| Boat onboard electrical equipment | | | | electricity that is available for use when required. |
| Electricity is a strange source of power. You can't | | | | The battery will store and produce DC power |
| see it, but you can certainly see its effects in the | | | | only, so a boat's electrical system has to be |
| form of lights and sparks. It is a versatile power | | | | based on this current. |
| source in that it can be used in the form of a | | | | DC power travels in only one direction along a |
| motor to drive machinery, as a source of easily | | | | wire which, in terms of the system itself, makes |
| controllable heat and light, and for powering | | | | very little difference. It is the ability to store |
| electrical devices. It can also be used to generate | | | | current in a battery which is such a vital element. |
| magnetic effects. It is the versatility and | | | | Not only does this ability enable you to use |
| convenience of electricity which makes it such a | | | | electrical appliances when the charging system is |
| good source of power in a boat. | | | | not operating, it also fulfils the vital engine starting |
| Electrical systems use metal wires to transport | | | | role, which in turn allows the generator to start, |
| energy from where it is generated to where it is | | | | so producing current to recharge the battery and |
| stored and used. The wire has to be insulated in | | | | supply the onboard systems. |
| order that the electrical current follows only the | | | | Boat Refrigerators and Freezers |
| chosen path, because any current leaking from | | | | Like most electric motors, the refrigerator motor |
| the wire or a connection can lead to trouble. Much | | | | will use a high current when starting up, after |
| of the secret of a sound electrical system is | | | | which the current will drop back to the continuous |
| ensuring that the current flows only where you | | | | use level. Refrigerators and freezers may be |
| want it to go; in some respects it can be likened | | | | rated with the current they will use when the |
| to a water supply which is contained within pipes. | | | | motor is running or they may have the average |
| However, while you can see and hear if the | | | | consumption per hour listed. When you arrive at |
| water is flowing, electricity is generally silent, | | | | your boat the refrigerator will have to run |
| making leaks and other problems hard to locate. | | | | continuously for an hour or more before it gets |
| One of the major difficulties on a boat is that in | | | | down to its normal operating temperature after |
| addition to being carried by metal, electricity can | | | | which it will run intermittently. Typical small boat |
| also be conducted by water. Anyone who has | | | | fridges will consume around 4 to 5 amps per |
| owned a boat knows how damp it can be both | | | | hour, although during the time the motor is |
| inside and out and the marine environment is a | | | | running the consumption could be as high as 12 |
| tough one in which to make electric systems | | | | amps, so the circuits must be rated higher than |
| operate satisfactorily. Electricity tends to follow | | | | this to cope with the higher starting power |
| the easiest path which could well be the route | | | | needed. |
| provided by water if it comes into contact with | | | | Boat refrigerators are one of the few motor |
| the system. An additional difficulty is that salt | | | | units on board which run on a more or less |
| water is also very corrosive, so it is important to | | | | continuous basis. This means that when the engine |
| remember that, in the marine environment, | | | | is stopped it will be one of the main users of |
| electricity and water should not mix. If they do, | | | | current and the most likely cause of a flat |
| the water will win, causing a breakdown of the | | | | battery if care is not taken. Some refrigerators |
| electrical system. Water will not only provide an | | | | include a device in the control circuitry to warn if |
| alternative path for the electric current, but also | | | | the battery voltage is dropping. In some cases |
| begin the process of corrosion which, if left | | | | this will automatically switch off the refrigerator if |
| without attention, can have serious consequences. | | | | this occurs, in order to prevent the battery from |
| Electricity comes in two forms, direct current | | | | becoming deeply discharged. |
| (DC) and alternating current (AC). AC is the form | | | | It is possible to buy dual voltage refrigerators so |
| we enjoy at home as it is easier to transmit over | | | | that they can operate on battery power at sea |
| long distances and offers greater flexibility in the | | | | and mains power in harbour. Another option is a |
| higher voltages needed in the domestic | | | | refrigerator which can operate from either bottled |
| environment. AC motors and generators are also | | | | gas or battery power. |
| more compact and reliable than DC. With AC | | | | Boat Heaters |
| current, the power flows in alternate directions | | | | Marine heaters tend to be gas or diesel powered |
| many times a second, hence AC power might be | | | | because the electrical loads would be too high |
| described as 240 volts, 50 cycles per second (the | | | | unless shore supply or generator power were |
| number of cycles being the number of times the | | | | available. The main requirement with the diesel |
| current changes direction every second). | | | | type of heater is for a power supply for the fan |
| In boats, AC power suffers from the major | | | | and ignition circuit; here the electrical load is low, |
| disadvantage that it cannot be stored in a battery | | | | probably around 2 amps on a 12 volt system at |
| but has to be supplied on a continuous basis by a | | | | the higher rated units, and perhaps 0.5 amps on |
| generator. On a boat you don't necessarily want a | | | | smaller units. Some heaters can incorporate water |
| generator running all the time. Moreover, a | | | | heating, using diesel or gas. The hot water |
| generator still needs power to start its engine. | | | | system is usually controlled and powered by the |
| This means that a battery is needed to store | | | | cold water pressure pump. |