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 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 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 that
shown 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 serving
classrooms, 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 serving
classrooms, 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 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 Care
Facilities”. 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.

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

2. Lumen Method Calculations

The 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 plane

n = number of lamps in each luminaire

N = number of luminaire

F = lighting design lumens per lamp, i.e. initial bare lamp luminous

flux

UF = utilisation factor for the horizontal working plane

LLF = light loss factor

A = area of the horizontal working plane

2.1 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 factor

LMF = luminaire maintenance factor

RSMF = room surface maintenance factor

2.1.1 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

(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 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.

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

2. Lumen Method Calculations The 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 plane n = number of lamps in each luminaire N = number of luminaire F = lighting design lumens per lamp, i.e. initial bare lamp luminous flux UF = utilisation factor for the horizontal working plane LLF = light loss factor A = area of the horizontal working plane 2.1 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 factor LMF = luminaire maintenance factor RSMF = room surface maintenance factor 2.1.1 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 (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 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. 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 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 (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 room W = width of room Hm = 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,

(5)

where A = total floor area

N = number of luminaires

Hm = mounting height

Under 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.

(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 high

Working plane at 0.7 m above floor

Reflection factors: Ceiling 70 %

Walls 50 %

Working plane 20 %

Light Loss factor: 0.779

Luminaires: 1800 mm twin tube with opal diffuser

Ceiling mounted

Downward light output ratio 36 %

SHR MAX 1.60 : 1

SHR NOM 1.50 : 1

Dimensions : 1800 mm long x 200 mm wide

Lamps: 1800 mm 75 W plus white

5800 average initial lumens per lamp

2 lamps per luminaire

Solution

(a) Initial calculation

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

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 layout

A 5 x 2 array is proposed fro the lighting installation. (A 10 x 1 array is an alternative.)

(c) Checking the proposed layout

Since 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,

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.

Distribution

One 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.
• 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.

WIRING CALCULATION FOR MULTI-FAMILY DWELLING

Multi - Family Dwelling
4 - door apartment

• Types of Service: 230 V
• 2 wire, Line to Ground System
• Floor Area per unit: 80 sq. m
• Total Floor Area: 320 sq. m

Determine the branch circuit protection, size of conductor wires and the main header.

SOLUTION:

Assume that the dwelling unit is equipped with one 5.1 kW cooking unit; one unit laundry ckt. at 1.5 kW

A. Circuit - 1 For Lighting Load per unit (see plan)

1. By the area method, refer to Table, General Lighting Load by occupancy for dwelling units.

80 sq. m x 24 watts per sq. m = 1920 watts


2. Compute for the Lighting Load. Divide:

1920 watts/230 volts = 8.35 A

3. Determine the size of the Branch Circuit conductor wire. Refer to Table. For 8.35 A load, use 2 pieces 2.0 mm² or No. 14 TW AWG copper wire

4. Determine the size of the conduit pipe. For number 14 AWG , TW wire use 13 mm minimum size of conduit pipe.

5. Determine the size or rating of the branch circuit protection. Refer again to Table. For 8.35 A load on a 2.0 mm² wire conductor size, use 15 A fuse or trip breaker.



B. Circuit - 2 For Convenience Outlet Load

1. Solve for the total current load.

8 receptacles x 2 gang per outlet x 180 watts = 2880 watts

2. Solve for the appliance current load. Divide.

I = 2880 watts/230 volts = 12.52 A

3. Determine the size of the Branch Circuit conductor. Refer to Table 9.1 or 11.1. For a 12.52 A load, a 2.0 mm² or No.14 TW AWG wire would be sufficient considering its 15 A ampacity that is bigger than 12.52 A as computed

4. But the National Electrical Code limits the size of convenience outlet wire to minimum of 3.5 mm² or No. 12 AWG copper wire. The code must prevail. Use No. 12 TW.

5. Determine the size of the conduit pipe. Refer to Table . For No. 12 TW wire, use 13 mm diameter pipe.

6. Find the Size of the Branch Circuit fuse protection. Refer to table. For 12.53 A non continuous load on convenience outlet, use 20 AT breaker.


C. Circuit - 3 Other Load

1. Laundry Circuit at 1500 watts per circuit (PEC provision)

1500 watts/230 volys = 6.52 A

2. Find the size of the branch circuit conductor. From Table, use 3.5 mm² or No. 12 TW copper wire, the minimum size for convenience outlet.

3. Find the size of the conduit pipe. From Table, use 13 mm diameter pipe.

4. Find the size of the branch circuit fuse protection. From Table. The 6.52 A load on convenience outlet requires 20 A fuse or trip breaker.


D. Circuit - 4 Cooking Unit

1. Total Load is 5.1 kW = 5100 watts

2. Refer to Table Demand load for household. For electric range, apply 80% demand factor.

Total load x demand factor (Df)
5100 watts x .80 = 4080 watts

3. Compute for the line current load. Divide:

4080 watts/230 volts = 17.74 A

4. Find the size of the branch Circuit wire. Refer to Table 0.1 or 11.1. For 17.74 A line current, use 5.5 mm² or No.10 TW copper wire.

5. Determine the size of the conduit pipe. From Table, for No.10 TW wire, use 20 mm diameter pipe.

6. Find the size of the branch circuit fuse protection. Refer to Table, for 17.74 A current load, use 30 A fuse or trip breaker.


E. Determine the sub-feeder per dwelling

1. Solve for the total connected load per dwelling.

Lighting load ........................................ 1920 watts
Convenience Load ,............................... 2880 watts
Other loads 5.1 + 1.5 kW........................ 6600 watts

TOTAL....................................11400 watts

2. Apply 80% demand factor (see Table)

TOTAL LINE CURRENT = (11400 watts x.80 df)/230 volts

= 39.65 A

3. Determine the Size of the sub-feeder and protection per dwelling for 39.65 A. For Table 9.1 or 11.1, use 8.0 mm² or No. 8 wire THW copper wire.

4. Find the size of the conduit pipe. For 8.0 mm² wire, specify 25 mm diameter pipe.

5. Determine the size or rating of the fuse protection. From Table, use 60 A molded Circuit breaker 2- wire 250 volts with solid bus.



F. Determine the Size of the Main Feeder

1. Solve for the Total connected Load on 4 dwelling units at 11400 watts each. Multiply:

11400 watts x 4 = 45600 watts

2. Refer to Table. For 4 dwelling units apply 45% demand factor. Multiply:

45600 watts x .45 = 20520 watts

3. Solve for the line current:

I = 20520 watts/230 volts = 89.22 A

4. Determine the Size of the Conductor wire. Refer to Table. For 89.22 A, use 2- 50 mm² TW copper wire or 2- 38 mm² THW copper wire.

COMMENT:

IT will be noted in Table, that the 89.22 A as computed does not exceed 80 % of the 120 allowable ampacity of 50 mm² TW copper wire or 125 ampacity of 38 mm² THW copper wire. Therefore, any one of these two types of wire could be used for main feeder.

5. Find the size of conduit pipe. Refer to Table. Use 38 nn diameter RSC or IMT pipe

6. Find the size or rating of the over-current protection. Refer to Table. Use 125 A safety switch,250 volts, 2 pole.

ILLUMINATION CALCULATION AND DESIGN FOR SINGLE FAMILY DWELLING

PRINCIPLES OF ILLUMINATION

6 – 1 INTRODUCTION

Illumination is defined as the intensity of light per unit area. When we talk of illumination, or simply lighting, we are referring to man made lighting. Daylight being excellent is not included, thus, we assume a night time condition.

Electric Illumination is the production of light by means of electricity and its applications to provide efficient, comfortable and safe vision. Specifically, when one speaks of lighting design, he refers to only two things:

1. The quantity of light

2. The quality of light

Quantity of Light – refers to the amount of illumination or luminous flux per unit area.

Quantity of light can be measured and easily handled because it deals with the number of light fixtures required for a certain area.

Quality of Light – refers to the distribution of brightness in the lighting installation. It deals with the essential nature or characteristics of light. In short, quality of light is the mixture of all the items related to illumination other than the quantity of light which includes several elements such as:

1. Brightness

2. Brightness ratio or contrast

3. Glare

4. Diffuseness

5. Color

6. Aesthetics

7. Psychological reaction to color and fixtures

8. Economics

There are four factors that affect illumination, namely:

1. Brightness

2. Glare

3. Contrast

4. Diffuseness

Brightness is the light that seems to radiate from an object being viewed. Brightness or luminance is the luminous flux (light) emitted, transmitted or reflected from a surface.

Contrast is the difference in brightness or the brightness ratio between an object and its background. The recommended brightness ratio between an object being viewed and its background is normally 3:1.

If a print on a white paper can be clearly seen on a light background, it is due to the effect called contrast. Likewise, if a light object is placed on a dark background, the light object reflects more light and looks brighter although bought have equal illumination. It is for this reason that office furniture are generally light colored, tan or light green for eye comfort.

Glare is a strong, steady, dazzling light or reflection. There are two types of glare:

1. Direct Glare is an annoying brightness of light in a person’s normal field of vision.

2. Indirect or Reflected Glare is much more serious and difficult to control. Technically, reflected glare is a glossy object.

Diffuseness refers to the control of shadows cast by light. Diffuseness is the degree to which light is shadowless and is therefore a function of the number of directions to which light collides with a particular point and the comparative intensities.

Perfect Diffusion is an equal intensities of light clashing from all directions producing no shadows. A single lamp will cast sharp and deep shadows. A luminous ceiling provides a satisfactory diffuse illumination and less shadows.

The color of lighting and the corresponding color of the object within a space is an important consideration in producing a quality of light.

There are three characteristics that define a particular coloration. They are:

a. Hue – is the quality attribute by which we recognize and describe colors as red, blue, yellow, green, violet and so on.

b. Brilliance or Value – is the difference between the resultant colors of the same hue, such as: white is the most brilliant of the neutral colors while black is the last.

c. Saturation or Chroma – is the difference from the purity of the colors. Colors of high saturation must be used in well lit spaces.

6 – 2 ESTIMATING ILLUMINATION AND BRIGHTNESS

In many respect, it is more important to know luminance measurements than illumination because the eye is more sensitive to brightness than simple illumination. However, it is more difficult to measure luminance than illumination.

There are three types of luminance meter, namely:

1. The Comparator type which requires the operator to make a brightness equivalence judgment between the target and the background.

2. The Direct Reading type is basically an illumination meter equipped with a hooded cell arranged to block oblique light.

3. The Accurate Laboratory Instrument which unsuitable for field work.

The quantity of light level of illumination can be easily measured or calculated with the aid of portable foot candle meter.

Footcandle (fc) is the amount of light flux density. It is the unit of measure used when describing the amount of light in a room and is expressed in lumens per square foot.

Footlambert (fl) is defined as “the luminance of a surface reflecting. Transmitting or emitting one lumen (lm) of illumination per square foot of area in the direction being viewed or the conventional unit of brightness or luminance. In the same manner, the lumens (lm) is the light output generated continuously by a standard wax candle

In our study of light, we are interested in the amount of light that fall on the areas that we want to illuminate. We also want to know the lumens per square foot or square meter in a space.

This quantity called Light Flux Density is the common term Foot-candle (fc) represented by the formula:

Footcandle = Lumens

Area

ILLUSTRATION 6 – 1

A 40 – watt fluorescent lamp 120 centimeters long produces 3,200 lumens of light in a room having a general dimension of 10 x 20ft. Find the illumination on the floor.

SOLUTION

Footcandle = Lumens

Area

fc = 3,200 lm. = 16 footcandle

10 x 20 ft.

The footcandle is an important unit of measure in calculating the desired illumination and layout of fixtures. In the absence of Tables of equivalent footcandles for a particular fixture, a rule of thumb of 10-30-50 illumination level is here presented.

10 – footcandle is adequate for halls and corridors

30 – footcande is sufficient for areas between work stations such as in offices other than desk areas.

50 – footcandle is satisfactory on spaces where office work is done.

However, providing an adequate quantity of light alone is not a guarantee for an efficient and comfortable vision. In fact, the quality of light is very important especially where difficult visual needs are required. The luminance or brightness of a diffusely reflecting surface is equal to the product of the illumination and the reflectance. Thus;

Luminance = Illumination x Reflectance factor or

Footlambert = Footcandle x Reflectance factor

ILLUSTRATION 6 – 2

From illustration 6 – 1, find the luminance if the reflectance factor of the wall is 40%.

SOLUTION

1. Footlambert = Footcandle x Reflectance factor

= 16 x 40% = 6.4

Metric Lighting Units

In English System of measure, the distance is expressed in feet and the area is in square feet. Under the Metric System (SI) the distance and area are expressed in meters and square meters respectively.

Meanwhile, Lumens flux remains in Lumens but illumination or light flux is expressed in Lux. Thus:

Lux = Lumens

Area (sq. m.)

Table 6 -1 APPROXIMATE REFLECTANCE FACTOR

In the metric system, Luminance or Brightness is expressed in Lambert which is defined as “the luminance or brightness of a surface reflecting, transmitting or emitting one lumen per square centimeter. Millilambert is more conveniently used than the lambert because the value of lambert is greater than what is usually encountered.

Table 6 – 2 TABLE OF COMPARISON

ILLUSTRATION 6 – 3

A 40 – watts x 120 centimeters long fluorescent lamp produces 3,200 lumens of light in a room having a general dimension of 10ft. x 20ft. Compute the illumination on the floor comparing the English and the Metric units.

SOLUTION BY COMPARISON

English Metric (SI)

Light Flux = 3,200 lm. …………………. 3,200 lm

Area = 10’ x 20’ …………………. 10 x 20

10.76

= 200 sq. ft. ………………… 18.59 sq. m.

Illumination = 16 fc ……………………… 172.16 lux

Another SOLUTION

Convert: 10 feet to meter = 3.048 m.

20……………. = 6.097 m.

Lux = 3,200 = 172.19 Lux

3.048 x 6.097

ILLUSTRATION 6 – 4

Compute for the brightness of a fixture with a 1’x 4’ plastic diffuser having a transmittance of .6 and illuminated by 2 pieces 3,200 lm. lamp assuming 100% use of light flux.

SOLUTION

1. Luminance = Total lumens x transmission factor

Area of diffuser

= 2pcs. x 3,200 x .6

1’ x 4’

= 960 footlambert

1. To obtain the metric equivalent, multiply:

Millilambert = Footlambert x 1.076

= 960 x 1.076

= 1032.96 millilambert

The Watts per Square Meter

Another method used in determining the illumination is the watts per square meter wherein the floor area is computed from the outside dimensions of the building excluding open porches.

Depending upon the size of the room, color of wall and ceiling, types of lighting units and methods of lighting used, the watts per square meter method is may produce 50 to 100 lux which is approximately 5 to 10 footcandles.

1. Twenty watts (20) per square meter will provide an illumination of 100 to 150 lux which is approximately 10 to 15 fc in industrial areas.

2. For commercial areas, two (2) watts per square foot or 22 watts per square meter is will provide from 80 to 120 lux when used with standard quality equipment.

3. Forty (40) watts per square meter will provide about 200 lux which is approximately 20 fc wherein greater illumination is required

4. Sixty (60) watts per square meter will provide about 300 lux or approximately 30 fc which is recommended for many conventional, industrial and commercial requirements.

5. Eighty (80) watts per square meter will provide from 300 to 350 lux and in excess of supplementary lighting is necessary.

6 – 3 COEFFICIENT OF UTILIZATION AND MAINTENANCE FACTOR

The usable Initial footcandle or lux is equal to the footcandle produced by the coefficient of utilization (cu).

Initial was emphasized because the output is of a light fixture is reduced with time as the lamp fixture is becomes old and dirty. Lamp output normally drops and is termed as Maintenance factor (mf). And to find the average maintained illumination, we reduce the initial illumination by the maintenance factor.

The efficiency of a light fixture is equals the ratio of fixture output lumens to lamp output lumens. What we need is to determine a number indicating the efficiency of the fixture room combination, or how a particular light fixture lights a particular room. This number is normally expressed in decimal value called coefficient of utilization represented by letter (cu).

The usable initial footcandle is equal to the footcandle produced by the coefficient of utilization (cu).

a.) Initial Footcandle = footcandle x cu.

Area

b.) Maintenance illumination = Lamp lumens x cu x mf

Area

* Lamp lumen therefore is simply the rated output of the lamp.

TABLE 6 – 3 COEFFICIENT OF UTILIZATION

TABLE 6 – 4 MAINTENANCE FACTOR

ILLUSTRATION 6 – 5

A school classroom with a general dimension of 24 x 30 ft. is lighted with 10 fluorescent of 4F 40 T12 WW rapid start lamp. Calculate the initial and maintained illumination in footcandles (English) and Lux (Metric) assuming that (cu) is 0.35 and (mf) is 0.70.

SOLUTION – 1 (English Measure)

1. Refer to Table 5 – 3. An F 40 T12 WW watts fluorescent lamp has 3,200 lm. output. Multiply:

Lamp lumens = 10 fixturesX 4 lamps per fixture X 3,200 lumens per lamp

= 128,000 lumens

Initial footcandle = 128,000 x 0.35

24 x 30 ft.

= 62.22 fc x 0.70 mf

= 43.55 footcandle

SOLUTION – 2 By Metric Measure (SI)

Convert feet to meter: 24 ft. = 7.32 m.

30 ft = 9.14 m.

Lux = Lumens x cu x mf

Area

= 10 x 4 x 3,200 x 0.35 x 0.70

7.32 m. x 9.14 m.

= 468.75 lux

Check the answer:

One lux = .09294

468.75 x .09294 = 43.56 fc.

Sometimes when the size of the room and the footcandle are given, the problem is how to find the number of lamps required in each fixture. The following example is offered.

ILLUSTRATION 6 – 6

An office room having a general dimension of 8 x 20 meters is to be lghted at an averaged maintained footcandle of 50 fc, How many 3-lamp fixtures of 120 centimeters long F40 T12 WW rapid start fluorescent lamps are required assuming the cu is 0.38 and the mf is 0.75?

SOLUTION

1. Lamp lumens = maintained footcandle x area

cu x mf

= 50 fc x (8m. x 20 m.)

0.38 x 0.75

= 28,070 lumens

2. Each 40 watt fluorescent lamp has an output of 3,200 lumens, the number of lamps will be:

Number of lamps = 28,070

3,200

= 8.77 lamps

3. Since there are 3 lamps for each fixture, divide:

8.77 = 2.93 say 3 lamps in ach fixture

3

Calculation involving a wide area is more confusing than by computing the number of lamp fixtures per bay or per row which is more meaningful and interesting.

This could be done easily by using the following formula:

Number of mixtures = Illumination x area

Lamp per fixture x lumens x cu x mf

This means that the area lighted by a single area is:

Area per fixture = lamp per fixture x lumens per lamp x cu x mf

Illumination

TABLE 6 – 6 EFFICACY OF VARIOUS LAMPS

ILLUSTRATION 6 – 7

An entire office floor is lighted at an averaged maintained 538 lux or 50 fc. The floor measures 20 meters by 50 meters and is divided into bays measuring 4 m. x 5 m. Using 2-lamp of F40 T12 CW rapid start preheat lamp, find the number of fixtures required. Assume an economy grade fixture with a lo cu of 0.35 and mf of 0.70

SOLUTION – 1

Solve for the number of fixtures per bay.

Refer to Table 5-3 for F40 T12 CW = 3,150 lm.

No. of Fixtures = Illumination x area

Lamp per fixture x lumens x cu x mf

Fixtures = 538 lux x (4 m. x 5m. )

2-lamps x 3,150 lm. x 0.35 x 0.70

= 10,760 = 6.9 fixtures

1,543

Accept 6 pieces per bay to make it symmetrical

SOLUTION – 2

1. From the following Formula, substitute the values:

Area per Fixtures = Lamp per fixture x lumen/ lamp x cu x mf

Illumination

Fixtures = 2-lamps per fixture x 3,150 lm. x 0.35 x 0.70

538 lux

= 1,543.5 = 2.87 sq.m. per fixture

538

2. Therefore, the number of fixture per bay is:

4 m x 5m = 6.9 say 6 pcs. Per bay for symmetry

2.87

6 – 4 MEASURING FOOTCANDLE

The unit measure of illumination is the footcandle or lux in the Metric System which is frequently used when describing the amount of light in a room. It is not enough to know how to calculate the illumination level but it is also equally important to know how to measure them in enclosed space. In measuring illumination level, the footcandle meter is held horizontally with its sensitive surface at least 30 centimeters from the body of the person holding the meter, The meter could be placed on a table and read from a distance to avoid obstruction of the light.

In conducting a general illumination check inside a room, the meter is held at least 80 centimeters above the floor. Reading is undertaken throughout the room and the results are recorded on the plan of the room.

a. All dimensions in meters

b. These spacing apply where desks and benches are next to wall, otherwise, one third the spacing between units is satisfactory.

c. The actual spacing of luminaries is usually less the maximum spacing to suit bay or room dimensions.

d. For mounting height of general diffusing and direct-indirect fixtures.

6-5 Uniformity of Light

The purpose of lighting calculations, by the foot-candle or lux, is to determine the average illumination in a room or lux, is to determine the average illumination in a room to a working level condition. This working level condition refers to the height of 75 centimeters above the floor being the approximate height of the table. The average illumination at the working level is directly related to the maximum spacing of the light to the mounting height ratio represented by the formula.

S/mh where: S = Spacing of light fixtures

mh = mounting height

Normally, the manufacture of light provides data with respect to spacing and mounting ratio. However, in the event that the manufacturer failed to provide these data, Table 6-8 was presented shoeing the spacing and mounting height ratio for particular lighting conditions.

Table 6-8 SPACING AND MOUNTING HEIGHT RATIO

ILLUSTRATION 6-8

A room with a ceiling height of 3 meters is to be lighted with direct concentrating fluorescent light. What is the maximum fixtures spacing?

SOLUTION:

1. For spacing and mounting ratio, refer to 6-8. The mounting height ratio od direct concentrating light is 0.40.

Therefore:

2. Substituting the given values, wherein mh is the ceiling height,

S = 0.40 x 3.00

Spacing: S = 1.20 meters maximum side to side of the fixtures.

ILLUSTRATION 6-9

A warehouse will install pendant dome incandescent lamps at a mounting ratio of 1.50 meters. The lamp will be mounted on a grid measuring 5.00 x 5.00 meters. What is the minimum mounting height of the lamps?

Solution:

Mounting height is; mh = Spacing

Ratio

mh = 5.00 m. = 3.30 meters

1.50

6-6 Classification of Lighting System

Lighting system is classified into four types, namely:

1. Direct lighting 2. Semi-direct lighting

3. Semi-indirect-lighting 4. Indirect Lighting

Direct Lighting. When the light on an illuminated area is focused downward coming directly from the lighting fixtures.

Semi-Direct Lighting. When the predominant light on the illuminated area is fed directly from the lighting units wherein the greater amount of light is obtained from the ceiling through the reflection.

Semi-Indirect Lighting. A lighting arrangement wherein 5% to 25% of the light is directed downward with more than half of the light focused upward and reflected from the ceiling.

Indirect Lighting. When the light is diffused and reflected from a wide ceiling area. This kind of lighting produces a soft and subdued effect due to low brightness and absence of sharp shadows.

FIGURE 6-6

CHART FOR ESTIMATING LIGHTING LOAD AND ILLUMINATION LEVEL CALCULATED FOR FAIRLY LARGE ROOM

6-7 Street Lighting

The Institute of Integrated Electrical Engineers instituted guidelines for adequate and acceptable illumination of the streets in order to promote safety. This concept was brought about by the continuously increasing speed of motor vehicles using the road.

The Philippine Electrical Code Committee prepared the guidelines for a standard practice on design of street lighting installation recommending the proper quantity and quality of light for traffic routes.

Definition of Terms

Lighting Installation – is defined as the whole of the equipment provided for lighting the roadway comprising the lamps luminaries, means of support and electrical installations including other auxiliaries.

Lighting System – refers to an array of luminaires having a characteristic of light distribution.

Luminaire – is a housing for one or more lamps comprising a body and any refractor, diffuser or enclosure associated with the lamps.

Road Width – is the distance between the edges of the road curbs measured at right angles to the length of the roadway.

Outreach – is the distance measured horizontally between the outer of the column or wall face or lamp post and the center of the luminaries.

Overhang – is the horizontal distance between the center of luminaires and the adjacent edge of the road.

Mounting Height – refers to the vertical distance between the center of the luminaire and the surface of the roadway.

Spacing – is the distance between the successive luminaries in an installation.

Maximum Light Utilization – In order to attain the maximum utilization of light from the fixtures, the luminaires should be mounted under the following specifications.

Working Voltage

Luminance are properly selected and mounted on a location most feasible and effective with minimum cost. For a 230 volt system, a voltage drop of 5% is allowed although in extreme cases 15% voltage drop is sometimes tolerated.

For street illumination, the following formula is adopted.

Where:

E=The illumination in lux

Al=Average lumens with a typical value of:

20 500 lumens for 40 watts

11 500 lumens for 250 watts

5 400 lumens for 125 watts

The value of Al varies depending upon the type of lamp specified.

mf- is the maintenance factor which depends on the following:

a). Maintenance practice of the company

b). Operation of light sources at rate current and voltage

c). Regular replacement of depreciated lamp

d). Periodic cleaning of the luminaires either 0.8-0.9

w = Width of the roadway

d = Distance between luminaires

cu = Coefficient of utilization which is dependent on the type of fixture, mounting height, width of roadway and the lenght of mast arm or outreach.

The values given are based on the favorable reflectances for asphalt road, the recommended illumination should be increased by 50%. For concrete road, the recommended value could be decreased by 25%.

In decreasing street illumination, consider the modern lighting today that will be obsolete tomorrow when the minimum light levels are raised. The increasing motor vehicle speed and the incerasing congestiin in the street requires higher level of highway lighting. Therefore, future needs for light should be considered in the design.

ILLUSTRATION 6-10

Considering the data as presented on Figure 6-7 when the night pedestrian traffic is estimated oto be light and the night vehicular traffic is to be medium, determine the required lumens if theroad concrete is a pavement.

SOLUTION

1. Refering to Table 6- 9, E= 6.46 for light pedestrian medium traffic classifications. For concrete road, the reflectance will be higher but let us accept the value of 6.46 lumens.

2. Determine the average pole distance.

E= 6.46 lumens per sq.m.

w= 7.00 meters

d= 50 meters

mf= 0.9

cu= 0.29 (type A fixture)

Under the Working Voltage, the mean lamp lumens of a 250 watts lamp is 11, 500 lumens, this is the nearest value to 8,662.83 average lumens. Therfore, a 250 watts lamp is acceptable.

Computing for the new actual illumination E

This is higher than the 6.46 recommended in table 6- 11. Therefore, the road is considered as adequeately lighted.