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Engr. Amando D.Lanuza, PEE
A newly passed Professional
12 years in government service as City
A former OFW
A former Barangay Electrician
3 time IIEE Chapter President of IIEE
Light- is a form of radiant energy
from natural sources(e.g. sun and
stars), and artificial sources (e.g.
candle and electric lamps). It travels in
a form of an electromagnetic wave,
so it has wavelength and a known
speed. Like other electromagnetic
radiation, it can be reflected and
Lighting – is the application of
light to illuminate objects,
surfaces, scenes, pictures and
Lighting on the other hand is
the application of light to
illuminate objects, surfaces,
scenes, pictures and people.
Luminous flux (Ø)- All the radiated
power emitted by a light source.
Luminous intensity - The
visible radiant intensity in
a particular direction. The
unit of measurement is the
candela ( cd )
Illuminance (E)- is a measure of
the amount of light falling on a
surface. Unit of measurement is
Luminous Efficacy (ŋ)
Luminous efficacy indicates the
efficiency of the light source with
which the electrical power
consumed is converted into light.
The unit of measurement is lumens
per watt ( lm/W).
The design for indoor
lighting system general
illumination is considered to
be more of an art than a
science and it involves many
Factors for indoor lighting
Size and shapes of the space.
Types of finishes on ceilings, walls and
The details of the construction
The economic consideration of both the
initial and operating cost.
The compatability of the lighting system
with the architectural design.
The type of activities that will be carried
out in a particular area.
Objectives and design
Determination of required level of
Area description and Use
Selection of System Luminaire.
Determination of required level
See table for recommended illumination level
for different types of occupancies by
Illuminating Engineering Society of North
Quality of Light
Pertains to the distribution of brightness in
the lighting installation. Involves the
comfort of seeing the environment .
Factors to consider are , brightness,
contrast or luminance ratio, glare,
diffuseness and color.
The quantity of light involves adequate level
of illumination for the average person under
Analyze the environment in which the
lighting system will operate. For example, are
dirt, water vapor, explosive gasses or
corrosive vapor present?
Area description and use:
A complete description is required for each
area to be lighted, this includes physical
characteristics such as room dimensions,
room reflectance and work location.
Selection of system luminaire
Selection of the type of luminare for a given
application depends upon the requirements
and conditions stated above.
The average illuminance level can be
determined when a given number of
luminaires used in a space is known.
Likewise, the number of luminaires
can be determined given the average
Within the room, the illuminance is
determined based on the horizontal
plane, which is considered as the
work plane. The work plane is
measured at the height of the visual
task. In the office this would generally
be at a height of 0.75 meter above the
floor, the average height of an office
table. In the corridors , the work plane
is usually considered to be the floor.
The general equation for the
illuminance in a work place
Ø(TOTAL) x CU x LLF
E WP = ------------------------------
E wp - Work plane illuminance, lx
Ø(TOTAL) – total system lamp lumen
CU – coefficient of utilization.
LLF- light loss factor
A wp – area of work plane , m²
Work plane illuminance,Ewp :
The average maintained luminous flux
that hits the work plane per unit area. The unit
of measurement is lx.
Total system lamp lumen output , Ø total:
refers to the quantity of light produced by
all lamps that are lighting a space.
Coefficient of utilization ,CU:
The ratio of the lumens that reaches the
work plane to the total lumens given off by
the lighting system
All the lumens from the lamps in a lighting
system generally do not reach the work
plane. Some of them are absorbed by the
floors, walls and ceilings before reaching the
work plane. The fraction of luminous flux
emitted by the lamps that reaches the work
plane in a space is the coefficient of
utilization. If 50% of the light given off by the
lamp reaches the work plane, then CU is 0.50,
in some cases the CU can be grater than 1.0
for rooms with higher reflectances and lamps
with higher efficacy.
Light Loss Factor (LLF):
is the ratio of illuminance
when it reaches the lower
level( just before corrective action
takes place) to the initial level.
The total light loss is the product
of all the individual factors that
contribute to the loss of light. It is
also known as the maintenance
Light Loss Factor (LLF) equation is:
LLF = LLD x LDD x RSDD
LLD - Lamp Lumen Depreciation Factor
The depreciation of lumen output of
lamp through life.
LDD- Lamp Dirt Depreciation Factor
With the passage of time, dirt
accumulates on lamps resulting to
loss of light.
RSDD- Room Surface Dirt
With the passage of time, the
accumulation of dirt on the surface of
the room further reduces the amount
of light that reaches the work plane
Indoor Lighting Calculation
The Lumen Method:
This method is used to design
general overall lighting of the
room. This method calculates the
illuminance that represents the
average of the values at all points
over the entire work plane of the
The average illuminace of the work plane (E)
TILL x CU x LLF
E = ----------------------
TILL = total initial lamp lumens
Find out if two -36WT8
fluorescent lamp is enough to
illuminate a typical dining room
with dimension 3m x 4m ,
assuming the CU is 0.65 and LLF is
Looking at the manufacturer’s data of 36WT8
fluorescent lamp, luminous flux is 3350 lm.
using the formula:
TILL x CU x LLF 2 x 3350 xo.65 x 0.95
E = -------------- = --------------- --------=
Area 3 m x 4m
= 334.78 lux
Looking at the Table:
Recommended level of
illumination by IESNA for Dining
rooms is 540 lux.
2 -36WT8 FL is not enough
Use 3 - sets
Uniformity of Light:
The average illumination at work plane is
directly related to the maximum spacing of
the luminaire to the mounting height ratio
ratio = -----
Where : S = spacing of light fixtures
MH = mounting height
Assume that the mounting height of lighting
fixture is 3 meters from the floor. What is the
maximum spacing of fluorescent.
Recommende spacing and mounting height
Type of light s/mh Ratio
Direct concentrating 0.40
Direct spread 1.20
Semi –direct/ indirect 1.50
Using the formula:
ratio = ------ =
s = 3 x 0.40 = 1.2m
An office room having a dimension of 8 m x 20 m
Is to be lighted with a maintained illumination.
How many 3- lamp 36wFL parabolic troffer are
From the formula:
illumination x area
N = ----------------------------------------
lamp per fixture x lumen x CUx LLF
Looking at the manufacturer’s data of
36watts fluorescent lamp , luminous flux
= 335000 lumens.
Recommended illumination level for offices is
Assume CU = 0.65
1600 (8 x 20)
N = ---------------------------
3 x 3350 x 1.0 x 0.95
N = 26.8
use : 24 sets or 28 to make it
The design of lighting system
requires knowledge of basic
lighting terms combined
simple mathematical or
graphical presentation and
The methods and calculation in the
lighting system design presented in
this presentation are based on the
recommended procedures of
Illuminating Engineering Society of
North America (IESNA) .The formula
presented are only meant to be a
general overview on illumination