Module 5 Lighting Calculations

Module 5 – Lighting Calculations Philippine Efficient Lighting Market Transformation Project (PELMATP)

Module 5

Lighting Calculations


ContentsContents

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 IlluminanceDetermining 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 EquationAverage 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 MethodThe Lumen Method

Means of determining the average workplane illuminance within a space with a given number of luminaires

ComponentsTotal system lamp lumen output

Coefficient of utilization

Loss factor determination

Calculated illuminance

Spacing criteria


Total System Lamp OutputTotal 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)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)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)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 DeterminationCU DeterminationUsing 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 DeterminationCU DeterminationIn 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 DeterminationCU DeterminationStep 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 DeterminationCU 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.



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 = 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 LuminaireCoefficients 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 FactorLight Loss Factor

Recoverable LLFLamp Lumen Depreciation (LLD)

Lamp Burnout Factor (LBO)

Luminaire Dirt Depreciation Factor (LDD)

Room Surface Dirt Depreciation Factor (RSDD)

Area of workplane (AWP)


Lamp Lumen DepreciationLamp 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 FactorLamp 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 DepreciationRoom 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 DepreciationLuminaire Dirt Depreciation


Area of WorkplaneArea 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 FactorLight Loss Factor

Non-Recoverable LLFLuminaire 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 TemperatureLuminaire 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 FactorHeat 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 FactorVoltage 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 FactorBallast FactorBallast 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 FactorBallast 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 FactorEquipment 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 FactorLamp 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 DepreciationLuminaire 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 DeterminationLoss Factor DeterminationExample 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 DeterminationLoss 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 IlluminanceCalculated 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 IlluminanceSubstituting 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 IlluminanceCalculated 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 IlluminanceBy 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 IlluminanceCalculated IlluminanceExample 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 IlluminanceCalculated IlluminanceStep 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 IlluminanceCalculated IlluminanceUsing 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 CriteriaSpacing 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 CriteriaSpacing CriteriaFor 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 CriteriaSpacing 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.



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 ComponentIlluminance 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 considerLuminous intensity

Distance

Orientation of the surface


Luminous IntensityLuminous Intensity

I

w

dw

Luminous Flux in a certain direction, radiated per unit of solid angle

Unit : Candela

Symbol : II = Luminous flux

Solid Angle=



Rotational symmetrical

Light distribution same in all planes

Usually Circular or ‘Bowl shaped’ luminaire



Planar symmetrical

Luminaire distribution is confined to two vertical planes separately

Typical distribution for Fluorescent Lamp luminaires and Road Lighting



Asymmetrical

Asymmetry present in one of the Planes of measurement.


DistanceDistance

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


DistanceDistance

PA

w

Light Source

Solid Angle

Plane

Distance

d

E = I/ d2

I


DistanceDistance

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 SurfaceOrientation 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 SurfaceOrientation of the Surface

P

Light Source

Plane

Distance, dCosine LawCosine Law

IE = I / d2 cos E = I / d2 cos



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.



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.



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



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.

Point Distance, m C C I LLF Emaintained

1 1.74 45 0 2300 0.85 463 lux

2 1.37 27 18 2225 0.85 893 lux

3 2.29 56 11 2100 0.85 194 lux


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 CalculationsSample 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 CalculationsSample CalculationsSample 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



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 CalculationsSample CalculationsSolution:

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 CalculationsSample CalculationsStep 2: Draw a cross section of the room and determine cavity

heights. Note there is no ceiling cavity.



Step 3: Calculate the cavity ratios using Equations and indicate dimensions.


Sample CalculationsSample CalculationsStep 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 CalculationsSample CalculationsStep 5: Determine the coefficient of utilization:

It is necessary to interpolate for RCR = 1.75

For luminaire 2, ñCC= 80% and ñW = 50%



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



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 CalculationsSample CalculationsStep 7: Calculate the total initial lamp lumens (TILL) using the

equation below:


Sample CalculationsSample CalculationsStep 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 CalculationsSample CalculationsStep 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.



- Number of rows required is 52/10 = 5

- Select 5 rows of 10 = 50


Sample CalculationsSample CalculationsStep 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 CalculationsSample CalculationsStep 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 CalculationsSample CalculationsStep 12: Draw plan of the room and indicate the locations of

luminaires



Step 13: Calculate the actual minimum maintained lighting level:

(within 4% of target value)



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.



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 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 CalculationsSample CalculationsRequired 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



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 CalculationsSample CalculationsLuminaire 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 CalculationsSample CalculationsCalculation:

Result:

24 luminaires (ç is rounded up)

Recommended arrangement:

3 rows of 8 luminaries



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



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 CalculationsSample CalculationsSelection 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



Step 2: Determine Cavity Ratio

If from manufacturer’s data, CU table are given based on Room Cavity Ratio


Sample CalculationsSample CalculationsIf from manufacturer's data, CU table are given based on Room Index

where:



Step 3: Obtain effective cavity reflectance:

Ceiling : cc = 70%

Wall : w = 50%

Floor : fc = 20%



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



by interpolation CU @ 1.34:

RCR = 0.64



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%



by Interpolation, x = 0.976 (RSDD)

LLF = 0.95 x 0.85 x 0.96 x 0.976

LLF = 0.76



Step 6: Compute for Initial Lamp Lumens (TILL) using equation below:



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



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 CalculationsSample CalculationsStep 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



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



Step 10: Draw plan of the room and indicate the locations of luminaries:



Step 11: Calculate the actual minimum maintained lighting level:

E = 343/343 x 400 lux = 400 lux (within the target value)



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 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



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



Compute for the the total initial lamp lumens (TILL)



Compute for the number of luminaires



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 CalculationsSample CalculationsTransverse 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



Draw plan of the room and indicate the locations of luminaries.



Calculate the actual maintained lighting level.



Calculate the unit power density (connected load), from lamp manufacturer’s data, the power input of 70W metal halide lamp

= 81.5 Watts.



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



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 PhilippinesA GE Lighting Application Design and Analysis (ALADAN)EUROPIC

OSRAM PhilippinesDiaLuxLight@work

Philips Lighting and ElectronicsCalcuLux

FUMACO IncorporatedRELUX 1 (Version 2.4 and 3.0)DiaLux



PHILIPS Calculux ProgramIndoor

Area

Road



PHILIPS Calculux ProgramIndoor

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



PHILIPS Calculux ProgramWhat 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 bestCalculux not only uses luminaires from an extensive Philips database, but can also use photometric data which is stored in the Philips Phillum external formatSimple 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



PHILIPS Calculux ProgramWhat 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



PHILIPS Calculux ProgramWhat 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



PHILIPS Calculux ProgramSample 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




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




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




Select Grids from the Data menuPerform 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




Sample printouts of the program



PHILIPS Calculux ProgramArea

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 applicationsSame principles and procedures apply as when using Calculux Indoor



PHILIPS Calculux ProgramRoad

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



OSRAM DiaLux Program



OSRAM DIALux ProgramCalculates 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



Advanced Lighting ProgramsCapable 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



Advanced Lighting ProgramsRadiosity

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



Advanced Lighting ProgramsRay-tracing programs

Much less common since it requires more computer time, data entry time and operator expertiseProduce superior visual results making them worth the time and expense for critical lighting designs and evaluationsCapable of demonstrating effects and issues caused by specular surfaces and are the only programs that render highlights, such as reflections in polished surfaces or glassDisplay lighted rooms in full color with accurate light patterns on room surfaces and partitions, and realistic shadows from realistic furniture



Advanced Lighting ProgramsSome programs, such as Lightscape, use radiosity for calculations then add a ray-tracing “layer” for realism of specular reflections and highlights



Other Lighting Software Programs

Module 5 Lighting Calculations

Documents

Transcript of Module 5 Lighting Calculations