = 0.95 LLD of metal halide lamp = 0.85 LDD = 0.96 RSDDF = 0.976 LLF = 0.95 x 0.85 x 0.96 x 0.976 LLF = 0.76
Sample Calculations Compute for the the total initial lamp lumens (TILL)
Sample Calculations Compute for the number of luminaires
Sample Calculations Compute for the number of luminaires/row Spacing Criterion = 1.2, does not apply since total of 179 luminaires cannot be placed on the given area. Assuming spacing criterion = 0.9 Spacing distance between luminaries = MH x SC Spacing (Longitudinal) = 3.5 m x 0.9 = 3.15 Number of luminaires/column = 100/3.15 = 31 luminaires Total length of column = 31 x 3.15 = 97.65 m Space at end of column = (100-97.65)/2 = 1.175 m Total luminaires at each row = 179/31 = 5.7 ~ 6 luminaires
Sample Calculations Transverse spacing = 15m - 2(1.175m)/5 = 2.53 m Total length of each row = 5 x 2.53m = 12.65 m Space at ends of row = (15 - 12.65)/2 = 1.175m Total number of luminaries = 6 x 31 = 186 luminaires
Sample Calculations Draw plan of the room and indicate the locations of luminaries.
Sample Calculations Calculate the actual maintained lighting level.
Sample Calculations Calculate the unit power density (connected load), from lamp manufacturer’s data, the power input of 70W metal halide lamp = 81.5 Watts.
Computer-Aided Lighting Calculations
Computer-Aided Lighting Calculations A wide variety of computer programs are available from lighting manufacturers to perform interior and exterior lighting calculations Some programs are very simple, while others are complex and can even interface with computer-aided design
Computer-Aided Lighting Calculations The following is a list of some of the software available but are not intended as a substitute for creating design but as an aid to the design process General Electric Philippines A GE Lighting Application Design and Analysis (ALADAN) EUROPIC OSRAM Philippines DiaLux Light@work Philips Lighting and Electronics CalcuLux FUMACO Incorporated RELUX 1 (Version 2.4 and 3.0) DiaLux
Computer-Aided Lighting Calculations PHILIPS Calculux Program Indoor Area Road
Computer-Aided Lighting Calculations PHILIPS Calculux Program Indoor Calculux Indoor is a software tool which can help lighting designers select and evaluate lighting systems for office and industrial applications Speed, ease of use and versatility are features of the package from Philips Lighting, which runs under the Microsoft Windows operating system Calculux Indoor is part of the Philips Calculux line, covering indoor, area and road applications
Computer-Aided Lighting Calculations PHILIPS Calculux Program What Calculux Indoor does Calculux is a very flexible system which offers lighting designers a wide range of options: You can use the package to simulate real lighting situations and analyse different lighting installations until you find the solutions which suits your technical as well as your financial and aesthetic requirements best Calculux not only uses luminaires from an extensive Philips database, but can also use photometric data which is stored in the Philips Phillum external format Simple menus, logical dialogue boxes and a step by step approach help you to find the most efficient and cost-effective solutions for your lighting applications
Computer-Aided Lighting Calculations PHILIPS Calculux Program What you can do with Calculux Indoor Perform lighting calculations (including direct, indirect, total and average illuminance) within orthogonal rooms Predict financial implications including energy, investment, lamp and maintenance costs for different luminaire arrangements Select luminaires from an extensive Philips database or from specially formatted files for luminaires from other suppliers Specify room dimensions, luminaire types, maintenance factors, interreflection accuracy, calculation grids and calculation
Computer-Aided Lighting Calculations PHILIPS Calculux Program What you can do with Calculux Indoor Compile reports displaying results in text and graphical formats Support Switching modes and Light regulation factors Support multiple languages
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project After installing the Calculux program in your PC, create an indoor lighting project by entering general project data, specify a room, perform a calculation and print a report Example: General lighting for an office given the following room dimensions: Width 3.5 m Length 5.6 Height 2.7 m
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project Select Project Luminaires from the Data menu Select Indoor Lighting Select the housing and light distributor of the luminaire Housing TBS 600/135 Light Distributor C7-60 Select Arranged Luminaires from the Data menu Click Add and select Room Block In the UF Method box you can see that 3.5 luminaires is sufficient for the requested illuminance level of 300 lux as general lighting
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project Click Generate A Room Block arrangement of 4 luminaires will be generated In the Definition box enter the name of the arrangement, enter: Name General Define a (calculation) grid Before a calculation can be performed a (calculation) grid has to be defined You can define your own grid, define a grid according to a rule or use a preset grid
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project Select Grids from the Data menu Perform a calculation Select Show Results from the Calculation menu The calculation will be performed Printing the report Select Print Report from the File menu Saving the project Select Save from the File menu Enter the file name Click OK to save the project Select Exit from the File menu to close the program
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project Sample printouts of the program
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project Sample printouts of the program
Computer-Aided Lighting Calculations PHILIPS Calculux Program Sample Indoor Project Sample printouts of the program
Computer-Aided Lighting Calculations PHILIPS Calculux Program Area Calculux Area is a software tool which can help lighting designers select and evaluate lighting systems for sports fields, parking places, areas for general use, industrial applications and even road lighting calculations. Calculux Area is part of the Philips Calculux line, covering indoor, area and road applications Same principles and procedures apply as when using Calculux Indoor
Computer-Aided Lighting Calculations PHILIPS Calculux Program Road Calculux Road is a software tool which can help lighting designers select and evaluate lighting systems for road lighting installations Calculux Road is part of the Philips Calculux line, covering indoor, area and road applications Same principles and procedures apply as when using Calculux Indoor and Calculux Area
Computer-Aided Lighting Calculations OSRAM DiaLux Program
Computer-Aided Lighting Calculations OSRAM DIALux Program Calculates the light exchange between luminaires and any other surfaces (direct lighting) and the light exchange between illuminated surfaces (indirect lighting) Lighting from the sky (daylight) or direct sunlight can also be calculated Calculation based on the radiosity method
Computer-Aided Lighting Calculations Advanced Lighting Programs Capable of extreme accuracy in spaces of complex geometry Most generate high quality semi-photorealistic images depicting interior and exterior lighting, including daylight Radiosity Ray-tracing programs Some programs combine the computational speed of radiosity with the accuracy and realism of ray tracing
Computer-Aided Lighting Calculations Advanced Lighting Programs Radiosity Advanced radiosity programs have greater capabilities than basic programs, including: Analysis of rooms of any shape Rooms can have sloping and complex ceilings Realistic objects in space Faster execution time Much more realistic renderings
Computer-Aided Lighting Calculations Advanced Lighting Programs Ray-tracing programs Much less common since it requires more computer time, data entry time and operator expertise Produce superior visual results making them worth the time and expense for critical lighting designs and evaluations Capable of demonstrating effects and issues caused by specular surfaces and are the only programs that render highlights, such as reflections in polished surfaces or glass Display lighted rooms in full color with accurate light patterns on room surfaces and partitions, and realistic shadows from realistic furniture
Computer-Aided Lighting Calculations Advanced Lighting Programs Some programs, such as Lightscape, use radiosity for calculations then add a ray-tracing “layer” for realism of specular reflections and highlights
Computer-Aided Lighting Calculations Other Lighting Software Programs