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SECTION 9-1
GENERAL DESCRIPTION

 

1. INTRODUCTION.

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:

SHFA - Single-conductor
DHFA- Twin-conductor
THFA- Three-conductor
FHFA - Four-conductor
MHFA- Multi-conductor
 
TTHFWA - Twisted-pair, telephone

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:

SSGA - Single-conductor
DSGA - Twin-conductor
TSGA - Three-conductor
FSGA- Four-conductor

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:

SCOP- Single-conductor, oil-resistant, portable.

DCOP- Double-conductor, oil-resistant, portable.

TCOP- Triple-conductor, oil-resistant, portable.

FCOP- Four-conductor, oil-resistant, portable.

MCOP- Multiple-conductor, oil-resistant, portable.

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.

DRLL- Double - conductor, radio, lead-sheathed.

MCSP- Multiple-conductor, shielded, pressure-resisting (submarine applications).

PBLW- Pyrometer base lead wire.

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:

Heat and flame resistant, non-flexing service.

Special purpose cables.

Twisted pair telephone cable, armored.

Heat, flame, oil resistant, repeated flexing service.

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

 
9-9
 
TYPE NUMBER OF CONDUCTORS CM AREA/
COND.
MAXIMUM APERES RATING AT 40°C AMB. MAXIMUM AMPERES RATING AT 50°C AMB. MAXIMUM VOLTAGE AC BETWEEN COND. MAXIMUM CONDUCTOR RESISTANCE
PER FOOT AT 25°C
ESTIMATED WEIGHT PER FOOT (LBS) MINIMUM RADIUS OF BEND-
INCHES
OVERALL DIAMETER-
INCHES
SIZE OF STUFFING TUBE TYPE
DRLL-4 2 4497 17 13 300 .295
X
.520
1.0 DRLL-4
MCSP-6 2 Shielded Pair
2 Singles
1005 Microphone Cable 300 .0114 .150 .595 1.0 C MCSP-6
PBLW-4 2 One wire is iron the other is Constantin Pyrometer Base Lead Wire .135 .480 PBLW-4
DSS-2 2 .00664 .390 DSS-2
DSS-3 2 .00415 .445 DSS-3
TSS-4 3 .00257 .500 TSS-4
FSS-2 4 .00664 .465 FSS-2
MSS-6 6 .0105 .490 MSS-6
RADIO HIGH VOLTAGE
SHFR-4 1 4497 32 30 3000 .135 .540 3.5 C SHFR-4
DHFR-4 2 4497 26 24 3009 .325 .844 5.0 G DHFR-4
THFR-4 3 4497 24 22 3000 .369 .883 5.5 G THFR-4
SRHLA-4 1 4494 - - 15000 - 1.10 - - SRHLA-4
DRHLA-4 2 4494 - - 15000 - 1.995 - - DRHLA-4

TABLE 9-1d. SPECIAL PURPOSE CABLES

 
9-10
 
TYPE NUMBER OF
SHIELDED
PAIRS
CM AREA/
COND.
CHARACTERISTICS ESTIMATED
WEIGHT
PER FOOT (LBS)
OVERALL
DIAMETER-
INCHES
MINIMUM
RADIUS OF
BEND- INCHES
SIZE OF
STUFFING
TUBE
TYPE
TTRSA-2 2 1119 (Sometimes used as Radio .290 .740 5.0 E TTRSA-2
TTRSA-4 4 1119 Frequency cable) .385 .800 5.5 F TTRSA-4
TTRSA-6 6 1119 .460 .940 6.0 J TTRSA-6
TTRSA-8 8 1119 Maximum voltage AC between .510 1.050 6.5 K TTRSA-8
TTRSA-10 10 1119 conductors - 300 (500v DC) .590 1.140 7.0 K TTRSA-10
TTRSA-12 12 1119 .650 1.160 7.5 L TTRSA-12
TTRSA-16 16 1119 Surge Impedance of a pair = 76 ohms .750 1.250 8.0 M TTRSA-16
TTRS-2 2 1119 - .680 D TTRS-2
TTRS-4 4 1119 Maximum Capac. of a pair = .160 .740 E TTRS-4
TTRS-6 6 1119 25 MMF/ft. at 25°C .315 .880 G TTRS-6
TTRS-8 8 1119 .450 .990 J TTRS-8
TTRS-10 10 1119 Maximum Resistance per Conductor .500 1.080 K TTRS-10
TTRS-12 12 1119 (coated) per foot = .0109 .560 1.100 K TTRS-12
TTRS-16 16 1119 ohms at 25°C .675 1.190 L TTRS-16

TABLE 9-1e. TWISTED PAIR, TELEPHONE, RADIO, SHIELDED CABLE - ARMORED AND UNARMORED.
 
9-11
 
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
SIZE OF STUFFING TUBE TYPE
DCOP-2 2 1608 6 4 300 .00722 .065 .330 A DCOP-2
*DCOP-3 2 2613 12 8 1000 .00443 .099 .425 B *DCOP-3
*DCOP-4 2 4121 16 11 1000 .00281 .115 .460 B *DCOP-4
*DCOP-6 2 6533 22 16 1000 .00176 .146 .510 C *DCOP-6
*DCOP-9 2 9045 29 20 1000 .00127 .167 .570 C *DCOP-9
*DCOP-14 2 14070 40 29 1000 .000810 .285 .705 D *DCOP-14
*DC0P-23 2 22910 58 41 1000 .000513 .402 .860 G *DCOP-23
*DCOP-30 2 30550 72 49 1000 .000382 .606 .960 J *DCOP-30
TCOP-2 3 1608 7 5 300 .00722 .049 .345 A TCOP-2
*TCOP-3 3 2613 10 6 1000 .00443 .092 .450 B *TCOP-3
*TCOP-4 3 4121 14 9 1000 .00281 .133 .480 B *TCOP-4
*TCOP-6 3 6533 19 12 1000 .00176 .174 .550 C *TCOP-6
*TCOP-9 3 9045 25 16 1000 .00127 .196 .600 C *TCOP-9
*TCOP-14 3 14070 33 21 1000 .000810 .305 .750 E *TCOP-14
*TCOP-23 3 22910 48 31 1000 .000513 .518 .900 G *TCOP-23
*TCOP-30 3 30550 75 43 1000 .000278 .958 1.250 L *TCOP-30
*FCOP-3 4 2613 8 5 1000 .00443 .127 .480 B *FCOP-3
*FCOP-4 4 4121 13 11 1000 .00281 .162 .550 C *FCOP-4
*FCOP-9 4 9045 21 18 1000 .00127 .273 .660 D *FCOP-9

*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,

 
9-17
 

DEGREES C=5/9 (DEGREES F-32)
DEGREES F=9/5 (DEGREES C)+32
RESISTANCE (R) OHMS PER CIRCULAR MILFOOT
FIGURE 9-1
RESISIVITY VS. TEMPERATURE
RESISTANCE (R) OHMS PER CIRCULAR MILFOOT

FIGURE 9-1
RESISIVITY VS. TEMPERATURE

 
9-18

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.

 
9-19

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