When It Comes To Electrical Systems,
Your Boat Is Not Your Home.
- If you haven't already noticed, we have not used household wiring systems as examples or illustrations in this manual. One of the principle reasons for this is the fact that your boat has two entirely separate electrical systems. The direct current (DC) electrical system derives its power from your boat's storage battery or batteries. In addition to providing starting power for the
engine (s), DC electrical power is used for such items as bilge pumps, running lights, the water pressure system and DC lighting.
- The source of power for your boat's alternating current (AC) electrical system is either a
shore-side connection or an on-board AC electrical generator. The AC electrical system provides electricity for appliances and fixed AC electrical equipment aboard the boat. It is your boat's AC electrical system that is examined in this manual.
While the principles of electric theory are the same on shore or a boat, the conductors, the methods of conductor installation, and many of the appliances and AC electrical equipment used aboard boats, differ considerably from those used
Because of color coding and polarity requirements, working with your boat's AC electrical system is uncomplicated. A grounding conductor or ground wire in an AC system is always green in color. The neutral wire or grounded conductor will be white in color. The ungrounded conductor or "hot" wire is identified by any color other than green or white and will usually be black or red.
ABYC standards require that marine AC electrical systems be "polarized". A polarized system is one in which the hot and neutral wires are connected in the same relation to all terminals on all devices in the circuit. For example, receptacles are connected in such a manner that the neutral wire attaches to the terminal identified by the letter "S", normally a silver color. The hot wire should be attached to the brass or copper terminal. The grounding wire green, is to be attached to the ground terminal on the receptacle. This procedure insures that the proper "polarity" is maintained and that the electricity will "flow" safely, without restriction, through each circuit. All marine devices manufactured by MARINCO have color coded terminal screws for easy identification.
In all marine electrical applications, minimizing the entrance or accumulation of moisture or water is of prime importance. Junction boxes, receptacles,
panel-boards, and other enclosures in which electrical connections are made, should be weatherproof or installed in a protected location. All current carrying conductors should be routed as far away, as practical, from areas where water may accumulate.
The conductors used in marine applications must he made of stranded copper wire. This is to say that the black, white, and green ground conductor in each cable or cord, must each be of the stranded wire variety. Household conductors, on the other hand, have a single, solid core wire. The number of strands required in each conductor in marine applications is directly related to the conductor's diameter and the degree to which the wire will be subjected to flexing through movement or vibration. As we mentioned earlier the conductor's size and diameter is also determined by the demand or amount of current the conductor must carry.
Good household wiring travels through the house in metallic tubing called conduit. The conduit supports and protects the wires within the walls and ceilings of your home. On your boat, conductors are supported throughout their length by a self draining loom or are secured every 18 inches by straps or clamps.
In areas other than the machinery compartments of your boat. nonmetallic straps or clamps are ideal for holding conductors firmly in place. Metal clamps lined with an insulating material that will minimize damage due to chafing are used in machinery areas.
A major difference between household wiring and the AC electrical wiring aboard your boat occurs when Two conductors or wires are joined together or a conductor is connected to a terminal on an appliance, receptacle, or circuit breaker. A common practice in household wiring is to splice wire to wire by means of electrical tape or wire nuts. Wire nuts or twist-on connectors have no place aboard a boat. Joining conductor to conductor in marine applications is best accomplished through the use of insulated, solder-less crimp-on connectors . The crimp-on connection may be covered with electrical tape but under no circumstances should electrical tape be used to join two conductors together. Besides assuring continuity of current, cramp-on connectors prevent the conductors from being pulled apart when flexed.
Note: When making any wire
connection to a terminal and/or terminal connector; be sure to apply dialectic
grease to the wire and connector before assembly.
Evaluating Your Boat's Electrical Needs
The boating public has become accustomed to the conveniences of electrical appliances both in their homes and aboard their boats. We seldom think about the capacity of our electrical system, we simply plug the appliance into a receptacle and expect it will work. Only when turning on the appliance causes the main AC breaker to trip do we realize that we are asking too much from the system.
The following formulas have been developed by ABC as guidelines for determining the total AC power required on a given boat. Since a boat can be supplied by either a single or multiple shore power system. these load calculations allow for "Leg A" and "Leg B" in order that the electrical power may be split between two separate systems, should the load exceed the amperage capacity of the single system. On a 50 ampere, 125/250 volt system, the load can be more evenly split between the two ungrounded conductors each carrying 115 volts.
With the increased popularity of air conditioning aboard boats, many boat builders have elected to provide a separate shore power system (or branch circuit) for the air conditioning. In smaller boars, a single 30 ampere system is adequate for lighting and small appliances, but insufficient to carry the load of an air conditioning unit. By "splitting the system" with one shore power cord supplying the air conditioning and the other providing service to the boat's other AC equipment, each system gives the boat uninterrupted AC electrical service.