Marine AC Safety

Marinco 153AYBy Terry Johnson , University of Alaska Sea Grant, Marine Advisory Program

We all live safely with alternating current (AC) electricity in the home. But with the same voltage, the marine AC system is potentially more dangerous because the boat and the people who work on it are surrounded by water.

A person who becomes part of the pathway between a hot wire and the sea can experience severe shock. Forget the blinding flash and the smoking flesh. It doesn’t take a lot of juice to kill a person. Remember, what makes the heart tick is a faint electrical impulse generated within the muscle itself. It takes only a very small amount of current through the chest to disrupt the heart rhythm, causing fatal fluttering of the heart muscle called fibrillation.

A critical factor is where the current passes through the body. Touching hot and neutral leads with one hand can give you a jolt and maybe even a burn, but won’t kill you. But grabbing a hot lead with one hand and a neutral with the other, or the lead with one hand while standing in water, can send the current through the chest.

One effect that electrical current has on the body is to make muscles contract, so a person getting a shock may be unable to release the item that’s carrying the current. The body isn’t a perfect conductor of electricity, but passing through the chest it takes only 0.05 amp to kill. That’s barely enough to light a small bulb, and an amount which easily can pass through a human body that becomes a conduit between a hot AC wire and ground.

No one intentionally grabs a hot wire, but things happen. Two-prong plugs get put into sockets backwards (a condition known as reverse polarity). Circuitry chafes or cracks, exposing bare wire. Wiring inside a power tool breaks and contacts the metal case. Pick up with one hand an electric drill that has a loose wire inside, while bracing against the engine block with the other hand, and you could be the next industrial fatality.

Battery

An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Batteries are a common power source for many household, industrial and transportation applications.Optima deep cycle battery

There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times.

Rechargeable batteries are what are used in automotive and marine applications. They can be recharged by applying electric current. Devices to supply the appropriate current are engine alternators or chargers.

The most common form of rechargeable battery is the lead-acid battery. This battery is notable in that it contains a liquid in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas produced by these batteries during overcharging.

Alternator

An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current. Usually the word refers to small rotating machines driven by automotive and other internal combustion engines.

Alternators are used in modern automobiles to charge the battery and to power a car’s electric system when its engine is running. Automotive alternators use a set of rectifiers (diode bridge) to convert the AC output of the alternator to the DC used in vehicle’s electrical system .

Marine alternators used in yachts are similar to automotive alternators, with appropriate adaptations to the salt-water environment. Marine alternators are designed to be explosion proof so that brush sparking will not ignite explosive gas mixtures in an engine room environment. They may be 12 or 24 volt depending on the type of system installed. Larger marine diesels may have two or more alternators to cope with the heavy electrical demand of a modern yacht. On single alternator circuits, the power is split between the engine starting battery and the domestic or house battery (or batteries) by use of a split-charge diode (battery isolator) or a mechanical switch (battery switch)

-adapted from Wikipedia

Anderson Connectors

Anderson connectorsAnderson Connectors or Anderson Plugs as they are more commonly known, are designed for connecting large cables used in high current applications.

Each plug is a mirror of the other and are simple to assemble, There is no Male & Female. One simply connects into another of the same amperage. The plugs push together to form a very solid and reliable connection.

A common application in marine would be in the wiring that distributes AC power.

From the Anderson Power Products website:

Anderson Power Products is an industry leader in the manufacture of high current, quick-disconnect power connectors and provides a variety of interconnect solutions for the material handling, telecommunications, medical, power electronics and other industries. Our connectors are available from 10 to 700 amp maximum ratings for use through 600 Volts continuous, AC or DC operation. We are well known for our ability to develop creative solutions for our customers’ power interconnect requirements. We are flexible and will make modifications to standard products or develop complete custom solutions to satisfy particular customers’ needs. APP provides a complete engineered interconnect solution for all types of power distribution needs.