Electrical system, part 2 – Electrical components

This appendix explains the symbols and other electrical components included in the overview of the electrical system.

Explanation of electrical symbols

A 12V or 24V DC generator is driven by a belt from the main motor. Also represents a rectifier and regulator that converts the electricity to the right shape to charge a battery with the same nominal voltage.

The symbol represents a battery or a battery bank. A battery bank consists of several batteries of the same type that are connected in parallel or in series. The batteries are used to store energy from the boat’s various energy sources. The batteries in our fictitious boat have 12V or 24V nominal voltage.

Battery separator
This component makes it possible to charge two different batteries with the same nominal voltage from a generator.

Powered by 230V AC which it converts to 12V DC or 24V DC to charge a battery or a battery bank. Today, most chargers charge after a so-called three-stage charge Bulk, Absorption, and Float. More about charging can be found in the article on Batteries.

DC/DC Converter
An electrical component that converts 12V or 24V DC to 12V or 24V DC. In some cases, a converter can be used as a battery charger. In this boat, all converters are powered by 24V DC. They are set to charge the battery in the second subsystem, which means that they have a 3-step charging function.

A diesel generator that produces 230V 50Hz or 120V 60Hz (USA). They are available in several different sizes and types of generators. If you have a diesel generator on board, you need to make sure that it is adapted to meet the power required to operate all 230V equipment that you want to be able to have running at the same time when the generator is running.

Ground (earth or sea)
The symbol represents a connection to an electrical earth point, a so-called zero potential. This means that the electrical voltage by definition becomes 0V at that point. On land, the ground is used as zero potential, on a boat the water around the boat is used as a ground point.

Powered by 24V DC and creates 230V AC 50 Hz. Inverters are available for different effects, a small inverter can deliver 200W while a large 24V DC inverter can deliver 3.5 kW 230V AC. This corresponds to approximately 16A of electrical current and is enough to operate an electrical stove.

Isolation transformer
An electrical component that is used in the shore power connection. It ensures that there is no metallic connection between the boat’s electrical system and the electrical system on land. This means that the electrical systems are galvanically separated. This eliminates galvanic corrosion caused by voltage differences between boat earth and land earth.

Other electrical device
The text in the symbol determines which electrical component is meant

Solar panels
The symbol represents solar panels, wind, or water generators with associated regulators that supply 12V or 24V DC to the boat’s batteries.

Start motor
The symbol represents a starter motor mounted on a main engine or diesel generator.

Terminal block
Terminal block for electrical cables. Used to connect several cables to the same electrical potential, eg 12V, 0V, or protective earth.

Other electrical devices

An AIS transponder connected to the navigation network, powered by 12V/24V DC. It has its own GPS receiver and is connected to its own VHF antenna on the boat. It can also connect to the navigation system’s network where it provides information on other AIS-equipped items (boats, ships, fishing gear, wind turbines, weather buoys, etc.)

Connected to 12V/24V DC. Consists of sensors for rudder angle and boat movements, steering computer, steering motor, and control panel. The autopilot is connected to the navigation system’s network where it retrieves information about course and speed and provides information about the controlled course, rudder angle, etc.

Bow thruster
Bow thruster with motor, control box, and control buttons, it is powered by 12V/24V DC.

Freezer box with compressor and control box, it is powered by 12V/24V DC.

Refrigerator with compressor and control box, it is powered by 12V/24V DC.

Electric furler for genoa, it is powered by 12V/24V DC and has an output of about 1kW

Furler ctrl
The control circuits for furlers for genoa and mainsail are powered by 12V/24V DC and may be placed in a different subsystem than the furler so as not to be affected by any voltage drop when the motor is running.

A diesel heater with sensor and control panel. It is powered by 12V/24V DC.

Lighting with light buttons, 12V, 24V, or 230V AC.
To avoid having an inverter running for lanterns and ordinary lighting, lamps powered by 12V or 24V are used. The lighting is divided into several circuits, kitchen, aft cabin, saloon port, saloon starboard, etc.

Lights on instrument panel
Connected to 12V/24V DC and sits on a circuit with a dimmer on the steering pedestal.

Navigation instruments, sensors, and the instrument network. Measure and display speed through the water, depth, compass, wind direction and strength, and GPS. Powered by 12V/24V DC.

Electrical socket 12V, 24V, or 230V wall socket.
A standard wall socket for 230V is made to withstand up to 16A, but it is easy for it to heat up with a little longer use.
The recommendation is to limit the electrical current to 10A (approx. 2kW) in a standard wall outlet.

A plotter with a separate control panel. Can be powered by 12V/24V DC. Consists of a screen for displaying charts and the boat’s position and other information from the navigation system’s network.

Power Source
Automatically selects which 230V energy source to connect to consumers. It also has the property of automatically distributing electricity to different consumers depending on which energy source is connected. For example, the chargers only receive electricity when shore power or power plants are energy sources. When the electricity comes from the inverter, there is no point in charging batteries.

The various pumps with their control boxes and sensors. Eg pump for fresh water, an electric toilet, or a bilge pump. Some pumps may use 230V AC, like the water pump to the air-conditioning.

Radar unit with connection to the navigation network, powered by 12V/24V DC. Connected to plotters used to display the radar image, sometimes superimposed on the chart.

Start motor
Represents starter motor, sensors, engine instrumentation, and starter control on the main engine. Since there is a diesel generator, there are two starter motors in the 12V Start system.

Amplifier with radio and FM antenna, speakers, media player, and control panel. It is most common that these are made for 12V DC.

1-phase, 230V AC with two or 3 induction or halogen plates. Some models may also have an electric oven with both under- and overheating. If you want to be able to use an electric stove without being connected to shore power, you need an inverter that can deliver the power that the stove requires, often over 2 kW.

Thruster ctrl
Control unit for bow thruster, powered by 12V/24V DC, and is placed in a subsystem other than the thruster so as not to be affected by any voltage drop when the bow thruster works.

Vhf radio that is permanently installed and connected to the navigation network. Connects to 12V/24V DC and a high-positioned VHF antenna on the boat. Some models also connect to the navigation network and retrieve position information that can be used when sending certain so-called DSC messages.

Washing machine
A washing machine that is operated with 230V AC and it uses at most about 10A when it is running.

Warm water
Water heater powered by 230V AC or heated by engine cooling water. The heating element in a 40-liter water heater has an output of about 1 kW, which corresponds to approximately 5A consumption when it needs to heat water.
Make sure that the water heater is connected to a circuit that only is powered via shore power or the diesel generator.

Produces drinking water from clean seawater. This model produces 120 liters per hour and is powered by 24V DC. The high-pressure pump has a power of about 800W and it uses about 35A during operation.

Electric winches with control boxes and control buttons, powered by 12V/24V DC, and have a power of around 800W for this boat size.

Electric anchor winch with control box and control buttons, powered by 12V/24V DC and has an output of about 2kW for this boat size.

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