The reliability of a ship' s electronic
distribution system depends largely on
its cable installation. Current carrying capacity of cables, their insulation
strength, and their ability to withstand
all kinds of service exposure, including
heat, cold, dryness, bending, crushing,
vibration, twisting, and shock are important - but the workmanship that goes
into the cable installations is just as important.
The ratings and characteristics of the
various classes of Navy shipboard cable
are given in General Specification S62-2,
NavShips 250-660-23 and supplementary
matter. This section contains all the
cable information needed by the electronics installation worker.
2. TYPES OF CABLES.
The principal classes of cable are
briefly described here, with notes on the
application of each.
a. HEAT AND FLAME RESISTANT
CABLES.-Most of the permanent wiring
on shipboard is done with heat-and flame-resistant cables having protective armor.
These cables use synthetic resin or
varnished cambric as primary insulation
supplemented by asbestos for heat-and
flame-resistance and covered by a braided, protective armor. They are designated by the letters "HFA" and include the
following types:
Multi-conductor cables are available
with up to 44 conductors, each conductor
having a cross-sectional area of 2828 circular mils.
Twisted-pair telephone cables are available with up to 60 pairs of conductors,
each conductor having a cross-sectional
area of 703 circular mils.
SHFA, DHFA, THFA, and FHFA type
cables are available in various sizes of
circular mils and are used mostly with
the power and lighting system.
b. REDUCED-DIAMETER CABLES. - The new, reduced-diameter, type "SGA"
cables are smaller and lighter weight
than the "HFA" types but have design
features that give them greater insulation
strength and equivalent heat-and flame-resistance as the larger cables and will
let them be used for the same service as
the "HFA" types. Widely used "SGA"
cables are:
Multi-conductor cable in this class
(Type MSCA) is made up of stranded conductors, each having seven strands of
0.016 inch diameter copper for a total
area of 1779 circular mils per conductor.
c. CABLES FOR REPEATED FLEXING
SERVICE.-Many applications aboard ship
require cables that can be bent and twisted
again and again without damaging the conductor, insulation, or protective covering.
9-1
Such cables are generally used with portable equipment but are sometimes permanently installed to connect circuits in
rotating structures to the distribution
wiring of the ship.
Flexible cables have synthetic rubber
or synthetic resin insulation and a sheath
that is resistant to water, oil, heat, and
flame. They are not as heat-and-flame-resistant as armored "HFA" and "SGA"
cables. Flexible cables are of the following types:
MCOS- Multiple-conductor, oil-resistant, shielded (shielding over individual pair or shielding over assembly).
New flexible cables, types SHOF, DHOF,
THOF and FHOF are identical in diameter and weight to corresponding sizes
of the COP cables. The only difference
between these two types is in the grade
of insulating material on the individual
conductors. The HOF cable uses a
special heat-resistant synthetic (butyl)
rubber insulation and may be operated
continuously at temperatures above the
limits permissible for type COP cables.
The result is a higher current-carrying
capacity and a reduction in cable weight,
since it is possible to use a smaller size
in type HOF cable than in type COP for
a given application.
d. OTHER CABLE TYPES. - Other
types of cables commonly used in electronic work are:
DRHLA- double - conductor,
radio, high-tension,
lead armored.
TTRSA- Twisted-pair telephone, radio shielded, armored,(characteristic impedance approximately
76(ohms).
DSS- Double conductor, special purpose, shielded.
TSS- Three conductor, special purpose, shielded.
FSS- Four conductor, special purpose,
shielded.
MSS- Multiple conductor, special purpose,
shielded.
More information such as current rating, resistance per foot, and stuffing
tube sizes is given for all of these types
in the tabulated data section.
c. WATERTIGHT AND NON-WATER-TIGHT CABLE. - The heat-and-flame-resistant, armored cables under Specification MIL-C-915 (Ships) are made
watertight by filling all voids within the
stranded copper conductors and all
spaces between insulated conductors
within the cable core with compounds
which block the entrance of water. The
new reduced diameter cables are of
watertight construction.
9-2
3. DESIGNATION OF CONDUCTOR SIZE.
Conductor sizes are designated by numbers that are to the nearest thousand of
the actual circular mil area. These
numbers follow the type and class designation.
EXAMPLE: TSGA-60 is a reduced-diameter, three-conductor, armored cable
for general shipboard use, with each conductor having a cross-sectional area of
60,090 circular mils.
4. MULTIPLE -CONDUCTOR -CABLE
DESIGNATIONS.
Multiple - conductor - cable types and
class designations are followed by a number that indicates the number of conductors.
EXAMPLES: MSCA-30 is a heat- and
flame-resistance, armored cable with
30 conductors.
For telephone cable, the number indicates twisted pairs.
TTHFWA-25
25 twisted pairs
TTRSA-4
4 pairs, individually shielded.
5. SELECTION OF CABLE SIZE.
Current-carrying capacity and voltage
drop limitations, determine the size cable
for a particular application. The current
capacity is dependent upon the type and
size of the conductor, the permissible
temperature rise, and the character of
the space in which the cable is installed,
6. BASIC CABLE INSTALLATION DATA.
a. CABLE CONNECTIONS. -All connections to cables and at normal breaks in
a cable, should be made in standard
appliances and fittings. Don't make
splice connections.
b. CABLE ENTRANCES. -Cables entering water-tight equipment should be
brought into the equipment through Navy
Standard Stuffing tubes. When cables
enter non-watertight equipment, the
following should be observed:
Sheet steel enclosures, bulkhead
mounted; use stuffing tubes
Sheet steel enclosures, overhead
mounted; use stuffing tubes or
cable clamps
Cast metal enclosures up to and
including 3/16 inch thick; use
cable clamps
Cast metal enclosures over 3/16
inch thick; use stuffing tubes
c. PASSING THROUGH DECKS AND
BULKHEADS.- Where cables pass
through decks and water -tight bulkheads,
watertight stuffing tubes should be used.
Where cables pass through non-watertight bulkheads 1/4 inches thick, or
more, no stuffing tubes are used; simply
pass cable through drilled, smoothed
holes. Where the bulkheads are less
than 1/4 inches in thickness, bushings
should be used. All cables passing
through decks should be protected from
mechanical injury by kickpipes or riser
boxes. A kickpipe is a length of steel
pipe welded to the deck and having a
stuffing tube threaded to the upper end.
d. CABLE BENDS.- Bending cables
too sharply will damage them. The
correct minimum radius for each type
of cable is given in table 9-1.
e. SUPPORTING CABLE ON DECKS
AND BULKHEADS. -The methods for
supporting cable depend upon the number and size of cables in a particular
run, thickness of bulkhead or deck, obstructions to direct runs, heat and
moisture conditions, structural material,
water-tight conditions and other conditions taken up later in the chapter.
9-3
SECTION 9-2
CHOOSING PROPER SIZE AND
CALCULATING VOLTAGE DROP
1. CABLE SERVICE RATINGS.
Cable installations are rated according
to the ambient temperature the cable operates in. Ratings are: general, restricted and isolated corresponding to normal,
poor and good heat conditions.
a. GENERAL CABLE RATINGS. -General ratings apply to cables installed under the conditions that are most common
in Naval service. (Ambient Temperature
40° to 50°C) Typical examples are:
Cables installed in racks, with not more
than three cables next to each other carrying current at the same time.
Cables spaced one-half inch apart no
matter how many of the cables are carrying current at once.
Cables installed in armored trunks,
when the load is intermittent and the armor
is more than two inches thick.
The current-carrying capacities given
in the tables apply to general cable ratings.
b. RESTRICTED CABLE RATINGS. - Restricted ratings apply to cables installed where the ambient temperature is
greater than normal (50°C or greater)
A typical example is:
Gables installed next to each other in
racks, with three or more cables carrying current at the same time.
When cables are installed so that restricted ratings have to apply, their
current carrying capacities are 15% less
than the values given in the tables for
general ratings. Every effort should be
made to install cables so that the restricted rating need not be applied.
c. ISOLATED CABLE RATINGS.- Isolated ratings apply when there are no
hot objects or loaded cables close by or
when heat insulation reduces the amount
of heat that can reach the cable. Typical examples are:
Single cables, in free air or clamped
to steel or aluminum decks or bulkheads.
Cables, in groups of two, clamped to
decks or bulkheads of steel, aluminum,
or other material that carries heat away
rapidly.
Cables in racks where none of the cables
run hot.
Under such favorable conditions, cables
can be loaded 10% above the current-carrying capacities given in the table
for general ratings.
2. CHOOSING CABLE SIZE.
To choose the right size cable for a
particular application, it is necessary
to know the following:
a. The maximum connected load
in amperes
b. The possible added load due to
future connection of more
equipment
c. The demand factor
d. The cable service rating
e. The maximum allowable voltage
drop for the part of the circuit
under consideration.
9-4
The first four govern the size of conductor necessary to carry the load without overheating; the last may call for an
increase in the conductor size so as to
reduce the circuit resistance enough to
keep the voltage drop below the allowable
value. The maximum connected load is
found by adding up the full-load ampere
ratings of all the equipment connected
to the circuit.
The demand factor is 1.0 for a power
cable supplying a single load; it is 0.9
for a power cable supplying a group
of several loads. The current value to
use in choosing the conductor size is
reached by adding the maximum connected load to the allowance for future load
and multiplying this total by the demand
factor. This value of resultant load
amperes is used to find, in Table 9-1,
a cable of the desired size that is safely
rated to handle the load. If the cable is
to have a restricted service rating, the
resultant load amperes figure should be
increased 15% before the conductor size
is chosen from Table 9-1. If the isolated
service rating is to apply, the resultant
load amperes figure may be decreased
10% before the conductor size is chosen.
The cable chosen on the basis described
above will be large enough to carry the
maximum load without overheating, but
it is also necessary to be sure the voltage
drop is below the allowable maximum.
Percentage voltage drop is the difference
in voltage between any two points on a
circuit expressed as a percentage of the
rated switchboard or transformer secondary no-load voltage.
For all electronic installations, the
maximum allowable percentage voltage
drop between switchboard or transformer
panel for circuits above 100 volts is 2%.
For circuits of less than 100 volts, such
as control and interlock, the maximum
allowable percentage voltage drop is 5%.
Since the majority of circuits use voltages above 100, Table 9-2 shows how
many feet of each standard cable size
can be used at different loads without exceeding the 2% voltage drop. These results are approximate. A method of
computing length of cable run for a desired percentage voltage drop is shown
in Section 2, Paragraph 4.
9-5
TABLE 9-1
Table 9-1 is a cable comparison chart
in which all the type cables the electronics installation worker may work
with are divided into four major groups,
as follows:
Cable sizes up to 30,000 circular mils
are included in most cases. Larger
sizes are not listed since their use in
electronic installations is limited.
A table on steel stuffing tube information is included here giving tube clearance drill size and the inner diameter
of the gland nut for all the sizes to make
the table 9-1 as complete and useful as
possible.
In conjunction with the use of these
tables, the following should be noted:
It should be noted that where a maximum DC voltage of 1000 is specified, the
maximum AC voltage is 600.
The reduced diameter cables (DSGA,
TSGA, FSGA, and MSCA) are being
procured for use on new construction and
certain electronics installations where
HFA types were formerly used.
Similarly, the HOF type cables (SHOF,
DHOF, THOF and FHOF) replace the
COP types (SCOP, DCOP, TCOP, and
FCOP) and are now called for on new
construction.
Cable types TTRS and TTRSA, twisted
pair telephone cable, have properties
which make them useful as R.F. cable.
These properties are listed in the table.
9-6
TYPE
NUMBER OF CONDUCTORS
CM AREA/ COND.
MAXIMUM AMPERES RATING AT 40 °C AMB.
MAXIMUM AMPERES RATING AT 50 °C AMB.
MAXIMUM VOLTAGE D.C. BETWEEN COND.
MAXIMUM CONDUCTOR RESISTANCE PER FOOT AT 25°C
ESTIMATED WEIGHT PER FOOT (LBS)
OVERALL DIAMETER- INCHES
MINIMUM RADIUS OF BEND- INCHES
SIZE OF STUFFING TUBE
TYPE
SHFA-3
1
2828
15
14
1000
.00392
.068
.355
2.5
A
SHFA-3
SHFA-4
1
4497
26
24
1000
.00246
.134
.500
3.0
C
SHFA-4
SHFA-9
1
9016
53
49
1000
.00123
.230
.556
4.0
D
SHFA-9
SHFA-14
1
14340
71
65
1000
.000784
.262
.684
4.5
D
SHFA-14
SHFA-23
1
22800
92
85
1000
.000493
.306
.719
4.5
D
SHFA-23
SHFA-30
1
30860
113
104
1000
.000365
.346
.749
5.0
E
SHFA-30
DHFA-3
2
2828
13
12
1000
.00400
.143
.530
3.5
C
DHFA-3
DHFA-4
2
4497
22
20
1000
.00250
.294
.778
5.0
E
DHFA-4
DHFA-9
2
9016
44
41
1000
.00126
.361
.842
5.5
G
DHFA-9
DHFA-14
2
14340
60
55
1000
.000800
.451
.922
6.0
G
DHFA-14
DHFA-23
2
22800
78
72
1000
.000505
.555
.992
6.5
J
DHFA-23
DHFA-30
2
30860
94
87
1000
.000362
.694
1.110
7.0
K
DHFA-30
THFA-3
3
2828
11
10
1000
.00400
.171
.560
3.5
C
THFA-3
THFA-4
3
4497
18
17
1000
.00250
.334
.812
5.0
F
THFA-4
THFA-9
3
9016
39
36
1000
.00126
.413
.881
5.5
G
THFA-9
THFA-14
3
14340
51
47
1000
.000800
.527
.968
6.0
J
THFA-14
THFA-23
3
22800
69
64
1000
.000505
.659
1.040
6.5
J
THFA-23
THFA-30
3
30860
84
77
1000
.000362
.855
1.170
7.5
L
THFA-30
FHFA-3
4
2828
11
10
1000
.00400
.205
.610
4.0
C
FHFA-3
FHFA-4
4
4497
18
17
1000
.00250
.389
.865
5.5
G
FHFA-4
MHFA-7
7
2628
8
6
1000
.00403
.383
.859
5.5
G
MHFA-7
MHFA-10
10
2828
8
6
1000
.00403
.516
1.04
6.5
J
MHFA-10
MHFA-14
14
2828
8
6
1000
.00403
.634
1.12
7.5
K
MHFA-14
MHFA-19
19
2828
8
6
1000
.00403
.764
1.21
8.0
L
MHFA-19
MHFA-24
24
2828
6
5
1000
.00403
,951
1.375
9.0
M
MHFA-24
MHFA-30
30
2828
6
5
1000
.00403
1.09
1.46
9.5
N
MHFA-30
MHFA-37
37
2828
6
5
1000
.00403
1.29
1.57
10.5
P
MHFA-37
MHFA-44
44
2828
5
4
1000
.00403
1.5
1.734
11.0
R
MHFA-44
TABLE 9-1a. HEAT AND FLAME RESISTANT, NON-FLEXING SERVICE
9-7
TYPE
NUMBER OF CONDUCTORS
CM AREA/ COND.
MAXIMUM AMPERES RATING AT 40 °C AMB.
MAXIMUM AMPERES RATING AT 50 °C AMB.
MAXIMUM VOLTAGE D.C. BETWEEN COND.
MAXIMUM CONDUCTOR RESISTANCE PER FOOT AT 25°C
ESTIMATED WEIGHT PER FOOT (LBS)
OVERALL DIAMETER- INCHES
MINIMUM RADIUS OF BEND- INCHES
SIZE OF STUFFING TUBE
TYPE
SSGA-3
1
2828
15
14
1000
.00392
.044
.305
2.0
A
SSGA-3
SSGA-4
1
4497
26
24
1000
.00246
.053
.323
2.0
A
SSGA-4
SSGA-9
1
9016
53
49
1000
.00123
.079
.371
2.5
A
SSGA-9
SSGA-14
1
14340
71
65
1000
.000770
.102
.414
2.5
B
SSGA-14
SSGA-23
1
22800
92
85
1000
.000486
.140
.453
3.0
B
SSGA-23
SSGA-30
1
30860
113
104
1000
.000358
.165
.484
3.0
B
SSGA-30
DSGA-3
2
2828
13
12
1000
.00400
.087
.441
3.0
B
DSGA-3
DSGA-4
2
4497
22
20
1000
.00251
.108
.477
3.0
B
DSGA-4
DSGA-9
2
9016
44
41
1000
.00126
.183
.594
4.0
C
DSGA-9
DSGA-14
2
14340
60
55
1000
.000785
.258
.680
4.0
D
DSGA-14
DSGA-23
2
22800
78
72
1000
.000496
.345
.781
5.0
E
DSGA-23
DSGA-30
2
30860
94
87
1000
.000365
.430
.852
5.5
G
DSGA-30
TSGA-3
3
2828
11
10
1000
.00400
.104
.461
3.0
B
TSGA-3
TSGA-4
3
4497
18
17
1000
.00251
.130
.499
3.0
B
TSGA-4
TSGA-9
3
9016
39
36
1000
.00126
.224
.625
4.0
C
TSGA-9
TSGA-14
3
14340
51
47
1000
.000785
.325
.718
4.5
D
TSGA-14
TSGA-23
3
22800
69
64
1000
.000496
.430
.812
5.0
F
TSGA-23
TSGA-30
3
30860
84
77
1000
.000365
.560
.902
5.5
G
TSGA-30
FSGA-3
4
2828
11
10
1000
.00400
.124
.497
3.5
B
FSGA-3
FSGA-4
4
4497
18
17
1000
.00251
.172
.563
4.0
C
FSGA-4
FSGA-9
4
9016
39
36
1000
.00126
.276
.680
4.5
D
FSGA-9
MSCA-7
7
1779
8
6
1000
.00637
.152
.534
4.0
C
MSCA-7
MSCA-10
10
1779
8
6
1000
.00637
.234
.672
5.0
D
MSCA-10
MSCA-14
14
1779
8
6
1000
.00637
.282
.718
5.5
D
MSCA-14
MSCA-19
19
1779
8
6
1000
.00637
.347
.788
6.0
E
MSCA-19
MSCA-24
24
1779
6
5
1000
.00637
.447
.905
6.5
G
MSCA-24
MSCA-30
30
1779
6
5
1000
.00637
.511
.951
7.0
J
MSCA-30
MSCA-37
37
1779
6
5
1000
.00637
.601
1.022
7.5
J
MSCA-37
MSCA-44
44
1779
5
4
1000
.00637
.732
1.134
8.5
K
MSCA-44
NOTE: SSGA replaces Type SHFA, SDGA replaces Type DHFA, TSGA replaces Type THFA, FSGA replaces Type FHFA, MSCA replaces Type MHFA.
TABLE 9-1b. HEAT AND FLAME RESISTANT, NON-FLEXING SERVICE
9-8
TYPE
NUMBER OF PAIRS
CM AREA/ COND.
INDIVIDUAL MAX. AMPS.
AVERAGE AMPS. AT 40°C AMB.
INDIVIDUAL MAX. AMPS.
AVERAGE AMPS. AT 50°C AMB.
MAXIMUM VOLTAGE D.C. * BETWEEN COND.
MAXIMUM CONDUCTOR RESISTANCE PER FOOT AT 25°C
ESTIMATED WEIGHT PER FOOT (LBS)
OVERALL DIAMETER- INCHES
MINIMUM RADIUS OF BEND- INCHES
SIZE OF STUFFING TUBE
TYPE
TTHFWA-1 ½
1 ½
704
4
4
3
3
500
.0162
.097
.380
2.5
B
TTHFWA-1 ½
TTHFWA-3
3
704
4
3
3
2
500
.0162
.139
.500
3.5
C
TTHFWA-3
TTHFWA-5
5
704
4
2
3
1
500
.0162
.180
.590
4.0
C
TTHFWA-5
TTHFWA-10
10
704
4
1
3
.50
500
.0162
.243
.690
4.5
D
TTHFWA-10
TTHFWA-15
15
704
4
.75
3
.375
500
.0162
.290
.800
5.5
F
TTHFWA-15
TTHFWA-20
20
704
4
.50
3
.25
500
.0162
.331
.889
6.0
G
TTHFWA -20
TTHFWA-30
30
704
-
-
-
-
500
.0162
.422
1.030
7.0
J
TTHFWA-30
TTHFWA-40
40
704
-
-
-
-
500
.0162
.507
1.130
7.5
K
TTHFWA-40
TTHFWA-50
50
704
-
-
-
-
500
.0162
.594
1.265
8.5
M
TTHFWA-50
TTHFWA-60
60
704
-
-
-
-
500
.0 162
.736
1.350
9.0
N
TTHFWA-60
* NOTE. Maximum voltage AC between conductors is 300.
TABLE 9-1c. HEAT AND FLAME RESISTANT, NON-FLEXING SERVICE
*Cables suitable for use through the pressure-proof hull
NOTE: HOF Types replace COP Types
TABLE 9-1f. HEAT, FLAME, OIL RESISTANT, REPEATED FLEXING SERVICE
9-12
TYPE
SIZE OF STUFFING TUBE
OVERALL DIAMETER-INCHES
ESTIMATED WEIGHT PER FOOT (LBS)
MAXIMUM CONDUCTOR RESISTANCE PER FOOT AT 25°C
MAXIMUM VOLTAGE D.C. BETWEEN COND.
MAXIMUM AMPERES RATING AT 50°C AMB.
MAXIMUM AMPERES AT 40°C AMB.
CM AREA/COND.
NUMBER OF CONDUCTORS
TYPE
*DHOF-3
2
2613
23
21
1000
.00437
.099
.425
B
*DHOF-3
*DHOF-4
2
4121
30
28
1000
.00281
.115
.460
B
*DHOF-4
*DHOF-6
2
6533
41
37
1000
.00176
.146
.510
C
*DHOF-6
*DHOF-9
2
9045
50
45
1000
.00127
.167
.570
C
*DHOF-9
*DHOF-14
2
14070
60
54
1000
.00081
.285
.705
D
*DHOE-14
*DHOF-23
2
22910
80
72
1000
.000513
.402
.860
G,
*DHOF-23
*DHOF-30
2
30550
90
83
1000
.000278
.606
.960
J
*DHOF-30
*THOF-3
3
2613
19
17
1000
.00437
.115
.450
B
*THOF-3
*THOF-4
3
4121
25
23
1000
.00281
.133
.480
B
*THOF-4
*THOF-6
3
6533
33
31
1000
.00176
.174
.550
C
*THOF-6
*THOF-9
3
9045
38
34
1000
.00127
.196
.600
C
*THOF-9
*THOF-14
3
14070
50
46
1000
.00081
.336
.750
E
*THOF-14
*THOF-23
3
22910
70
64
1000
.000513
.518
.900
G
*THOF-23
*FHOF-3
4
2613
17
16
1000
.00437
.127
.480
B
*FHOE-3
*FHOF-4
4
4121
23
21
1000
.00281
.162
.550
C
*FHOE-4
*FHOE-9
4
9045
36
34
1000
.00127
.273
.660
D
*FHOF-9
*Cables suitable for use through the pressure-proof hull
NOTE: HOF Types replace COP Types
9-13
TYPE
NUMBER OF CONDUCTORS
CM AREA/COND.
INDIVIDUAL MAX. AMPS.
AVERAGE AMPS. AT 40°C AMB.
INDIVIDUAL MAX. AMPS
AVERAGE AMPS. RATING AT 50°C AMB.
MAXIMUM VOLTAGE D.C. BETWEEN COND.
MAXIMUM CONDUCTOR RESISTANCE PER FOOT AT 25°C
ESTIMATED WEIGHT PER FOOT (LBS)
OVERALL DIAMETER-INCHES
SIZE OF STUFFING TUBE
TYPE
MCOP-7
7
2613
8
5
6
4
1000
.00437
.200
.627
D
MCOP-7
MCOP-10
10
2613
8
5
6
4
1000
.00437
.286
.795
E
MCOP-10
MCOP-14
14
2613
8
5
6
4
1000
.00437
.377
.844
G
MCOP-14
MCOP-19
19
2613
8
5
6
4
1000
.00437
.480
.995
J
NICOP-19
MCOP-22
22
2613
8
4
6
3
1000
.00437
.649
1.070
K
MCOP-22
MCOP-26
26
2613
8
4
6
3
1000
.00437
.700
1.160
L
MCOP-26
MCOP-30
30
2613
8
4
6
3
1000
.00437
.762
1.190
L
MCOP-30
MCOP-37
37
2613
8
4
6
3
1000
.00437
.889
1,290
M
MCOP-37
MCOP-44
44
2613
8
3
6
2
1000
.00437
1.111
1.420
N
MCOP-44
MCOS-2
2
1608
5
5
4
4
1000
.00708
.126
.460
B
4COS-2
MOOS-4
4
1608
5
3
4
2
1000
.00708
.162
.510
C
MCOS-4
MCOS-6
6
1005
2.5
1
2
1
500
.0114
.102
.465
B
MCOS-6
MCOS-7
7
1608
5
2.5
4
1.5
1000
.00708
.230
.595
C
MCOS-7
MHFF-2
2 (PR)
2613
11
9
9
8
1000
.00437
.107
.460
B
MHFF-2
MHFF-4
4
2613
11
8
9
7
1000
.00437
.152
.520
C
MHFF-4
*MHFF-7
7
2613
11
7
9
6
1000
.00437
.197
.627
D
*MHFF-7
*MHFF-10
10
2613
11
7
9
6
1000
.00437
.300
.795
F
*MHFF-10
*MHFF-14
14
2613
11
7
9
6
1000
.00437
.386
.844
G
*MHFF-14
*MHFF-19
19
2613
11
7
9
6
1000
.00437
.502
.995
J
*MHFF-19
*MHFF-24
24
2613
11
7
9
6
1000
.00437
.672
1.120
K
*MHFF-24
*MHFF-30
30
2613
11
7
9
6
1000
.00437
.793
1.194
L
*MHFF-30
*MHFF-37
37
2613
11
5
9
4
1000
.00437
.914
1.290
M
*MHFF-37
*MHFF-44
44
2613
11
4
9
3
1000
.00437
1.130
1.420
N
*MHFF-44
* Cables suitable for use through a pressure-proof hull
9-14
STEEL STUFFING TUBE INFORMATION
TUBE SIZE
TUBE CLEARANCE DRILL SIZE (INCHES)
I.D. GLAND NUT INCHES
A
.562
.406
B
.687
.515
C
.812
.640
D
.937
.750
E
1.00
.812
F
1.00
.843
G
1.125
.953
J
1.250
1.062
K
1.375
1.171
L
1.437
1.265
M
1.562
1.406
N
1.750
1.515
P
1.875
1.625
R
2.0
1.750
S
2.125
1.875
T
2.375
2.062
V
2.500
2.187
W
2.687
2.312
X
2.812
2.5
Y
2.937
2.609
Z
3.125
2.781
AA
3.187
2.875
BB
3.437
3.125
TABLE 9-li
9-15
D. C. or Single Phase - 2% Voltage Drop - 117 V.
Three Phase - 2% Voltage Drop - 117 V.
Navy Standard Cond. Size
Base Column 1 Amp
3 Amp.
6 Amp.
12 Amp.
20 Amp.
30 Amp.
40 Amp.
50 Amp.
Base Column 1 Amp.
3 Amp.
6 Amp.
12 Amp.
20 Amp.
30 Amp.
40 Amp.
50 Amp.
-3
276
92
46
23
-
-
-
-
318
106
53
26
-
-
-
-
-4
438
146
73
36
21
-
-
-
506
168
84
41
24
-
-
-
-9
878
292
146
73
43
29
22
-
1012
337
168
84
49
33
25
-
-14
1397
466
233
116
70
46
35
28
1612
537
269
134
80
53
40
32
-23
2220
740
370
185
111
74
55
44
2560
853
427
213
128
85
63
50
-30
3004
1003
501
250
150
100
75
60
3470
1160
577
292
173
115
86
69
-40
3794
1265
633
316
190
126
95
76
4375
1460
731
364
219
145
109
87.7
-50
4785
1595
797
390
239
159
119
95
5520
1840
918
449
275
183
137
109
Notes:
1. Fractional calculations for above were rounded off to the next lowest whole numbers.
2. Where Line Voltage is 220 V., multiply maximum allowable length by 1.88.
3. Where Line Voltage is 440 V. , multiply maximum allowable length by 3.76.
4. For applications where MHFA and MSCA are used, limit the current rating
of each conductor to 1/2 Amp. With a load of 1/2 Amp. through a single phase
circuit, the following maximum length of cable may be run to keep under the
2% voltage drop requirement:
MHFA (2828 C. M.) - 552 feet.
MSCA (1779 C. M.) - 347 feet.
TABLE 9-2
MAXIMUM ALLOWABLE LENGTH OF CABLE RUN FOR A GIVEN LOAD WITH A 2% VOLTAGE DROP
9-16
3. USE OF TABLE 9-2.
Table 9-2 shows the maximum lengths
of cable run permissible at a given load
current. The table may be applied to
all cable types but the results are approximate.
To demonstrate the use of Table 9-2,
two typical problems and their solutions
are worked out.
Problem 1: Find the most suitable
cable size for a 12-amp. , 117V. , single-phase load, to be run 69 feet. Percentage voltage drop to be less than 2%.
Solution: Refer to Table 9-1 and find
the smallest cable size which allows a
maximum load current of 12 amps. This
would be size 3. Therefore our selection must be size 3 or larger.
Refer to Table 9-2 now, and under
the vertical column 12 amps. , read down
until a figure slightly greater than 69
is reached (in this case 73) and read
horizontally to the left to get correct
cable size, in this case 9.
Problem 2: Find the proper cable size
for a 10 ampere, 117 volt, single phase
load to run 25 feet. Percentage voltage
drop to be less than 2%.
Solution: Since there is no column computed for 10 amperes, it is necessary
to make use of the base column, computed on 1 ampere. The run in feet is
a linear function of current, so the base
column may simply be divided by the
load current to obtain the maximum
allowable run for that load.
For DSGA-3, a 1 -ampere load permits
a run of 276 feet. Therefore, a 10-ampere load allows a run of 276 y 10
or 27.6 feet which is within the limits
required. DSGA-3 has a maximum rating of 12 amperes at 50°C, so that the
cable is not overloaded with this choice.
4. MATHEMATICAL MEANS OF DETERMINING CABLE LENGTH.
An example calculation is given below
showing the method for determining the
length of cable that can be used for a
maximum of 2% voltage drop using a
given conductor size at a temperature
of 45°C.
It is known that:
1. the source voltage is 117V.
2. single - phase operation
3. a load of 1 ampere is to be
drawn
4. cable desired is HFA 3
(2828 CM)
The formula for finding the percent
voltage drop is:
Percent voltage drop =
(R x 2l- x I x 100) / C.M. x E
(for single phase operation).
l= Length of cable
R = Resistivity of copper in
circular mil feet at a given
temperature (see Figure 9-1)
C.M.= Circular mil area of one
conductor
E = Terminal voltage
(1) Therefore:
l=((% V.D.)(C.M.)(E)) / ((R)(2)(I) x 100)
The C. M. area may be found from
Table 9-1 as corresponding to the standard conductor size (opposite any DHFA
3, THFA 3, etc.) as being, in this case
2828 C. M.
The resistivity (R) is in ohms per C.
M. ft. at 45°C and is found from Figure 9-1,
Resistivity at 45 °C is approximately
12 ohms per circular mil foot. With
the resistivity calculated it is a simple
matter to substitute in formula (1) to determine length of conductor.
(1) l =
((2 x 2828 x 117) / (12 x 2 x l x 100))
= 275.72 feet
The same procedure may be followed
for voltages of 220 and 440 or if the
length of feet is calculated for 117
volts; and entered in a chart, multiply
the length by 1.88 or 220 volts and
3.76 for 440 volts at whatever load is
to be used.
For 3-phase operation the formula used
is:
(2) l =
((% V.D.) (C.M.) (E)) /
((R) squareroot(3) (1) x 100))
As can be seen, the differences between
formulas (1) and (2) is the squareroot(3) substituted for 2l. For this reason, to obtain 3 phase length, if those for single
phase operation have already been calculated, multiply by 1.15. These
lengths of course, represent the lengths
for corresponding conductor size and
load.