Section 120.340 - Cable and wiring requirements(a) If individual wires, rather than cables, are used in systems greater than 50 volts, the wire must be in conduit.(b) All cable and wire must:(1) Have stranded copper conductors with sufficient current carrying capacity for the circuit in which they are used;(2) Be installed in a manner to avoid or reduce interference with radio reception and compass indication;(3) Be protected from the weather;(4) Be installed with metal supports spaced not more than 610 millimeters (24 inches) apart, and in such a manner as to avoid chafing and other damage. The use of plastic tie wraps must be limited to bundling or retention of multiple cable installations, and not used as a means of support;(5) Not be installed with sharp bends;(6) Be protected by metal coverings or other suitable means if in areas subject to mechanical abuse. Horizontal pipes used for protection shall have 6 millimeter (.25 inch) holes for drainage every 1,520 millimeters (5 feet);(7) Be suitable for low temperature and high humidity if installed in refrigerated compartments;(8) Not be located in a tank unless the cable provides power to equipment in the tank; and(9) Have sheathing or wire insulation compatible with the fluid in a tank when installed as allowed by paragraph (b)(8) of this section.(c) Conductors in power and lighting circuits must be No. 14 American Wire Gauge (AWG) or larger. Conductors in control and indicator circuits must be No. 22 AWG or larger.(d) Cable and wire for power and lighting circuits must:(1) Meet Section 310-13 of the NEC (NFPA 70) except that asbestos insulated cable and dry location cables can not be used;(2) Be listed by Underwriters Laboratories (UL), as UL Boat or UL Marine cable; or(3) Meet § 111.60-1 in subchapter J of this chapter for cable and § 111.60-11 in subchapter J of this chapter for wire.(e) Cable or wire serving vital systems listed in § 119.710 of this subchapter or emergency loads must be routed as far as practicable from high risk fire areas, such as galleys, laundries, and machinery spaces.(f) Cable or wire serving duplicated equipment must be separated so that a casualty that affects one cable does not affect the other.(g) Each connection to a conductor or terminal part of a conductor must be made within an enclosure and have either:(1) A pressure type connector on each conductor;(2) A solder lug on each conductor;(3) A splice made with a pressure type connector to a flexible lead or conductor; or(4) A splice that is soldered, brazed, or welded to a flexible lead or conductor.(h) A connector or lug of the set screw type must not be used with a stranded conductor smaller than No. 14 AWG except if there is a nonrotating follower that travels with the set screw and makes pressure contact with the conductor.(i) Each pressure type wire connector and lug must meet UL 486A, "Wire Connectors and Soldering Lugs for Use With Copper Conductors," or other standard specified by the Commandant. The use of twist-on type wire nuts is permitted under the following conditions:(1) The connections must be made within an enclosure and the insulated cap of the connector must be secured to prevent loosening due to vibration.(2) Twist-on type connectors may not be used for making joints in cables, facilitating a conductor splice, or extending the length of a circuit.(j) Each terminal block must have 6-32 terminal screws or larger.(k) Wire connectors utilized in conjunction with screw type terminal blocks must be of the captive type such as the ring or the flanged spade type.(l) A cable must not be spliced in a hazardous location.(m) A cable may be spliced in a location, other than a hazardous location, under the following conditions:(1) A cable installed in a subassembly may be spliced to a cable installed in another subassembly;(2) For a vessel receiving alterations, a cable may be spliced to extend a circuit;(3) A cable having a large size or exceptional length may be spliced to facilitate its installation; and(4) A cable may be spliced to replace a damaged section of the cable if, before replacing the damaged section, the insulation resistance of the remainder of the cable is measured, and it is determined that the condition of the insulation is unimpaired.(n) All material in a cable splice must be chemically compatible with all other material in the splice and with the materials in the cable.(o) Ampacities of wires must meet Section 310-15 of the NEC (NFPA 70), or other standard specified by the Commandant. Ampacities of cables must meet table A6 of Institute of Electrical and Electronic Engineers (IEEE) Standard 45, "Recommended Practice for Electrical Installations on Shipboard," or other standard specified by the Commandant. Ampacities for Navy cable must meet NAVSEA Design Data Sheet (DDS) 304-2 "Electrical Cable, Ratings and Characteristics" as appropriate.(p) Conductors must be sized so that the voltage drop at the load terminals does not exceed 10 percent. Table 1 to § 120.340(p) indicates the size of conductor required for corresponding lengths and steady state (stable) values to obtain not more than this voltage drop at the load terminals of a two conductor circuit.Table 1 to § 120.340(p) -Conductor Sizes for Amperes-Lengths
| Total current on circuit, amperes | Length of conductor in meters (feet) from source of current to most distant fixture |
3.1
(10) | 4.5
(15) | 6.1
(20) | 7.6
(25) | 9.2
(30) | 10.7
(35) | 12.2
(40) | 13.7
(45) | 15.2
(50) | 16.8
(55) | 18.3
(60) |
| 12 volts, 2-wire-10 percent drop wire sizes (A.W.G.) |
| 5 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 12 | 12 | 12 |
| 14 | 14 | 14 | 14 | 12 | 12 | 12 | 10 | 10 | 10 | 10 | 8 |
| 15 | 14 | 14 | 12 | 10 | 10 | 10 | 8 | 8 | 8 | 8 | 8 |
| 20 | 12 | 12 | 10 | 10 | 8 | 8 | 8 | 8 | 6 | 6 | 6 |
| 25 | 10 | 10 | 10 | 8 | 8 | 8 | 6 | 6 | 6 | 6 | 4 |
Other values can be computed by means of the following formula:
View Image
Where:
cm = Circular-mil area of conductor.
K = 3.28 ohms/mil-meter (metric)
K = 10.75 ohms/mil-foot (english)
(a constant representing the resistance of cooper).
I = Load current, in amperes.
L = length of conductor from center of distribution, in meters (feet).
E = Voltage drop at load, in volts.
(q) If used, each armored cable metallic covering must:(1) Be electrically continuous; and(2) Be grounded at each end of the run to:(i) The metallic hull; or(ii) The common ground plate on nonmetallic vessels; and(3) Have final sub-circuits grounded at the supply end only.(r) A portable or temporary electric cord or cable must be constructed and used in compliance with the requirements of § 111.60-13 in subchapter J of this chapter for a flexible electric cord or cable.CGD 85-080, 61 FR 928, Jan. 10, 1996; 61 FR 20556, May 7, 1996, as amended at 62 FR 51352, Sept. 30, 1997; USCG-2016-0498, 82 FR 35092 , July 28, 2017 USCG-2016-0498, 82 FR 35092, 7/28/2017