All boats, regardless of size or sophistication, are required by regulation to have circuit protection on every positive wire outside of the engine starting circuit. If an electrical circuit is overloaded with excess current, the wire insulation can melt with a fire the likely outcome. Circuit breakers and fuses are designed to protect the wires in all main and branching electrical circuits.
CIRCUIT BREAKERS: Are an automatic safety switch that protects an electrical circuit from overload and subsequent catastrophic failure. Similar in function to a fuse, a circuit breaker can be reset after tripping. Marine circuit breakers are actuated magnetically or thermally and they also incorporate a manual switch that can be used to shut off specific circuits. Circuit breakers are typically grouped together as a cluster and mounted in a suitable breaker panel. Panel mounting of circuit breakers provides for an organized and easily serviced electrical system. Circuit breakers are designed to protect circuits- not equipment.
CIRCUIT BREAKER TYPES:
The Push Button Reset-Only Circuit Breaker is an economical choice when circuit switching is not needed or is operated in a different location. This style of circuit breaker is typically available in amperage ratings from 3 - 60A. The Reset-Only type is a "Trip-Free" design which means that it cannot be held ON during a fault current condition.
The Toggle Switch Circuit Breaker combines switching and circuit protection into a single unit. Single pole circuit breakers are typically used for protecting DC or AC branch circuits. Double pole circuit breakers are often used for 120 Volt AC Main circuit protection. Triple pole circuit breakers can be used for 240 Volt AC main circuit applications. This style of circuit breaker is also a "Trip-Free" design which means that it cannot be held ON during a fault current condition.
The Rocker Switch Circuit Breaker also combines switching and circuit protection into a single unit. The Rocker Switch style is available in Flat Rocker, Restricted OFF Rocker and Raised Rocker configurations. Single pole circuit breakers are typically used for protecting DC or AC branch circuits. Double pole circuit breakers are ofter used for 120 Volt AC Main circuit protection. This style of circuit breaker is also a "Trip-Free" design which means that it cannot be held ON during a fault current condition.
The Residual Current Circuit Breakers (GFCI and ELCI) functions as a Ground Fault Circuit Interrupter (GFCI) and as a Equipment Leakage Circuit Interrupter (ELCI). These devices provide protection for shore power connections (AC) and can reduce electrocution risks to persons on the boat, at the dock and in the water.
FUSES: Are another version of an automatic safety switch that protects an electrical circuit from overload and subsequent catastrophic failure. Similar in function to circuit breakers, fuses are designed fail when the current in the circuit exceeds the amperage rating of the fuse. The wire in the fuse melts and breaks the circuit leaving it in an open condition. Fuses are available in numerous styles and amperage ratings.
Panel mounting of fuses provides for an organized and easily serviced electrical system. Fuses are also found on most electronic devices either built into the housing or in the positive feed wire. Fuses are designed to protect circuits and equipment, if installed correctly. Generally fuses are available in lower range of amperage ratings making them ideal for protecting sensitive electronic equipment.
The glass-capsule fuse has been in use for many decades. Glass fuses generally consist of a glass tube with metal caps on both ends. A strip of metal joins the two caps and is visible through the glass tube. The metal strip is the actual fusible material - it is the sacrificial element that melts when the current draw exceeds the fuse rating. Glass fuses are sometimes thought to be "old-fashioned" - however, they are simple, reliable, low in cost and readily available. Glass fuse designations: AGA, AGC, GMA, MDL, SFE.
Advantages of the glass-fuse:
Drawbacks of the glass-fuse:
Blade type fuses (also called spade or plug-in fuses), are constructed with a transparent plastic body and two flat blades that fit into fuse block sockets. They are typically found in automotive and marine applications. Each fuse is printed with the Rated Current in Amperes on the top. The plastic body is conveniently color coded to further identify the amperage rating. These types of fuses come in four different physical dimensions: low-profile mini (APS), mini (APM / ATM), regular (APR / ATC / ATO), and maxi (APX) heavy-duty. Blade type fuses are rugged, compact and easily replaced without tools.
Advantages of the Blade-fuse:
Disadvantages of the Blade-fuse:
Typical Amperage Color coding of ATM, ATO/ATC Blade-fuses:
Other common Fuse designations and features
MIDI or AMI Fuses: A compact fuse for main or branch circuit protection.
MRBF Terminal Fuses (Marine Rated Battery Fuse): A space-saving ignition protected fuse for 30 to 300 Ampere loads. Must be used with a matching Terminal Fuse Block.
MEGA or AMG Fuses: Used with matching MEGA or AMG fuse blocks for an economical system for 100 to 300 Ampere circuit protection.
Class T Fuses: Used with matching Class T fuse blocks for circuit protection of devices including converters.
ANL Fuses: Used with matching ANL Fuse Blocks for many applications with 35-750 Ampere loads.
A well designed electrical system incorporates circuit breakers and fuses in order to protect the electrical wiring circuits along with the equipment connected to it.
NOTE: The U.S. Coast Guard and other regulatory agencies require all circuits, except the starting circuit, to be protected with a circuit breaker or a fuse.
Power Distribution Panels are at the heart of a boat's electrical system. Current flows from a power source to a panel and is distributed to various loads throughout the boat. Most panels provide switching functions along with circuit protection (fuses and or circuit breakers).
CIRCUIT BREAKER PANELS: Are available assembled and wired from the manufacturer with an array of circuit breakers, panel meters, indicator lights, battery switches, switch labels, etc. These fabricated panels are offered in a wide variety of configurations, sizes and voltages (DC, AC, or both).
FUSE SWITCHING PANELS: Are available assembled and wired from the manufacturer with an array of fuses, switches, indicator lights, switch labels, etc. These fabricated panels are offered in a wide variety of configurations, sizes and voltages (DC).
ABOVE DECK PANELS: Are ruggedly designed for exposure to the elements. Available with fuses or circuit breakers these waterproof panels are typically installed in open helm applications.
BELOW DECK PANELS: Are available with fuses or circuit breakers and are suitable for use as extensions to existing panels or as replacements. These panels are not for use above decks or in exposed locations.
CONNECTORS and INSULATORS
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.
Electrics Companion, by Pat Manley, will help you figure out how much energy you are consuming and how much each item uses per day. Most of the equipment we 'switch on' consumes electricity, even the panel lights and voltmeter all add up. Author Pat Manley's guide will help you understand your battery capacity and charging requirements.
Simple Boat Electrics, by John Myatt, contains all the information needed to troubleshoot 12-volt electrical systems. It explains how to locate a fault, correct the problem when you can, or adopt a "get-you-home" solution if you can't. Provides some basic theory so you can understand what you're doing with a special emphasis of seamanlike practice of anticipating and preventing trouble.
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.
12 Volts Made Easy - DVD, is a nuts and bolts 12 volt electrical systems primer that is presented in a clear and easy manner. Subjects covered include: basic electrical theory, circuits, battery maintenance, basic wiring diagrams, controls, transducers, recharging, marine components, lights, motors, troubleshooting, basic repairs, installations, and more. Running Time: 60 minutes.
The 12 Volt Sailor - DVD, will help you to learn how to design and build an efficient electrical system for any vessel. This program illustrates how to integrate the radar, watermakers, windlasses, single side band radios, auto pilots, and GPS devices into any D.C. System. Running Time: 45 minutes.