These are the recommendations for marine electrical system wiring from the American Boat and Yacht Council.
"11.14 SYSTEM WIRING
11.14.1 CONDUCTORS - GENERAL
22.214.171.124 Minimum surface marking of the individual conductors and their jackets shall include:
126.96.36.199.3 wire size, and
188.8.131.52.4 temperature rating, dry.
EXCEPTION: Flexible cords in Table VII-A and B
184.108.40.206 Conductors shall be at least 16 AWG.
Good luck finding any marine grade, tinned-copper, 18 AWG wire -Kevin Hannula
- 18 AWG conductors may be used if included with other conductors in a sheath and do not extend more than 30 inches (760mm) outside the sheath.
- 18 AWG conductors may be used as internal wiring on panelboards.
- Conductors that are totally inside an equipment enclosure.
- Conductors on circuits of less than 50 volts having a current flow of less than one amp in communication systems, electronic navigation equipment and electronic circuits.
- Pigtails less than seven inches (178 mm) used as wiring on panelboards.
220.127.116.11 In engine spaces the conductor insulation shall be oil resistant and have a temperature rating of at least 167oF (75°C) dry.
11.14.2 CONDUCTORS FOR DC SYSTEMS
18.104.22.168 Conductors and flexible cords shall have a minimum rating of 50 volts.
22.214.171.124.1 The construction of insulated cables and conductors shall conform with the requirements of:
126.96.36.199.1.1 UL 1426, Cables for Boats, or
188.8.131.52.1.2 the insulating material temperature rating requirements of:
184.108.40.206.1.3 SAE J378, Marine Engine Wiring, and
220.127.116.11.1.4 SAE J1127, Battery Cable, or SAE J1128, Low-Tension Primary Cable.
18.104.22.168 Conductors may be selected from the types listed in TABLE V, 2Table VII and TABLE VIII. The temperature ratings shown contemplate the routing of wires above bilge water in locations protected from dripping, exposures to weather, spray, and oil.
22.214.171.124 Flexible cords shall conform with the National Electrical Code, and shall be selected from the types listed in TABLE VII.
126.96.36.199 Conductors and flexible cords shall be stranded copper according to TABLE XI.
188.8.131.52 Conductors used for panelboard or switchboard main feeders shall have ampacities as determined in E-184.108.40.206. Conductors used for branch circuits or in electrical systems that do not use a panelboard or switchboard shall have their ampacities determined by their loads (See 2TABLE II).
220.127.116.11 Voltage Drop - Conductors used for panelboard or switchboard main feeders, bilge blowers, electronic equipment, navigation lights, and other circuits where voltage drop must be kept to a minimum, shall be sized for a voltage drop not to exceed three percent. Conductors used for lighting, other than navigation lights, and other circuits where voltage drop is not critical, shall be sized for a voltage drop not to exceed 10 percent.
18.104.22.168 Conductor Size - To determine conductor size and insulation temperature rating, use the ampacity as specified in E-22.214.171.124 in conjunction with TABLE VI. Then use TABLE IX or TABLE X to check the conductor size for compliance with the maximum allowable voltage drop specified in E-126.96.36.199. In the event of a conflict between the ampacity table and the voltage drop tables, the larger conductor size shall be used.
188.8.131.52.1 To use TABLE IX and TABLE X , measure the length of the conductor from the positive power source connection to the electrical device and back to the negative power source connection. Use the conductor length, the system voltage, and the ampacity as specified in E-184.108.40.206, in conjunction with the appropriate volt drop table, i.e., three percent or 10 percent – TABLE IX or TABLE X, to determine conductor size.
- The power source connection may be the battery, or a panelboard or switchboard, if used.
- If the ampacity as specified in E- 220.127.116.11 exceeds the ampacities in TABLE IX and TABLE X, the conductor size necessary to keep voltage drop below the maximum permitted level may be calculated by means of the following formula:
CM= (K x I x L/E)
CM = Circular mil area of conductor.
K = 10.75 (constant representing the resistivity of copper)
I = Load current in amperes
L = Length of conductor from the positive power source connection to the electrical device and back to the negative power source connection, measured in feet.
E = Maximum allowable voltage drop at load in volts (e.g., for a three percent voltage drop at nominal 12V, E= 0.03 x 12 = 0.36; for a 10 percent voltage drop at nominal 12V, E = 1.2).
Use TABLE XI or TABLE XII to convert circular mils (cm) to conductor gauge. If the cm area falls between two gauge sizes, the larger conductor shall be used.
11.14.3 CONDUCTORS FOR AC SYSTEMS
18.104.22.168 Conductors shall have a minimum rating of 600 volts.
22.214.171.124 Flexible cords shall have a minimum rating of 300 volts.
126.96.36.199 The temperature rating of conductors and flexible cords shall be at least 140oF (60oC) dry.
NOTE: Conductor rating temperatures refer to the insulation maximum operating temperature of the conductors.
188.8.131.52 All conductors and flexible cords shall meet the flame retardant and moisture resistant requirements of UL 83, Thermoplastic-Insulated Wires and Cables.
184.108.40.206 All conductors and flexible cords shall meet the requirements of the applicable standards of Underwriters Laboratories Inc.
220.127.116.11 Conductors and flexible cords shall be stranded copper according to TABLE XI. NOTE: Some currently available wire types that meet all of the above requirements are listed in Table VIII.
18.104.22.168 Conductors and flexible cords shall be of size according to 2TABLE VI and TABLE XII
22.214.171.124.1 Where single conductors or multi-conductor cables are bundled for a distance greater than 24 inches (610 mm), the allowable ampacity of each conductor shall be reduced as shown in TABLE VI and 2TABLE XII .
NOTE: When determining the allowable amperage of bundled conductors using TABLE VI and TABLE XIII, the AC grounding conductor and a neutral conductor that carries only the unbalanced current from other conductors are not considered to be current carrying conductors.
126.96.36.199.2 The AC grounding conductor shall be permitted to be one size smaller than the current carrying conductors on circuits rated greater than 30 amperes.
11.14.4 WIRING IDENTIFICATION
188.8.131.52 FOR DC SYSTEMS
184.108.40.206.1 Each electrical conductor that is part of the boat's electrical system shall have a means to identify its function in the system. EXCEPTION: Pigtails less than seven inches (175mm) in length.
220.127.116.11.2 Insulated grounding conductors shall be identified by the color green or green with yellow stripe(s).
18.104.22.168.3 The color code shown in TABLE XIV identifies colors for DC conductors used for general wiring purposes on boats.
NOTE: The color code shown in Table XIV identifies one selection of colors for use as an engine and accessory wiring color code. Other means of identification may be used providing a wiring diagram of the system indicating the method of identification is provided with each boat.
22.214.171.124.4 Color-coding accomplished by colored sleeving or color application to wiring shall be applied at termination points.
126.96.36.199.4.1 Tape used to mark a wire, shall be at least 3/16 inch (5mm) in width, and shall have sufficient length to make at least two complete turns around the conductor to be marked. The tape shall be applied to be visible near each terminal.
188.8.131.52 FOR AC SYSTEMS
184.108.40.206.1 Conductors shall be identified to indicate circuit polarity as follows:
11.14.5 WIRING TERMINALS
220.127.116.11 Wiring connections shall be designed and installed to make mechanical and electrical joints without damage to the conductors.
18.104.22.168 Metals used for the terminal studs, nuts, and washers shall be corrosion resistant and galvanically compatible with the conductor and terminal lug. Aluminum and unplated steel shall not be used for studs, nuts, and washers.
22.214.171.124 Each splice joining conductor to conductor, conductor to connectors, and conductor to terminals must be able to withstand a tensile force equal to at least the value shown in Table XV for the smallest conductor size used in the splice for a one minute duration, and not break.
126.96.36.199 Terminal connectors shall be the ring or captive spade types. (See FIGURE 17)
EXCEPTION: Friction type connectors may be used on components if
- the circuit is rated not more than 20 amperes or the manufacturer's rating for a terminal designed to meet the requirements of UL 310, “Electrical Quick-Connect Terminals”, or UL 1059, “Terminal Blocks, and
- the voltage drop from terminal to terminal does not exceed 50 millivolts for a 20 amp current flow, and
- the connection does not separate if subjected for one minute to a six pound (27 Newton) tensile force along the axial direction of the connector, on the first withdrawal.
188.8.131.52 Connections may be made using a set-screw pressure type conductor connector, providing a means is used to prevent the set-screw from bearing directly on the conductor strands.
184.108.40.206 Twist on connectors, i.e., wire nuts, shall not be used.
220.127.116.11 Solder shall not be the sole means of mechanical connection in any circuit. If soldered, the connection shall be so located or supported as to minimize flexing of the conductor where the solder changes the flexible conductor into a solid conductor.
EXCEPTION: Battery lugs with a solder contact length of not less than 1.5 times the diameter of the conductor.
NOTE: When a stranded conductor is soldered, the soldered portion of the conductor becomes a solid strand conductor, and flexing can cause the conductor to break at the end of the solder joint unless adequate additional support is provided.
18.104.22.168 Solderless crimp on connectors shall be attached with the type of crimping tools designed for the connector used, and that will produce a connection meeting the requirements of E-22.214.171.124.
126.96.36.199 The shanks of terminals shall be protected against accidental shorting by the use of insulation barriers or sleeves, except for those used in grounding systems.
11.14.6 INSTALLATION - GENERAL
188.8.131.52 Junction boxes, cabinets, and other enclosures in which electrical connections are made shall be weatherproof, or installed in a protected location, to minimize the entrance or accumulation of moisture or water within the boxes, cabinets, or enclosures.
184.108.40.206.1 In wet locations, metallic boxes, cabinets, or enclosures shall be mounted to minimize the entrapment of moisture between the box, cabinet, or enclosure, and the adjacent structure. If air spacing is used to accomplish this, the minimum shall be 1/4 inch (7.0 mm).
220.127.116.11.2 Unused openings in boxes, cabinets, and weatherproof enclosures shall be closed.
18.104.22.168 All conductors shall be supported and/or clamped to relieve strain on connections.
22.214.171.124 When AC and DC conductors are run together, the AC conductors shall be sheathed, bundled, or otherwise kept separate from the DC conductors.
126.96.36.199 Current-carrying conductors shall be routed as high as practicable above the bilge water level and other areas where water may accumulate. If conductors must be routed in the bilge or other areas where water may accumulate, the connections shall be watertight.
188.8.131.52 Conductors shall be routed as far away as practicable from exhaust pipes and other heat sources. Unless an equivalent thermal barrier is provided, a clearance of at least two inches (51 mm) between conductors and water cooled exhaust components, and a clearance of at least nine inches (230 mm) between conductors and dry exhaust components, shall be maintained. Conductors shall not be routed directly above a dry exhaust.
- Wiring on engines.
- Exhaust temperature sensor wiring.
184.108.40.206 Conductors that may be exposed to physical damage shall be protected by self-draining loom, conduit, tape, raceways, or other equivalent protection. Conductors passing through bulkheads or structural members shall be protected to minimize insulation damage such as chafing or pressure displacement. Conductors shall also be routed clear of sources of chafing such as steering cable and linkages, engine shafts, and control connections.
220.127.116.11 Loom used to cover conductors shall be self-extinguishing. The base product (or resin) shall be classified as V-2 or better, in accordance with UL 94, Tests For Flammability Of Plastic Materials.
18.104.22.168 Conductors shall be supported throughout their length or shall be secured at least every 18 inches (455mm) by one of the following methods:
22.214.171.124.1 By means of non-metallic clamps sized to hold the conductors firmly in place. Nonmetallic straps or clamps shall not be used over engine(s), moving shafts, other machinery or passageways, if failure would result in a hazardous condition. The material shall be resistant to oil, gasoline, and water and shall not break or crack within a temperature range of -30°F (-34°C) to 250°F (121°C);
126.96.36.199.2 By means of metal straps or clamps with smooth, rounded edges to hold the conductors firmly in place without damage to the conductors or insulation. That section of the conductor or cable directly under the strap or clamp shall be protected by means of loom, tape or other suitable wrapping to prevent injury to the conductor;
188.8.131.52.3 By means of metal clamps lined with an insulating material resistant to the effects of oil, gasoline, and water.
EXCEPTIONS: Exception to E-184.108.40.206:
- Battery cables within 36 inches (910mm) of a battery terminal.
- Cables attached to outboard motors.
220.127.116.11 No more than four terminals shall be secured to any one terminal stud. If additional connections are necessary, two or more terminal studs shall be connected together by means of jumpers or copper straps.
18.104.22.168.1 Multiple conductors may be swaged or crimped into a terminal provided that:
22.214.171.124.1.1 The combined Circular Millimeters of the conductors does not exceed the Circular Millimeter capacity of the terminal and
126.96.36.199.1.2 The connection is tested in accordance with E-188.8.131.52 pulling on the smallest conductor according to its rating in TABLE XV.
184.108.40.206 Ring and captive spade type terminal connectors shall be the same nominal size as the stud.
220.127.116.11 Conductors terminating at panelboards in junction boxes or fixtures shall be arranged to provide a length of conductor to relieve tension, to allow for repairs and to permit multiple conductors to be fanned at terminal studs.
18.104.22.168 FOR DC SYSTEMS
22.214.171.124.1 Wiring shall be installed in a manner that will avoid magnetic loops in the area of the compass and magnetically sensitive devices. Direct current wires that may create magnetic fields in this area shall run in twisted pairs.
126.96.36.199.2 Battery cables without overcurrent protection shall comply with the following:
188.8.131.52.2.1 Battery cables shall be routed above normal bilge water levels throughout their length;
184.108.40.206.2.2 Battery cables shall be routed to avoid contact with metallic fuel system components;
220.127.116.11.2.3 The ungrounded battery cable shall be routed to avoid contact with any part of the engine or drive train.
18.104.22.168 FOR AC SYSTEMS
22.214.171.124.1 All connections normally carrying current shall be made in enclosures to protect against shock hazards.
126.96.36.199.2 Nonmetallic outlet boxes, flush device boxes and covers shall meet the requirements of UL 514C, Non-metallic Outlet Boxes, Flush Device Boxes and Covers."