UC-NRLF
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Engineering
Library
THE
ELECTRICAL CONTRACTOR
McGraw-Hill BookCompany
Electrical World The Engineering and Mining Journal
Engineering Record Engineering News
Railway Age Gazette American Machinist
Signal Engineer American Engneer
Electric Railway Journal Coal Age
Metallurgical and Chemical Engineering P o we r
THE ELECTEICAL
CONTRACTOR
PRINCIPLES OF COST-KEEPING AND ESTIMATING,
WIRING AND. ILLUMINATION CALCULATIONS
AND OTHER TECHNICAL PROBLEMS
OF THE BUSINESS
BY
LOUIS W. MOXEY, JR.
VICE-PRESIDENT, KELLER-PIKE CO.
PHILADELPHIA, PA.
FIRST EDITION
McGRAW-HILL BOOK COMPANY, INC.
239 WEST 39TH STREET, NEW YORK
6]AND 8]BOUVERIE STREET, LONDON, E. C.
1916
/A
Engineering
Library
COPYRIGHT, 1916, BY THE
McGRAW-HiLL BOOK COMPANY, INC.
/iu: c A < x
THK MAI'LK I'KKSS YORK PA
PREFACE
Only a few years ago the electrical contractor was an
individual mechanic. The period of evolution to the
organized business of today has been too short to permit
of much standardization in systems of methods of han-
dling work, and many men are suffering today the costly
consequences. The need of better methods in both the
commercial and technical phases is evident to anyone
who comes in contact with the average contractor's
organization and work.
In the hope that the essentials of the writer's system,
developed during the past twenty years, and the tech-
nical data accumulated in connection therewith, may be
of assistance to other contractors, the author has ven-
tured to publish this material in book form. Much of
the material has already appeared in the Electrical World.
L. W. M., JR.
PHILADELPHIA, PA,
February, 1916.
338063
CONTENTS
PAGE
PREFACE v
CHAPTER
I. Profit and Overhead Expense 1-6
II. Bookkeeping 7-13
III. Cost-keeping 14-40
IV. Estimating 41-45
V. Calculating Wire Sizes for D. C. Currents 46-52
VI. Calculating Wire Sizes for A. C. Currents 53-61
VII. Illumination Calculations 62-73
VIII. General Data 74-80
INDEX 81
vn
THE
ELECTRICAL CONTRACTOR
CHAPTER I
PROFITS AND OVERHEAD EXPENSE
PROFITS
The two primary requisites for achieving success in
the conduct of an electrical-contracting business are
a knowledge of business principles and methods and a
knowledge of electrical construction and the related
engineering problems. Each of these factors is of equal
importance, and real success in the electrical-contract-
ing business cannot be obtained if either of these two
factors be lacking.
Of primary importance to every contractor and every
business man is the subject of profits. Every man in
business desires to make a profit, but many have only a
vague idea of the meaning of the word. To illustrate
what is meant by the word " profit" take the case of a
corporation. It has not made a profit on its year's
business unless the amount of money received or assur-
able of collection without cost within a reasonable length
of time exceeds the amount of money expended during
the year. The amount of money expended by a cor-
poration doing, for example, an electrical-contracting
business includes not only the amount paid for labor
and material actually used on its jobs but all amounts
l
2 THE ELECTRICAL CONTRACTOR
paid for labor and material whether chargeable to any
particular job or not. In other words, the material
item should embrace the cost of engines and dynamos as
well as ink and pencils, and the labor item should include
not only the pay of the journeymen and helpers but also
the salaries of the president and other officers.
If a corporation makes a profit on its year's business
only under the conditions outlined, an individual or a
group of individuals can make a profit only under the
same conditions. The error which many persons who
do a small business make is that they fail to include in
the amount of money expended for labor during the year
a salary for themselves. This should be equal to the
sum that they would have to pay a person or persons
for doing their work and producing the same results.
Hence many persons doing a small business and neglect-
ing to include a salary for themselves in the labor item
do not make a profit. What appears to be profit may
merely be a salary perhaps meager at that.
OVERHEAD EXPENSE
There are two items which combined compose the
cost of conducting an electrical-contracting business.
These must be taken into consideration when figuring
profits. The first item includes the cost of materials
and labor actually used on jobs, such as engines, dy-
namos, panelboards, conduit, wire, etc., together with
the salaries of the foreman, journeymen, helpers and
apprentices. This item may be called, for convenience,
shop or raw cost.
The second item includes the cost of materials and
labor expended in securing a contract and in the exe-
cution of the job. It embraces the salaries of the officers,
PROFITS AND OVERHEAD EXPENSE 3
bookkeeper, stenographer, bill clerk, draftsman, super-
intendent, etc., and the cost of rent, heat, light, taxes,
insurance, stationery, postage, telephone and the like.
This item is called manufacturer's expense or overhead
charge. The shop or raw cost is always more or less
an uncertain one and will be dwelt upon in detail in
Chap. Ill, while overhead charges can be fairly well
determined.
From a collection of data compiled by the National
Electrical Contractors' Association on the costs of con-
ducting an electrical-contracting business, it appears
that the overhead expense of an electrical contractor
lies between about 15 and 25 per cent, of his shop cost
and that the average profit is figured at from 5 to 15
per cent, of the gross cost, depending upon the terms of
the contract and the nature of the work.
The following outline gives a list of items which enter
into a contractor's overhead expense:
Officers' salaries.
Salaries of office employees.
Salary of superintendent.
Estimating and selling expense (car fare, railroad fare, entertaining,
etc.).
Stationery and sundries.
Postage, telephone, telegrams.
Depreciation of tools and furniture.
Insurance on property, furniture, stock, etc.
Liability and compensation insurance (if any).
Interest on investment.
Rent (if owner of building, taxes and depreciation).
Heat and light.
Repairs.
Attorneys' fees.
License fees (if any).
Association dues.
Miscellaneous.
4 THE ELECTRICAL CONTRACTOR
This list may be said to include the items which almost
every electrical contractor must include in figuring his
overhead expense, but not necessarily all the items which
he must include. Most contractors find it necessary to
employ one or more automobiles in their business. If
such is the case, the interest on the investment made for
automobiles, the depreciation of the machines, the cost
of garaging, the cost of operating and the cost of upkeep
must be included in the overhead expense. Some con-
tractors have other expenses, such as advertising, etc.,
that are properly considered as items in overhead ex-
pense. Hence, the list given is not complete but merely
suggestive of the items which enter into a contractor's
overhead expense.
METHOD OF COMPUTING AND APPLYING OVERHEAD EXPENSE
AND PROFIT
From the preceding paragraphs it can readily be seen
that any estimate for work which does not include, in
addition to an estimate of shop cost, an item for manu-
facturer's expense is one that will result in a loss to the
contractor.
The writer has found it more convenient and logical
to compute the manufacturer's or overhead expense as a
percentage of the shop cost, instead of as a percentage
of the selling price. An estimate of overhead expense
should be made at least once or twice a year and the per-
centage thus obtained added to the shop cost in all esti-
mates made in the succeeding period to obtain the real
cost. For example:
Shop cost:
Pay of foremen, journeymen, helpers and apprentices $80,000.00
Cost of material, engines, generators, conduit, wire, etc. . 200,000.00
Total shop cost $280,000. 00
PROFITS AND OVERHEAD EXPENSE 5
Overhead expense:
Salaries of employers, co-partners or officers $30,000.00
Salaries of office employees bookkeepers, clerks, etc 8,000.00
Salaries of superintendent, draftsman and engineer 10,000.00
Stationery, telephones, taxes, insurance, rent, etc 8,000 . 00
Total manufacturer's expense $56,000.00
Manufacturer's or overhead expense as a percentage of shop cost equals
$56,000 -T- $280,000, or 20 per cent.
The real cost, therefore, of the year's business would
be the shop cost, $280,000, plus the overhead expense
of $56,000, or $336,000. Should the selling value of this
work be $369,600, the contractor has made a profit of
10 per cent, on the investment made. Should the selling
value, however, be only $334,992, he has lost 3 per cent,
on his investment. A true estimate should, therefore,
be made for any job as follows:
Shop cost $10,000.00
Overhead expense at 20 per cent 2,000. 00
Real cost $12,000.00
Profit at 10 per cent 1,200 . 00
Amount of proposal. $13,200.00
Some contractors figure their overhead expense as a
percentage of the selling price. If a contracotr's over-
head expense is 20 per cent, of his selling price and he
desires to make a profit of 10 per cent, on the selling
price, he would not make it if he used the following
method:
Shop cost $1,500.00
20 per cent, overhead expense plus 10 per cent, profit 450 . 00
Amount of proposal $1,950 . 00
To get the results desired namely, 20 per cent, of
selling price as overhead expense and 10 per cent, of
6 THE ELECTRICAL CONTRACTOR
selling price as net profit the estimate should be made
in the following manner: If the shop cost is $1,500,
this amount must represent 70 per cent, of the selling
price, for the overhead expense is taken as 20 per cent,
of the selling price and the profit is taken as 10 per cent,
of the selling price. Hence the selling price should be
($1,500 -r- 70) X 100, or $2,142. The overhead expense
is 20 per cent, of $2,142, or $428, and the profit is 10 per
cent, of $2,142, or $214. The sum of these two items,
$642, subtracted from the selling price leaves the origi-
nal shop cost of $1,500. Hence the previous method
of estimating was in error by $2,142 - $1,950, or $192,
as shown.
But the entire principle of applying overhead expense
and profit as percentages of the selling price is wrong.
Profit on a job is actually interest on an investment.
The investment in the contractor's business is the sum
of the shop cost and the overhead expense. Hence the
profit should be computed as a percentage of this sum.
CHAPTER II
BOOKKEEPING
Different systems of bookkeeping are, of course, in
use by electrical contractors. Some lack merit and
others are of great usefulness. In designing any book-
keeping system it should be borne in mind that the
simpler the system can be made the more satisfactory
and efficient it will prove to be, provided that it gives
all the information that the contractor should have
about his business, such as overhead expense, cost of
labor and materials for each individual piece of work
and the gross profit of the same.
The system of bookkeeping to be described is the one
employed by the firm with which the writer is connected.
This system has been found very satisfactory and
requires the minimum of labor.
Upon the receipt of an order for performing a certain
piece of work, an order card (Fig. 1) is filled out and
turned over to the credit department, where the rating,
financial responsibility, etc., of the prospective customer
is examined. If the result of this inquiry is satisfactory,
the card is passed to the bookkeeping department,
where the information contained on the card is entered
in the contract ledger and the card filed in the order-
card index file.
In the contract ledger, under the entry for the job, are
charged all labor and material actually used on the job
until the work is completed, no entry being made, how-
ever, for office expense.
7
ELECTRICAL CONTRACTOR
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BOOKKEEPING 9
After the plans and specifications for the work are
received the engineering department lays out the work,
straightens out any discrepancies between the plans and
the specifications, and secures any other information
which may be necessary for the construction depart-
ment to know before proceeding with the actual work.
The plans and specifications are then turned over to the
construction department, the superintendent of which
fills out a job card (Fig. 1) with the name of the man
who has been selected to be foreman of the work. The
card then becomes the foreman's order for the work
and is kept by him until the completion of the job.
When the card is returned, the bookkeeping department
knows the job has been completed and is ready for
billing. This process is repeated in the case of any ex-
tra work which may be ordered by the customer, no
foreman or workman being permitted to do any extra
work on a contract until a job card for the same has
been issued.
When the construction department starts a piece of
work the superintendent fills out a stock-requisition
sheet (Fig. 2). To guide him in ordering materials a
copy of the estimate showing the estimated amounts of
materials needed is also given him. Upon the receipt
of the material at the job a second list is filled out on a
special receipt form and receipted by the man in charge.
After a job is completed, the surplus material is again
listed and returned to the stock room, where the stock
clerk enters the amount of material received on another
special receipt form. Sheets such as those described are
also filled out by the foreman in charge when material
is transferred from one job to another and does not pass
through the stock room.
10
THE ELECTRICAL CONTRACTOR
Note: -No material will be given
Separate sheets must be n
taken that no writing or it
Materials can not always be
but must be purchased. Thereto
much ahead as possible of the d
actually needed. In urgent case
available make requisition by ph
written sheet to confirm it. Try
requisitions in at least as early
ials are needed. Stockroom is o
No. JOB NAME
O PAl
STOCK-REQUISITION SHEET Week Ending
without a requisition neatly and completely filled out.
lade out for each job or extra, and in making out requisitio
larks be made in right hand column.
sent from our stockroom,
re make requisitions as
ate when materials are
8 whern K telephone ia rpt nt* W
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particularly to have all
as the day before mater-
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KELLER-PIKE CO.
KELLER-PIKE CO.Gentlemen:-Please send the following material for use on job of which I have c
Ordered
Amoun'
Filled
From
Supply
Amount
Filled
From
Stock
Amount
Wanted
DESCRIPTION OP Amount
/alue from Stock
Order No
ARTICLES WANTED Brought Fwd.
FIG. 2. Requisition sheet for construction materials.
BOOKKEEPING 11
By referring to the stock-requisition sheet (Fig. 2),
it will be noticed that the amount of material desired is
placed in the fourth column from the left, the amount
of that material supplied from the stock room in the
next column, and in the adjoining two columns the
amount of that material furnished by any local supply
house, together with the initials of the supply house
and the contractor's order number to the supply house.
All material going to a job is, therefore, entered, but
only that portion of the materials supplied from the
stock room is valued on the sheet, the amount being
credited to the stock room and charged to the job. The
material furnished by the supply house is billed by the
supply house, whose account in the main ledger is cred-
ited and the amount charged in the contract ledger.
The list of materials on the requisition sheets becomes,
therefore, the bookkeeping department's " sheet of origi-
nal entry," and these sheets are filed in an indexed loose-
leaf ledger. The other material sheets mentioned are,
on the other hand, simple memoranda for checking and
receipts for materials.
To charge the stock room and credit a job on the
return of materials, or to credit one job and charge
another where materials have been transferred without
passing through the stock room, a sheet similar to the
requisition form, but of different color, is filled out in
the office from the data contained on the other types of
material sheets mentioned.
The bills for work done can be made out readily, the
price being already established. In time-and-material
work it is necessary for the billing clerk to refer to his
contract ledger and copy down all material and labor
items which have been charged to the work, giving the
12 THE ELECTRICAL CONTRACTOR
DISTRIBtlTIO'N OF PAYROLL WEEK Els
rnrvn 19
NAME OF JOB
LABOR
EXTRAS
TOTAL
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TOTAL
FIG. 3. Form of payroll (itemized).
BOOKKEEPING 13
price at which the same were charged and noting whether
the material was furnished from the stock room or from
a supply house. This bill is made out in pencil and
turned over to the construction department, by which
it is examined and, if found correct, passed to the person
pricing the material and labor.
The distribution of the labor on various jobs is made
by the pay-roll clerk on a pay-roll sheet (Fig. 3), and
the various jobs are charged and the cash account cred-
ited from this sheet.
CHAPTER III
COST-KEEPING
In order to obtain figures on costs it is necessary for a
contractor to employ such cost-keeping systems as will
enable him to know the unit costs of performing the
various operations entering into the execution of any
wiring contract. Unless a contractor does employ such
cost-keeping methods, he can hardly be said to be en-
gaged in business, for he is merely playing a game of
chance with his entire investment and business future
at stake.
In estimates for work there are two items of costs :
1. Costs of material.
2. Costs of labor.
No accurate figures for use in estimating the cost of
the materials used on a job can be given, owing to the
constant changes in price of most of these materials,
such as wire, conduit, etc. On the other hand, while
the rates paid for labor change, the changes are not of
frequent occurrence and tables of labor costs can be
worked out on the present rates for labor and any in-
crease or decrease of rates can be taken- care of by
employing a percentage correction factor.
For engines, generators, motors, transformers, etc.,
it is always best to secure a bid on the apparatus direct
from the manufacturer, especially if a reasonable time
be given the contractor to prepare his estimate. It is
preferable to have these quotations include the cost of
14
COST-KEEPING 15
the apparatus delivered and erected in position, as well
as the cost of foundations, templets, bolts, painting,
etc. There are two reasons for this procedure: First,
unless the percentage of profit is large, the contractor
should not undertake the risk of accepting the apparatus
f.o.b. point of delivery and taking the responsibility
for any damage that may occur to the same before it
is accepted by the owner. Second, the contractor is
very likely to omit a number of items in estimating on
such apparatus, and these items combined may amount
to a considerable sum even though each is small itself,
Should, however, the job be a large one and the time
for preparing an estimate be short, the approximate
cost of the apparatus could be determined if the con-
tractor has prepared curves of cost for the various
sizes of such apparatus in the past and had frequently
checked them. Such checking is absolutely necessary,
as apparatus may vary considerably in price within
comparatively short periods of time. Fig. 4 shows how
these curves should be prepared.
Separate curves or tables should be prepared for
directly connected and belted, single and four-valve or
Corliss engines, also for directly connected and belted,
direct-current and alternating-current generators of
various types, as well as for motors of low, medium and
high speeds, etc.
The same method could be followed for figuring the
cost of certain other kinds of materials, although greater
accuracy must be used in plotting some curves, for in
some cases price differences of a few cents may be de-
sired. This method is not intended to be pushed to
its logical conclusion and made to apply to such items
as switches, outlet boxes, receptacles and the like, the
16
THE ELECTRICAL CONTRACTOR
4UU
4600
4400
4200
4000
3800
3600
3400
3200
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
600
/
/
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) 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 40
Sizes of Generators in K.V.A.
FIG. 4. Curves showing the cost of directly connected engine-driven
direct-current and alternating-current generators installed under ordi-
nary conditions, the bases being furnished by engine contractor.
COST-KEEPING 17
prices of which the contractor generally has at his finger
tips, but it can be applied advantageously to such mate-
rial as panel boxes, panelboards, doors and trim, an-
nunciators, watchmen's clocks, etc.
For checking purposes or naming approximate costs
to an owner for work being done on a time-and-material
basis, this method can be used with the labor and material
costs, combined as the data for these costs can be secured
in the contract ledger from the completed jobs.
Take the following example, which is the cost for
wiring a new residence of brick-and-joist construction
b*y the concealed-conduit method. The service cables
were run down the outside wall, the meter being in-
stalled in the basement. The system was three-wire,
110-220-volt, single-phase. The panelboards were of
slate with 30-amp. type B switches, mounted in iron
boxes, with wooden doors and trim. The switches were
of Cutter manufacture and the receptacle of the flush
wall type and of Pringle manufacture. The wire was
rubber-covered and of the National Electrical Code
standard.
The shop cost as shown by the contract ledger was
$400.75, the cost items being as follows:
Materials $254 . 36
Labor 136 . 74
Car fare, etc 9 . 65
Shop cost $400.75
The residence had 32 light outlets, 28 switch outlets
and 20 receptacle outlets. The cost of a switch plus
the labor of installing it was $1 and the cost of a recep-
tacle plus the labor of installing it was $1.10.
If all outlets were light outlets, the shop cost would
18
THE ELECTRICAL CONTRACTOR
have been approximately $400.75 - [(28 X $1) + (20
X $1.10)] or $350.75. Dividing $350.75 by the total
number of outlets, which is 80, $4.38 is obtained. Hence
$4.38 is the cost of wiring per light outlet. The cost of
wiring a switch outlet is $4.38 + $1, or $5.38, and the
cost of wiring a receptacle outlet is $4.38 -f $1.10, or
$5.48.
This method is fairly accurate for small-residence
work, and any number of costs per outlet may be com-
piled to cover the various types of wiring construction,
wiring systems, etc.
Tables I to XI, 1 inclusive, give data from which such
curves can be plotted, or, if desired, the data may be
retained in tabular form. Too much emphasis, however,
cannot be laid on the advisability of preparing such tables
and curves from one's own records.
1 Figures in Tables I, II, III and V are the figures the electrical con-
tractor would secure from his subcontractors. Tables IV, VI, VII, VIII,
IX, X and XI include the contractor's overhead expense and profit.
TABLE I. COST OF ENGINES AND THEIR FOUNDATIONS INSTALLED
READY FOR STEAM-PIPE CONNECTIONS 1
Horsepower rating
Single
Tandem-compound
Four-valve
50-100
100-200
300 and above
$16.00
15.00
14.00
$26 . 00
24.00
$25.00
23.00
1 Installed ready for steam-pipe connections under ordinary condi-
tions. The figures given are based on data from the Ames Iron Works,
Oswego, N. Y.
COST-KEEPING
19
TABLE II. COST OF DIRECTLY CONNECTED DIRECT-CURRENT AND
ALTERNATING-CURRENT GENERATORS 1
Direct-current
Alternating-current
Rating, kw. Cost per kw.
Rating, kva.
Cost per kva.
25
$25.00
50
$16.00
35
23.00
75
14.00
50
20.00
125
13.00
75
16.00
135
12.00
100
15.00
185
10.00
125
14.00
250
9.00
150
13.00
312
9.00
200
12.00
350
8.00
250
12.00
375 and above
8.00
300 and above
12.00
1 These prices are based on engine-driven generators installed under
ordinary conditions, the sub-bases for the erection of the generators being
furnished by the engine contractor. The values given are based on data
obtained from the General Electric Company.
TABLE 111. COST OF SWITCHBOARDS, INCLUDING DYNAMO AND FEEDER
PANELS, 220 VOLTS OR LESS 1
Direct-current
Alternating-current
Rating, kw.
Cost per kw.
Rating, kva.
Cost per kva.
25- 50
50-100
100 and above
$5.00-$10.00
4.00- 8.00
3.00- 6.00
50-125
125-350
350 and above
$4.00-$6.00
3.00- 4.00
2.00- 3.00
1 The range of prices is due to variations in the grade of materials and
workmanship, the number of instruments, switches, etc. These figures
include the switchboards erected complete and ready for the connection
of generator cables, power and light feeders, etc. The prices are based on
data obtained from the Walker Electric Company, Philadelphia.
20
THE ELECTRICAL CONTRACTOR
TABLE IV. COST OF DYNAMO CONNECTIONS'
Direct-current
Alternating-current
Rating,
kw.
Lead-sheathed
rubber
insulation
Rubber-covered
cable in
conduit
Rating,
kva.
Lead-sheathed
rubber
insulation
Rubber-covered
cable in
conduit
25- 50
50-100
100 and
above
$50.00-$ 150. 00
75.00- 250.00
100.00- 350.00
$25.00-$125.00
50.00- 225.00
75.00- 325.00
50-125
125-350
350 and
above
$100.00-$300.00
200.00- 400.00
300.00- 500.00
$75.00-8275.00
175.00- 375.00
275.00- 475.00
1 The average flat distance between dynamo and switchboard has
been assumed as 25 ft.
TABLE V. COSTS PER HORSEPOWER OF MOTORS AND NECESSARY RHEO-
STATS AND CONTROLLERS ERECTED 1
Direct-current
Alternating-current
Horsepower
Cost
Horsepower
Cost
1 3
$50 . 00
1 - IH
$60.00
5 - 7H
40.00
IK- 2
50.00
7K- 10
30.00
2-3
40.00
10 - 15
25.00
3 - 7H
30.00
15 - 25
20.00
7^-10
25.00
25 - 50
18.00
10 -20
20.00
50 -100
15.00
20 -35
18.00
100 -250
13.00
35 -75
15.00
250 and above
12.00
100 and above
13.00
1 Motors are assumed to be of standard speeds, voltage, etc., and to be
erected on floor, cost of foundations not being included. The costs
include delivery and erection ready for wiring connections and are based
on data obtained from the General Electric Company.
COST-KEEPING
21
TABLE VI. COSTS OF WIRING AND CONNECTING MOTORS, INCLUDING
ALL LABOR AND MATERIALS 1
Horsepower
Porcelain
Molding
Conduit
1- 5
$7 . 50-$75 . 00
$10.00-$100.00
$15.00-1150.00
5-10
30.00-120.00
40.00- 170.00
60.00- 240.00
15-25
75.00-250.00
90.00- 300.00
150.00- 300.00
25-50
100.00-400.00
125.50- 500.00
200.00- 500.00
50 and over
150.00-500.00
200.00- 600.00
300.00- 600.00
1 The range of figures is due first to structural difficulties, second to the
type of motor panel desired, third to the voltage, and fourth to the circuit
distance. The lower figures represent the minimum structural difficul-
ties, with fused switches in an iron box and with starting device mounted
exposed on wall to side of motor, 220-volt service and 50-ft. to 100-ft.
circuit distance. The higher figures represent the maximum structural
difficulties, motor panels with circuit-breakers, 110-volt service and 150-ft.
to 300-ft. circuit distance. The figures do not include the cost of motors,
rheostats and regulators.
TABLE VII. AVERAGE COSTS PER OUTLET FOR WIRING FOR LAMPS IN
NEW BUILDINGS 1
Outlets
Exposed
porcelain
Wood
Metal
conduit
molding
molding
Light ....
$4 . 00-S8 . 00
$5.00-$10.00
$8.00-$16.00
$7.00-$14.00
Switch. .
. 1 5.00-10.00
6.00- 12.00
9.00- 18.00
8.00- 16.00
Wall receptacle 5.00-10.00
6.00- 12.00
9.00- 18.00
8.00- 16.00
Floor receptacle
7.00-14.00
8.00- 16.00
11.00- 22.00
10.00- 20.00
Fan
6.00-12.00
7.00- 14.00
10.00- 20.00
9.00- 18.00
Iron
9.00-18.00
10.00- 20.00
13.00- 26.00
12.00- 24.00
Electric heater 7.00-14.00
8.00- 16.00
11.00- 22.00
10.00- 20.00
Vacuum control switch 2 12.00-24.00
13.00- 26.00
16.00- 32.00
15.00- 30.00
1 For use where the total cost of the work is about $2,000. For
residences the lower figures should be used. For public buildings, such
as banks, office buildings, churches and the like, a figure midway be-
tween the range of figures given should be used. Where best grade of
material and workmanship is required the higher figures should be used.
Prices do not include costs of fixtures or appliances, but do include
switches and receptacles. For wiring old buildings where porcelain
work and conduit work is concealed the figures given should at least be
doubled. If porcelain or conduit work is to be installed exposed in
either old or new buildings, the figures should be increased at least 25
per cent., the difference of cost depending upon the purpose for which
the building is or was designed.
2 Includes automatic starter at motor.
22
THE ELECTRICAL CONTRACTOR
TABLE VIII. AVERAGE COSTS FOR SIGNAL SYSTEMS RUN CONCEALED
IN NEW BUILDINGS 1
Costs per outlet (connected
Bell wiring
as one outlet)
Porcelain
Conduit
Per push-button and bell
$6.00
4.00
$12.00
8.00
Per drop on annunciator
1 For work on old buildings the figures given above should be doubled-
The cost of push-buttons, bells and annunciators is included.
TABLE IX. AVERAGE COSTS OF PRIVATE TELEPHONES
Porcelain
Per desk telephone .
Per wall telephone .
$30-$50
25- 45
Conduit
$40-$60
35- 55
TABLE X. AVERAGE COSTS OF PUBLIC TELEPHONES IN NEW BUILDINGS,
CONCEALED WORK*
Conduit
Per outlet. .
$5 . 00-$ 15 . 00
1 Cost of wires is not included since the electrical contractor very seldom
does the wiring. The range of the figures is due to variations in the dis-
tances between outlets. Instruments are assumed to be furnished and
installed by the telephone company.
TABLE XI. COST OF INSTALLING MISCELLANEOUS WoRK 1
Apparatus
Porcelain
Conduit
Time clocks
$30 00-$45 00
$35 . 00-$50 . 00 per clock
Time stamps
Fire alarms
Watchmen's stations
65.00- 85.00
20.00- 30.00
25.00- 35.00
70 . 00- 90 . 00 per stamp
25 . 00-35 . 00 per alarm
30 . 00- 40 . 00 per station
1 The range of the figures given above is due to differences in the grades
of workmanship and materials. For old buildings the figures given
should be increased from 25 to 50 per cent. These figures include the
cost of apparatus as well as the cost of all conductors, conduits and labor.
COST-KEEPING
23
WEEK ENDING
1 LABOR
>'CONDT.
1 LABOR
2"CONDT.
LABOR
^C14. D.W
O *
3 s
LABOR
OUTLET BOXES
LABOR
FIX.SUP'P.
LABOR
SW.BOXES
LABOR
SWS.
LABOR
PANEL BOXES
LABOR
PANEL B'D.
LABOR
DOOR & TRIM
LABOR
METER B'D.
&SW.
TOTAL
LABOR
y z c.
2 C.
14 D.
%w.
LT.B.
F.S.
SW.B
sw.
P.B.B
P.B.
D.&T
M.B.
.
FIG. 5. Unit cost sheet compiled by clerk.
24 THE ELECTRICAL CONTRACTOR
It is essential for the contractor to know the unit costs
of labor for performing the various operations entering
into the execution of any wiring contract as the method
previously described will not give this information.
The labor item in the electrical-contracting business
is subject to changes due to variations in the price of
labor resulting from increases or decreases of rates and
to variations in the unit costs with the nature of the
building construction. The latter variations may
amount to 100 per cent, or more.
The cost of labor can be determined with a fair degree
of accuracy for buildings of various types, such as those
of brick-and-joist construction, structural-steel construc-
tion with terra-cotta or concrete floors, and reinforced-
concrete construction, by the following method, which
may be worked out as elaborately as necessary and made
to cover not only the labor required for installing dif-
ferent sizes of conduit, wires, etc., but also the labor
required for connecting various sizes of wires to switch-
boards, dynamos, lugs, etc.
When a contract is secured in which the unit price of
labor for certain parts of the work is not accurately
known to the contractor, this information being desired
for future use, he should endeavor to obtain these data
by having a sheet such as shown in Fig. 5 prepared for
his pay-roll clerk. A copy of this sheet should be given
to the foreman on the job with instructions to mark
his time sheets according to the symbols for the labor
items as shown in Fig. 5, the time sheet thus marked
being shown in Fig. 6.
At the end of the week the pay-roll clerk inserts on
his unit-cost sheet the amount of money expended dur-
ing that week for the various labor items on the job
COST-KEEPING
25
Pom 8-W-6J
TIME
I y-i- H 8. H. L
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Notice Pay Roll close. Wednesdays. Time not then reported, will not be paid until the
- following week. Hours:8 to 12 A.M. 12.30 to 4.SO P.M.
KELLER-PIKE CO.
Hour
DESCRIPTION OF WORK
EXPENSES
1
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MrtitAJLAtL*^ Unfits &0, Ik
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FIG. 6. Time sheets showing symbols for labor items.
26 THE ELECTRICAL CONTRACTOR
under way, the total of these items equaling the total
pay-roll for that job. This process is carried on until
the completion of the work, at which time the total labor
for each item is ascertained. Dividing the total labor
for installing a certain material by the total amount of
the materials installed, as ascertained from the con-
tract ledger, a unit price is obtained for installing that
material.
It is very often desirable, however, to know what the
unit price of labor is at the end of each week, especially
if the job is some distance from the contractor's office
and is visited by his superintendent only once or twice
during the progress of the work. This can be accom-
plished by the use of material sheets (Fig. 7) issued to
the foreman. Taking, for example, the report on con-
duit work, the foreman fills out the lines marked A, B,
C and D for the first week, after which only the lines
A, B and C are filled out.
The line A designates the job. The line D, which is
filled out only when the first slip is issued, indicates
the amount of conduit on the job at the time the foreman
arrives, while the line 5, which is filled in by the fore-
man every week, indicates the conduit received during
that week. Now, the line C, which is filled out by the
foreman every week, indicates the amount of conduit on
hand at the end of the week. Hence, the sums of the
amounts of materials entered on the lines B and D minus
the amounts entered on C, that is, B -\- D C, for the
first week indicate the amounts of the different sizes
of conduit installed during that week.
After the first week the sums of the amounts of con-
duit along the line D of the first week's report and along
the line B of all subsequent weekly reports, minus the
COST-KEEPING
27
REPORT ON CONDUIT WORK
THE FIRST WEEK THE FOREMAN WILL FILL OUT THE LINES A. B. C AND O. AFTER THAT THE LINES A. B ANO C ONLY. KELLER-PIKE CO.
Z
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REPORT ON WIRE WORK
L FILL OUT THE LINES A. B. C AND D. AFTER THAT THE LINES A. B AND C ONLY. KELLER-PIKE CO.
1
2
i
5
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REPORT ON OUTLET WORK
THE FIRST WEEK THE FOREMAN WILL FILL Our THE LINES A. B. C. AND D. AFTER THAT THE LINES A. a ANO C ONLY. KELLER-PIKE CO.
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28 THE ELECTRICAL CONTRACTOR
amounts along the line C of the last report, indicate the
amounts of the different sizes of conduit installed up
to the time of the last report.
The labor costs from the weekly time sheet (Fig. 6)
are then inserted along the line marked ' 'labor cost,"
and the unit prices are accurately figured and placed
along the line marked " price per unit." If the price
per unit for any item is higher than the estimated price,
the head of the construction department indicates this
by placing a red cross opposite the particular item to
which he desires to call the attention of the superin-
tendent. The latter immediately investigates the mat-
ter, reporting on any possible causes for the increased
costs and on the possibility of reducing the unit
price.
This same process is carried out for wire work and
outlet work. In the usual installation these items of
conduit work, wire work and outlet work are by far the
largest portion of the labor item, so that the work on
signal systems, bells, etc., can be neglected. Otherwise
the cost involved for ascertaining unit prices on the
minor work would far overbalance the benefits of know-
ing these particular labor costs.
In Tables XII to XXIX as obtained by the above
method are given the unit costs of labor. The data,
however, cannot be considered general in their applica-
tions, for conditions vary widely in the electrical con-
tracting field. Every contractor should make his own
tables and curves, utilizing his records for the purpose.
In all the following tables it is assumed that the rates
for labor are 55 cts. per hour for foremen, 45 cts. per
hour for wiremen, and 25 cts. per hour for helpers.
All figures given include an allowance for what has been
COST-KEEPING
29
found to be necessary supervision by the foreman in the
class of work under consideration.
TABLE XII. COST PER KILOWATT FOR ERECTING BELTED GENERATORS
Size in kw.
Normal
condition
Easy
Difficult
Cost of
painting
1 - 5
$1.00
$0.75
$1.50
$0.60
5 -12^
1.00
0.75
1.50
0.60
12^-25 "
1.00
0.75
1.50
0.50
25 -50
1.00
0.75
1.50
0.40
75
0.80
0.60
1.25
0.30
100
0.75
0.60
1.20
0.25
150
0.60
0.50
0.90
0.20
200
0.50 0.40
0.80
0.18
300
0.40 0.30
0.60
0.15
500
30 20
50
12
TABLE XIII. COST PER KILOWATT OF FOUNDATIONS FOR BELTED
GENERATORS 1
Size in kw.
Normal condition
Easy
Difficult
1-5
$2.00
$1.50
$3.00-$4.00
5 -12K
2.50
2.00
3.75- 5.00
12^-25
2.00
1.50
3.00- 4.00
25 -50
1.50
1.00
2.25- 3.25
75
1.20
0.85
1.80- 2.80
100
1.00
0.75
1.50- 2.50
150
0.85
0.60
1.25- 2.25
200
0.75
0.60
1.00- 2.00
300
0.60
0.50
0.90- 1.80
500 0.50
0.40
0.75- 1.50
1 The items under this heading include the cost of labor and materials,
which is the usual method of estimating this class of work. The figures
are based on the average cubical contents of foundations specified by
generator makers. If the electrical contractor is to furnish the belt or
belts, the labor for putting them in place should be included.
30 THE ELECTRICAL CONTRACTOR
TABLE XIV. LABOR FOR ERECTING SWITCHBOARD PANELS
Dynamo panel
without
sub-base
Dynamo panel
with
sub-base
Feeder panel
without
sub-base
Feeder panel
with
sub-base
Cost per panel
$10.00
$12.00
$12.00
$15.00
TABLE XV. LABOR PER LEAD FOR CONNECTING SWITCHBOARD AND
DYNAMO LEADS 1
Size, B. & S.
Paper and lead
Rubber and lead
Rubber or
slow-burning
insulation
14-8
$0.33
$0.30
$0.21
6
0.45
0.41
0.28
5
0.55
0.50
0.33
4
0.66
0.60
0.40
3
0.80
0.72
0.49
2
0.87
0.79
0.53
1
0.92
0.84
0.56
1.00
0.90
0.60
00
1.04
0.94
0.63
000
1.08
0.98
0.65
0000
1.14
1.03
0.69
Circ. mils
250,000
1.18
1.08
0.72
300,000-350,000
1.34
1.22
0.78
400,000-450,000
1.43
1.30
0.84
500,000-550,000
1.60
1.44
0.90
600,000-650,000
2.10
1.90
1.00
700,000-750,000
2.50
2.25
1.25
800,000-850,000
2.95
2.65
1.50
900,000-950,000
3.30
3.00
1.75
1,000,000
3.75
3.40
2.00
1 These figures are the labor costs for soldering cables into lugs at the
switchboard and generators, also for soldering light and power cables into
lugs of switches on the switchboard. They include the cost of arranging
the cables in a neat and workmanlike manner at these locations.
COST-KEEPING 31
TABLE XVI. LABOR COSTS (IN CENTS) PER FOOT OF CONDUIT WORK [
Size of
conduit
Steel-terra-cotta
construction
Concrete
construction
Slow-burning
construction
Exposed
Concealed
Exposed
Concealed
Exposed
Concealed
Small
am't
Large
am't
Small
am't
Large
am't
Small
am't
Large
am't
Small
am't
Large
am't
Small
am't
Large
am't
Small
am't
Large
am't
\
effective lumens per lamp
where S = the number of square feet floor area of the
room and 7 = the required average intensity of illumi-
nation required in foot-candles. The term " effective
lumens per lamp" refers to the total light flux from
lamps that is available for illumination purposes.
To illustrate this method the following examples may
be cited. A storeroom to be lighted measures 40 ft. by
100 ft. Considering the goods to be sold, it is decided,
72 THE ELECTRICAL CONTRACTOR
after referring to the table of foot-candle intensities
recommended for various classes of service (Table
XXXIX), that 3 ft.-candles is sufficient for general
illumination. Then the total lumens of light flux re-
quired would be three times the area in square feet, or
40 X 100 X 3, which is equal to 12,000 lumens. By
turning to Table XL of effective lumens for tungsten-
filament lamps it is found that under ordinary conditions
the number of 25-watt, type B lamps necessary would
be 12,000 -5- 120, or 100. With 40-watt lamps 12,000
-T- 200, or 60, would be required.
These calculations are subject to correction for color
of the wall and ceilings, types of reflectors used, etc.
For example, if clear holophane reflectors are to be used
in the store referred to above, and the walls and ceiling
are of medium tint, the effective lumens from the lamps
may be considered as 10 per cent, greater. If opaque
reflectors were used instead of clear glass, the increase
in illumination resulting from light ceilings and walls
would be negligible, while if certain kinds of opal glass
shades were used the influence of color of the ceiling
and walls would be greater. It is somewhat difficult to
estimate the difference in resulting illumination with
different color decorations, and in residence work, where
the wall paper may be changed from time to time, it is
not wise to rely too much on reflection from surfaces.
For lighting by the use of indirect-lighting fixtures
the writer has found the flux-of-light method to be
very satisfactory when based on 0.4 watt per foot-
candle for each square foot of horizontal surface to be
illuminated.
To find the proper type of reflectors to be used curves
like those shown in Fig. 15 may be employed. To find
ILLUMINATION CALCULATIONS
73
the proper shade to be used, knowing the height of the
unit above the floor level and the spacing between units,
follow the vertical line representing the spacing between
s
OC
/
/
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/
/
/
/
/
/
32
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246
10 12 14 16 18 20 22 24 26 28 30 32 34
Spacing Between Outlets in Feet
40 42
FIG. 15. Curves for selecting type of reflector.
units until it intercepts the horizontal line marked
"mounting height,' 7 and use the shade which is shown
by the diagonal line to be nearest the point thus located.
CHAPTER VIII
GENERAL DATA
Such data as have been found necessary for the esti-
mating and laying out of both large and small interior
and underground electrical installation is included in
this chapter. Data such as can usually be obtained from
tables in the National Electric Code and from manu-
facturers' literature are, in general, omitted.
INTEKIOR CONSTRUCTION
Conduit, Elbows and Couplings. Dimensions referring
to this material are omitted as the same can be obtained
in the conduit manufacturers' catalogues.
Wire. The diameters, weights and resistances for
different sizes of wire can likewise be obtained in the
wire manufacturers' catalogues.
TABLE XLI. OUTSIDE DIAMETERS OF BUSHINGS AND LOCKNUTS
Size, in.
Outside
diameter of
bushings, in.
Outside
diameter of
locknuts, in.
Thickness
of bushings,
in.
Thickness
of locknuts,
in.
H
1
1H
Ke
H
H
1K6
IKe
%
>^
i
Ifc
w
H
^2
IK
1%
2Ke
He
Ke
1H
2H
2^6
KG
2
2^
3>^
%
%6
2y 2
3^
3%
M
KG
3
4
4%
%
KG
3>i
4Ke
5M
1
KG
4
5
5%
1
KG
74
GENERAL DATA
75
Locknuts and Bushings. It is usually necessary to
know the outside diameter of locknuts and bushings the
diameters of which establish the spacing distances of
conduits entering junction boxes, etc.
Panelboards. The approximate sizes of panelboards
are included as such sizes very often determine their
location.
TABLE .XLII. APPROXIMATE SIZES OF PANELBOARDS 1
Number of
circuits
Two-wire mains, two-wire branches,
dimensions, inches
Three-wire mains, two-
wire branches, dimensions,
inches, 110 volts
110 volts
220 volts
2
5.75 X 12
7 X 12
5.75 X 13.5
4
8.00 X 12
10 X 12
8.00 X 13.5
6
10.25 X 12
14 X 12
10.25 X 13.5
8
12.50 X 12
17 X 12
12.50 X 13.5
10
14.75 X 12
21 X 12
14.75 X 13.5
12
17.00 X 12
24 X 12
17.00 X 13.5
14
19.25 X 12
27 X 12
19.25 X 13.5
16
21.50 X 12
30 X 12
21.50 X 13.5
18
23.75. X 12
34 X 12
23.75 X 13.5
20
26.00 X 12
37 X 12
26.00 X 13.5
22
28.25 X 12
40 X 12
28.25 X 13.5
24
20.50 X 12
43 X 12
30.50 X 13.5
26
32.75 X 12
47 X 12
32.75 X 13.5
28
35.00 X 12
50 X 12
35.00 X 13.5
30
37.25 X 12
53 X 12
37.25 X 13.5
1 For panels where N.E.C. inclosed fuses of 30 amp. and under are
employed. No switches are assumed to be used on branch buses, and
the main buses are assumed to be without switches or fuses.
76
THE ELECTRICAL CONTRACTOR
TABLE XLIII. APPROXIMATE SIZES OF PANELBOARDS, DIMENSIONS IN
INCHES 1
Number of
circuits
Two-wire mains, two-wire branches
Three-wire mains, two-
wire branches, 110 volts
110 volts
220 volts
2
7 X 22
7 X 22
7 X 22
4
11 X 22
11 X 22
11 X 22
6
15 X 22
15 X 22
15 X 22
8
17 X 22
' 20 X 22
17 X22
10
20 X 22
23 X 22
20 X 22
12
23 X 22
27 X 23
23 X 22
14
27 X 23
32 X 23
27 X 23
16
29 X 23
35 X 23
29 X 23
18
32 X 23
39 X 23
32 X 23
20
35 X 23
44 X 24
35 X 23
22
39 X 23
48 X 24
39 X 23
24
41 X 24
52 X 24
41 X 24
26
44 X 24
56 X 24
44 X 24
28
48 X 24
60 X 24
48 X 24
30
52 X 24
64 X 24
52 X 24
1 For panels where fuses and switches of 30 amp. and under are em-
ployed for branches and where no fuses or switches are provided on the
main buses.
Knife Switches.
TABLE XLIV. AVERAGE OVERALL DIMENSIONS OF N.E.C. FUSED AND
FUSELESS SWITCHES, FRONT-CONNECTED l
Size
Double-pole,
inches
Three-pole,
inches
Four-pole,
inches
Five-pole,
inches
Fuseless switches.
H. W. D.
H. W. D.
H. W. D.
H. W. D.
30
11 7 291s
11 10 29fe
11 12 29i6
11 15 29ie
60
13 8 2%
13 11 2%
13 14 2%
13 17 2^
100
15 9 3H
15 12 3K
15 15 3}4
15 19 3H
200
19 10 4^6
19 13 4$i6
19 17 4*1 6
19 21 4*A6
Fused switches. . .
H. W. D.
H. W. D.
H. W. D.
H. W. D.
30
11 7 2iMe
11 10 2i?l6
11 12 2i?ie
11 15 2iMa
60
13 8 3?6
13 11 3H
13 14 3H
13 17 3H
100
17 9 4ft
17 12 4ft
17 15 4#
17 19 4H
200
21 10 5
21 13 5
21 17 5
21 21 5
Data furnished by the Walker Electric Company, Philadelphia.
GENERAL DATA
77
From the above table the sizes of iron boxes for knife
switches may be obtained.
General. Such data as the carrying capacity of wires,
the number of wires in a single conduit, the sizes of such
conduits and so forth can be found in Rules 18 and 28,
1915 National Electrical Code, as issued by the National
Board of Fire Underwriters.
UNDERGROUND CONSTRUCTION
Excavation. The average contractor sublets this por-
tion of his work, the cost of which will average between
50 cts. and $2 per cubic yard depending upon the soil.
Concreting. What has been said regarding excava-
tion applies to this item likewise, the cost of which will
average between $9 and $15 per cubic yard. For con-
tractors' estimates on their own concrete work the fol-
lowing table giving the various amounts of concrete,
sand and stone per cubic yard of rammed concrete in
different proportions, will be found useful.
TABLE XLV. AMOUNTS OF CEMENT, SAND AND STONE REQUIRED PER
CUBIC YARD OF RAMMED CONCRETE
Stone, mixtures 1 in. and under
Screened-out amounts
Concrete
Sand
Stone
Concrete, bbls.
Sand, cu. yd.
Stone, cu. yd.
1
2.0
4
1.46
0.44
0.89
1
2.5
5
1.19
0.46
0.91
1
3.0
5
1.11
0.51
0.85
1
3.0
6
1.01
0.46
0.92
1
3.0
7
0.91
0.42
0.97
1
4.0
7
0.83
0.51
0.99
1
4.0
8
0.77
0.47
0.93
Brick Work in Manholes. What has been said regard-
ing the above items applies to this item likewise, the
78
THE ELECTRICAL CONTRACTOR
cost of which will average between 75 cts. and $1.50 per
cubic foot.
Vitrified Ducts.
TABLE XLVI. OUTSIDE DIMENSIONS OF VITRIFIED DUCTS
Type
Bore, round or square, in.
Outside dimensions, in.
Single-way
3U
5 X 5 X 18
Two-way
Three-way
Four-way
3^
3^
3U
4 X 9 X 24
5 X 13 X 24
9 X 9 X 24
Six-way
3U
9 X 13 X 36
Nine-way
Nine-way
3>i
2
13 X 13 X 36
9 X 9 X 36
Telephone Cables, The usual literature of wire manu-
factures does not give the outside diameters of paper-
covered lead-encased telephone cables. The following
table applies to type G lead-covered telephone cables
as manufactured by the Western Electric Company.
TABLE XL VII
No. of pairs
Outside diameter, in.
No. of pairs
Outside diameter, in.
5
H
40
2 %2
10
KG
50
%
15
X
60
7 A
20
%6
75
15 /16
25
%
100
IKe
30
5 /8
120
1^2
35
ll Ae
150
1%2
200
1%
Electric Light and Power Cables. The usual literature
of wire manufactures does not give the outside diameters
of rubber-covered, lead-encased cables.
GENERAL DATA
79
Single Conductor.
TABLE XL VIII. OUTSIDE DIAMETERS OF CABLES FOR 600 VOLTS
PRESSURE OR LESS
Size
Thickness
of rubber, in.
Thickness
of lead, in.
Outside diameter
Solid, in.
Stranded, in.
14
%4
%4
0.28
0.30
12
%4
%4
0.30
0.31
10
%4
%4
0.33
0.34
8
%4
%4
0.35
0.38
6
KG
KG
0.47
0.47
5
KG
KG
0.50
0.50
4
KG
KG
0.52
0.52
3
KG
KG
0.53
0.55
2
KG
KG
0.56
0.58
1
%4
KG
0.63
0.66
%4
KG
0.69
00
%4
KG
0.73
000
%4
KG
0.78
0000
%4
KG
0.84
250 M
3 /32
%4
0.95
300 M
3 /32
%4
1.02
350 M
3 /B2
%4
1.08
400 M
3 /32
%4
1.11
450 M
3 /32
^4
1.19
500 M
3/ 32
%4
1.20
550 M
%4
%2
1.33
600 M
%4
%2
1.34
650 M
%4
3 /32
1.38
700 M
%4
%2
1.41
750 M
%4
%2
1.44
800 M
%4
%2
1.47
850 M
%4
%2
1.50
900 M
%4
%
1.53
950 M
/ D 4-
%4
Xo Z
%2
1.56
1000 M
%4
%2
1.59
80
THE ELECTRICAL CONTRACTOR
Duplex Conductor.
TABLE XLIX. OUTSIDE DIAMETERS OF CABLES FOR 600 VOLTS
PRESSURE OR LESS
Size
Thickness of
rubber, in.
Thickness of
lead, in.
Outside diameter,
stranded, in.
14
%4
H4
0.30 X 0.50
12
X*
H4
0.31 X 0.53
10
H4
H*
0.34 X 0.59
8
%4
KG
0.41 X 0.69
6
KG
KG
0.47 X 0.81
5
KG
KG
0.50 X 0.88
4
KG
KG
0.52 X 0.91
3
KG
KG
0'.55 X0.97
2
KG
H4
0.61 X 1.06
1
W4
H4
0.69 X 1.22
H4
%4
0.72 X 1.28
00
4
H4
0.77 X 1-.38
000
H4
%4
0.81 X 1.47
0000
H4
^4
0.88X1.59
250 M
%i
Ha
0.95 X 1.64
300 M
3 /32
Hi
1.02 X 1.88
350 M
3 /32
Ha
1.08 X 2.00
400 M
3 /32
%2
1.11 X 2.06
450 M
3 /32
.H2
1.19 X 2.22
500 M
3 /32
H?
1 . 20 X 2 . 24
Triplex Conductor.
Size
Thickness of
rubber, in.
Thickness of
lead, in.
Outside diameter
stranded, in.
14
H4
KG
0.59
12
%4
KG
0.63
10
%4
KG
0.70
8
%4
KG
0.77
6
Ke
%4
0.94
5
KG
^4
1.00
4
KG
^4
1.03
3
KG
%4,
1.09
2
KG
Hi
1.13
1
%4
*/32
1.19
%4
H 2
1.28
00
%4
H 2
1.38
000
%4
%2
1.50
0000
%4
H2
1.64
INDEX
AMPERES PER H. P. FOR A.-C. MOTORS 57
ANNUNCIATOR SYSTEMS, COST OF. ..." 22
B
BELL SYSTEMS, COST OF 22
Bookkeeping 7-13
Bills and billing 9, 11, 13
Contract ledger 7, 11, 17, 26
Main ledger 11
Pay-roll distribution 12, 13
Order cards for jobs 7, 8
Order cards for workman 8, 9
Requisition sheet 9-11
Transferring materials on jobs 9,11
BUSHINGS, DIMENSIONS OF 74
Cables.
Cost of connecting at dynamo and switchboard 30
Cost of pulling and splicing 39, 40
Dimension of single-conductor electric 79
Dimension of double-conductor electric 80
Dimension of three-conductor electric 80
Dimension of telephone 78
Candle Power.
Curves of 64, 65
Definition of 62, 63
Concreting.
Cost of 77
Various proportions used in 77
Conduit.
Cost of laying rigid 38
Cost of running rigid 31
Cost of running flexible 31
Construction Department.
Method of checking weekly costs 26-28
81
82 INDEX
Requisition sheets 9,10
Special receipt sheets 9,11
Stockroom 9,11,13
Sup't 9,26,28
Time sheet 25
Workman's order card 8, 9
Costs 14-40
Curves of 15-17
Items of 14
Method for obtaining approximate 15-18
Method for obtaining unit 23-29
Pay-roll clerk's sheet of unit 23
Tables of approximate 18-22
Tables of unit 29-40
Time sheet lor ascertaining unit 25
Weekly sheets of unit 26, 27
CROSS-ARMS, COST OF ERECTING 37
CURVES, METHOD OF PREPARING 15-17
D
Ducts.
Cost of laying 38
Dimension of 78
DOUBLE NEUTRAL MAINS 49
Dynomas.
Cost of 19
Cost of connecting cables 20, 30
Cost of erecting belted 29
Cost of foundations for belted 29
E
ENGINEERING DEFT., WORK OF 9
ENGINES, COST OF 18
Estimates 41-45
Detail of branches 42
Detail of mains 43
Interior construction 41-42
Logical arrangement 41, 42, 44, 45
Overhead construction 44, 45
Underground construction 44
EXCAVATING, COST OF 77
Expenses (Manufacture or Overhead} 1-6
Items of 3, 4
Meaning and nature of 2, 3
INDEX 83
Method of applying 5, 6
Method of computing 4, 5
National electrical contractors association, data of 3
FAN OUTLET, COST OF INSTALLING 21
FIRE ALARM SYSTEMS, COST OF INSTALLING 22
FIXTURE SUPPORTS, COST OF INSTALLING 34
FOOT CANDLES, DEFINITION OF 63
FOOT CANDLES, TABLE OF 71
FLUX OF LIGHT METHOD 70-72
G
GLOBES, ABSORPTION OF LIGHT BY 69
H
HEATER OUTLET, COST OF INSTALLING 21
HENRY'S METHOD OF CALCULATING 58, 59
Illumination 62-73
Absorption of light by globes 69
Calculating size of units 68-71
Candle-power, definition of 62, 63
Candle-power, curves 64, 65
Desirable size of squares for spacing 69
Effect of reflection from walls 67, 68
Foot-candles 63, 71
Flux of light method 70-72
Indirect lighting-watts per foot-candle 72
Intensity of illumination 63-66, 71
Lumens, definition of 70
Lumens, table of effective 71
Reflectors 72, 73
IMPEDANCE 59
INDUCTANCE 53-59
IRON OUTLET, COST OF INSTALLING 21
J
JOBS, TRANSFERRING MATERIALS ON 9, 11
84 INDEX
K
Knob-and-tube Work.
Cost per foot for concealed 35
Cost per foot for exposed 36
L
LABOR, VARIATIONS IN COST OF 24, 28
LIGHT OUTLETS, COST OP INSTALLING 21
LOCKNUTS, DIMENSION OP 74
LOSSES A.-C. circuits 53-61
LOSSES D.-C. circuits 46-52
LOSSES at contacts 50
LUMEN, DEFINITION OF 70
LUMEN, TABLE OF EFFECTIVE 71
M
MANHOLES, COST OF . 77, 78
MOLDING WORK, COST OF 36
Motors.
Cost of 20
Cost of installing and connecting 33
Cost of installing and connecting control apparatus .... 34
Cost of wiring and connecting 21
Current consumption of A.-C 57
MULTIPLYING FACTORS FOR A.-C. CIRCUITS 56
O
OHM'S LAW 47
ORDER CARDS JOB 7, 8
ORDER CARDS WORKMAN 8, 9, 10
OUTLETS, COST OF WIRING VARIOUS 21, 22
Outlet Boxes.
Cost of installing light 34
Cost of installing switch 34
Cost of installing receptacle (floor) 34
Cost of installing receptacle (wall) 34
P
Panel Boards.
Cost of installing 33
Dimension of .' 75,[76
PAY-ROLL, DISTRIBUTION SHEET FOR
INDEX 85
POLE LINE CONSTRUCTION 44, 45
Poles 37
Cost of digging holes for 37
Cost of erecting (iron) 37
Cost of erecting (wood) 37
Cost of erecting cross-arms on 37
Cost of guying 37
Cost of shaving 37
Cost of stepping 37
Profit 1-6
Meaning and nature of 1,2,5,6
Method of applying 5, 6
National Electrical Contractors Association, data of .... 3
Power-factor.
Definition of 53, 54
Table of averages 54
R
REACTANCE 58, 59
RECEIPTS SPECIAL 9, 11
Receptacles.
Cost of installing and connecting 33
Cost of installing boxes for 34
Cost per outlet for floor 21
Cost per outlet for wall 21
REFLECTORS, CURVES OP PROPER 72, 73
REQUISITION SHEETS 9, 10
Resistance.
Method of approximating 48
Of 1/0 wire 48
Of a circuit carrying a given current 51
S
SELF-INDUCTION 58
SHOP OR REAL COST 2
SIGNAL SYSTEMS, COST OF 22
SKIN EFFECT 53
STOCK ROOM 11
Switches (Push button).
Cost per outlet 21
Cost of installing and connecting 33
Cost of installing boxes for 34
SWITCHES (KNIFE), DIMENSION OF 76
86 INDEX
Switchboards.
Cost of 19
Cost of connecting cables at 20, 30
Cost of erecting 30
T
TELEPHONE SYSTEMS, COST OF 22
THREE-WIRE BALANCE SYSTEM 48, 49
TIME CLOCK SYSTEMS, COST OF 22
TIME SHEETS 25
TIME STAMP SYSTEMS, COST OF 22
U
UNDERGROUND CONSTRUCTION 44
V
VACUUM CONTROL OUTLETS, COST OF 21
VOLTAGE LOSSES ON A.-C. CIRCUITS 53-61
VOLTAGE LOSSES oisi D.-C. CIRCUITS 46-52
W
WATCHMAN'S CLOCK SYSTEMS, COST OF 22
Wire.
Calculating sizes for A.-C. circuit 53-61
Calculating sizes for D.-C. circuit 46-52
Cost per ft. fishing conduits and pulling 32
Cost per ft. stringing 38
Method of approximating resistance of 48
Multiplying factor for A.-C. circuits 56
Relative sizes of for D.-C. and A.-C. . 55
t
3380
153
Engineering
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UNIVERSITY OF CALIFORNIA LIBRARY