Marine Wire Connectors, Terminals, Wire Ties, Cable Clamps, Heat Shrink Tubing explained
Is there really any difference between "Marine Grade" and "Automotive Grade" electrical wiring components?
In a word yes.
Marine electrical wiring must survive in the harshest of conditions. Saltwater corrosion resistance, heat, oil, fuel and overall chemical resistance are all important considerations.
Automotive grade (SAE, Society of Automotive Engineers) wire is typically constructed from bare copper stranded wire. Bare copper wire has no special corrosion resisting qualities. Marine grade wire (AWG, American Wire Gauge) features individual tinned copper strands for maximum corrosion resistance. AWG wire is also approximately 10% larger than SAE wire.
Automotive grade crimp terminals typically use PVC sleeves as insulators. Marine grade terminal fittings use high performance nylon sleeves that are more crack, puncture and corrosion resistant when compared to PVC. Marine terminals are made from tin plated electrolytic copper that provides greater corrosion resistance and better conductivity which means less electrical power loss.
Wire Terminals and Connectors
Solderless, crimped wire terminals have replaced nearly all soldered connections in marine electrical applications. Soldering wire connections is slow, labor intensive and costly. If properly done, crimping wire terminals will produce an excellent mechanical and electrical connection. Crimp fittings are tinned copper terminals that have a round shank and typically feature a plastic insulated sheath. Available terminal configurations include: non-insulated, vinyl insulated (PVC) and nylon insulated wire fittings.
Nylon Insulated Terminals and Connectors
The best quality terminals and connectors feature nylon insulation. Nylon won't split or crack like automotive grade vinyl (PVC) insulation. Nylon is easy to crimp and extremely durable, resisting water, oil, chemicals, acids and damaging ultra-violet rays. The metal component of these terminals are manufactured from a high grade tin plated electrolytic copper. Tinning of the copper provides greater corrosion resistance and better conductivity which equals minimal power loss.
Adhesive Lined Heat Shrink Terminals
Heat shrink insulated terminals provide a number of improvements over conventional wire connectors. Adhesive-lined heat shrink material, when properly crimped and shrunk, improves corrosion resistance by providing a durable seal, resistant to water, salt, steam and other contaminants. The mechanical connection between the wire and terminal is improved by the adhesive-lining. The adhesive-lining adheres, when shrunk, to both the connector and the wire insulation increasing pullout strength and while providing strain relief. The heat shrink insulation is tough, durable, resists abrasion, scoring, cut-through, and forms a water tight seal.
Wire Terminal and Connector types:
- Ring Terminals provide the most secure connection, since the terminal screw must be completely removed in order to disconnect the wire.
- Spade Terminals (AKA Fork terminals) are inferior to ring terminals since the connections can pull off the screw if it becomes loose. However, spade terminals are a good choice if the terminal screw is of a captive type.
- Flanged Spade Terminals (AKA Captive Fork terminals) are similar to spade types but with the addition of bent ends to improve holding power and security.
- Blade Disconnect Terminals (AKA Disconnects) are available with an insulated grip and as fully insulated male and female terminals. Disconnect style terminals are useful when a portable device is frequently removed and reconnected to the electrical harness.
- Bullet Disconnect Terminals (AKA Snap Plugs) are similar in operation to the blade disconnect terminals above.
- Butt Connectors are used with appliances and devices that have short wire leads that must be attached to primary wiring. A disadvantage of butt connectors is that once assembled, the wire and connector joint cannot be visually inspected for corrosion, etc. Some electricians prefer to make solder joint connections. Another alternative to butt connectors utilizes ring terminals and a junction block to make an easily inspected and disassembled connection.
- Step-Down Butt Connectors are used to join a pair of wires to a third wire, all of the same size or conductors of different sizes.
- Three-Wire Connectors are used to join a three wires securely without the need of a junction block.
Insulated Wire Connector color coding and sizes:
- RED - AWG 22 to 16 - small
- BLUE - AWG 16 to 14 - medium
- YELLOW - AWG 12 to 10 - large
Heat Shrink Tubing
When heated, heat shrink tubing conforms to the size and shape of the terminal, connector, and wire. Heat shrink provides protection from mechanical damage, abrasion and corrosion. Heat shrink tubing installs quickly, easily and provides extra protection for many applications. A heat gun (similar to a hair dryer) will do the best job of shrinking the tubing, however, a lighter or small gas torch will also give acceptable results.
Standard Heat Shrink Tubing is available in a variety of sizes and an assortment of colors for coding connections. Shrink tubing is used to insulate wiring splices and terminal connections. It provides an insulating cover for exposed wire connections that is vastly superior to electrical tape. To cover a splice, select shrink tubing sized about twice the diameter of the wire to be covered. The shrink tubing will provide a tight seal once heat has been applied to the sleeve.
Adhesive Lined Heat Shrink Tubing is also available in a variety of sizes and an assortment of colors for coding electrical connections. The heat activated adhesive lining provides a superior seal over splices and terminal connections. Heat activated adhesive lining creates a water, oil and acid resistant seal that prevents corrosion at the electrical connection.
Adhesive lined tubing can also be used for line whipping (rope ends) or for line end color coding. The heat shrink tubing may also be ink marked for identification purposes.
Wire Management: Wire Ties, Cable Clamps, Wire Loom, Grommets
The use of the best quality marine grade wire and terminals is only part of a good wiring installation. The next part of the process is to select and utilize a wide assortment of products to secure and protect the newly installed wiring harnesses. Listed below are the main categories of wire management solutions.
Nylon Wire Ties (AKA Cable Ties) and Cable Tie Mounts
Nylon cable ties are an excellent and economical choice when you need keep your wiring organized. Wire ties are made from UV resistant black or natural nylon (white). They are available in a wide range of sizes and lengths to suit numerous applications. Some cable ties have mount holes that accept screws for semi-permanent installations. Self adhesive wire tie mounts provide maximum flexibility when installing wiring runs and harnesses.
Nylon Cable Clamps (AKA Loom Clamps)
Nylon cable clamps are used to secure or organize bundles of wire, wire loom, tubing, hose and similar items. The most economical clamps are made from UV resistant black or natural nylon (white). They are available in a range of sizes and diameters to suit each application.
Stainless Steel Cable Clamps (AKA Cushion Clamps)
For more difficult applications that require maximum performance and durability, rubber cushioned stainless steel is the clamp of choice. Typical applications include: holding hydraulic hoses, larger wire harnesses, and heavier cables.
Wire Loom (AKA Split Loom, Spiral Wrap, Corrugated Loom)
Corrugated split wiring loom is an inexpensive and practical solution for protecting bundles of wire. The split wiring loom is easily installed and closes naturally over existing wiring. Loom is available in different sizes and temperature ratings. High temperature loom is the best choice for applications around engines and other heat sources.
Rubber Vinyl Grommets are designed to provide abrasion protection for wires passing through electrical panel holes and other metal housings.
Marine Electrical Resources
Boatowner's Mechanical and Electrical Manual 3rd Edition, by Nigel Calder, is an excellent resource and an essential troubleshooting guide for any boater, from the extreme novice to seasoned veteran. If it is on a boat and has screws, wires, or moving parts, it is covered in the Boatowner's Mechanical and Electrical Manual. Nigel Calder provides comprehensive advice on: battery technologies, 12 and 24 volt DC systems, corrosion, bonding & lightning protection, generators, inverters, battery chargers, electric motors, electric lights, marine electronics, antennas, RFI, diesel engines, transmissions, shaft brakes, and propellers.
The Arco Electrical Technical Manual, is packed with information to help you become more proficient in servicing sophisticated marine electrical systems. The Arco Electrical Technical Manual explains the fundamentals of troubleshooting electrical systems. Written in easy to read style with lots of illustrations and examples. Written by mechanics for mechanics.