Albert Irvin Frye.

Civil engineers' pocket book; a reference-book for engineers, contractors, and students, containing rules, data, methods, formulas and tables online

. (page 150 of 182)
Online LibraryAlbert Irvin FryeCivil engineers' pocket book; a reference-book for engineers, contractors, and students, containing rules, data, methods, formulas and tables → online text (page 150 of 182)
Font size
QR-code for this ebook


.0M1382
.0001434
.0001724


.0001532
.0001589
.0001911


.




.2576
.2380
.7294


52128
44488
41339


.0007765
.001066
.001335


.0008675

.001191

.001379


.0009614

.001320

.001629


.0001660
.0001828
.0001967


.0001743
.0002042
.0003196


.0001932
.0002263
.0002435






.2200
.2043
.2030


38013
32784
32365


.001460
.001963
.002014


.001631
.002193
,002250


.001808
.002431
.002494


.0002139
.0002480
.0002613


.0002890
.0002771
.0002807


.0002649
.0003071
.0003111






.1819
.1800
.1650


25999
25447
21382


.003122
.003258
.004615


.003487
.003640
.005156


.003865
.004034
.005714


.0003128
.0003196
.0003803


.0003496
.0003570
.0004249


.0003873
.0003957
.0004709




9


.1630
.1480
.1448


20618
17203
16351


.004963
.007129
.007892


.005545
.007965
.008817


.006145
.008827
.009772


.0003944
.0004727
.0004973


.0004406
.0005281
.0005656


.0004883
.0005853
.0006158




10
11


.1340
.1285
.1200


14103
12967
11310


.01061
.01255
.01650


.01185
.01402
.01843


.01314
.01554
.02042


.0006766
.0006271
.0007190


.0006442
.0007007
.0008033


.0007140
.0007765
.0008903




12


.1144
.1090
.1019


10283
9331
8155


.01996
.02423
.03173


.02229
.02707
.03545


.02471
.03000
.03928


.0007908
.0008715
.0009972


.0008835
.0009736
.001114


.0009791
.001079
.001235




13
14


.0950
.09074
.08300


7088
6467
5411


.04199
.05045
.07207


.04692
.05636
.08052


.05200
.06246
.08924


.001147
.001257
.001603


.001282
.001405
.001679


.001420
.001657
.001861




16


.08081
.07200
.07196


5129
4072
4067


.08022
.1273
.1276


.08962
.1422
.1425


.09983
1576
.1679


.001586
.001997
.001999


.001771
.002231
.002234


.001968
.002473
.002476


14


16
17


.06600
.06408
.0580


3318
3225
2642


.1916
.2028
.3028


.2141
.2266
.8377


.2878
.2511
.3742


.002451
.002531
.003078


.002738
.002817
.003439


003084
.003122
.008811



laoo




70.-


ELECTRIC POWER AND UGHTING.




]


1. COPPBR WiRB TABLB op THB-


_






(See Opposite Page for Areas in Squan Bills.)






Osges.


Weight.




Leocth.


dasloi*


U


Ares
Circ.
MUs.


Lb. per
Foot.


Pounds per Obm.


Pt.


Feet per Ohm.


^2^1


@20»C.
-68«F.


d 80«C.
-122T.


% 80«»C.


O20»C.

-6«»F.


-i22«Fl(-i:rr.


15
16


18


.06707
.05082
.049


8257
2583
2401


.009858
.007818
.007268


3.101
1.950
1.685


2.776
1.746
1.509


2.504
1.675
1.361


101.4
127.1
137.6


314.5
249.4
231. S


281. 5
223.1

207.6


2S4(

2ets
iffi


17
18


19


.04626

.042

.0403


2048
1764
1624


.006200
.005340
.0049! 7


1.226

.9097
.7713


1.098
.8143
.6904


.9906

.7347
.6230


161.8

187.8
203.4


rn.e

170.4

156.t


m.i

151.5
140.4


13; fi
iM.r


19


20
21


.03589

.035

.082


1288
1225
1024


.003899
.003708
.003100


.4851
.4387
.8066


.4348

.3927
.8744


.8918
.8543

.2476


256.5

169.7
822.6


124.4

118.J
98-90


111.4
106.9
88.52


MS

KM

78.16


10

ai


22


.08196
.02846
.028


1022
810. 1
784.0


.003092
.002452
.002378


.3051
.1919
.1797


.2731
.1717
.1608


.8464

.1550
.1451


323.4
407.8
421.4


9R.66
78-24
75.72


88.21
70.03
67.78


79-6
$3.1!

61.14


2S
2S


23


.02535

.025

.02257


642.4
625.0
509.5


.001946
.001892
.001542


.1207
.1142
.07589


.1080
.1022
.06793


.09746
.09224
.06129


514.2
528.6
648.4


62.06
00 36
49.21


59.54
54-03
44.04


soil
48:5
29:4


24


24

25


.022
.0201
.020


484.0
404.0
400.0


.001465
.001223
.001211


.06849
.04771
.04678


.06130
.04272
.04187


.05631
.03855
.03778


681.6
817.6
825.9


46.75
89.02
38.68


41.8^
94. 83

34.6^


37.75
21.52
21.21


26


26
27


.018
.0179
.016


324.0
82U 4
266.0


.0009808
0009699
.0007749


.08069
08002
! 01916


.02747
.02687
.01715


.02479
.02424
.01548


\m

1081
1290


81 29
30.95
14.73


28.81
27.70
22.13


25.27
24. M

19. IT


26
27


28


.01594
.0142
.014


254.1
201.5
196.0


.0007692
.0006100
0005933


.01888
.01187
.01123


.01690
.01063
.01006


01535
.009588
.009071


1300
1639
1685


24.54

19.46
18.91


11.8?
17.42
16. M


18-83
15.21


28


29
30


.013

.01264

.012


169.0
159.8
144.0


.0005116
.0004837
.0004359


.008350
.007466
.006062


.007474
.006683
.005426


.006744
.006030
.004896


1955
2067
2294


1682
16.43
18.91


14.61
13.82
12.49


13 IS
12 4-
11 23


29
30


31


.01126
.01003
.010


126.7
100.5
100.0


.0003836
.0003042
.0003027


.004696
.002953
.002924


.004203
.002643
.002617


.008792
.002385
.002361


2607
8287
3304


1124

9.707
9.658


10. 9«
8.68i
8.845


9 881

7-S*
7.8H


31


32
33


.009

.008938

.008


81.00
79.70
64.00


.0002452
.0002413
.0001937


.001918
.001857
.001197


.001717
.001662
.001072


.001549
.001500
.0009672


4078
4145
5162


7.823
7.698
6.181


7.082
6.880
6.533


C.3I8

6- 21:
4.98Z


32
33


34


.00795
.00708
.007


63.21
50.13
49.00


.0001913
.0001517
.0001483


.001168
.0007346
.0007019


.001045
.0006575
.0006283


.0009436
.0005933
.0009669


5227
6501
6742


6.105
4.841
4.733


5.464
4.331
4.236


4.836
2.818

2.822


34

35
36


85


.006305
005615
.005


39.75
31.52
25.00


.0001203
.00009543
.00007668


.0004620
.0002905
.0001827


.0004135
.0002601
.0001636


.0003731
.0002347
0001476


8311
10480
13210


ai.839
3.045
2.414


8.436
2.726
2.161


2.101
2.459

1.981


37


36


.004453

.004

.003965


19.83
16.00
15.72


.00006001
00004843
.00004759


.0001149
.00007484
.00007210


.0001029
.00006699
.00006454


.00009281
.0000604&
.00005824


16660
20650


1.915
1.54G
1.519


1. 714
1.283
1.2S9


1.54J
1 249


38


21010


l!22l


39
40




.003531
.003145


12.47
9.888


.00008774
.00002993


.00004545
.00002858


.00004068
.00002559


00003671
.00002309


33410


1.101


1.078
.8648


.8781
.TTll



Note.— Sq. mils-circ. mils X 0.785306; circ. mils-sq. mUsXl.S7SI0.

Digitized by VjOOQ IC



COPPER WIRE TABLE,



1891



, — Am. In8t.


OF Elbctrical Enoinbbrs.— Concluded.




■^h:


(See Opposite Page for Areas in Circular Mils.)








- Ini.


Area
iDSq.
MU8.*


Ohmi per Lb.


Ohms per Ft.


9 20^


^ 60^.

-i2rF.


d 80-C.

-176«F.


d 20*^.
- 68'F.


^ 6U«C.
-122«F.


^ 80^
-176«F.


'^^ .05707
.05082
.04900


2558
2029
1886


.3225
.5128
.5933


.3603
.5729
.6629


.3993
.6349
.7346


.003179
.004009
.004312


.003552
.004479
.004818


.003936
.004964
.005339


.045M
.04200
.04030


1609
1885
1276


.8158
1.099
1.296


.9109
1.228
1.448


1.010
1.361
1.605


005065
:006870
.006374


.005648
.006658
.007122


.006269
.007267
.007891


.03581
1 .03600
i .08200


1012
962.0
804 2


2.061
2.279
8.262


2.303

2.547
8.644


2.652
2.822
4.039


.008038
.008453
.01011


.008980
.009443
.01130


.009951
.01047
.01262


.03198

.02848

2 .U2800


802.0
636.8
615.8


3.278
6.212
6.566


8.662
6.823
6.217


4.058
6.453
6.890


.01014
.01278
.01321


.01182
.01428
.01475


.01255
.01588
.01635


.02585

:3 .0250

.02257


504.6
490.9
400.2


8.287
8.756
13 18


9.259

9.783
14.72


10.26
10.84
16.32


.01612
.01657
.02032


.01801
.01851
.02271


.01996
.02051
.02516


24 .0220
.02010

25 .0200


380 1
317.3
314.2


14.60
20 95
21.38


16.31
23.41
23.88


18.08
25.94
26.47


.02139
.02.%63
.02588


.02390
.02863
.02892


.02649
.03173
.03206


26 .018

.0171

17 .016


254.5
251.7
201 1


82.68
33.82
62.19


36.40

37.22
68.31


40.34
41.25
64.62


.03196
.0.1231
.04045


.03570
.03610
.04519


.03957
.04001
.05008


.01504
.0142
9 .014


199.6
158.3
158.9


62.97
84.28
89.04


59.18
94.11
99.48


65.59
104.3
110.2


.04075
.05138
.05283


.04562
.05740
.05902


.05045
.06362
.06541


9 .013

.01204
.012


132.7
125.5
118.1


119.8
133.9
165.0


133.8
149.6
184.3


148.3
16.5.8
204.2


.06127
.06479
.0719


.06845
.07239
.08033


.07586
.08022
.08903


.01120
.01003
.010


99.53
78.94
78.54


2130
338.6
342.0


237.9
378.3
382.1


263.7
419.3
423.5


.0817
.1030
.1035


.09128

.1151

.1167


.1018
.1276
.1282


t .000
.008020
.008


63 62
62.60
50.27


621.3
638.4
836.1


582.5
601 6
933.0


645.6
666 7
1034.


.irs

.1299
.1618


.1428
.1451
.1807


.1583
.1608
.2003


.00705
.00708
.007


49.64
89.37
38.48


856.2
1361.
1425.


956.6
1621.
1592.


1060
1685.
1764.


.1638
.3066
.2113


.1830
.2308
.2361


.2028
.2558
.2616


.006305
.006019
.005


81.22
24.76
19.64


2165.
3441.
5473.


2418.
3845.
6114.


2680.
4262.
6776.


2605
.3284
.4142


.2910
.3G69
.4627


.3226
.4067
.5129


.004458

.004

.008965


15.57
12.67
12.36


8702.
13360.
13870.


9722.
14930.
15490.


10770.
16540.
17170.


.6222

.6471
.6686


.5835
.7230
.7367


.6466
.8011
.8164


.003581
.003145


9.79

7.77


22000.
34980.


24580.
39080.


r2io.

43320.


.8304
1.047


.9277
1.170


1.028
1.296



find area in square inches, divide by 1.000,000.



d by Google



ISdd Td.— ELECTRIC POWER AND UGHTING.

and impedana. The former may be assumed to be no greater thaa
the "drop" in volts on the line (and from that down to about one-thiid of the
amount), while the latter is usually so small as to be practically negligible,
say 5 per cent of the inductance. Hence from 5 to 10 per cent may be
added for losses in alternate-current circuits over those for continuous;
in other words the areas of the wires may be increased by this amount.
(3) In a single-phase two-wire circuit the size of wires is the same as for
continuous current plus 5 to 10 per cent for inductance. (4) In a two-phase
four-wire circuit the area of each wire is one-half that for the continuous
current circuit plus 6 to 10 per cent for inductance; that is, the same toritM
of wire is required as for the single-phase two-wire alternating circuit. (6) ux
the three-phase three-wire circuit the area of each wire is one-half that
for the continuous ciurent circuit plus 5 to 10 per cent for inductance; that
is, only three-fourths the weight of wire is required as for the l-phase 2-wire,
and 2-phase 4-wire, circuits.

Problem 2. — In solving Problem 1 we find that the size of copper wire
required is about 110,000 circular mills in area, corresponding to about
No. B. & S. gage. Now, from the foregoing discussion, what sizes of
wire would probably be installed for the three types of alternating circuits?
And what would be the theoretic relative weights of total amount of copptr
in the four systems?

Continuous current 2-wire; each 110,000 circ. mills; total weight, 1.00
AU*mo*,v,c { 1-phase 2-wire; " 120,000 " " ^^ IM

ri^f^ ^ 2-phase 4.wire: " 60.000 1.09

Current / s.phase 8-wire; " 60,000 " " " 0.82

The 3-pha8e 3-wire system is the most commonly used.



d by Google



1308



•NATIONAL ELECTRIC CODE."



Rules and Requirements of the National Board of Fire Underwriters

for the Installation of Wiring and Apparatus (for Light, Heat

and Power) as Recommended oy the Underwriters'

National Electric Association.

Edition of 1907.

The National Electric Code (originally drawn in 1897) is the result of
the united efforts of the various electrical, architectural, insurance and
other allied interests which, through the National (inference on Standard
Electrical Rules, composed of delegates from various national associations,
unanimously voted to recommend: it to their respective associations for
approval or adoption.

The following is a list of the associations composing the National Con-
ference on Standard Electrical Rules: — American Institute of Architects.
American Institute of Electrical Engineers. American Society of Mechanical
Engineers, American Institute of Mining Engineers, American Street and
Interurban Railway Association, Associated Factory Mutual Fire Ins. Od's.,
Association of Edison Illuminating Companies, International Association of
Municipal Electricians, National Board of Fire Underwriters, National
Electric Light Association, National Electric Contractors' Association,
National Electric Inspectors' Association, Underwriters' National Electric
Association.

GENERAL PLAN QOVERNINQ THE ARRANGEMENT OP RULES.*

Class A. — Stations and Dynamo Rooms. Includes Ontral Stations; Dy-
namo. Motor, and Storage-Battery Rooms; Transformer Sub-
stations, etc. Rules 1 to 11.
Class B. — Outside Work, all systems and voltages. Rules 12 to 13A.
Class C. — Inside Work. Rules 14 to 39. Subdivided as follows:

General Rules, all systems and voltages. Rules 14 to 17.
Constant-Current Systems. Rules 18 to 20.
Constant-Potential Systems: —
General Rules, all voltages. Rules 21 to 23.
Low-Potential Systems, 550 volts or less. Rules 24 to 34.
High-Potential Systems, 550 to 3500 volts. Rules 35 to 87.
Extra-High-Potential Systems, over 3500 volts. Rules 38 to 89.
Class D. — Fittings, Materials, and Details of Construction, all systems and

voltages. Rules 40 to 63.
Class E. — Miscellaneous. Rules 64 to 67.
Class F.— Marine Work. Rules 68 to 83.



' Central Suggestions. — In all electric work, conductors, however well
insulated, should always be treated as bare to the end that under no condi-
tions, existing or likely to exist, can a ground or short circuit occur, and ao
that all leakage from conductor to conductor, or between conductor and
ground, may be reduced to a minimum. ^

In all wiring, special attention must be paid to the mechanical execution
of the work. Careful and neat running, connecting, soldering, taping of
conductors, and securing and attaching of fittings, are specially conducive
to security and efficiency, and will be strongly insisted on.

In laying out an installation, except for constant current systems, every
reasonable effort should be made to secure distribution centers located in
easily accessible places, at which points the cut-outs and switches controlling
the several branch circuits can be grouped for convenience and safety of
operation. The load should be divided as evenly as possible among the
branches, and all complicated and unnecessary wiring avoided.

The use of wire-ways for rendering concealed wiring permanently acces-
sible is most heartily endorsed and recommended; and this method of
accessible concealed construction is advised for general use.

Architects are urged, when drawing plans and specifications, to make
provision for the channeling and pocketing of buildings for electric light or
power wires, and also for telephone, district messenger and other signaling
system wiring. og^ed by GoOglc



1804 70.— electric power and ughting.

cum a.—stations and dynamo rooms.

Includes Central Stations, Dynamo, Motor and Storagb-Battbrt
Rooms, Transformer. Sub-stations, Etc.

I. Qeneratora. — a. Mtist be located in a dry place.
It l8 recommended that water^proot eovers be provided, which may be latd ti
oaae of emergency.

b. Must never be placed in a room where any hazardous process is
carried on, nor in places where they woiild be exposed to inflammable gases
or flyings of combustible materials.

c Must, when operating at a potential in excess of 550 volts, have their
base frames permanently and effectivelv grounded.

Must, when operating at a potential of 550 volts or less, be thorotichlT
insulated from the grotmd wherever feasible. Wooden base frames used for
this purpose, and wooden floors which are depended upon for insulation
where, for any reason, it is necessary to omit the base frames, must be k^
filled to prevent absorption of moisture, and must be kept clean and dry.

Where frame insulation is impracticable, the Inspection Depcutment
having jurisdiction may, in writing, permit its omission, in which case the
frame must be permanently and effectively grotmded.

A high potential machine should be surrounded by an Insulated platfonn. This
may be made of wood, mounted on Insulating supports, and so arran^d ttttt a bbsq
must always stand upon It in order to touch any part of the machine.



In case of a machine having an insulated frame, it there is trouble trom statte
_..ptrlclty due to bolt friction. It should be overcome by placing near the belt a
metnlllc comb connected with the earth, or by grounding the trame thrmigh a re-



eleotrlclty due to bolt friction, Tt should be overcome by placing near the belt a
metnlllc comb connected with the " "~ """" "* '~'

slstanoe of not leas than 300.000 c

d. Constant potential generators, except alternating current machines
and their exciters, must be protected from excessive current by saie^ fuses
or equivalent devices of approved design.

For two-wire. direct-curr«att gmerDtors. slnfde pole protection will be eonaldera!
as satisfying the above rule, provided the safety device Is located In ttie toad not
connected to the series winding. When supplying three-wire systems, the gmen-
tors should be so arranged that these protective devices wni come in the outside
l«*d8. . ^ _^

For three-wire, direct-current generators, a safety device must be placed in each



armature, direct-current lead, or a double pole, double trip circuit breaker In eacS
outside generator lead and corresponding equaliser connection.

In general, generators should preferably have no exposed live parts and the



leads should be well Insulated and thoroughly protected against meehanlcal bijiny.
This protection of the bare live parts against accidental ccmtaot would apply also to
any exposed, uninsulated conductors outside of the generator and not on Uke switch-
board unless their potential is practically that of the ground.



Where the needs of the service make the above requirements Impraetlcabte. the
Inspectl(m Department having Jurisdiction may, in writing, modify them.

e. Must each be provided with a name-plate, giving the maker's name,
the capacity in volts and amperes, and the normal speed in revolutxcms per
minute.

f . Terminal blocks when used on generators must 1^ made of appro»d
non-combustible, non-absorptive, instuating material, such as slate, niaxi>]e
or porcelain.

2. Qondactors. — From generators to switchboards, rheostats or other
instnmients. and thence to oustide lines: —

a. Must be in plain sight or readily accessible.

Wires from generator to switchboard may. however, be placed in a coodidt Is

I brick or cement pier on which the generator stands, provided that proper —

cautions are taken to protect them against moisture and to thoroughly insulatie t



the brick or cement pier on which the generator stands, provided that proper ]ve>
cautions are taken to protect them against moisture and to thoroughly insulatie tnsa
from the pier. If lead-covered cable Is used, no further proteetloo will be reqidied.
but It should not be allowed to rest upon sharp edges which in tinoe ml^t cvt tats
the lead sheath, especially If the cables were liable to vibration. A smooth nawt?
Is desired. If iron conduit Is provided, double bialded rubber-covered wire ttss
No. 47) wUl be satisfactory.

b. M\ist have an approved insulating covering hs called for by rules ic
Class "C" f or similar work, except that in central stations, on exposed circuits.
the wire which is used must have a heavy braided, non-combustible outer
covering.

Bus bars may be made of bare metal.

Rubber insulaUons Ignite easily and bum freely. Where a number of vties sic
Drought dose together, as Is generally the case in dynamo rooms, especially about Ike



STATIONS AND DYNAMO JUX>MS. 1806

switchboard. It to tberefore neecBBair to surround thto InflamnmMe material with a
tight. noQKombuBtible outer cover. If this is not done, a fire once started at this
point would spread rapidly a'ong the wires, producing Intense heat and a dense
smoke Where the wires have such a covering and are well Insulated and supported,
using only nwi-eombustlble materials. It Is believed that no appreciable fire nazard
exists, even with a large group of wires.

Flame proofing should be stripped back on all eablesa sufficient amount to give
the necessary insulation distance for the voltage of the circuit on which the cable
Is used. The stripping back oi the flame proofing is neoessary on account o( the poor
insulating qualities of the flame proofing material now available. Flame proofing
may be omitted where satisfactory fire-proofing Is accomplished by other means,
Mich as eompartments, etc.

c Must be kept so rigidly in place that they cannot come in contact.

d. Must in all other respects be installed with the same precautions as
required by rules in Class *C" for wires carrying a current of the same
volume and potential.

e. In wiring switchboards, the gxotmd detector, voltmeter, pilot lights
and potential transformers must be connected to a circuit of not less than
No. 14 B. & S. gage wire that is protected by an approved fuse, this circuit
is not to carry over 660 watts.

For the protectloo of Instruments and pilot lights on switchboards, approved
ff. E. Code Standard f^doeed Fuses are preferred, but approved enclosed nises of
other designs of not over two (.2) amperes eapacitv. may be used.

Voltmeter switches having concealed connections must be idalnly marked.
Bbowlng connections made.

3 Switchboards. — a. Must be so placed as to reduce to a minimum
the danger of communicating fire to adjacent combustible material.

Special attention is called to the fact that switchboards should not be built down
to the floor, nor up to the celling. A space of at least ten or twelve Inches should be
left between the floor and the board, except when the floor about the switchboard Is
of concrete or other fireproof construction, and a space of three feet. If possible,
betweoi the celling and the board, in order to prevent nre from communicating from
the switchboard to the floor or ceiling, and also to prevent the forming of a partially
concealed space very liable to be used for storage of rubbish and oily waste.

b. Must be made of non-combustible material or of hardwood in skele-
ton form, filled to prevent absorption of moisture.

If wood is used all wires and all current carrying parts of the apparatus on the
switchboard must be separated therefrom by non-combustlUe. non-absorptive In-
sulating material.

c Must be accessible from all sides when the connections are on the back,
but may be placed against a brick or stone wall when the wiring is entirely
on the face.

If the wiring Is on the back, there should be a dear space of at least eighteen
Inches between the wall and the apparatus on the board, and even if the wiring Is
entirely on the face, it is much better to have the board set out from the wall. The
space back of the board should not be dosed In. except by gratlne or netting either
at the sides, top or bottom, as such an enclosure Is almost sure to be used as a doset
for dothlng or for the storage of oil cans, rubbish, etc. An open space Is much more
likely to be kept dean, and Is more convenient for making repali^ examinations, etc

d. Must be kept free from moisture.

e. On switchboards the distances between bare live parts of opposite
pobuitv must be made as great as practicable, and must not be less than those
given tor tablet-boards (see No. o3 A).

4. Resistance Boxes and Eiyiializen. — (For construction rules, see No.
60.) a. Must be placed on a switchboard, or if not thereon, at a distance of
at least one foot from combustible material, or separated therefrom by a
non-combustible, non-absortive insulating material such as slate or marble.

This will require the use of a dab or panel of non-combustlble, non-abeorptlve
insulating material such as slate or marble, somewhat larger than the rheostat, which
shall be secured In position Independently of the rheostat supports. Bolts for sup-

Krtlng the rheostat shall be countersunk at least i Inch below the surface at the
ck of the dab and filled. For proper mechanical strength, dab should be of a
thickness consistent with the size and weight of the rheostat, and In no case to be
leas than i inch



Online LibraryAlbert Irvin FryeCivil engineers' pocket book; a reference-book for engineers, contractors, and students, containing rules, data, methods, formulas and tables → online text (page 150 of 182)