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Illumination Calculation and Design for Multi

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ILLUMINATION CALCULATION AND DESIGN FOR MULTI-FAMILY DWELLING UNIT Interior lighting. (1) Within all buildings of three or fewer storeys in building height, having a building area not exceeding 600 square metres and used for residential occupancies, business and personal services occupancies, mercantile occupancies or medium and low industrial occupancies. (1) Every exit (except those serving not more than one dwelling unit), public corridor or corridor providing access to exit for the public shall be equipped to provide illumination to an average level of not less than 50 lux at floor or tread level and at all points such as angles and intersections at changes of level where there are stairs or ramps. (2) Emergency lighting shall be provided in: (a) Exits; (b) Principal routes providing access to exit in an open floor area; (c) Corridors used by the public; (d) Underground walkways; and (e) Public corridors. (3) Emergency lighting required in Subsection B(1)(b) shall be provided from a source of energy separate from the electrical supply for the building. (4) Lighting required in Subsection B(2)(b) shall be designed to be automatically actuated for a period of not less than 30 minutes when the electric lighting in the affected area is interrupted. (5) Illumination from lighting required in Subsection B(2)(b) shall be provided to average levels of not less than 10 lx at floor or tread
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Page 1: Illumination Calculation and Design for Multi

ILLUMINATION CALCULATION AND DESIGN FOR MULTI-FAMILY DWELLING UNIT

Interior lighting.

(1) Within all buildings of three or fewer storeys in building height, having a building area not exceeding 600 square metres and used for residential occupancies, business and personal services occupancies, mercantile occupancies or medium and low industrial occupancies.

(1) Every exit (except those serving not more than one dwelling unit), public corridor or corridor providing access to exit for the public shall be equipped to provide illumination to an average level of not less than 50 lux at floor or tread level and at all points such as angles andintersections at changes of level where there are stairs or ramps.

(2) Emergency lighting shall be provided in:

(a) Exits;

(b) Principal routes providing access to exit in an open floor area;

(c) Corridors used by the public;

(d) Underground walkways; and

(e) Public corridors.

(3) Emergency lighting required in Subsection B(1)(b) shall be provided from a source of energy separate from the electrical supply for the building.

(4) Lighting required in Subsection B(2)(b) shall be designed to be automatically actuated for a period of not less than 30 minutes when the electric lighting in the affected area is interrupted.

(5) Illumination from lighting required in Subsection B(2)(b) shall be provided to average levels of not less than 10 lx at floor or tread level.

(6) Where incandescent lighting is provided, lighting equal to one watt per square metre of floor area shall be considered to meet the requirement in Subsection B(5)(e).

(7) Where self-contained emergency lighting units are used, they shall conform to CSA C22.2 No. 141-M, “Unit Equipment for Emergency Lighting”.

(8) Every public or service area in buildings, including a recreational camp and a camp for housing of workers, shall have lighting outlets with fixtures controlled by a

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wall switch or panel.

(9) When provided by incandescent lighting, illumination required in Sentence (1) shall conform to Table § 629-36B(1).

(j) When other types of lighting are used, illumination equivalent to thatshown in Table 36.B.(1) shall be provided.

(2) Within all buildings exceeding three storeys in building height or having a building area exceeding 600 square metres or used for other occupancies not described in Subsection B(1).

(a) An exit, a public corridor, a corridor providing access to exit for the public, a corridor serving patients or residents in a Care and Treatment occupancy or Care occupancy, a corridor servingclassrooms, an electrical equipment room, a transformer vault and a hoistway pit shall be equipped to provide illumination to an average level not less than 50 lux at floor or tread level and at angles and intersections at changes of level where there are stairs or ramps.

(b) Rooms and spaces used by the public shall be illuminated as described in Subsection B(1)(h),(i) and (j).

(c) Elevator machine rooms shall be equipped to provide illumination to an average level of not less than 100 lux at floor level.

(d) Every place of assembly intended for the viewing of motion pictures or the performing arts, shall be equipped to provide an average level of illumination at floor level in the aisles of not less than two lux during the viewing.

(e) Every area where food is intended to be processed, prepared or manufactured and where equipment or utensils are intended to be

(2) Within all buildings exceeding three storeys in building height or having a building area exceeding 600 square metres or used for other occupancies not described in Subsection B(1).

(a) An exit, a public corridor, a corridor providing access to exit for the public, a corridor serving patients or residents in a Care and Treatment occupancy or Care occupancy, a corridor servingclassrooms, an electrical equipment room, a transformer vault and a hoistway pit shall be equipped to provide illumination to an average level not less than 50 lux at

Page 3: Illumination Calculation and Design for Multi

floor or tread level and at angles and intersections at changes of level where there are stairs or ramps.

(b) Rooms and spaces used by the public shall be illuminated asdescribed in Subsection B(1)(h),(i) and (j).

(c) Elevator machine rooms shall be equipped to provide illumination to an average level of not less than 100 lux at floor level.

(d) Every place of assembly intended for the viewing of motion pictures or the performing arts, shall be equipped to provide an average levelof illumination at floor level in the aisles of not less than two lux during the viewing.

(e) Every area where food is intended to be processed, prepared or manufactured and where equipment or utensils are intended to be

In a service space in which facilites are included to permit a person to enter and to undertake maintenance and other operations; and On a shelf and rack storage system, which includes walkways, platforms, unenclosed egress stairs and exits providing means of egress.

(j) The minimum value of the illumination required by Subsections B(2) (h) and (i) shall be not less than one lux.

(k) In addition to the requirements of Subsections B(2)(h) to (j), the installation of battery-operated emergency lighting in health care facilities shall conform to the appropriate requirements of CSA Z32, “Electrical Safety and Essential Electrical Systems in Health CareFacilities”. C. For parking lots, walkways, stairs, porches, verandas, loading docks, ramps or other similar areas, a minimum level of illumination of ten lux (0.90 foot-candle) at ground or tread level and at angles and intersections at changes of level where there are stairs or ramps.

Introduction to the Lumen Method

The lumen method is applicable to design of a uniform (general) lighting scheme in a space where flexibility of working locations or other activities is required.

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The lumen method is applied only to square or rectangular rooms with a regular array luminaires as shown in Figure 2.

2. Lumen Method CalculationsThe lumen method is based on fundamental lighting calculations. The lumen method formula is easiest to appreciate in the following form.

 (1)

where E = average illuminance over the horizontal working planen = number of lamps in each luminaireN = number of luminaire

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F = lighting design lumens per lamp, i.e. initial bare lamp luminousfluxUF = utilisation factor for the horizontal working planeLLF = light loss factorA = area of the horizontal working plane2.1 Light Loss Factor

Light loss factor (LLF) is the ratio of the illuminance produced by the lighting installation at the some specified time to the illuminance produced by the same installation when new. It allows for effects such as decrease in light output caused by(a) the fall in lamp luminous flux with hours of use,(b) the deposition of dirt on luminaire, and(c) reflectances of room surfaces over time.In fact, light loss factor is the product of three other factors:

(2)

where LLMF = lamp lumen maintenance factorLMF = luminaire maintenance factorRSMF = room surface maintenance factor2.1.1 Lamp Lumen Maintenance Factor

Lamp lumen maintenance factor (LLMF) is the proportion of the initial light output of a lamp produced after a set time to those produced when new. It allows for the decline in lumen

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output from a lamp with age. Its value can be determined in two ways:(a) by consulting a lamp manufacturer's catalog for a lumen depreciation chart, and(b) by dividing the maintained lumens by the initial lamps.2.1.2 Luminaire Maintenance Factor

Luminaire maintenance factor (LMF) is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time. It constitutes the greatest loss in light output and is mainly due to the accumulation of atmospheric dirt on luminaire. Three factors must be considered in its determination:(a) the type of luminaire,(b) atmospheric conditions, and(c) maintenance interval.2.1.3 Room Surface Maintenance Factor

Room surface maintenance factor (RSMF) is the proportion of the illuminance provided by a lighting installation in a room after a set time compared with that occurred when the room was clean. It takes into account that dirt accumulates on room surfaces and reduces surface reflectance. Figure 4 shows the typical changes in the illuminance from an installation that occur with time due to dirt deposition on the room surfaces.2.2 Utilisation Factor

Utilisation factor (UF) is the proportion of the luminous flux emitted by the lamps which reaches the working plane. It is a measure of the effectiveness of the lighting scheme. Factors that affect the value of UF are as follows:

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(a) light output ratio of luminaire(b) flux distribution of luminaire(c) room proportions(d) room reflectances(e) spacing/mounting height ratio

2.2.1 Light Output Ratio of Luminaire

Light output ratio of luminaire (LOR) takes into account for the loss of light energy both inside and by transmission through light fittings. It is given by the following expression.

(3)Example 1

The total, upward and downward lamp output from a lamp are 1000 lm, 300 lm and 500 lm respectively. Calculate upward light output ratio (ULOR), downward light output ratio (DLOR), light output ratio (LOR) of luminaire and percentage of light energy absorbed in luminaire.

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Amount of light energy absorbed in luminaire = 100 - 80 = 20 %A greater DLOR usually means a higher UF.A simple classification of luminaires according to their distribution is based on flux fractions, as shown in Figure 5. Upward flux fraction (UFF) and downward flux fraction(DFF) are used as a basis of comparison.Example 2

For data given in Example 1 determine upward flux fraction (UFF), downward flux fraction (DFF) and flux fraction ratio(FRR).

Figure 5 Flux Fraction of Various Luminaires

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2. Lumen Method CalculationsThe lumen method is based on fundamental lighting calculations. The lumen method formula is easiest to appreciate in the following form.

 (1)

where E = average illuminance over the horizontal working planen = number of lamps in each luminaireN = number of luminaireF = lighting design lumens per lamp, i.e. initial bare lamp luminousfluxUF = utilisation factor for the horizontal working planeLLF = light loss factorA = area of the horizontal working plane2.1 Light Loss Factor

Light loss factor (LLF) is the ratio of the illuminance produced by the lighting installation at the some specified time to the illuminance produced by the same installation when new. It allows for effects such as decrease in light output caused by(a) the fall in lamp luminous flux with hours of use,

Page 10: Illumination Calculation and Design for Multi

(b) the deposition of dirt on luminaire, and(c) reflectances of room surfaces over time.In fact, light loss factor is the product of three other factors:

(2)where LLMF = lamp lumen maintenance factorLMF = luminaire maintenance factorRSMF = room surface maintenance factor2.1.1 Lamp Lumen Maintenance Factor

Lamp lumen maintenance factor (LLMF) is the proportion of the initial light output of a lamp produced after a set time to those produced when new. It allows for the decline in lumen output from a lamp with age. Its value can be determined in two ways:(a) by consulting a lamp manufacturer's catalog for a lumen depreciation chart, and(b) by dividing the maintained lumens by the initial lamps.2.1.2 Luminaire Maintenance Factor

Luminaire maintenance factor (LMF) is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time. It constitutes the greatest loss in light output and is mainly due to the accumulation of atmospheric dirt on luminaire. Three factors must be considered in its determination:(a) the type of luminaire,(b) atmospheric conditions, and

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(c) maintenance interval.2.1.3 Room Surface Maintenance Factor

Room surface maintenance factor (RSMF) is the proportion of the illuminance provided by a lighting installation in a room after a set time compared with that occurred when the room was clean. It takes into account that dirt accumulates on room surfaces and reduces surface reflectance. Figure 4 shows the typical changes in the illuminance from an installation that occur with time due to dirt deposition on the room surfaces.2.2 Utilisation Factor

Utilisation factor (UF) is the proportion of the luminous flux emitted by the lamps which reaches the working plane. It is a measure of the effectiveness of the lighting scheme. Factors that affect the value of UF are as follows:(a) light output ratio of luminaire(b) flux distribution of luminaire(c) room proportions(d) room reflectances(e) spacing/mounting height ratio2.2.1 Light Output Ratio of Luminaire

Light output ratio of luminaire (LOR) takes into account for the loss of light energy both inside and by transmission through light fittings. It is given by the following expression.

 (3)

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Example 1The total, upward and downward lamp output from a lamp are 1000 lm, 300 lm and 500 lm respectively. Calculate upward light output ratio (ULOR), downward light output ratio (DLOR), light output ratio (LOR) of luminaire and percentage of light energy absorbed in luminaire.

Amount of light energy absorbed in luminaire = 100 - 80 = 20 %A greater DLOR usually means a higher UF.A simple classification of luminaires according to their distribution is based on flux fractions, as shown in Figure 5. Upward flux fraction(UFF) and downward flux fraction (DFF) are used as a basis of comparison.

Example 2For data given in Example 1 determine upward flux fraction (UFF), downward flux fraction (DFF) and flux fraction ratio (FRR).

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Figure 5 Flux Fraction of Various Luminaires

2.2.2 Flux Distribution of Luminaire

Direct ratio is the proportion of the total downward luminous flux from a conventional installation of luminaires which his directly incident on the working plane. It is used to assess the flux distribution of luminaire. Since the intensity distribution pattern of the light radiated from a luminaire in the lower hemisphere will affect:(a) the quantity of the downward flux falls directly on the working plane and(b) the quantity of flux available for reflection from the walls in a given room,Direct ratio depends on both the room proportions and the luminaires.Direct ratio has a low value with a narrow room

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(small room index) and a luminaire which emits most of its light sideways (BZ 10), and on the contrary, a high value with a wide room (large room index) and a luminaire which emits most of its light downwards (BZ 1).2.2.3 Room Proportion

Room index (RI) is the ratio of room plan area to half the wall area between the working and luminaire planes.

 (4)where L = length of roomW = width of roomHm = mounting height, i.e. the vertical distance between the working plane and the luminaire.2.2.4 Room Reflectances

The room is considered to consist of three main surfaces:(a) the ceiling cavity,(b) the walls, and(c) the floor cavity (or the horizontal working plane).The effective reflectances of the above three surfaces affect the quantity of reflected light received by the working plane.

2.2.5 Spacing to Height Ratio

Spacing to Height ratio (SHR or S/Hm) is defined as the ratio of the distance between adjacent luminaires (centre to centre), to their height above the working plane. For a rectangular arrangement of luminaires and by approximation,

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 (5)where A = total floor areaN = number of luminairesHm = mounting heightUnder a regular array of luminaires the illuminance on the working plane is not uniform. The closer spaced the luminaires for a given mounting height, the higher the uniformity; or the greater the mounting height for a given spacing, the greater the uniformity. If uniformity of illuminance is to be acceptable for general lighting,(a) SHR should not exceed maximum spacing to height ratio (SHR MAX) of the given luminaire as quoted by the manufacturer, and(b) geometric mean spacing to height ratio of the luminaire layout should be within the range of nominal spacing to height ratio(SHR NOM) of the given luminaire as quoted by the manufacturer, i.e.

(6)

3. Summary of Procedures for Lumen Design Method

(a) Calculate the room index.(b) Determine the effective reflectances of the ceiling cavity, walls and floor cavity.

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(c) Determine the utilisation factor from the manufacturer's data sheet, using the room index and effective surface reflectances as found in (a) and (b) above.(d) Determine the light loss factor.(e) Inert the appropriate variables into the lumen method formula to obtain the number of luminaires required.(f) Determine a suitable layout.(g) Check that the geometric mean spacing to height ratio of the layout is within the SHR NOM range:

(h) Check that the proposed layout does not exceed the maximum spacing to height ratios (SHR MAX).(i) Calculate the illuminance that will be achieved by the final layout and check against the standard.Example 3

Design a lighting installation for a college seminar room so that the average illuminance is 500 lux on the horizontal working plane, using the data listed below. Suggest the layout and check appropriate spacing to mounting height.Room dimensions: 12 m long x 8 m wide x 3.2 m highWorking plane at 0.7 m above floorReflection factors: Ceiling 70 %Walls 50 %Working plane 20 %Light Loss factor: 0.779

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Luminaires: 1800 mm twin tube with opal diffuserCeiling mountedDownward light output ratio 36 %SHR MAX 1.60 : 1SHR NOM 1.50 : 1Dimensions : 1800 mm long x 200 mm wideLamps: 1800 mm 75 W plus white5800 average initial lumens per lamp2 lamps per luminaire

Solution(a) Initial calculation

From manufacturer's photometric data sheet (Table 3), utilisation factor (UF) is 0.5336 by interpolation.

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Therefore, the number of luminairs is 10.Initial check on S/Hm ratio gives:

From the manufacture's photometric data, maximum S/Hm is 1.6 : 1. Therefore, it should be possible to use 10 luminaires.(b) Proposed layoutA 5 x 2 array is proposed fro the lighting installation. (A 10 x 1 array is an alternative.)(c) Checking the proposed layoutSince 2 x 1.8 m = 3.6 m < 8 m (width of room), the proposed layout will fit.(Usually checking only the linear dimension of the fitting for space is enough as the other dimension (i.e. 200 mm in this case) is much smaller.)

For long axis,

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For short axis,

Note that if the checks had worked out to be unsatisfactory, the number of luminaires should be reconsidered and the calculations on the illuminance should be repeated. For example, a 3x3 array for lower lux level or a 4x4 array for higher lux level.

DistributionOne of the primary functions of a luminaire is to direct the light to where it is needed. The light distribution produced by luminaires is characterized by the Illuminating Engineering Society as follows:

Direct ( 90 to 100 percent of the light is directed downward for maximum use.

Indirect ( 90 to 100 percent of the light is directed to the ceilings and upper walls and is reflected to all parts of a room.

Semi-Direct ( 60 to 90 percent of the light is directed downward with the remainder directed upward.

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General Diffuse or Direct-Indirect ( equal portions of the light are directed upward and downward.

Highlighting ( the beam projection distance and focusing ability characterize this luminaire.

The lighting distribution that is characteristic of a given luminaire is described using the candela distribution provided by the luminaire manufacturer (see diagram on next page). The candela distribution is represented by a curve on a polar graph showing the relative luminous intensity 360 around the fixture ( looking at a cross-section of the fixture. This information is useful because it shows how much light is emitted in each direction and the relative proportions of downlighting and uplighting. The cut-off angle is the angle, measured from straight down, where the fixture begins to shield the light source and no direct light from the source is visible. The shielding angle is the angle, measured from horizontal, through which the fixture provides shielding to prevent direct viewing of the light source. The shielding and cut-off angles add up to 90 degrees.

The lighting upgrade products mentioned in this document are described in more

detail in Lighting Upgrade Technologies.

POSTED BY  ELECTRICAL DES IGN1   AT  3 :40 PM  LABELS:  F . WEEK 10 AND 11

1 C O M M E N T :

1.

Srikanto BormonApril 6, 2013 at 9:05 PM

A new hydro power technology is being developed by Sarfraz Ahmad Khan of Pakistan. In theory these hydro plants would not require a reservoir and would have a minimal impact on the environment. They could be run side-by-side in rows and would be much cheaper to build, operate and maintain. Sarfraz has high hopes that his ideas could revolutionize hydro power in his country and across the globe. He is currently seeking expert confirmation of his ideas; this article provides a brief summary of his ideas along with some of the 3D images he has created. You can help him by leaving your comments at the bottom of the page, or by joining the discussion that inspired this article. In the early 19th century, an increasing number of scientists became interested in electricity.hydro electric | hydro electric power | what is hydro electric | inventhistory | power generator | wind power generator | solar and power | electric transportationVisit the website and get more information =>www.inventhistory.com

Light Guide

Page 21: Illumination Calculation and Design for Multi

Useful FormulasELECTRICAL FORMULASDemand for Power (kW) = System Input Wattage (W) ÷ 1,000

Energy Consumption (kWh) = System Input Wattage (kW) x Hours of Operation/Year

Hours of Operation/Year = Operating Hours/Day x Operating Days/Week x Operating Weeks/Year

Lighting System Efficacy (Lumens per Watt or LPW) = System Lumen Output ÷ Input Wattage

Unit Power Density (W/sq.ft.) = Total System Input Wattage (W) ÷ Total Area (Square Feet)

Watts (W) = Volts (V) x Current in Amperes (A) x Power Factor (PF)

Voltage (V) = Current in Amperes (A) x Impedance (Ohms) [Ohm's Law]

ECONOMIC FORMULASSimple Payback on an Investment (Years) = Net Installation Cost ($) ÷ Annual Energy Savings ($)

5-Year Cash Flow ($) = 5 Years - Payback (Years) x Annual Energy Savings ($)

Simple Return on Investment (%) = [Annual Energy Savings ($) ÷ Net Installation Cost ($)] x 100

DESIGN FORMULASFootcandles & Lumens

Footcandles (fc) = Total Lumens (lm) ÷ Area in Square Feet

1 Lux (lx) = 1 Footcandle (fc) x 10.76

Lux = Total Lumens ÷ Area in Square Meters

Calculating Light Level at a Point

For planes perpendicular to the direction of candlepower (Inverse Square Law):

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Footcandles (fc) = I ÷ D2

I = Candlepower in candelas (cd)D = Direct distance between the lamp and the point where light level is calculated

Many workplanes are not perpendicular to the direction of light intensity, which is why calculating light level at a point is useful for such applications. In these cases, we often must determine light levels on workplanes that are not horizontal and perpendicular but tilted or even vertical. For tilted-horizontal or vertical planes:

Horizontal Footcandles (fch) = (I ÷ D2) x H

Vertical Footcandles (fcv) = (I ÷ D2) x L

I = Candlepower in candelas (cd)D = Direct distance between the lamp and the point where light level is calculated

H = Distance between the lamp and the point direct below on the workplane

L = Distance between that point and the point where light level is being calculated

D = Square Root of (H2 + L2) or D2 = H2 + L2

Calculating Average Light Level Throughout a Space (three formulas)

Average Maintained Illumination (Footcandles) = (Lamps/Fixture x Lumens/Lamp x No. of Fixtures x Coefficient of Utilization x Light Loss Factor) ÷ Area in Square FeetAverage Maintained Illumination (Footcandles) = (Total Lamps x Lumens/Lamp x Coefficient of Utilization x Light Loss Factor) ÷ Area in Square Feet

Average Maintained Illumination (Footcandles) = (Lamps in One Fixture x Lumens/Lamp x Coefficient of Utilization x Light Loss Factor) ÷ Area in Square Feet/Fixture

Lumen Method

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Required Light Output/Fixture (Lumens) = (Maintained Illumination in Footcandles x Area in Square Feet) ÷ (Number of Fixtures x Coefficient of Utilization x Ballast Factor x Light Loss Factor)

Light Loss Factors (more on Light Loss)

Light Loss Factor (LLF) = Ballast Factor x Fixture Ambient Temperature Factor x Supply Voltage Variation Factor x Lamp Position Factor x Optical Factor x Fixture Surface Depreciation Factor x Lamp Burnouts Factor x Lamp Lumen Depreciation Factor x Fixture Dirt Depreciation Factor x Room Surface Dirt Depreciation Factor

Lamp Burnout Factor = 1 - Percentage of Lamps Allowed to Fail Without Being Replaced

Zonal Cavity Method (determining cavity ratios)

Room Cavity Ratio (for regular rooms shaped like a square or rectangle) = [5 x Room Cavity Depth x (Room Length + Room Width)] ÷ (Room Length x Room Width)Room Cavity Ratio (for irregular-shaped rooms) = (2.5 x Room Cavity Depth x Perimeter) ÷ Area in Square Feet

Ceiling Cavity Ratio = [5 x Ceiling Cavity Depth x (Room Length x Room Width)] ÷ (Room Length x Room Width)

Floor Cavity Ratio = [5 x Floor Cavity Depth x (Room Length x Room Width)] ÷ Room Length x Room Width

Room surface reflectances can be predicted in a new design or measured in an existing facility. If existing facility:

Room Surface Reflectance (%) = Reflected Reading ÷ Incident ReadingReflected Reading = Measurement from a light meter holding it about 1.5 feet away from the surface with the sensor parallel and facing the surface.

Incident Reading = Measurement from a light meter held flat against the surface and facing out into the room.

Calculating Number of Lamps And Fixtures And Spacing

Required No. of Fixtures = (Lumens/Lamp x No. of Lamps x Coefficient of Utilization x Light Loss Factor x Area in Square Feet) ÷ (Lumens/Lamp x Lamps/Fixture x Coefficient of Utilization x Light Loss Factor)

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Required Lamps = Required Lumens ÷ Initial Lumens/Lamp

Maximum Allowable Spacing Between Fixtures= Fixture Spacing Criteria x Mounting Height

Fixture Spacing Criteria: See the manufacturer's literatureMounting height: Distance in feet between the bottom of the fixture and the workplane

Spacing Between Fixtures = Square Root of (Area in Square Feet ÷ Required No. of Fixtures)

Number of Fixtures to be Placed in Each Row (Nrow) = Room Length ÷ Spacing

Number of Fixtures to be Placed in Each Column (Ncolumn) = Room Width ÷ Spacing

For the above two formulas, round results to the nearest whole integer.

Spacingrow = Room Length ÷ (Number of Fixtures/Row - 1/3)

Spacingcolumn = Room Width ÷ (Number of Fixtures/Column -1/3)

If the resulting number of fixtures does not equal the originally calculated number, calculate impact on the designed light level:

% Design Light Level = Actual No. of Fixtures ÷ Originally Calculated No. of Fixtures

To calculate fixtures mounted in continuous rows:

Number of Luminaires in a Continuous Row = (Room Length ÷ Fixture Length) - 1

Number of Continuous Rows = Total Number of Fixtures ÷ Fixtures Per Row

MAINTENANCELamp Life

Calendar Lamp Life (Years) = Rated Lamp Life (Hours) ÷ Annual Hours of Operation (Hours/Year)

Lamp Burnout Factor

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Lamp Burnout Factor = 1 - Percentage of Lamps Allowed to Fail Without Being Replaced

Group Relamping Cost

Annualized Cost ($) = A x (B + C)

A = Operating Hours/Year ÷ Operating Hours Between Relampings

B = (Percentage of Lamps Failing Before Group Relamping x Number of Lamps) x (Lamp Cost + Labor Cost to Spot Replace 1 Lamp)

C = (Lamp Cost, Group Relamping + Labor Cost to Group Relamp 1 Lamp) x Number of Lamps

Spot Relamping Cost

Average Annual Cost ($) = (Operating Hours/Year ÷ Rated Lamp Life) x (Lamp Cost + Labor Cost to Replace 1 Lamp) x Total Number of Lamps

Cleaning Cost

Cleaning Cost ($) = Time to Wash 1 Fixture (Hours) x Hourly Labor Rate ($) x Number of Fixtures in Lighted Space

ENVIRONMENTAL IMPACTAverage Reduced Air Pollution (lbs. Carbon Dioxide) = Energy Savings (kWh) x 1.6 lbs.

Average Reduced Air Pollution (g. Sulphur Dioxide) = Energy Savings (kWh) x 5.3 g.

Average Reduced Air Pollution (g. Nitrogen Oxides) = Energy Savings (kWh) x 2.8 g.

Pounds = Grams ÷ 454

Tons = Pounds ÷ 2,000

 

- See more at: http://www.lightsearch.com/resources/lightguides/formulas.html#sthash.HA4QlDDL.dpuf


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