THESIS
AN TULUM AE CON ag HSA SED LS
RAYMOND C. KINNEY
oho P4
Cort
EE eae
~~
- oF,
‘sa
~~
~
“
wa
.
sy,
c- ye
. «
._ =
a J
NN .
-
. ee
~~ ; ;
—_*
Ee
* f
THESIS
A
A
Commercial Lighting In
Offices, Stores and Show windows
A
Report Subimtted to the Faculty of the
Michigan Agricultural College
Raymond C. Kinney
A
Candidate for the Degree of Bachelor of Science.
June 1021.
THESIS
401993
CONTENTS
Preface----------- - 2-22 - + e+ - ee = 2-2
Bibliography-----------------------------------------
IMTBODUCTION
Fundamental Concepts
Units OF Measure
The Candle
Mean Sph. Candle Power
The Lumen
Foot Candle
Foot Candle Meter
CHAPTER 1
The Story of Artifielal Light
CHAPTER 2
COlor
The Language of Color
Effect of Color oh and Ceiling
Meas. of Refl. Factor of Walls
Color Chart
Chapter 5
Good Lighting Practice
Glare
Eliminatio of Glare
CHAPTER 4
Caleulation of the Lighting Installation
Candle Power realtions
Method of Using tables
Flux of Light Method
Utilization Constants
Medified Flux of Light Method
Examples
Revising a Present Installation
CHAPTER §
Tests on Various Unite
Phantom View of Comm « Unit
Comperisen of Types of Units
CRAPTER 6
Lighting of Office Buildings
liethods
Comparison of Systems
Spacing of Outlets
Wattage Required
¢
e
4
07
105
106
107
109
211
117
118
CONTENTS (Cont 'D)
Lignting Corrédors 120
Misc. Uses of Light 122
Examples 125
Poair Graph of Duplexalite 127
Guplexalite Units and S hades 28
Hxamples 129
CHAPTER 7
Store Lighting : 133
Utilization of Light 133
Quantity of Light Required 133
Cause of Effect 134
Direct Lighting 134
Semi Ind. Lighting 157
Indirect ,ighting 139
Lighting biassware 139
Totally Bncl. Globes 140
Ceiling Outlets 141
Light and Advertisement 141
Dppartment and Larke Stofes 145
Stores ov Medium Size 149
Exclusive Stores 1§1
Small Stores 162
Yiuumin . Intensities 154
Coeff. OF UTILIzation 184
Calculation Of Required Wattage 156
Amount of Light Required 158
Classes of Installation 189
Comments 166
Examples 167
CHAPPER S
How to Plan Window Lighting L171
Comparison of Illuminants 173
Brightmess of Window 173
Importance of Background 175
Reflectors and their use 176
Possibilities in Color Brfects 183
Spacing Rfelectors 187
Concealment of Tiluninants 188
Sign Transparencies 1.89
CHAPTER 9
Maintenance of Lighting Sgstem 1021
Depreciation of Lamps 192
" " * Reflectors 195
Surroundings 1398
CONTENTS (Cont'd)
oystem of Cleantng
Method of Cleaning
TABLES
NO.
1 Intensity on Horiz. Plame
8S Zumen output Of Masada Lamps
S0Spacing Mounting Height
42 Spacing ceiling Height
13 Classification
14 Watts Per Sq git. (Semi Enel. Unit)
ist" (Sotally Encl. )
16 ” " " (8ndirect )
17 " " " (Semi-End. )
18 " " " (Duplexalite )
CURVES
SYMBOLS
199
201
205
204
205
206
207
209
210
211
212
215
214
219
PREFACE
In th’s thesis the author has attempted to
compile under one cover all necessary information
necessary to properly design the artificial illumina-
tion for offices, sto-es and store windows, There are
no books on the market to date which combine the
theoretical with the commercial side of the designing.
As far as possible the author has given concrete
examples and illustrations of the different methods
in use and their epplication. Although the greater
part of this thesis is not original with the writer,
he cannot help but feel that the time has been well
spent, since a quick reference library on commbrecial
lighting has been the result.
The author is indebted to Frof. Foltz of the
of the electrical department for his preliminary course
on flluminatinpns, and for his his many timely sugges-
tions as to available material.
BIBLIOGRAPHY
BULLETINS
ITllum. Design Data
Effect of Color on Walls
Brascolite
Lighting of Office Buildings
Calculation of the Lighting inst.
Numerous trade publications
Transac. of EF. F. S.
BOOKS
Illuminating Eng. Prac.
Tha Lighting Art
MAGAZINES
FE. Worid
E. World
E. Rev?
Gen. Flec., Rev.
Blec. Jl.
ZH. World
Elec. Rev. & West. Flec.
Blec. Rev. & West. Flec.
Bul. 41 W. E. Co.
Bul. L. D. 102 G. E.
Cat. No. 8
Bul. L. D. 108 G. FE.
Bul. L. D. 117 G, E.
Vol. IX No. 2.
Vol. X No. 8
Tll. Eng. Soc.
Luckiesh
Vol. 52, No. 2.
Vol 73, No. 7
Oct. 5, 1918.
Mey 1918.
June 1917
July 14, 1°17
May 12, 1917.
Aug. 25, 1917.
INTRODUCTION
"Twas a light thet made
Darkness itself appear
A thing of comfort."
Light is one of the dominating agencies in life and progress
for it is important to our most important educative sense-
vision. The possibilities extend into all those activities
which make their appeal to human oonsciousness thru the door-
way of tision. The importance of lighting is limited only
by the bounds of human activities and its broadest sense, its
importance extends even beyond them, for it is one of the most
important in the scheme of creation. The activities of primi-
tive man were practicall: bounded by sunrise and sunset, and
darkness was feared as the abode of evil spirits and of lurk-
ing dangers. Doudtless light was merely a by-product of the
fire whose primary function was to furnish heat, nevertheless
we may imagine primitive man with his burning kno® exultent
in his victory over Nature. This achievement was one of the
most important mile stones on the highway of human progress.
Man's activities were no longer limited to daylight hours end
greater opportunities were before hin.
In the early days of lighting as a distinct profession,
the engineering aspects were given prominence. In fact,
lighting today is practiced largely from this standpoint not
withstanding that the efficiency and adaptability of modern
Llluminants have made possible the realization of lighting to
meet very largely all the requirements of the human activities
-_ fF
and desires in respect to this agency. With this growing atten-
tion to lighting we find as in many other activitics, that
ag in-many other wetivittes; thet the deeper we delve the more
extensive are the ramifications and comparitively smaller is
the part of the apparent whole with which we are thoroughly
familiar. For this reason arg the -hysiologist and ophthal-
mologist have been attracted to the problems of lighting which
involve the visual organs. The physicist ppecializes in many
of the problems of production and utiligation of light. The
psychologist finds an unexplored field for his endeavors for
finally the problem of lighting is largely psychological. fhe
artist finds an outlet for his ability in clothing scientific
lighting principles with artistic exteriors in lighting fix-
tures, also in using lighting as a decorative medium by
"nainting” with licht as obtained primarily from the lighting
units. As we delve deeper into the problem of lighting we
find many intimate relations between lighting and the various
sciences and arts all of which must be appreciated by the
lighting practitioner before he is worthy of the title of
lighting expert.
The illuminating engineer should recognize that the esthe-
tics sense however dormant, is possessed by all humen beings
as is evidenced by the things about us. Perhaps we would not
a-ply the term, artistic, to magy of the scenes that greet us
during our daily routine; however, as we critically view any
of these scenes and eliminate in our imagirea tion all that is
not purely utilitarian, how different they would appeer.
Imagine this done to everything on earth and a fair apprecia-
tion of the value of the artistic and beautiful is obtained.
On theother hand the artist should appreciate that in a broad
sense in lighting, utility cannot be divorced from beauty. In
fact it is misleading to use these two terms as if they had
nothing in @mmmon. Beauty is in itself certainly useful as
veiwed from the brodd outlook upon life. The philosophy of
the deautiful teaches us that beauty is the harmonious en-
semble of the various parts, hence in lighting figtures
beauty in a broad sense is the harmony of scienoe and art.
But the consideration of the artistic aspect of lighting
should not end at the fixtures. In faot the greater figsld
lies beyond them in the distribution of light on the various
surfaces, such as walls and floor, and in the prduction of
shadows appropriate to thes etting and in the color which best
fits the spirit or mood of the occasion. This is one of the
most neglected aspect of lighting altho it is one of the most
extensive fields for development. Inasmuch as the prime object
of the lighting specialist is to sefeguard vision he secks for
rules which limit brightness and brightness-contrasts to safe
values. Research is contributing much of value by direct
attack on these problems. However, a rule which it seems safe
to follow, is that if the lighting does not offend the finer
esthetic sensibilities it is mot likely to be seriously hara-
ful in its physiological effects. Such a rule cannot be app-
lied safely as a criterion of the best possible illumination
~
but glaring lighting conditions have no place in an esthetic
harmony of light, shade and color.
In the industires and in various other activities in which
the vision is taxed the problems of lighting are not solved
by providing a sufficient intensity of illumination on the
working planes. In each case the various specific activities
should be studied in order to arraéug at the very best scondi-
tions for seeing. Sometimes objects on which the eyes are
focused are best seen as high lights on a dark ground and
other cases as dark shades against a relatively brighter
ground, The character of the shadows which is determined by
the position and angular extent ot the light source and by
the amount of scattered light reflected from the surroundings,
is of importance in distinguishing objects. The color of the
surroundings the spectral character of the illuminant and the
environment as a whole are factors that should be considered
and controlled by the lighting specialist in so far as he is
able.
What is Good Ligh‘ ing?
fhe anawer to the above question depends upon the interpre-
tation of the word "good", and this interpretation depends
upon the viewpoint of the observer. An interior may be well
lighted from the utilitarian viewpoint, with good uniformity
and sufficient intensity and yet badly lighted from the
artistic viewpoint. There is a great hisunderstanding regerd-
ing what constitutes artistic lighting. Some believe that
artistic lighting fixtures in the same ssale of mamificance
as the interior decorations should be conaidered. In faot,
t:i8 is the general impression of "ertistic lishting” and it
has become so prevalent that those who are not skilled along
this line have come to feel that, for the average atore or home,
artistic lighting is an extravagance far beyond realization.
This misunderstanding has arisen because no general information
has been circulated resarding the true relation of esthetics
to lighting. This relation is so {mportant that to neglect it
is positively detracting from the complete value of lighting
to the consumer, a detraotion which no eleetrical salesman
should allow to exist in his community, and one which i8 is
possible to avoid, providing a little consideration is given
to the subleot. Every salesman who has to come in contact
with the consumer realizes that the consumers’ satisfaction is
the bigzest asset in the salesman’s and his company's favor.
Satisfied customers do not complain, and become “boosters”
instead of “knockers,” and every corporation needs as many
friends az it can get.
Satisfaction from lighting depends on something more than
economy. The consumer who si continually subjected to the
“eoonomy" argument is alway s anticipating, and demanding
greater economy. And economy, like everything else, has its
limit, although it is difficult to draw the dividing line in
sich cases. For example, the proprietor of a drug store was
dissatisfied with the lighting of the glass urns filled with
colored solutions, suapended in his window, and requeated a
b
local electricrl salesman to suggest some method of improv-
ing same. The salesman after a superficial study of the con-
ditions recommended that larger Mazda lamps be used. In
accordance with the usual method of lighting such urns the
lemps were placed in sockets attached to flexible and adjust-
able tubing so that they were placed directly behind each urn,
constituting a misereble ineffective and inefficient arrange-
ment, for the contents of the urn could only be effectively
illuminated when the observer wes standing in one position--
Girectiy in front. The view from the side dis closed the
lamp and the glare was so great that the whole effectiveness
of the urn and its oolor was destroyed. In addition, the
larger lamps increased the current consumption and at the end
of the month the druggist became infuriated, upon receipt of
a bill considerably in excess of his average amount. The
salesman in his anxiety to satisfy his customer went from one
extreme to énother and installed Mezda lamps of the smallest
possible type, which failed utterly to reveal the coloring
matter in the urns, leaving the druggist thoroughly dissatis-
fied despite the reduction of his bill which ensued. By chance
ea lighting expert in the employ of the lighting company was
consulted and suggested that lamps of the originsl size be
used in a new way. The novelty of his suggestion immediately
eroused the interest of the druggist and 1t was carried out.
The colore’ solutions were remcved from the slaas urns and
their inner surface wae steined with ordinary lamp coloring.
The lamp wes then pleced inside end the effect when lizhted
~~}
was that of a uniformly colored turn, equally attractive from
any viewpoint, either by night or ‘by day. The opal coloring
which was used gave translucency without bprensparency and
neither the lamp itself nor its filement could be seen through
the colored glass. The dumgsist wes not only satisfied but
enthusiastic and became a first-oless "pooster" for the com-
pany, assisting their district representative on more than
ene occasion to close a prospect. This is mm example of food
lighting and good business combined, and where you find one
\ .
you will usually find the other.
The Practical Side of| It.
There is such a wide variety of Lighting equipment available
to-day that there is positively no excise for not specifying
the right thing. It is just es easy to give a customer what
he needs, instead of what he thinks he needs, if you oan pre-
sent the facts to him so he cm grasp them. Don't make the
mistake of letting a man buy the wrong fixture because he
thinks it's right, for eventually you will be blamed for the
transaction. Be careful as to the size of a sixture with ref-
erence to the interior or space it is to ocmpy. Nothing 1s
more crude or inartistic than a massive fixture in a small
interior or ceiling area, and a very small delicate fixture in
a large room. After you havéd determined your watts per sQuare
foot distribute them so that the effect to the eye will be
harmonious and pleasing. Never specify lighting systems with
direct a great deal of light upon a ceiling unless the ceiling
is a good condition and will stand such exposure.
Avoid gaudy ornamentation on glessware and fixtures.
Those festoons, wreaths, and dedallions stamped out of cheap
metal and soldered to cheap fixtures should be blacklisted.
They are the stock in trade of the alley-way electrician and
junk man. QObdtain some photographs showing examples of good
taste in lighting for large and small stores and residences.
Show these but don't make the cistake of copying exactly--
inject some originality tnto each particular case, and tell
your pepsepect why he Should be determined to have something
different.
Remember that the efficienty of the Mazda lamp is so great
that energy cost need not restrict you from planning and ocarry-
ing out any lighting scheme which may decur to you, providing
same is based upon the recognized prindiples of efficient direct
indirect, or semi-indirect illumination. Don't expect to use
the lamp é@nefficiently and obtain an artistic effect, tthat
is where the principles cf illuminating engineering must be
carefully observed. When inexpensive bowls are used, avoid
"prassy" finishes (even brushed brass is becoming too common, )
amd other finishes can de obtained even in the cheapest kind
of fixtures.
Under conditions where blefiding or toning a fixture's
metal work in with the celling is not possible you will get the
best results from a bronze finish, which is le sting and does
not depreciate so quickly from the effeots of dirt and general
wear and tear. The idea of "matching a figture with the
radiators and steam piping is a mistaken one from an esthetic
viewpoint. Pipes and radiators are never objects of art, and
their ugliness should be concealed by painting them (in a dead
finish? to blend exactly with their background. Then they are
unnoticeable.
The same treatment applies to wall switch plates and panel
boxes, lighting men seldom have the power to make stoh
changes but they ought to know about them, and make sugges-
tions whanever possible. Do not recommend silk shades which
are so thin that the filament of the lamp shows throught If
you are obliged to recommend such lamps, instruct thepurchaser
how to cut a slit in the inside lining and introduce therin a
filler of thin white paper (between the inner and outer
lining) which will eliminate this defect.
lu
Fundamental Concepts +
A mastery of the principles of illumination can ge grined
only by studying the subject from the ground up. In this, as
in other scientific subjects, it is necessary at the outset
for us to familiarize ourselves with the various terms used
in the art, especially those terms which designate units of
measurement, for these terms constitute the foundrtion work
upon which the final structthre is to be built. Just as we onoe
had to learn that there is a unit called the yard which is used
to measure length and t\at this unit has been subdivided into
three feet and each of these in turn into twelve inches, that
the gallon is a unit used to measure quantity and contains 251
cubic inches, so in illumination we have certain fundemental
units to study before measurements can be made and before de-
finite relations of cause and effect can be comprehended or
expressed. Basic definitions have a very academic and some-
times avery technical sonnd, although the units themselves,
once their definitions have been assimilated, and not merely
learned by rote, are comparatively simple. The @efinitions
which appear from time to time in this bulletin need not,
therefore, be committed to memory but should be thoroughly
digested so that the reader will grasp the distinction between
the different units end obtain a working knowledge of what
each stends for and the quantity it represents. The school-
# N. L. Wks of G. £.
li
boy may be able to define an acre wery accurately, but a farner
may not even know hew many square feet there are in an acre
and still heve a better conception of the extent of an acre;
the one point they both must first appreciate is that the acre
is a unit of area rather than oflength or volume. Very few
electricians or électrical engineers could off-hand give a
basic definition of the ampere, although they might all know
that it is a measure of the rate of flow of electric current
and have a praoticaé& conception of the maghitude of the unit.
If illumination it is of more practical value to have a con-
ception of the quantity of light represented by one lumen--to
,
ce
e
{, ds
Cane ee
\ Only a slender cone of light reeches the eye. |
know that, for example, 75 of these units represent the quantity
of light given off by a lO-watt lamp--than it is to be able to
tell precisely what a lumen is. If the unit of length which
we call amile were arbitrarily made shorter, the distance
between New York and Chicago would still be the sam, or if
the dey were divided into ten equal parts instead of 24 hours
tie planets would not change their speed of trave) or rate of
rotation. Obviously, it is of adv-ntage to standardize certain
units so that relations of magnitude can be expressed and under-
stood with precision, although the value we arbitrarily assign
as a standard is of little pmportence except from this stand-
point.
Units of Measure
The Candle
A generation or two ago when new light sources began to
supersede the cendle, it was sost natural that the illumina-
ting power of these new sources should be expressed in terms
of the candle familiger to all. It is probable that the very
first comparisons of two light sources were made by setting up
the two lemps in the line of vision and geuging them by means
of the eye, the most natural direction in which to look at
the sources being the horizontal. The eye is capable of measur-
ing only a very slender cone of light at one tim; in fact;
if the eye is an appreciable distance from the source, the
cone of licsht coming from a light assumes a straignt line.
While there are an infinite number of directions from which
the eye might look at the source, the light-giving power in a
horizontal direction was made the basis of oomparisons, and
the streagbh of the light in this direction from a candle made
according to certain definite specifications, was abbitrarily
chosen as the unit of intensity and called a candle. The
newer illuminants appearing on the soene were rated accorddng
to their strength in t is same direction and were steted to
Give so many candles, so that when we say a lamp gives 10 can-
dles we really mean that its intensity or strength in a horizon-
tal direction is equal to that of a group of ten standard can-
dies. This rating of a lamp is made by means of an instrument
called a photometer. a description of which will follow later.
One essential point to remember in t is connection is thet the
candle-power of a lamp represents the intensity in one direc-
tion only. In practice it has been customary for years to
rotate the lamp about a vertical axis while the candle-power
was being deter: ined and the result was known as the mean or
average horizontal candle-power, but even this determination
gives an average value of the intensity in the horizontal
directions only. It should be stated, however, that in compar-
>?
pe
«- . .
” , “. were oe
c . PMp tee eek - _— a .
” ~-ye me - - -. - Lone . en Oar eee , ee e ) 1
° . wat ~ , . ’
oF
Via
pie wo
.
. =
be . oe >
The Candle-Power in the Direction of the Photometer is
Not Changed by Partially Surrounding the light Source With a
Non-Refleoting Surface.
ing lamps on the basis of their horizontal candle-power,
the light in directions other than the horizontal was not
really ignored, for it was taken into consideration that mort
eources of light then in use gave off their light in about the
eame proportions in the different directions and that for this
reason the candle-power in a single dttection furnished a cri-
terion sufficiently accurate for the needs of the time.
To carry our conception of candle-power a little further,
let us asevume the conditons existing es the diagram above.
In Case A we have on the left a» stendard candle end on the
right a photometer pointed toward the candle. Prom what has
elready been stated, it iroveious that when the photometer is
balanced it will indicete an intensity of 1 candle. In Case B
we have surrounded the candle with a ephere having a moderately
large opehing. The inside of the sphere, we will say, has
been painted a dead black so that none of the rays striking it
are reflected but are absorbed and cease to be lisht--in other
words, are thrown away as far as our experiment is conderned.
In this case the photometer will still indicate ean intensity of
one candle in spite of the fact that a great deel of light has
been thrown away. In Case C, we have used a sphere with a
much smaller opening and are therefore wasting still more of
the light, but even in this case our photometer will indicrte
an intensity of 1 candle. In fact, our reading wi!l be 1 can-
dle regerdless of the size of the opening, that is, regardless
of the quantity of light we allow to be emitted, provided the
direct rays from the condle to the photometer are not obstruct-
ed. The proverbial candle hidden under a bushel will still
give an intensity of 1 cendle if there is a small hole in the
bushel for a beam to escape, although as far ae its illuninat-
ing value is concerned, it is still "hidden under a bushel”.
This leads us to the important conclusion that the candle-
power of source gives noindication of the total quantity of
light emitted by that source. Cendle-power, we may sry, is
A. Opening OR has Area of 1 square foot and emits 1 Lumen
B. one Lumen fails on Surface OPGR
analogous to a measurement of the depth of a pool of water
at a certain point on its surface--a measurement which is use-
ful for certain purposes but in itself gives no indication of
the quantity of water in the nook.
The firat fundsmental concept we have to deal with in
illuminetion, then, is ceandle-power, which is the measure of
etrength of a source to preduce illwninetion in a given direc-
tion, and thepower in a horizont:1] direction of a crndle made
according to certain specifications and burning under certain
conditions has been arbitrarily chosen as the unit 6or mensur-
ing this strength.
The mean spherical candle-power os a lamp is simply the
average of all the candle-powers in 811 directions about that
lamp.
Fig. 6--The Illumination on a Surface Varies Inversely as the
Square of the Distance from the Source to the Surface.
this same beam of light would have to cover four times the
area of A; and, inasmuch as we cannot get something for noth-
ing, we would find @hat the average intensity on B, 2 feet away,
would be one-fourth as high as that on A, 1 foot away, or one-
fourth of a @oot-candle.. In the same way, if B also is remov-
ed and the same beam allowed to fall upon plane C, 8 feet away
from the source, it will be spread over an area nine times as
great as A, and ep 6h; at a distance of 5 feet we would have
only one-twenty-fifth of a foot-candle. From this we deduce
that the intensity of illumination falls off not in propor-
tion to the distance, but in proportion to the square of the
distance. This relation is commonly known as the inverse
square Law.
Important Relation Between Foot-Candle and Lumen.
If we refer back to Fig. 3B we see that the surface OPQR
is illuminated every point to an intensity of 1 foot-candle.
We also know by definition that the quantity of light falling
on the plane OPQR is 1 lumen. This gives us the important
law that if 1 lumen is so utilized that all of the light is
spread over a surface of 1 square foot, that surface will be
lighted to an average intensit:: of 1 foot-candle. This rela-
tion greatly simplifies the designing of a lighting installa-
tion, for once the number of square feet to be lighted and the
intensity of illumination which it is desired to provide are
known, it is a simple matter to find how many lumens must fall
on the working plane. If, for example, it is desired to il-
luminate a surface of 100 square feet to an average intensity
of & feot-candles, 500 lumens must be utilized. The designing
of a lighting installation is taken up more in detail in
succeeding pages.
Foot-Candles Meter.
An instrument calicd the foot-cendle meter has recently
been designed to measure foot-candle intensities quickly and
with a fair degree of accuracy. It is very simple in operation,
so light that it oan be easily cerried about, and so small
that readings can be taken in very restricted speces. The
instrument is shown in Pig. 7. In operation, it is placed up-
on or adjacent to the surfece on which a messurement of the
foot-candle intensity is desired. rticularly advisable for wall
tints where there is a large window exposure to the north and
east light. It is a well known fact that the strong rays of
light existing et certain seesons of theyear are very irritat-
ing and injurious to the human eye, if they ere allowed to
enter through a large window surface and strike the eye directly
or indirdéotly from polished surfaces at certrin angles. If
light tinted walls extended down to the floor line, employees,
when looking up from their work, would be confronted with a
ef. ZK. 8. 8S. Vol IX No. 2,1014.
b4
bright wail surface which would to a certain extent, reflect
too high an intensity of light and thus affect the visuel
acuity or seeing efficiency of their eyes. With light green
walls, the strong deylight rays are absorbed, diffused and re-
duced in intensity, so that far more hygienic conditions are
furnished the office worker. The same principle holds true
with artifioiel Lllumination coming from overhead general i11l-
uminetion. From a utiliterian standpoint, it is self apparent
that a light green painted wall surfece is ersier to keep clean
then one of a lighter color, when either a painted or celcimined
finish is employed. Painted walls and ceilings, in preference
to calcimined surfaces, are coming into use quite generally,
because they are conceded to be preferable from both a sanitary
and a utilitarian standpoint.
Measurement of Reflected Facér.
There are a number of laboratory metho’s of obtaining
this value, some of which employ elaborate apparatus, and which
take into account with a high degree of accuracy the direction
of the incident light, color of incident light, and similar
features. :st since the area of the
oblique plane AC is obtained by dividing that of the normal
Plane AB by cos a, the illumination of AC is that of AB
multiplied by cos a, or for oblique illuminsetion,
In= 608 Dosccccscccvcsecsccecserer (4)
But from the triangle 08 A’
h So
—- = COB Bececcccccsccesccesse (5) OF
d SA
h
Ee cece ccc ce cn cece eccesccccesee (6)
COS a
h
Squering, a? n_- cece cece ecco cecescvee(t)
cos a
Suystituting for a® in eqqation (4)
In ne Cos” Becccccccccccsvscccescses (8)
Where In is the intensity in foot-candles on the horizontal
plane.
Equation (8) is known es Lambert's law, and is very use-
So
ful in the calculation of illumination. In the reat of the
bulletin on page 22 will be found values of cos”
a for
different values of "a" from 1 deg, to 90 dig. To facilitate
the use of the above formula there are given in Tabhe No. 1
values of illuminrtion on horizontal planes at different
heights and at different horizontal distances of a light
souree of 1 candle-power and also the corresponding angles
made by the light rays with the perpendicular to the plane,
or angle "a".
Method of Using Tabhe
Odtain the distribution ourve of the lamp and reflector
in use or to be used. Take from Table No. 1 the value [in
foot-cendles) of flluminstion which a 1 crndle-power light
source would produce at the point seleoted. Also note the
engle corresponding to this point. From the distribution
curve of the lamp, take the scandle-power at the correspond-
igg angle. Multiply this velue by the illumination value
found in the table, and the result will be the illumination,
in foot-candles at the point selected, of the lamp under
consideration.
For example: Required the illumination produced by a 200-
watt bowl enameled Mazda C lamp with RIM standard dome reflec-
tor at a point 12 ft. below thelamp, and 12 ft. to one side.
From Table No. 1, the value corresponding to these dis-
tances is 0.0088, and the corresnondign angle is 45 deg.
From the distribution curve of the 200-watt bowl enemeled
Magda C lamp with RLM standard dome refilestor the candle-
SS
power at 45 deg. is approximately 475, then 0.025 x 475
equals 1.1878, which is the lllumimation 18 foot-pendles at
the specified point. The illuminrtion on a certain spot
where there is more than one lnmp in the firld of vision may
be obtained in a similar manner, using the respective dis-
tances, from the point directiy beneath the lemps to the spot
and the vertical height of the lamps above the plane. Obtain
values from Table No. 1 end proceed as above. The sum of
the values thus obtained will be the total amount of Light
on that specific point.
Illumination of Vertical Surfaces,
For formulee for the calculation of illumination on
vertical eurfaces and surfaces at other engles than the normal
or horizontal, see a paper by Mr. F. A. Benford , Jr., entitled
"fhe Theory and Caleulation of Illuminating Curves," Trans-
actions of Illumination Engineering Society, Volume 7, 1912.
Flux of Laght Method (method No. 2)
While the "point by point" method is fundamental and
must be used in calculations involving equipment whose cheracter-
istics are not fully determined, it will be found too ocumber-
some for general use and a more convenient formala would ob
necessity be essential.
A lumen is a qurentity of light which will illuminate 1
squere foot of area to an intensity of 1 foot-candle. A
table is here giving intensities in foot-candles recommended
for the various classes of lighting service. The floor area
So
of any given room is readily ascertainable, and this multi-
plied by the desired foot-candle intensity gives at once the
lumens which should be effective on the working plane.
From an inspection of the distribution curve of any lamp
or of a lamp and reflector combination, it is apparent that
all of the light flux (emitted lumens) from the lamp does not
reach the working plane; for in the case of a bare lamp
approximately one half of the total light is emitted upward,
and to reach the working plane must strike the ceiling 6 end
side walis and then be reflected. Since there is no perfect
reflecting surface, any reflection is accompanied by abdsorp-
tion and lose of light. This is true e-en in cases where re-
flectors sare used, for a reflector, no matter what its re-
flecting ecurface may be, has a certainportion of the light
absorbed by it. This may be shown by comparing the light
emitted by a bare lemp and the seme lamp equinped with a re-
flector.
An obvious method of determining this loss of light is
to set up &n an average size room with certain colored walls
and ceilings, an installation of one type of reflector; then
to actually measure the illumination on a horizontal working
plane, and also determine the total light supplied, or gener-
ated lumens. Many such investigations have been made with
various types of units from the direct steel refledtors
to totally indirdct units, and utilization faetore thus de-
terminédg may be found in Table No. 2. mhe values in this
table represent the percentage of thé total lumens emitted
by lamps thet reaches an assumed working plane. WHILE THE
values of the constants civen in this table may appear to be
a little low, theyrepresent average conditions of service
Table No. 2.
Utilization Constants - Per Cent Lumens Effective
Allowing a 25 Per Cent Service Depreciation.
Celling...srrcsccveseree Light Médium Dark
Wall@.cccecrcscceese kt. Med. Dark Lt. Med. Dark Hed. Dark
Reflector
R.L.M. Standard
Dome, Clear ....... .40 .47 .45 .48 .46 .44 .48 .44
RIM Stendard dome
Bowl enameled........42 .41 .39 .41 #.40 #«F8 22 #=.38
Deep bowl, steel
CleOarterccsccccccseseseh «oD 097 239 .88 1.37 58 .57
Reflecto Cap Diffuser
Clearecccvecscccceesedd 0% of 4.34 655 = 66310 W528 SL
Deep sowl, Glass
Bowl enameled........40 .88 .56 .357 .385 .33 .32 «312
Dagfusing, onc. globe
Clear.... S®ese0n0vee#e# @ eal 204 coe 2d eo eon end 209
Light opal, semi-
ind. Clear....csce ev4 eel. ,28 .29 .26 1.25 21 «41
Dense opal, semi-
ind. Clear @e79#2t 68 8 one on? 25 2a enn of 028 214
Totally indirect
Clear.wcccccessecve e027 25 wero e820 118 1.16 12 210
“Bowl enameled lamp, not generally recommended with the deep
bowl opaque reflectors on account of the pocketing of light
and resultant low utilization.
with surroundings and equipments as indicated, taking into
consideration a depreciation in lamp and reflector equipment
JL
of 25 per cent due to normal dirt and dust collection. The
results obtained from such testing, supplemented by calcula-
tions, may be made use of in two ways.
There are times when it is desirable to know the illumina-
tion from an existing system and a portable photometer is not
available. By the use of Table No. 2, the average foot-candles
may be obtained in the following manner. The total lumens
generated dy the lamps may be obtained from Table No. 6. Know-
ing the type of fixtures and color of the walis and ceilings,
a utilisation factor, appiicable to the special case, may
be found from Table No. 2. The total generated lumens, mul-
tiplied by this factor, will give the total lumens effective
on the working plane. Again, the total effective lumens
divided by the area of the floor in square feet will give the
average foot candles. I2 this way, the flux of light method
is applicable for use with existing installations.
On the other hand, it is also possible to determine the
size of lamp necessery in a proposed installation where it is
desired to obtain a certain foot-candle intensity on the work.
In this case, the area of the floor is multiplied by the
foot-candles desired, which will give the total effective lu-
mens necessary. Dividing this fugure by the utilization
factor adaptable for the proposed installation, found in
Table No. 2, will give a total emitted or generated lumens
which must be furnished by all of the lamps. The lumens per
lamp may then be found by dividing the total by the number of
outlets, and then referring to Table No. 6, giving the total
.
a”
fw
lumens for any stenderd lamp, the necessery sizes of lamp may
be selected. It is always advisable to use a lerger rather
than a smaller lamp, if there is a smell difference in choice
as a safety facoor.
The spsecing and hanging heights of the units will be
discussed at length in the following method.
Modified Plus of Light Method (method No. 3)
In order to facilitate the work of laying out an instal-
lation by eliminating as many calculations as possible, a sys-
tem of tables based upon the avove discussion, has been drawn
up to show the relation of the watts per square foot of floor
area to the foot-candles of illumination, for different
reflector equirments and grades of colors of yvalls end ceil-
ings.
Accordingly the following is =» short end yet reagson-
ably accurate method of desicning a generrl Lirchting instal-
lation.
Before attemtping to lay out a lighting installation, there
are a few facts concerning the building or room which are
essential.
These are:
Character of work to be carried on.
Floor dimensions.
Ceiling height (maximum hanging height)
Distance between columns (if any)
Color of walls and ceilings.
In order to facilitate the gork, the first step should
Jey
be $o make a sketch to scale of the room under consideration.
Having the information, before proceeding further ,it is
necessary to determine the type of reflector which is to be
used. Having determined the proper reflector for the special
Glass of building, proceed tc Case 1 for direct lighting
units, and to Case 2 for seni-indirect and totally indirect
units.
Case 1. For Direct Lighting Units.
Waen an even illumination is desired over the entire
working crea, there is a fixed relation between hanging height
and apacing for the severel types of direct lighting fixtures.
It is always ecviseble to hang the units as hizh as possible
due first of all, to the fact that there will be more cross
light and thus less dense shadows, and again, by increasing
the heigit, the epacing is increased and a iess number of
cutlets with the sore efficicnt larger sizes of lemps may
be used.
The celling heish:t cannot be taken as the maximun hang-
ing height, however, as some space is taken up by reflector
and fittings. Where it is possible to heng the units close
to the ceiling, 1 foot clearsnce should be allowed. In other
words, a ceiling 15 feet high would have a mazimum henging
height of 14 feet. Again, if there is consideradle overhead
horizontal belting which would osst objectionable shadows
from lamps hung above it, the maximum hanging height is the
heicht of the lowest horigontel belting.
Ys
To determine hanging height and spacing of units for the
case uméer consideration proceed as folows:
From table 10 showing the relation of the henging height
of a unit to its spacing, determine the maximum distance be-
tween units.
Divide the widty of the room by the maximum spacing
obtained above to determine the number of fows of outlets in
the room. If this spacing does not divide into the width
evenly, take the next larger whole nunber, wich will be the
number of rows of outlets.
In cease the roc is divided into bays by columns, as is
usual in mill construction, consider each bay as a small
serarate room.
Divide thie number into the width of the room, finding
the new sprcing, and thus determine the new henging heicht
from Table 10.
The dist«nee between outlets in each row should be
approximately the seze as the distance jetween rows, and still
have the length of the room evenly divided.
Divide the length of the roomby the specing between rows
determined above, and if this does not come out asa a whole
number, take the rext larger whole number, which will be the
number of outlets per row.
Now locate the outlets on sketch so that the distence
from wall to first lamps will be one half the distence between
outlets (see Fig 2). We have now determined the spacing and
hanging height of the units. It remains to decide upon the
Ju
size of the lamps to be used.
Multiply distance between rows by distance between out-
lets in rows to find the square feet area to be covered by
each lamp.
Refer to Intensity Table No. 13 for foot candles required
for the partkcular class of work to be carried on.
Find the equivalent watts per square foot from Talbes
Nos. 14-18 for theparticular type of reflector to be used, and
multiply this fugure by the area per outlet. The result will
be the watts necessary per outlet.
Salect the nearest sise of Kasda lamp, preferably the s
size larger.
Case 2. For Semi-indireot and Totally Indirect Units.
A method of rrocedure similer to Gase 1 may be followed
for these types of fixtures, using the values given in
Tables 19 and 12. for spacing and hanging height instead of
those of Curve No, l.
Determine maximum speéing for e siven célling height from
table No.1¢ and determine suspension length of fix:ure for fin-
al sapecing from Talb@e 12. The size of lamp to be used is
found in a manner similar to Case 1. Using the vrlues of watts
per square foot for the desired foot-candles, found in tables
14 to 18.
Revising a Present Instellation.
Many times it is advisable or necessary to use the
present out-lets in a building which is already wired for
lighting, but where the new high intensity has not been in
Ib
use. In such cases, it is first necessary to determine the
floor area of the building in square feet.
Divide the area by the numberof ou‘ lets to obtain the
average area to be taken care of by each lamp.
Multiply this by the watts per square foot found in
table 14 to 18. for the particular work and surrounding
conditions.
Seleet the nenreat size of lamp, preferably the one
larger, which will be the necessary size to use.
To determine the hanging height, knowing distence be-
tweer. outlets use table 12. If this value ia much grerter
than the raximum permissible, due to a low celiling, even
4llumination will not be obtained, and more outlets will be
necessary. The room should be rewhred #nd celeulstions made
as outlined in Cases 1 snd 2.
94
CHAPTER V
TESTS IN VARIOUS TYPES OF UNITS
Thies chapter deals with various arrangements and types
of reflecting wnits installed in offices of the same size
and finish, where the conditions for careful teating are
especially feaovrable., The results of illumination tests
are shown for the various systems on a basis of equal quantity
of light flux generated and also in terms of the wattese
which would be required to give an average intensity of 5&
foot-candles. The character of the walls and ceiling surface
is fully described and the results of surface brightness tests
sre tabulated so as to indicate the contrasts which exist
with various systems, and are given on a basis relative to
white blotting paper and also in absolute vabues. Corridor
lighting, loss of light due to dust collection and effect
of room size on utilization factor are touched upon.
The lamps used for tests were selected so as to give their
rated csundle-pewer when cperated at the test voltage. The
voltage for the test eireuite was reguiated by hand, thereby
doing away with the necessity for voltage-eandle-power cor-
rections. In the tests which will be direotly compared, the
same lamps were used except where one test required clear
lamps and the other bowl-frosted. The bowl-frosted lamps
were rated before being frosted and the "clear' values used
in computations.
With the thought in mind that contrasts on the walls and
ceiling are important factors in an illuminaticn design, sur-
28
face brightness readings wore taken at what arpeared to be the
brightest and dimnest spots. These are siven in terms of
equivalent foot-candles on white dlotting paper, for the rea-
gon that it is a very simple and conveniont method and alse
because the valnes so given furnish, it is believed, a better
conception of the magnitudes than such wnits as ecandle-power
per unit of area.
fhe data would be incomplete without including velues
showing the reflecting ability of the walls and ceiling.
These reflection characteristics are given relative to white
blotting paper, that is the ratio’ of brightness of the surface
in question to that of white blotting paper in the same posi-
tion and under constant and diffused light conditions.
The various systems employed in these standard offices
ere:
(A) pour direct,opal glass units fitted with bewl-
frosted tungsten-filament lamps.
(B) Same as A except that reflectors are inverted and
clear lamps used.
(C) One semi-indiresct bowl with Glear lamps in central
outlet.
(D) One dndirect plaster bowl with clear lamps in central
outlet.
‘B) Four mirrored glass indirect units with clear lamps.
(F) pour direct prismatic glass, intensive, with bowl-
frosted lamps.
A single wnit of each system is shomm.in Fig. 7.
marie
System A is the cne gcnerally adoptod throughout the
offices. The -thers are used in places where the require-
nents are cpeoilal or where spocial consi ‘eration was givne te
tne individual tastes of the occupant.
In the tests A-F lamps of equal luminous output were
used so that compariscns show the reeults obteineble with the
different systems with the same amount of light generated at
the lamps. It is hardly necesssry to state ‘nat the same
wattage is not to be recommended; horever, it was thought
best for purposes of comparison to make teste on this basis.
Reflectors in ell cases were of the oorrect sise for the wat-
tage of lamps used, except that in the mirrored glass re-
flectors 1% was necessary touse an extension in order to in-
sure the proper lamp position.
A summery of the results of tests A-F, as outlined ebove,
is given in Table s 1 and 2.
Before comparing these systems with one another and with |
the efficiensy figures in other installations, the exact con-
ditions es regards spacing of outlets end character of walls
an' ceiling surface should be borne in mind. The walls are
finished with a greenish-grey paint which reflects 53 per
cent ef much tungsten fllament light as does white blotting
paper used in cll these tests showed on measurement by the
Rutting# reflectometer method, a coefficient of reflection of
77 per cent. The walls, therefore, absorb 59 per cent. The
*Tiluminating Engineering gociety Transrotions, Oct. 1912.
alr
ceilings refi: ‘6% 76 per cent. as compared with the blotting
paper, and, therefore, absord 41 percent. of the light fali-
ing upon then.
fable I. - Intensity Distribution.
Description Test
Direct, 4 units
opal glass, bowl
frosted lamps A
Semi-indirect,
4 units, opal
glass clear
lamps B
Semi-indiresot, 1
unit, diffusing
bowl, clear
lamps C
Indirest, 2 unit
plaster bowl,
Clear lamp..... D
Indireot, 4 units,
mirrored glass
Glear lamps B
Direct, 4 units
prismatic, bowl-
frosted lamps “°F
Reom area--257.5 square feet and
each test.
Tilliumination Foot-
candles on °O" plane
Avera Maxie Mini-
age mum 806 BU
4.68 §.54 3,8
2.69 5.91 2,32
3.10 §.6€8 1.78
2ece 3.66 1,42
2.65 ©el4 2.20
5.00 5.78 4.33
Brficiency
Lumens Per Cent
por Btili zation
watt efficiency
<.%5 02.8
1.70 19,9
2.05 22.6
1.54 17.0
1770 318.7
o.22 35.8
4--100-watt lamps used in
Celling height, 11 ft. 10 in. Height of unit above floor,
Tests A, Band F, 10 ft., & in.3
Test FE, © ft. 9 in.
Tests C and D, S ft 6 in.
Fable 2. - surface Brightness Distribution.
“Surface brightness foot-candles equivalent
to white blotting paper.
Ceilings
Mazi- Nini-
Description Test num THU
Direct, 4 units opal
giase déwil-frosted iamps A §.23 0.663
Semi-ingieect, 4 units
opal glass, cleer lamps “38 1.98a 2.8¢1b
Semi-indirect, 1 unit,
diffusing bowl, clear
Indirect, 1 unit plaster
bowl, clear lamps D 65.16 9.280d
Indirect, 4 units, mirrored
glass, clear lanps ¥ 60.8a 1,940b
Direct, 4 mits, prismatic
bowl-frosted lamps F 5.59a 09.995b
Fable 3S.
Walls
Maxi- Wini-
mum mum
6 0368 8462
2.13@ 0.477f
1.356 2.593f
1.32¢@ 0.2635f
2.528 9.461f
2.67@ o.782f
Reflection coefficient, per scent
Relative to white blotting
paper as obtained by dright-
Surface nese readings.
White blotting paper
Walls in standard offices
Ceilings in standerd offices
New faotory white paint, worst
New factory white paing, best
New white finish plaster
90
120
120
Absolute
It 4s possible with the best white paint to obtain a
coefficient of reflection as high as &5 per cent.
Measurements
on new white finished piaster surfaces showed coefrfieient of
Urs
refleetion aa high as 02 per sent. Therefore, with the very
best possible conditions, as regards ceiling, the illwmina-
tion of the indireet systems could be raised more than 650 per
cent. The semi-indirect systems could, of course, be made to
shew nearly as great an increase if the best possible ceiling
surfaces were used.
Table © is a summary of reflection data for all tests.
The lighting of reoms of a character similar to those
tested involves not only the illumination of the working
plane, but many other considerations such as the lighting
of the walls, the elimination of cense shadows on the desks,
etc. Utilization efficiencies given apply strictly only to
this one size room with the same character of walls and
eeiling. fThey are not representative of what may be obtained
with larger spaces, an example of which appears later in the
paper. However the size of the room and the finish of walls
and celling represent a fair average of office buildings in
general.
From Table 1 it may be seen that the four 19°0-watt
direot prismatic units gave an average illumination of & foot
eandles, which 46 hisher than for any ofhthe others. since
the wattage in each test wes the same, the prismatic units
gave also a higher efficiency. Teble 4 shows the wattaze
which would have to be used to obtsin the same auantity of
light on the 30-inch plane.
The differences in the direct, semi-direct and indirect
LU4
syatems of lighting would, of course, be decreased if the
celling were of a high coefficient of reflection. Even
though the coefficient of reflection of the cefling is only
Sv per cent., it has been termed a good white celling by
meny observers, and so perhans does not differ greatly from
tne averace cellins used in semi-indirect and indirect systems.
Table 4
Wattage necessary
to produce an
| intensity of 5 foot-
Desoription. Test. cendiles.
Direet, 4 units, onsl glass, bowl
frosted lamps. A 1909
Semi-indiresct, 4 units, opal
gless, clear lems. B 186
Semi-indirect, 1 unit, dif-
fusing bowl, clear lamps C 157
Indirect, &@ unit, plaster bowl, clear 1
lanps,. D 209
Indirect, 4 units, mirrored
glass, clear lanps E 180
Direct, 4 units, prismatic
bdowl-frosted lamps F 100
fhe
“duel ouy JO afeTS se ze
-UTDTT@ puw uUOTSfA JO OUTT yOOLTp ouy WOU YUuSMBTT} duet ay} ST 3200U0)--TeOg JO Jigg JoMOT
ALTP pus FSup JO UOTZBTNUMOIN BYUEASTY ‘YuUSIZS TIN us eMOp BuTzoeT Jou out youed 04 ‘TaOQG
wory sAvl pezZoeT jeu ous pus duet ou4 wmouy sAvl plvadn Oud TTS SZ}uleg--Taog JO Jeg Zeddg
*eusrtd BSuyysox 92 pakusdy Weyq 8yoorTpoezd pues sAew puvadn
UY SOUOIeD “VULTT THJowsea TTB BSxoeudD *poeToeusus uTeToolod eV ° 19098 JO Opay--10}7900TJ9G
*4yuN 944 JO {ated Aue JO Olen SseTZ 9} Buyaocmeu
quourxfa uoTytsod szedoad oy4 0% duet ou3 Jo quemisnfpe Agee o7, saoTTy--dasuEH eTQayeul py
"LOPLOY o.% UF SYOTINO OY YFnoLYy
IFS pezysou-Joins [[w soATAp pus Buyuedo Tl wus sTyy sxeque Upe Loos jo fky4ueTg--exequl ITy
°890ds 3ZUBTUQ Pus BSUTL HOSTQ ‘saopeus Buy yusresd
‘SUTTTOO oyy 0% plwadn JEIXTTS 0% BUBITT JO Zunome BUST ey yang szyyused -meyy seyngzsy
-3TD ple suazzos ‘QUBTT jo safer pruadn au4 szouzen ‘“‘ssuTB TedoO Jo epey--d6H0gq FUT OCTIey
‘ITw peyesiuszadns
JO 47X@ OU% JOJ WTA Bodin 84fT UT pepTAocud syoT3aNO ‘eos 94 AQ poyroddNns--ddSpTOH TVeyzoR
"§ONOOS PUd OGBUqQ CUBT Oy BOLJ Cmvy~ suzy JO Yuou suyzy 8zZIITJOPD 19938T
I
SUL “fO
BIUIDIIA *¥JOJION
ANVdWOD ¥ SVWOHL ‘f ’s
O8DI1y) “OD s0j;2aYfay Koy-xX JoUoHON
wapsig Ourzy617 js0fwoy akq ay) Aq payourwn))7
hil Doses
PM
ie |
se
— Pitas
pe
-
J
i =
>
with the present low cost of light, a tinted ceiling is
justified where essential to the decorative scheme of the
room or where lighting o8 a certain color tone is desired.
fhe lumincus-bowl type of indirect unit produces the
same gen-ral character of illuminetion as thet produced by
striatly indirect units, but the auxiliary bowl, being
luminous, give s a direct component which assists slightly
in illuminating vertical surfaces, and, in the opinion of
many, adds to the decorative value of the installation.
Semi-indirect units of dense or toned glass give an
effect very similar to that given by liuminous-bdowl indirect
units, but they transmit a higher percentage of the light,
and are, under usual condition, slightly more efficient.
With bowls of light density, she results approach more nearly
those obtained from opal-giass enclosing units; contrary to
what might be expected, however, the semi-indirect system is
often more efficient due to the fact that less light ia
abosrbed by the bowl, less light is emitted in angles near
the horizontal, and more light is directed to and diffused
from the ceiling at effective angles.
It is possible to obtain either indirect or semi-indirect
bowls in exclusive designs harmonizing with the decorations
and conforming to the testes of the user; regerdless cf the
design of the exterior, however, it is of the utmost import-
enoe that the interior be a hard, smooth reflecting surface
in order that good efficiency may be maintained. In an in-
stalintion which rune into any considerable e xepnditure,
popes
4t ie well worth while to secure the opinion of a competent
architect or decorator before determining upon a definite
exteriof design.
Lighting units of the same general type as are used on
the main floor are suitable for the upper floors of large
stores; often a smaller size of the same design may be chosen.
In some cases, a well designed direct-lighting system may
meet the requirements satisfactorily. With open reflectors,
powl-frosted lamps should always be installed and the units
should be suspended at such a height that they will be, as
nearly as possible, outside the range of ordinary vision.
As previously stated, Mazda lamps of larger than 200 watts
should not be used in open reflectors. Semi-enclosing units
are available, however, which operate on much the same prin-
ciple as an open reflector but which are provided with a dif-
fusing glass bowl below the reflector which screens the lamp
from view. With such units, any size of lamp may be used.
Their efficienesy compares favorably with that of the prismatic
% pe of enclosing unit. Onall floors, the fixtures should be
located symmetrically with respect to the divisions or bays
usually formed in the celling by the constructional features
of the building, unless it is desired to arrange the lighting
to enhance some architectural effect in light and shade, or
color, in accordance with a skillful designer's well consider-
ed plan.
Stores of Medium Size
The lighting requirements of stores of medium aize are
cae
pact itera 4° ae
i a } nko es
ens Sia
ree ’ : me a
: it 3
i jail! weenie
t jut? wane
at
'
-
tie same as these cited for large stores, except that a loo-
ation amid less impressive surroundings may decrease the
neéd for purely decorative features. In ti:is olass of store
& semi-indirect asretem employing some form of inexpensive
medium-density bowl will often fully meet the recuirements of
a distinctive and economical installation. A well designed
direet-lighting system, auch as micht be used @n the unper
floors of large stores, is very frequently deened entirely
satisfactory,--espoctally where a semi-enclosing unit, of
which No. 1, Fig. 1, is a type, is used.
Fxelusive Stores.
Exclusive smell stores or shops, found principally in
the larger cities, lend themeelves to an artistic trecstment
which is impossible in larger areas. In many coses, the use
of colored lmmps to provide lighting of a distinctive tone
is highly desirable, while uniforiity of illumination is to be
avoided rather than sought. The fixtures may well be of
special design but care should be taken to avoid the very
common error of allowing too brillisnt light sources within
the range of vision. Modifications of semi-é@ndirect,
indirect, and enclosing fixtures are used aimost entirely.
A prismatic glass semi-indirect unit has been recently de-
veloped which consists of two glass bowls between which may
be placed flowered silk, oretonne, or other G6edorative fabric
of any pattern desired. The prisms, which line theouter
surface of the inner bowl where they are protected from dust,
insure an efficient distribution of the light; the decorative
- 6
‘,
LO)
fabdrie may be changed at will.
Small Stores in General.
Effioetency is the first requirement of a lighting
system for the usual small store. A high intensity is neces-
serv for the convenience of customers and for advertising
purposes, but the fixtures may be of very simple design. Con-
sequently, direct lighting with open reflectors of the prise
matic or dense-opal type, or with a good type of semi-enclos-
igg unit, is, as a rule, most applicable sithough often the
installation of en inexpensive semi-indirect or enclosing
unit is preferable.
cemi-enclosing units possess ang advantege over open
reflect ors in t at they diffuse the light from the filament
cvér a comperatively large area; hence they may be used with
any sige of lamp, and in locations where open reflectors
would sause annoying clare. They possess an advantage over
opalenclosing units in that they distribute light in muoh the
same yay 9s a Jerse opal open reflector and are therefore less
derendont for their efficiency upon the finisn of the walls
and ociling.
A common mistake in sinall store lighting is the installae-
tion of a single row of direct-lighting refiectoss along
the center of the etore, whore at least two rows of small
units should be used tc prevent the customer's shadow from
interfering with hic examination of the wares, and to iilumin-
ate the shelving or hich cesce slong the sidewalls. A
—
singie row of semi-indirect or enclosing unita is, however,
usually antisfactory. An exception to the use of bowl-
frosted lamps with oncn reflectors may be made in the case
of small jewelry stores where b#illiant refleetions in gens
and eut glass may be desirable; the units should, however,
be placed well above the ususrl line of vision to avoid glare.
Illumination Intensities.
A lighting installation serves : couble purpese: first,
it permits the merchandisc to be examined with comfort;
second, it advertises the store. Light is recognized as one
of the least expensive and most effective advertising nédiums
and hence intensities higher than abdsolutely necessery for
comfortable vision are almost universally demanded. The three
f-etors which govern the selection of an intensity for any
particular case are: the nature of the merchandise---for
dark goods require a higher intensity than light gooda to
a pear equally well illuminated’ the illuminaticn standerd
of the immediate neighborhood; and, t ¢ amount which the
owner feels is expedient to apportion fer the advertising
value of a high intensity. The lower values of any tabdie
of intensitiés should, therefore, be used cautiously and full
weight given to local conditions. However, values aprilying
to average conditions are useful as a basis upon rhich to
estimate desirable intensities, and such values are civen in
Table l.
Coefficients of Utilization
Intensities of illumination are commonly expressed in
foo
foot-candies and are not in themselves measures of the total
quantity of light. To determine tne quantity of lisht re-
quired te previde a given averege Liitensity, it is only
necessary to multiply the earcrn in squere fest of the surface
to be flluminated by the desired intensity in footecandles}3
the result will be tie quentity of licsht flux, or lurens,
which must te supplied to the ares tc rroduce the desired
feot-cendles inteneity. Obvicusly, if just sufficient
wettace le inetelled tc aunnly the nurber of lémens so cale-
culated the Jlluminetion will fell fer short of the desired
value because of the light flux which wjJllbe ebeorbed by the
reflector ecuippent end by the celling and verticel surfaces.
The proportion of the light flux generated by the lempe
which ie effective in illuminating the "working plene”,
that is, an imaginary surface perallel to the floor and at a
height of 2 1/2 to 2 feet above it depending upon the height
of sounters, cesses, goods etc., depends upon the tyre of
fixture selected, the color of the ceiling and walls, and
the size of the room. Ceilings in stores are usually fairly
light in color and @he walls are, in most cases, lined with
shelves; hence, it is possible to give values for the propor-
tion of light which is effective in illuminating the working
plane for various reflector equipments for the different
Classes of stores. These values, which are called coefficients
of utilization, are given, as fractions of the total light
of the bare lamps, in Tabie 2.
156
Calsulation of the Required Wattage
In oaloulating the wattage required for a certain store
the first atep is to decide, at least tentatively, upen the
type of fixture, in accordance with the general principles
discuesed above. The second step is to decide upon the in-
tensity in foot-candles which will be needed on thwe working
plane; Tavle 135 will be found helpful in determining this
intensity. The t..ird step is to determine the lémens required
to produce this intensity; this is calculated by multiplying
the area of tine room in square feet by the intensity in foot-
candles. Tne fourth step is to divide the calculated number
of lumens by the coefficient of utilisation, expressed as a
fraction; this fraction may be obtained from Table 2. The
recult obtained will be the number of lumens which thex lamp
must furnish to give the desired intensity. In order to take
care of tne decrease from initial to average lignt output
of the lamps, the number of lumens go calculated should be
inersased by 19d per cent. A further number should be added
to allow for depreciation due to the scollestion of dust upon
tne lamps, reflectors, celiing, and walls. It is fo great
imnortance that a schedule providing for regular and frequeng
Gleaning be adopted, but even where units are cleaned thorough-
ly once a ronth, 10 per cent additional lumens should be
allowed for dust depreciation. The final value, then, re-
presents the liwsene which the vere lamps should provide initial-
ly.
ues
The lumens initially given by the Mazda lamps commonly
used in store lighting are given in Table 6. With the total
lusens known, the required number of lamps of any given
wattage may be readily approximated by reference to Table 3%.
Size of Lamp, Henging Height, and Spacing Distance.
Of the lamps which will supply the required quantity
of light, the sise to be chosen depends upon the ceiling
height and upon the type of fixture, @.60., whether the fixture
distributes the light over a large or a small area. Z@nclosing
units and open reflectors should, as a rule, be suspended as
high above the flcor as is consistent with good apperrance
in order that the light sources may be as far removed as
possibic from the renge of vision. This allowable hanging
height determines the permissible spacing of units of any
given type for reasonable uniformity of illumination. The
maximum ratios 6f the spacin,; distance to the height of the
unit above the working plane (not above the floor), which may
be used with fair uniformity of flillumination with the various
types of units discussed in toils bulletin, are given in
Table lv. If greater spacing distances than tiose JIvctermined
by tnese ratios seem desirabic, it should be remembered that
as the spacing is increasec the degree of uniformity decreases
rapidly. The greater the permissible spacing distance, the
darger the lamps whioh may be used and the fever the nunber
requirec. The fewor the units of a given type, the less the
installation and operating expense, but the greater tre area
affected by the failure of a lamp end the denser the shadows.
15s
Gowever, if the ratios given in Table 10 are not exceeded,
no trouble from t+ is source need be anticipated. It should
be noted that conditions governing the hanging height and
apacing distance for indirect and semi-indireot units are
somewhat different sinse in installations of this type, the
celling acta as the licht source. The hanging height may,
in suoh installations, be chosef @rom considerations of con-
venience snd appearance but it should be borne in mind that
if units are hung close to te ceiling, the aress direotly
ebove thr units will be brichtly lighted in contrast to
“Antermediate areas; thie effect may be considered desirable
or it may be considered undesirable, depending upon the effect
which it fa desirecéd to produce. Shadows cast by the bowl of
the unit and by the suspension rode or cheins may, if consid-
ered objecticnable, be eliminated by dipping the lamps in an
etechinz solution. The especing distence is debermined dy the
helent of thse cellinz since the ceiling acts as the Light
source.
As previously mentioned, it may be Gealrable to obtain
especial licht and shade effects in certain instances; where
t..is is the case, the rules giver above ds not, of sourse,
apply.
Amount of Light Required.
The first step in planning an installation {ia to deter-
mine how much light will be required. The illuminstion te be
supplies in any elven case will, of course, depend upon the
purpose for which the light is used. An offices where people
Poy
are working continuously reavires relotively much more Light
than en cuditorium. A store displaying derk colcred cerehane
‘ise reoulres a creater illumination then one dierleying
lisht colored voods, for dirk coeds reflect te the eye only
a very sreall proportion of the lfeht thet fells uron them.
Again, beceuse of the neture of their business, sare stores
require hisher intensities of Lllumincticen tren ethers of
differert cherecter. A Seweler shevld heve brivhter lighting
than a herdwere merehent. Then, too, the locetion cf the
etore influences the degree to weich it shovld be lichted.
In the brightly lic>tec downtown retail section, mere light
48 demended than in en cutlging or side-atreet business district.
The fundementel requirements of satisfactory stors
lighting installations ere:
1. Sufficient illuminetion of uniform intensity over
the entire aree.
2, Freedom from glare, claring reflections, extreme
contrasts in brightness, and troublesome shzdows.
&, A system of good eprearance which is simple,
reliable, ersy to maintain, end reasonable in operating cost.
two Classes of Instellations
In plannigs a commereial lighting inetalletion, one of
the two following conditions is presentad:
1. Where the building hes not been wired previcusly, or
where, if wired, the customer is willing to reorranga outlets,
{if necesscry, to secure adequate illumination. Here the
Wea;
at
greatest freedom is allowed in plaennigg the installation,
which latitude permits t oroughly satisfactory lighting results.
©. Where no change or addition is to be made in existing
outlets. In this case one has but to decide unon the proper
type end size of unit to replace the present fixtures. The
udvantage to be gained by changing over is then dependent
entirely uoon the greater officiency end diffusion of light
furrisned t” the newer units in comrerisen with less modern
quipment,.
The Planning or Jlluminabing for New Buildings of for
Old Bulldirngss VWaere rxistins Outlets Need Kot be Utilized.
e. Choose ti.c bype of lighting unit beat «depted te
tne location, with due regerd to the several suggestions
siven in tables.
Db. Measure the ceiling neight of the room and decide
upon the greatest praeticel mountings height of the lighting
unite above the flocr consistent with the satisfactory
appearance,
For Encloaing and Semi-Enclosing Unita.
In case the mounting may be close to the ceiling
approximately ona foot must be allowed as the minirum
mountable distarce tetreen the oeiling and the ocxter of
the lamp fllement, as shorn.
For Indirect Units.
Ths cellirg is the principal listht source, hence the
total distance from flcor to celling sivould be ccnsidered the
mounting height.
6. Refer to the Spacing-Mounting Height Table, or the
Spacing-Ceiling Height Table corresponding to the unit selec-
ted, and find what the average distance between units should
be that will correspond to the mounting height determined upon.
The proper drop from the ceiling for Indirect and Semi-
Indirect Fixtures is aiso shown in the table.
@. Make a diagram to scale of the floor area of the room
to be lighted and lay out on it the position of lamp outiets.
If the width of the room is not much greater (fr.m 2 to & feet)
then the spacing value just found, one row of outlets down
the center will probably be sufficient, unless much work is
performed near the walls. Otherwise, the outlets should be
laid ou’ in two or more rows in the form of squares, or
approximately so (see fig. 2) The distance between units being
approximately the spacing distance found in c.
( see blue print )
at end of chapter
Fig. 2. Showing how lighting outlets should be laid out
to provide a practical degree of uniformity in light distribu-
tion. Here each lighting unit is civen a definite area to
illuminate,i.e., all the space falling within 7 feet from a
point directly beneath the lighting unit.
The distance between the outside row of units and walis
should hot be greater than one-half the spacing distance
(see fig.2). For office spaces it should be approximately
=n
Cc”
«
one-third the spacing distance. (The exception to this is in
the case of general offices and other locations where it is
essential to have a very good lighting clear out to the wails.
Here two or more rows of wits are almost always necessary.)
@. Compute the total floor area of the room by multi-
plyihg its length in feet by ite width in feet (making due
@llowance for irregularities in contour).
f. Divide the area thus found by the number of outlets.
This will give the average number of square feet which each
unit must alluminate.
&- Find from the Caassification Table, the class to
which the lighting installation belongs.
h. From the Table showing Watts per Square Foot
corresponding to the type of fixture under consideration,
select the column which most nearly describes t'e interior
to be lighted. Tn this colum find the figure (watts per
square foot) which applies to the Classification determined
in g. multiply t::i8 value of watts per square foot by the
area to be illuminated by each lamp. The result will indicate
the size in watts of lamps to be used.
i. The mounting height of units may be finally corrected
for the actual spacing chosen under d. in accordance with
Table. In other words, it is not necessary that totally and
semi-enclosing units be placed right against the ceiling if
the spacing permits a lower mounting height. Also, in the
ease of units in the indirect class the drop from the ceiling
abe
should be corrected according to the spacing-Ceiling Height
for the actual spacing distance chosen.
Thus the problem is solved, as size of lamps type of
fixnture, mounting height and spacing have been determined.
For offices, stores, and other business places, a
general system of illuminetion consisting of regularly
spaced cutlets and units of uniform size is in almost every
ease desirable. However, in auditoriums, churches, etc.,
sometimes more pleasing and decorative effeots can be ob-
tained otherwise, although more often a uniform lighting
system is used in such locations also.
Case II--Planning an Installation Where Existing Outlets
Must be Utilized.
Here, in addition to choosing the type of fixture to be
employed it is only necessary to decide upon the size of
lamp and the mounting height of the units. Items b,o and d,
as determined in Case I, need not here be cauculated.
@. Compute the total floor area of the room to be light-~
ed by maltiplying the length in feet by the breadth in feet
(making due allowance for irregularities in contour)
f. Divide the area in square feet thus found by the
number of outlets. This will give the average number of
equare feet which each unit must illuminate.
g. Find from classification Table No. 10 the class 66
which the lighting installation belongs.
h. From the Table showing Watts per Square Foot
corresponding to the type of fixtures under consideration,
select the column which most nearly desgribes the interior
to be lighted. In this colwan find the figure (watts per
square foot), which applies to the classification (g).
Multiply this value of watts per square foot by the area to
be iliuminated by each lamp. The result will indicate the s
size in watts of lamps to be used.
i. It now only remains to determine the proper mounting
height of the units. For enclosing and semi-enclosing units,
when there is only one row of units, take the distance (A)
between two units, See Fig. 3, of the width (B) of the room,
4f this value is larger than (A), find the best mounting
height above floor gor this spacing.
RPnelosing and Semi-Enclosing Units.
If there is more than one row of units, determine the
best mounting height, using the larger of the two spacing
values, Aor A’ (see fig. 3). If, as is sometimes the case,
the celling is not Quite high enough tp pespmit this mounting
height, place the units as close to the ceiling as possible.
But when the discrepancy between the mounting height indica-
te@ by the Table , and the greatest height which the celling
permits, is large, the number of outlets in the room is not
sufficient to make possibile a lighting installation which
will give uniform and sstisfactory light with any kind of
lighting fixture. The customer should be urged to re-wire.
For Indirect Units.
For fixtures of the indirect class a check should be
made from the Spacing-Ceiling Height Table II, to see if the
ceiling is high enough to give aprroximately uniform illumina-
tion with the distance which exists between outlets and alse
to obtain @he proper drop from these units from the ceiling.
If the spacing is found to be much too wide for the ceiling
height the oustomer should be urged to re-wire. In ense the
customer re-wires the lighting layout must be recalculated on
the basis of figuring outlined under the Planning of Iliumina-
tion for yew puildings or in Old puilldings where Existing
Outlets Need Not be Utilized,
Comments.
Frequently it may be hard to decide between specifying
one or two rows of lighting units,or the installation may
so figure out that one is undecided as to whether, Gor exam-
ple, 100 or 150-watt lamps whould be used. In such cases one
must depend upon his best judgment and experience in arriving
at the correct solution.
In this connection it is well to keep in mind that in a
store, absolutely uniform illumination is not necessary,
and so the spacing ratios may be stretched a little where
there is a considerable advantage to be gained by so doing.
On the other hand, in an office, uniform illumination is a
prime requirement, and when there is any doubt as to whether
one row of units or two should be used always install two.
Likewise, in deciding between two sizes of lamps, if it
is felt that the location is one in which especially good
lighting will not be s-preciated, one may be justified in
choosing the smaller of the two. In the ed, however, the
customer will usually be better satisfied with an ample
intensity of light even though the first cost of installation
and the current consumption may be a little hggher.
Recommendations shold in nearly all cases be based
on the highest lighting ‘ntensity classification as shown in
Classification Tables. The better illumination which results
is ensily worth the slight increase in initial cost and upkeep.
rome
cr
e }
Rzample Ro. 1.
Lay out a lighting system for a newly built shoe store
in the downtown distrist, requiring very good illwnination.
Assume dark walisand ceilings and dimensions as follows:
Length, 55"; width, 40's height, 16'
a. The Ivanhoe Ace, a onespiece semi-e slosing unit,
is chosen for this store. This unit is particularly suitable
where the questionof maintenance is of considerable importance.
B®. Sinee the ceiling height is 16° the greatest height
at which the center of the fixture could be above the floor
will be approximately 15'. However, in a room of these propor-
tions a fixture suspended by 1 to 4 feet of chain would pre-
sent a much better aprearance., We shell, therefore, set 13'
as a tentetive mounting height.
¢. Referring to the Gpacing-Mounting Height Table, 10.
we find that for a mounting height of 13’ the units should
be 16'6" apart.
ad. Pig. 4 shows how to diagram the room to seale and
locate the outlets. It is evident that by dividing thelength
of the room by the spacing distance (18'°6") we get the re-
quired number of units lengthwise amd approximately 3 1/2.
Oovicusly we should specify 4. Dividing the width of the store
by the same spacing gives us arproximately 2 1/2 units. Bo
we will have to put in three units across--12 units in all.
This will mean a lengthwise spacing 1f 14° with 6'6" between
end units and end walls, and a erosswise spacing of 14° with
6' between the two outer rows of units and the side walls.
Lbs
@e. Area of floor is 40x55x2200 sq. ft.
£. Average number of sq. ft. each unit must illuminate
is 2200 ¢¢ 12 or 185.
6. Turning to the Classification Table #135 we find that
for very good lighting this shoe store requires an illumina-
tion of 6 foot-cendles; that is, it falis in Class 6.
h. Referring to Table 14, Watts per Square Foot for
Semi-enclosing Units, it is found that a room witnr dark
walls and ceiling having more than one row of units in class
6, requires 1.15 watts per square foot. 1.15 x 1835 = 210,
which figure represents the wattage of the lamps to be used.
Since Mazda C lamps are not made in the 210-watt size
200-watt lamps should be specified,
enaus the problem is solved, and twelve 200-watt mazda
C lamps in Ivanhoe Ace units should be installed, located as
in Pig. 4.
i. With our exact spacing (14 feet) determined we
refer aghan to our Sproing-Mounting Height Table 10, and
find that this spacing corresponds to a height of 11'6"
above the floor. A length of chain which will bring the units
approximately in this position will insure a good appearance
and yoo@ illumination results.
Should the sewner desire to economize on the number of
outlets to the greatest possible extent it would of course
be possible to place the units very close to the ceiling, thus
securing a mounting height 0° 16'. From the Spacing-Mounting
bY
Height Table it will be seen that this height corresponds to
@ spacing of 20', and under these condtions two rows of three
units--8ix units in all--seuld setisfy the requirements. A
study of the problem will show that 400-watt lamps should be
used in this case.
merase fe 2- Showing how sore ee hoe
-O----%--loutlets should be laid out — at*
to provide a practical degree Coie x
_ fof uniformity in light dis-
}tribution. Here each light-
ing unit is given a definite |
area to illuminate, i.e.,all
the space falling within 7
-—jfeet from a point direotly
beneath the lighting unit.
a
fond
i
!
eats
LP ata eres
:
Pe een 2 Fig 3 = To the left is shown
; fr op the ground plan and an end
; elevation of a long narrow
store, while Lower: down we
have a store of the same
length and height but of
nh emma sbi 3 eo AC he Pe Oo Rd ct 2
narrow stores when one row
i of outlets is sufficient,
r the width of the store should
| aes "i be taken as-the spacing fig-
bre $e ure if it is greater than
Babi the actual distance between
a ; the outlets. When there are
two or more rows of outlets
7 the ideal arrangement is
b——« —| that of squares though rect-
angles are satisfactory if
the difference between the ~
length and breadth of the
rectangle is not too marked.
rd
a Arrangement PY OLS co
example eh Dy p Nee
van)
i
Be > ;
ene Cee hd
- Lei
. CHAPTER V2tt
HOW TO PLAN WINDOW LIGE&TING
The information contained in this thesis is the same sim-
ple and complete ever compiled onshow window lighting. There
is no superfluous technical data. The engineering of this
important matter is boiled down and simplified so that mer-
chants can quickly determine what is best for their particular
windows.
THB SHOW WINDOWS OF A MERCANTILE SSTABLISHMENT CAN BF
MADE AS EFFECTIVE BY NIGHT AS BY DAY BY PROPER CONSIDERATION
OF THE PRINCIPLES OF GOOD ILLUMINATION --- NEW EFFECTS POSé@
SIBLE BY SPECIAL CONTROL OF LIGHT DIRECTION AND COLOR
The show window is an adjunct of recognized value in mer-
chandising and should receive treatment in keeping with its
commercial importance. » ae be
soiree WB se SL
°
=
3
=
38
Co fF
=
£5
3?
3
ze
acs
es
s
“_
3a
ge
=.
= &
as
3
SG
Serial Ne. 201, Description-Over
_ s
{ Be | 7 Sa
kj
a: a
L. WHITE COMPANY
Columbus, Ohio
Zz.
y=
ey
ans
S
ness of the display near the window glass, this result can be
obtained by combining the 18° reflector with the 30° and 45°
reflectors in a ratio of 5 to l.
X-Ray Reflectors
Every window presents a distinct problem in lighting, and
is treated as such with X-RAY reflectors. Those shown herein
are the results of years of constant perfecting, experimental
work and study, so that now we oen confidently present a
reflector that meets any problem of window lighting.
Clessification of Reflectors.
For large rindows use the Jove or Jupiter with 100 Watt
Mazda C lemps.
For everage windows use the Scocp or Hood with 75 Watt
Mazda C lamps.
For very small windows use the Scoopette or Hoodette
with 15 watt Mazda B lamps.
Classification of Background Conditions.
If the backsround permits people inside the store to seo
the window lichting equipment use only Jupiter, Hood or
Hoodette. If the equipment is not visible any of the reflec-
tors may be used, fitting the proper style to the window under
consideration. :
Size Classification.
For shallow windows use Jupiter, Hood or Hoodette, For
average or deep windows use Jove, Scoop or Scoopette,
These classifications will some time interfere. It is
then necessary to decide which of the wrong conditions will
Pra da
BNA
Brie)
SG,
oy
Byes
ae
Si
/ .
MMA hy)
wes WY) iy
Wile 7
least interfere with the production of perfect lighting, and
sacrifice that one.
Make note of the size, bvackground conditions and depth of
your windows, check these against the above classifications
and you will have no trouble in determining the proper reflec-
tor. To secure perfect results you must use the lamp for which
the reflector was designed and also the proper reflector holder.
Spacing.
In average installations the spacing, or distance from
center to center for these reflectors, is about as follows:
Jupiter-=- 100-Watt Masda C lamp........-.24 in.
Jove -- 100-Watt Mazda C lamp..........24 in.
Scoop - 76-Watt Mazda C LaAMpPwocccces seed in.
Hood -
75-Watt Mazda C lamp.......2ee28 in.
Poseibilities in Coler Fffects#
Cclor is, of course, one of the show-window dresser's
most effective tools, yet full advantage is seldom taken of
the possibilities of artificial lighting in the renditionof
colors. The color contrast in a display depends, among other
things, upon the color quality of the light which is used. A
favric is said to be red in daylight because it absorbs prac-
tically all the other colors in the spectrum and reflects mainly
the red. Under a green or a blue light, in which red rays
are absent, the same fabore would appear almost black. Mazda
lamps give all the colors of the spectrum, but their light
contains relatively more of red and yellow rays than does day-
*See chapter on color.
light. Hence, these lamps emphasize the reds, yellows and
browns, and likewise fail to bring out the blues and violets
in their proper weight. By the cereful sel otion of color sc-
reens, (see figure 1.) however, any color may be given emphasis.
Thus for instance, if 1t is desirable to emphasize the
whiteness of goods, on display or to bring cut the blurs in
dressgoods *« color screen should be used which will absord a
part of the excess red rnd yellow rays while freely permitting
the others to pass. Blue-green glase of the proper selection
will do this, but if correct color walue of ti:e light and
a high efficicnoy are to be obtained a thorough knowledge of
color must ve used in the sel ction. Lamps designated as
Mazda C-2 lamps have been developed,whioh, through the effect
of special coloring elemdénts mixed with the ingredients of
the glass from which the bulbs are blown, give a light of
afternoon sunlight quality at about the efficiency of the Mazda
Blamp. The lamp manufaocutrer has placed the proper wWwuks
color in the bulb instead of depending on auxiliary equipment,
since other glass having the same anpearence as thet used in
Magsda C-2 lamps might, bo the user's disedvantage, transmit
light. of very different color value.
Color variation is, perhaps, the most effeotive mecns of
holding attention. A florist's window, for example, cen be
made to change wonderfully by simrley changing the solor quality
of the light which illuminates it. It it is lighted entirely
by a white light, such as is obtained with Mazda C-2 lamps
the whites, blues, greens and violets will appear to stand
out because the reds, yellows and browns with which they are
contrasted will be depressed. If the color qurlity of the
light is made to change by adding tc the white light, brown and
yellow lisht from amber-colored bulbs, the colors that first
eppeerdd prominent will sppear to fade and the ysllows and
browns will be given prominence. Again, if red light is
addec to the white light, the effect will be to make the cons
trasts between red and the other colors more marked.
Such effects, cs mentioned, may be rea@ily secured by
having aveileble in the window the colored lamns necessary.
Tne chanzes from cne color to another may be made by a suite
able flashing device and méy be sudden and contresting, or
they mat be gradual and harmonious. The colors in rugs,
dressgoods, wallpaper, pictures, reintings, etc., ere suscept-
ible to the seme treatient. A window dresser who will make a
etudy of the possibilities of colored li,ht as well as the
possibilities of lisht direction will be nble to nroduce
beautiful and unusual effects.
The Intensity Necessary for Effective Lighting.
The intensity required for show-window lighting depends
largely on the brightness of the surroundings. Show windows
located on "white ways” will require a greater intensity than
those loceted on a der! side street. However, as light is
one of the most inexpensive and effective means of advertising,
an intensity higher than is absolutely necessaryfor suitable
lighting can usually be employed to advantage. Another factor
LSet
Which must be considered in determining the intensity is the
color of the display. An object is seen by the light which
it reflects, and, therefore, dark-colored displays require
more light than do those 6f Righter colors. Since the display
of a show window is frequently changed doth in material and
color, the flexible arrangement of lamp sockets suggested for
securing directional lighting effects offers a method of vary-
ing the intens ity at will. In general the intensities for
window lighting range from 10 to 50 food-candles.
The advantage of using reflecting equipment in show-win-
dow lichting should be generally understood. When lamps are
used without reflectors a greater part of the light falls on
the walls, background and ceiling before it reaches the dis-
play. Usually window backgrounds and ceilings are poor re-
f'ectors and much of the light, which by the use of reflectors
could be utilized, is lost. The mo t satisfacotyr reflectors
for window lighting are the prismatic and the morrored glass.
These reflectors afford good control of the light with a high
efficiency.
In lighting a show window the first question is usually one
of how much light is needed. The statement that so many foot-
candies are required is only of value when the equivalent is
given in wattage. Many times the ammount of light required is
expressed in watts per square foot of the window floor. While
this designation is satisfacotry for windows in which the dis-
play covers only the floor surface, it fails to do justice to
to those many windows where the displays cover a considerable
portion of the background as well as the floor. In other
words, the floor space of a window is not the only consideration
which enters into the determination of the wattage necessary
to light a window properly.
Simple Method of Caloulating the Lamp Fquipment.
The following is a simple method of finding theintensity
suitable for any show window re ardless of the display arrange-
ment. This met':od is based on the efficiency of Mazda C lamps
and of prismatic or mirrored-glass reflectors. For the purpose
of calculatton show windows may be divided into ten olasses
on the basis of intensity of illumination desired. Class 1
includes t ose windows in which the lowest standard of ill-
umination will be permissible--an intensity, in fact, which
would not be adequate in most cases. Class 2 includes the
average country store, where a low intensity is sufficient.
Classes 5 to 6 cover the average store; Classes 7 to & the de-
partment stores of most cities. The finest windows of the
largest stores end exclusive shops located on brightly lightcd
streets fall in Class 9 or 10, representing the highest inten-
sities which can be used to direct advantage.
The first step in the calculation is to place the specified
window in one of the ten classes. The next step is to add the
Gepth of the window, in feet, to the height of the lamps above
the window floor, in feet, and multiply this sum by the elass
number of the window. The result will give the required watts
per running foot of window frontage, assuming that 100-watt
Mazda C lamps are to be used. To get the number of lamps
neeessary the number of watts per running foot of window
frontage should, of course, be multiplied by the window front-
age in feet, and this result divided by 100. Should the window
be other than rectangular in shape the length of the window f
frontage whould be taken as the averace of the length of the
actual window front and the length of the window background.
This met od of calculation as described applies only where
windows are to be lighted by a dirdot system using well de-
signed mirrored glass or prismatic reflectors placed at the
top of the window. Where Mazda C-2 lamps are to be used,
since the 150-watt C-2 lamp cives approximately the same inten-
sity as that of the 100-watt Mazda C lamp, due to the absorp-
tion of light by the colored bulb, the number of units to be
used is the same in either case.
Location of Spacing of Reflectors.
The spacing of reflectors varies from distances of 12
inches between centers (minimum) to 24 inches between centers
(maximim). It would be absurd to define any set rules regard-
ing the number of reflectors per window, eince every merchant
has decided ideas regarding the brightness of his own window
and insists upon carrying them out. Reflectors should be placed
as close to the front of the window as possible to give best
results.
If a window is open on two sides, and it is necessary to
illuminate the rear of a display, this can be accomplished by
a second line of lights carried around th the side and equipped
with reflectors of the proper type.
mm certain lines of business the color of the display
varies greatly, being either white or very dark. The dark dis-
play requires much more light to bring out the quality of the
merchandise. For t is reason it is desirable to have two sep-
arate circuits, one 6or displays which are light in color and
both for dark displays. Suggestions for this sort are greatly
appreciated by users of electric light.
Concealment of I) luminants.
In order to give a finished appearance to a window, the
illuminants should be concealed behind a strip of valance
which may be formed of silk, paper, or paint upon the back of
the window glass. The exposure of lights in a display window
distracts the attention of the observer from the displey and
is therefore undesirable. Another objection is the glare
caused by exposed lamps which make it impossible for anyone to
see the display clearly. The concealing strip can be placed
directly below the transom bar in windows of medium height and,
if the ceiling extends above this, the units can be placed
upon a rack attached to the bar which is also coneealed by
the valance. By lowering the lights in t:.18 wey and bringing
them nearer to the display additional brightness is obtained.
Moreover, in any high windows, the blank space above the mer-
chandise is of no advertising value and, if brightly lighted,
distracts attention from the trim. Such concealment of lighting,
when well done, gives decided charsoter to a display window.
MNO
Sign Trensparencies.
Tremslucent signs, painted on the back of the window glass
at the top of display windows, require illuminetion, but it is
westeful aml extravagent to employ translucent reflectors for
this purpose. While the light which they emit in an upward
direction accomplishes the effect, a considerable quantity is
wasted in illumineting the ceiling. Such transparencies can
be illuminated in a far more economical and attractive manner —
vy placing behind them boxes containing small 15 watt Mazda
lamps in aluminum reflectors, arranged so that their light is
directed against the white inner surface (back) of the enclos-
ing box, which diffuses the light, bhereby illuminating the
sign perfectly without the characteristic "spotty" effect
resulting from placing lamps directly behind sign letters.
Incident Considerations.
Whenever possible the polished surface of sabinet work
within a window should be depolished, since it acts as a
mirror in reflecting the images of the lamps and reflectors,
causing a streak of light which detracts from the finished
effect of a window and distracts attention from the display.
To facilitate comparisons in window lighting a temporary
strip of moulding, wired end fitted with lrmps, sockets, and
reflectors, can be prepared and instelled in any window wi th-
out disturbing the display. In this way one window may be com-
pared with another and it is possible to immediately see any
improvement which esists. This method is very effective in
demonstrating the superiority of Mazda lemps over gas lamps
and incandescent lamps of the carbon filament type. It also
serves to show the greater efficiency and better light of the
100-watt Mazda C lamp compared with the 100-watt Mazda B lamp.
Actual comparisons are always most convincing and “seeing is
believing."
CHAPTER IX
MAINFFNANCR OF THE LICUTING SYSTEM *
The proper maintenance of the lighting equipment is a
very inportant factor in Lllumineticn. The housewife, for
cxample, realizes that the home would soon become e very poor
piace in which to dwell unless she msde periodic house cleane-
ings ané attermed to the household duties in this respedat from
day to day. T'.¢ industrisl plant, or office, would soon be-
come unsenitary unless sorup people were employed. Qn the
other hand, lighting equipment is often neglected from the
time it 4s installed until it becomes obsclete. Fersons seem
{2 believe that after onoe henging a fixture and screwing
a lamp into « sccket no further attention needs to be given
to this part of the home of office. A widespread campaign
of educating the public in this respect is most essential
and it is up to everyone interested in lighting to preach thk
gospel of proper maintenance. The eleatrical contractor,
ynen he has finished an installation of lighting, should not
ieuve the job without advising the customer as to the necessity
of cleaning. To quote a prominent officiel of the Department
of Labor of an important industrial state, when addressing
the annual convention of eleotric contractors, and dealers:
* If you sell a man a motor, you usurlly give him an
instruction ecard telling him how to ofl the motor, adjust the
brushes, and the like. If y:u did Bbhe dem this and he did not
%= TdT 7 7 On
a ® Je -/ e@ ye oh! ~' @ ° ue
a
attend to the matter tirousn his own appreciation of the sub-
jeot, the motor would sccr stall, turn out, and you would be
justiy blamed. on the ether hand, many a lighting installation
is sold sith no instructions or suscestions as to its maine
tenance.
"A ilgnting system demands careful maintenance. If it
does net receive it, the intersity will scon drop so low that
the men cannot see to perform their work. Ycu will get the
blame. You will ve told that tre installation you dealigned
anc installed is not adequate for the purpose. Your engineer-
ing judgment will be criticized."
Depreciation of Lamps.
Inherent: As the Mazda larp is burned small particles of
tungsten are evaporated from the filament and coltect on the
lamp bulb in the form cf a dark deposit. with the Magda “C*
lamp the gas current carries these particles to the upper part
of the bulb, where they have lese effect in absorbing light
than when deposited directly opposite the filament. Never-
theless, any accumulation on the interior surfece cf the bulb
ebsorbs light, and blackened lamps should, of course, be re-
placed. It is comparatively simple to figure out the most
economic point at which to remove lamps from the sokket,
taking into account the price of lamps and the cost of current.
For average conditions, when the candle-power has depreciated
to between 75 and 89 per cent of initial rating the lamp should
ve discarded. Of course, a photometric test might be desired
to determine exactly the percentage of depreciation, but
190
ebservation and experience will soon indicate to tre Maintene
ance Depsrtrent when a lamp has depreciated to approximately
this velue. The Mazda lamp is designed to maintain ite
cendle-power ebove the linits mentioned above for an average
1ife of 1000 hours’ burning, and at the end of this period |
shouk@ be removed and discarded if the moat economic conditions
are te prevail.
Acquired: Not only does a black deposit occur on the inside
of the lamp bulb, but dust coll: ets on the cuter surfece;
flying particles of o11, or similar materials, are also de-
posited here. Thie accumulaticn cuts down the light from the
lemp and should te removed at the time reflectors are
Cleaned. This is often more serious than realized.
A ® @ concrete case, we mizht quote a test om some lamps
which were installed in a grinding room, where the air was
moist, and laden with stcel dust particles. talf of the lamps
instalied for the test were removed st the end of a week and
thr weneincor at the end of three weeks. The lamps vere taken
toe the photometric lcoberatory end tasted. Those with a.
weck's accumuleticn of dire showed en average absorption
ef 16 por cent. Those removed et the end of three woens
nad an everage ebsronption of 22 por cent. This cces not take
intc account the loes of lignt which would Gcoeu due to the
grease and dirt on the reflector. Putting this in other
words, at ins end of a weit an increase over 15 per cent in
Wattage, and at the end cf tiree vecks nearly 2c per cent
increase in wattage, would be required in order to obtain the
same illumination as secured when the lamps were clean. Of
course, many conéitions are not as severe as this, and some--
for example, the foundry or large shop--are even more severe.
Another important point, in regard to the lamp, is the
question of having lamps of the proper voltage in use. While
initially the installation may be correct as to voltage, on
replacing or ordering additional lamps, an error may be made
in specifying the voltage of these lamps. Mazda lamps are
designed to operate at the voltage indicated on the label.
This voltage rating takes into account renewal and energy costs.
If the circuit voltage is appreciably higher than the label
voltage, short life of lamps will result. If the voltage
at the socket is considerably lower than that indicated on the
lebel of the lamp in use it will not emit the peoper quantity =
of light. To make up for this loss of illumination, it would
be necessary to install additional lamps. yor instancéd,
seven Mazda lamps operating at rated efficiency will give the
equivalent amount of light of eight Mazda lamps operating
4 volts below the rated efficiency of the lamps. Before
ordering lamps it is desirable to determine what average
voltage is actually attained at the socket. where the volt-
age of the system fluctuates during the day, or where it
varies in different parts of the installat'on, it is proper
to order lamps as near the average of this variation as
possible.
1 oe
195
Depreciation of Reflecting Equipment.
All Bamps and reflectors should be regularly washed and
Cleaned. Thezx period between cleanings will vary with locality
and type of equipment. Obviously, a stedél direct lighting
reflector will not depreciate as rapidly as an indirect unit.
In the case of the former the under surface of the reflector
offers very little opportunity for dust to gather, and that
on the lamp bulb will be the rpimary cause of loss. In the
case of the inverted unit, however, a thin layer of dust soon
settles on the entire reflecting surface,as well as on the
lamp, which will reduce the light output appreciably in a
very short time. Not only is this ture, but the very arrange-
mont of parts makes the accumulation greater. With the direot
lighting equipment, the reflector itself shields the lamp
from falling particles, while they enter directly into the
inverted unit.
Table No. l.
Approximate Loss in percentage of initial illumination on
Working Plane.
Weeks... 4 8 18 18 20
RIM standard dome...; § 8 10 12 14
Dense opal bowl direct
Lighting. .ccveccsescers 7 10 15 16 19
Prismatic bowl direct
LICHt~INg. -ecccccsccccs 9 13 16 19 22
Li~ht density opal
vowl direct lighting... 12 18 24 28 30
Semi-indirect. ®@eeee8e@ee 14 22 29 58 40
Totally indirect..cece. 20 29 S7 44 §0
—_—r
aes ee
Se ate a
5
weet ee ee ee ee er ee ee ee oem.
Cee 8 we ore
na ew ewe
wee Ons cu ee
en 2 0
ee Se ae owe
—- —— ew -
_
-e — © ew
e-em ee —
=o me oe
fae
fees
qs
+4
< re
1
: .
~«
.
‘ - - -
,
‘
, 1
2 oe a —_— * - = 5 -~-- -@$@- -m2 «a= eee eee
¥ .
1
' .
‘
. us -
.
‘ .
1 “
‘
»
‘
~ - — - * - 4 “+e - - ws - - - -- '
= Y
sam
”
.
.
- we ee ewe ee _- - - {
.
~~
L
. - .« ‘
ce em
~
' ,
a * e _ -
i
' ’
\
‘
‘
- -- -- =e eo -- -- . = 1
4
{
\
‘ - 4
Table No. 1 presents figures on the approximate loss of
iight for various lighting systems, based on average office
conditions in an inudstrial city. For s me other locality
other figures will apply. The country town will have less
depreciation than the busy city. The figures presented,
however, are fairly typical of average conditions. It can
be seen that the steel reflector depreciates least, while
the opal reflectors for direct lighting vary as to the
density of the reflector. This is to be expected, considering
that, with a ligt density unit, more light is transmitted
through the glassware, and dirt on the outer surface will
have appreicably more effect.
Another feature enters in comparing direct and indirect
systems. with direct lighting, the dirt gathers on the
exterior surface and is readily visible to the occupants of
the room. with the semi-indirect and totally indirect systems,
the dirt gethers on the inner or reflecting surfaces and is
not noticed until conditions become so aggravated that the
illumination drops far below that intensity for which it was
designed. Hence, a more careful maintenance of any ind:rect
system ia exteemely important.
Depreciation of Surroundings.
As pointed out in another bulletin, the questionof
color of walls and ceilings is very important. No matter
how carefully painted a room may be, soot, smoke and other
Loy
agencies soon darken the surfaces of the room and cause it
te lose considerable of its refleeting power. Any porous
paint, suches calcimine or whitewash, is pergticularly suscept-
idle to this effeet. In industrial localities it is fre-
quentiy necessary, if maximum economy of iighting is to be
obtained, to paint the ceilings every year and a half and
sidewalls every three years. A test, to determine the
reflection coefficient of the ceiling and walls at frequent
intervals, may save considerable on the lighting bill. In
general, paint is far eheaper than electrical energy, and in
dirty piants painting or cleaning is especially important.
System of Cleaning.
Haphasard cleaning has not usually been found satisfactory,
since the accumulationis so gradual that it is not readily
noticed by those responsible. Much better success has been
secured by organized cleaning, at stated intervals, under the
charge of a maintenance department where one person is
absolutely responsible for this. As pojnted out before, the
periods between cleaning will vary with the locality and
with the equipment. Considering average conditions and
typical equipment, the fixtures in an office should be wiped
out at least once every month, and removed for careful wash-
ing emce every three or four mont s. In the foundry it is
probably necessary to carefully clean fixtures once each week.
The cost of cleaning again varies with the type of
equipment and lator charges. As typical figures Gor indus-
trial plants with direct lighting reflectors, from 3 to 5 cebhss
UU
for cleaning might be considered as average. Some figures o
ovtained in a large office building where semi-indirect units
of a fairly simple design are inuse, indicate that the cost
for cleaning by wiping lamps and reflectors with a damp cloth
and then drying is approximately 5 cents per unit. Removing
the semi-indireot bowl from the fixture and carefully weshing
costs approximately 10 cents. The most economic perio€ for
cleaning a given installation can be obtained by taking into
consideration the cost of power, the burning hours per day,
the loss of light due to the accumulation of dirt, and the
cost per cleaning. The caloulation is not involved, as indi-
cated by the following exampéaéa.
Using figures of light depreciation as given in Table
No. 1, costs of cleaning, as quoted above for semi-indirect
units, and a power eost of 5 cents per Kwehr., average burning
hours per day assumed as 6, and 2)0-watt lamps in use.
For a l2-week peridd, the following caloulatéons apply:
total kwehr. consumed= 6 hours x 6 days x32 woeks x 200 wattts
v9
= 86.4 kwe-hr.
Case A, Fixtures wiped every 2 weeks, washed every 12 weeks.
Cost of cleaning, 5%+5+5+5+5 ¢ 10 = 35/7
Equivalent power loss, 4% (from curve) or 86.4 x .04 = 3.45 kw-hr.
Cost of loss energy, 3.46 x .05 = $.173
Case B. Fixtures wiped every 5 weeks, washed every 12 weeks.
Cost of cleaning, 5 +5 + 5 410 = 25¢
Equivalent power loss, 5.5% 0 986.4 x .055 = 4.75 kwehr.
204
Cost of energy &e 4.75 x .05 = $.24
Case C. Fixtures wiped every 4 weeks, washed every 12 weeks.
Cost of cleaning, 5 + & # 10 = 20¢
Equivalent power loss, 7% or 86.4 x .07 = 6.05 kw-hr.
Cost of lost energy, 6.05 x .05 = $.30
Case D. Fixtures wiped every 6 weeks, washed every 12 weeks.
Cost of cleaning, 5 + 10 = 15¢
Equivalent power loss, 9% or 86.4 x .09 = 7.8 kw-hr.
Cost oflost energy, $.8 x .05 = $.39
——
Case BE. Fixtures washed every 12 weeks.
Cost of cleaning, 10¢
Equivalent power loss, 14 1/2% or 86.2 x .145 = 12.5 kw-hr.
Cost of lost energy, 12.5 x .05 = $.625
Method of clesning.
For dry diré, wiping with a dry sloth or brush, then with
a damp cloth, and finally drying all surfaces, will prove
satisfactory. Greasy or wet accumulations en any type of
reflector must be removed by washing. Seap and water are
goed agents, but care must be taken to remo e the film of
seap by rinsing thoroughly as dried soap accumulates dust very
rapidly. There are a number of cleaners on the market, but
before these are used on a polished surface care should be
taken to see that they are soshoth as not to make microscopic
scratches on the glass, and should not leave a film of clean-
ing material. Most of these may be applied with a piece of
cotton waste of soft cloth and polished off with dry waste
or c’oth. Where lamps are hung high, and it is necessary
to use a ladder to reach them, it is advisable to have on
hand an extra gloye, or reflector, which may be put in place
of the dirty globe, and the latter carried to the cleaning
place. After washing, the clean globe can be substituted for
the next dirty one, and so on. This procedure necessitates
only one trip up the ladder for each globe or reflector.
2U0
Table No. 1.
Showing the Intensity of Illumination in Foot-Candles on Horizontal
site Plane at various distanced from a Light source of 1 Candle-
&3 Power.
od
Table 6 # £=Lumen Output of Mazda Lamps.
Subject to change Without Notice
Size of 110-125 Volt
220-250 Volt
Lamp Standard Lighting Service |
in
Mazda C Mazda B Daylight Mazde C Mazda B
Watts Mazda
Lumen Output
10. 76
15 125
25 226 191
490 o72
50 450% 480 442
60 575
75 6865 600
100 1260 875 995 945
159 2049 14290
200 51299 200 ZOOL
3900 4849 3.60 41900
§00 8750 5600 7850
750 15900
1090 19300 17500
*White Mazda
Gu
TABBE J #
Spacing-Mounting Height Table for Semi-Enclosing and Total
Enclosing Units.
Stores Offices
Mounting Permissible Permissible Permissible Permissible
Height of Distance Distance Distance Distance
Unit above Between Between Between Between
Floor Outlets Outlets Outlets Outlets
and and
Side Walls Side Walls
9! ~ io? §' 10° 3!
9'e" 11° 5'6" 10 '6* 3'6"
10° 11 °6" 6! 11! 3'6"
10 '6" 12°6" 6'6" 12° 4!
11' 13 '6" yt 13° 4!
11 ‘'e" 14! 7! 13 '6" 4'e"
12! 18! 7'e" 14° 4%e"
13! 16 '6" 8 6" 16' 5!
14! 18'e" g ten 17! 5'e"
18° 20' 10! 19° 6!
16! 21'6" 11° 20° 6'e"
17° 23 '6" 12° 22' 7°
1s! 25' 12°'6" 23! 7'e"
19° 26 '6" 13 '6" 25' gS!
20° 28'6" 14'6" 26' 8'g"
*W. EF. Bulletin
200
TABLE 12.
Spacing-Ceilling Height Table For Indirect Semi-
Indirect and Duplexalite Units.
Stores Offices
Ceiling Permissible Permissible Permissible Permiss- Drop
Height Distance Distance Distance ible from
Between Between Between Distanoe ceil-
Outlets Outlets Outlets Between ing
and and to top
Side walls Side wallef Unit
Q! 9°" 6! 9'6" 4' 16"
9°66" 10'6" 5 '6" 10 'g" 4'6" 19°
10! 11' 5'6" 13° 4's" 29"
o'e" = 12! 6° 12" g' 21°
11! 12'6" 6'6" Lee" 6' 22°
11'6" 13'6" 7" 13 '6" 5'6" 23"
12¢ 14! 7° 14! 5'6" 25"
13 = s-18"6" 8! 15'6" e'e" 26"
14° 17° 6'6" 17° 7% SO"
15! iste" 9 '6" 18°68" 7*e" = 32"
16! 20! 10! 20! gt 35"
17" 22" 11° 22" s'6" 39"
18! 23° 11'6" 23! Q' 45"
19! 26' 12%" 25' 1a! as"
20! 26" 13! 26! 10'6" 64"
“W. E. Bulletin.
TABLE 13%
Ciassification Table
Stores and Other Commercial
Buiidings Classified on the
basis of Lighting Requirements.
Department Stores and Large
Specialty Stores
Main Floors and Basement
Other Floors
Stores of Medium Size
Book and Stationery
Clothing
Drug
Dry Goods
Furniture
Grocery
Exclusine Small Stores
Light Goods
Dark Goods
Small Stores in General
Cigar
Clothing
Confectionery
Decorator
Drug
Dry Goods
Florist
Furrier
Grocery
Haberdashery
Hardware
Hat
Jowelry
Leather
Keat
Millinery
“W. E. Bulletin.
Average
Lighting
Class
(foot
candles)
AAA PAOHMATAHARAAA AAA Off BHhhARA HM
Very Good
Lighting
Class
(foot
candles)
~
vos RoaVrevDna Oo
-
DOADNADMMMOADMDDWGOAASBAD
Claseification Table (Continued)
Stores and Other Commercial
Buildin s Classifieg on the
Basos if Lighting fF quirements
Small Stores in General (con't)
Music
Notion
Piano
Shoe
Tailor
Tobacco
General
Avditorium, Churoh
Automobile Showroom
Bank
Barber Shop
Dance Hall
Depot--waiting room
Drafting Room
Bétel
Lobby
Dining Room
Library Reading Room
Lunch Room
Office
Restaurent
School, Class and Study Rooms.
Average
Li ghting
Class
(Foot
Candles)
mm f mh hh
Omnand & WD
2
hm OR sv lw
t~
>
_
Ss
Very Good
Lighting
(Foot
Candles)
QADMDRAAAGA
pas
m= vVrA OOD &
peo
Or OAD
TABLE 14 #
Zable of Watts per Square Foot for Stores, Offices etc.,
When illuminated vith Semi-Snclosing Units
and Clear Mazda C Lamps.
sClass of One Row of Unite
Tllumination
as Expressed in Light Wallis Dark Waile Lizht Wells Dark Walls
Foot Candles. and Ceiding and Cling and Ceiling and C'ling.
More than one row of Units
Watts per Watts per Watts per Watts per
Square Foot Square foot Squere foot Square foot
1 ood ond aed 028
2 085 64 045 . 48
5 072 84 96 65
4 004 1.10 o 75 82
§ 1.45 1.55 91 2.00
6 1.95 1.55 1.98 1.15
g 1.75 2.05 1.35 1.59
190 2.15 2.59 1.790 1.88
12 2.50 5 O00 1.98 2.2
Lé
2 00 oO 2.08 2,85
#*N, B. Bulletin.
*# This table of Watte per Square Foot is based on the
illumination requirements as shown in the classifisation
Tables, pages 25 and 27. The number of each class is
expressed directly in foot-candles.
For the information of the engineer, it may be stated
that the watts per square foot as given in this and following
tables have been computed on the basis of the average lumens
per watt for the most common sizes of Madda C lamps, and the
approximate coefficient of utilization for the conditions
assumed. An allowence has also been made to cover deprecia-
tion in light output due to dust, etc.
~
&
Class of
Tlilumina-
tion as
Expressed
in Foot Watts per
Candles. foot
1 40
2 78
3 1.09
4 1.26
5 1.60
6 1.85
8 2.45
LO 2.8
“200
2 W. F. Bulletin.
TABLE 15+
One Row of Units
Light Walls Dark Walls
and ceiling and c'ling
Watts per
foot —
57
1.10
1.40
1.80
2.25
2.60
5.50
4.290
5.90
Watts per
foot
029
® 5%
07S
9S
1.15
1.05
1.80
216
269
6q.
For Mazda Daylight lamps increase these figures 50%
Dark Walls
and o'ling
Watts per
foot.
42
079
1.0§
1.50
1.65
1.99
2.58
2 9S
0.65
Table of Watts per Square Foot for Stores, Offices, etc.,
When Illwainated with
Totally Enclosing Units and Clear Mazda C Lamps.
Hore than one row of Units.
Light Walls
and ceiling
TABLE 16 #
Table of Watts per Square Foot for Stores, Offices etc.,
When Illuminated with
Indirect Units and Clear Mazda C Lamps.
For Mazda Daylight lamps increase these figures 50%
Class of One Row of Units
Tllumina- Li
tion as Light Walls Dark Walls
Expressed and Ceiling and C'ling
in Foot-
Candles. Watts per Watts per
eq. foot eq. foot
,43
82
1.10
1 40 Not re@-
1 «70 commend-
2.00 ed
2.65
5.20
5.80
wpoOeCaaeusr-
ee
eW. EB. Bulletin.
More than One Row of Units.
Light Wal&is Dark Wallis
and ceiling and c'ling
Watts per Watts per
sq. foot sq. foot.
250
1.05 Kot re-
1.50 commend-
1.50 ed.
Indirect lighting is especially dependent on the reflecting
power of the ceiling and should not be used with dark colored
ceilings. On the other hand, the reflecting power of the
walls ocoes not make much difference in the illumination, and
the values given above can be used with safety under most
eonditions of walls. If, however, the walls are very dark
and there is some question as to size of lamp the larger
size should be used.
wdez
TABLE 17%
Table of Watts per Square Foot for Stores, Offices, etc.,
When Illuminated with
Semi-Indirect Units and Clear Mazda C Lanps.
For Mazda Daylight lamps increase these figures 50%
Class of One Row of Units More than One Row of Units
Tllumina-
tion as Light Walls Dark Walls Light Walis Dark Walls
Expressed and Ceiling and C'ling anc Ceiling and C'ling.
in Foot
Candles. Watts per Watts per Watts per Watts per
sq. foot eq. foot sq. foot sq. foot.
1 ~ 40 250
2 76 - 5 7
5 1.00 78
§ 4.60 commend=- 1920 Gommend-
6 ‘1.85 ed 1.40 ed
8 2.45 1.88
190 2.95 2.20
12 3.50 2.65
*W. Z. Bulletin.
Indirect lighting is especially dependent on the reflect-
ing power of the ceiling and should not be used with dark
colored ceilings. On the other hatid, the reflecting power
of the walls does not make much difference in the illumina-
tion, and the values given shove can be used with safety under
most conditions of walls. If, however, the walls are very
Gark and there is some question as to size of lamp the
larger size should be used.
9 4%
ode
TA BLE 18 #
Table of Watts per Square Foot for Stores, Offices, etc.,
When Tliuminated with
Duplexalite Units and Clear Mazda C Lamps.
For Mazda Daylight lemps increase these figures 50%
One Row of Units More than One Row of Units
Class of |
Tlliumina- Light Walls Dark Walls Light Walls Dark Walis
tion as and Ceiling and C'ling and Geiling and C'ling
Bxpressed
in Foot Watts per Watts per Watts per Watts per
Candles. sq. foot sq foot Sq. foot sq. foot.
1 40 250
2 76 57
S 1.00 78 76
4 4.25 Not recom- 96 Not recom-
& 1.60 mended 1.20 mended
6 1.88 1.40
8 2.45 1.85
20 2.95 2.20
12 5.50 2.65
“Ww, B. Bulletin.
Duplex lighting is especially dependent on the reflecting
power of the ceiling and should not be used with dark col-
ored ceilings. On the other hand, the reflecting power of
the walls does not make much difference in the illumination
and the values civen above can be used with saefety under
most conditions of walls. If, however, the walla are very
dark and there is some question as to size of lamp the
larger size should be used.
Pea eee) a of ar | :
3 0008 p00 | 6009 002 Poot poe Oo DOr. 208. D
N ; ‘ ; + ; 7 o—
i sot Lee ete
4 4 at = peste
| AE | OTe
9: : OOF
4, Os
8
>
| ic." ald
| = | O08
| ad:
it ppt oe:
a cy ao PE UETSSS ~--
u Say “ vO fOTO: oe
ry SAL us} Or |= Soeeen
we BEE ew OTS gg
4 by ut ey wOm ET a
i 4 oT " * ‘ ie STT wlio o-; Zt wy
Oa, StLaos lant esl ary 04 fo ony fe ee a7
iepeqyusbused PUTMOTTOS 29U4 Ae eTrwIos aud ha peutu
-1ezep) e2Vzppem oty sseerouyt LO, LT OF Gn wre ied
ESUOTF IPED: OJ} SSUTHA FOSUTO9} UFSICO-OY- 1 O- OT Peat os
BYUBTOY BuT4imiow ups yoeuscs £7 eFemProU ide peaspts>
hEOS pa feu pounsu sqtuy a, LSwmpeyao} sentpea Tasted
| —*Paet—rao0g
| 6Q Au vere suy 10g pouypnteu s34zBH [Te3Z0> seme pestis
| UTSdlea Get CF ATTeKAuozgquoy useuy ‘peutsep Apes ges.
=e re aT eT puES: ZOOS JO sarnd- 173 3 Fe UOT yOSsSTSs Uy O50
LT Leo
4I9A) 9OBd
fh. CLUS SUutT
%04}O> UC
Bere 97007 |.
‘pucwentiewelE £q ee eq 0} vous sup mLe 0g.
NOILYNIMOT
OK may te
LS oF
BLIG Svu¥g
Ela bwty
a
-~ &
:
oon
wey
a 8
~
5
a
a
——
. 4
ae
rt
ran
Gy
7 4
|
‘ -
Ae
a
a
”
_
”
»
-
-
a
_
_—
1
~ - -~-@ -—
‘
‘ “a
o » we ey . 4
oe et owe Sa we we ee 4 oe
- ‘ uns
“4 : .
° é
: o _
~ - .
C
(
‘
\
‘
”
a)
N
ode
—~
wb
.
4
a. ws
a
'
.
—
eo
- one ——_
.
‘
{
' ,
. . ,
47
4
rot, : ‘ ‘ af ‘ 4 : ' :
mo Po EG “ /
. .
v t ‘
» rot : . ’ ‘
a oo 6 2 3 . ‘
‘ r
, .
.
. t !
° 1 - e , v +
4 , 1
. \
+ Ca Ae. ke 1 to
- . a
-
, , a
ow fe xo. Z
. - .
” ,
, . SY .
7 a o
4 wv
: a“
? s
. * are? - e a
> - de o-¢ eo bv weve aw ee eg: ~ o - ~ > 7 , ao:
a yf
‘ ‘to peat dove , \ ¢ 4 Pa
: ’ Lou. . / ¢
. * .
. 4 r ,
. ’ -
€
' Yr . a
} ‘ ood f
, . : . ot _ ZY
a r
4
of
7
- 7 - * / : oe
j a f°
4 /
aw
7
ao
. 4
: l ,
a St
ao
io r ‘
a
ff f 1
J vt
- - ~ 4
é
‘
, a
o ao
7 .
: 4 Weal
i °
Q f
y ,
s a a f
ft
Z fo
;
‘ -
4
f
rd - foo . -
’ , e
Sf. / +. n
a “oy
f v
wo
Sof
- , . ’
: . ,
'
- 1
~~~ —- en -_- ora. nares — —e oe _——o— —e
. \
1
. 1)
‘ ' '
- ennai .
'
‘ :
»
” q t -
- ‘. ® ,
{ ;
' |
e I 1
4 -> Tf . -* Y re a v Ny vw we a: 14 a
. t , i .
‘ ay - ‘ : -
’ 1
- - . - a 4 - ~ -4 ame me
1
t ‘
‘ | 4
{ ;
'
: ' , , : i
' {
4
| ‘ 4 a ~
1 1 | b
1 ‘ ‘ é ‘ |
: : | 1
t } : oe “ - ..
‘ L. [. { oh ‘
+
'
. - - - : - 1
——_ eee
_ -— — —- me — +
- a -
-+ eo ae =
- —* -
———
-ortmes. 3. ae ae ore. .
me ER ee nee ee Oe ee ee Ow we?
°
2re
»
‘
.
.
. J .
wy.
1
é
so .
t
.
to
“e--
§
é
4
~-«
Le
‘
<
“™
1
‘ xv
a?
Te
we.
ve
sa
,
ae
wn
vr
an
wt
-s
C
wa
ay
ow .?
»
’ o-
, * a» ee
os pr alh
waw-cte?
@