Important components of any marine electrical system include a DC electrical panel, an AC panel if there are multiple AC circuits on board, circuit protection devices (CPDs) such as fuses or circuit breakers, and disconnect switches for easy circuit disconnect.
ELECTRICAL PANELS
Electrical loads on a boat are distributed through pre-wired main electrical panels or subpanels. They provide safe, convenient wire connection points, a CPD, and a disconnect switch for each circuit.
Main panels distribute the majority of DC and AC house appliance loads. Main panels vary in style, complexity, and power source (DC or AC).
- DC electrical panels distribute and control power from the positive side of the DC electrical system. The power feed to a DC main panel typically comes from the house battery bank(s) through the load side of a main battery switch or a positive buss bar. The negative sides of the loads are joined at a negative distribution post or buss bar.
- AC main panels distribute electricity from shore power or generators to the AC circuits on board, and typically include a reverse polarity indicator.
- For small boats with basic DC electrical systems, inexpensive electrical panels with six to eight load circuits, each with a CPD and disconnect switch, are usually sufficient.
- Main panels with additional load circuits, master switches, meters to display circuit voltage and load current, and other options are available.
Subpanels are often used for branch circuits that are different than those in the main panel, such as heavy draw loads or circuits with different power requirements. They are also available in a variety of configurations.
- AC subpanels are used for power that is different from the main AC source. In North America, main AC power is 120VAC/60Hz, while in Europe the power is 240VAC/50Hz. Cruising boats often have a main panel for the predominantly used AC power source and a subpanel for the other AC source.
- Most boaters find that standard off-the-shelf electrical panels meet their needs.
- Some manufacturers offer custom electrical panels that can be tailored to your exact specifications, including custom lettering and graphics.
CIRCUIT PROTECTION DEVICES (CPDs)
- CPDs are used for each circuit in an electrical system to provide overcurrent protection.
- CPDs can be replaceable fuses or circuit breakers that can be reset.
- While fuses have traditionally offered economical circuit protection, most marine electrical panels are now equipped with circuit breakers.
- Heavy-duty CPDs are used for windlasses, electric winches, inverters and chargers, and house bank overcurrent protection.
DISCONNECT SWITCHES
- All loads in an electrical panel have toggle or rocker switches to disconnect the appliance by breaking the positive side of the circuit.
- Switches are sized for the maximum current draw of the load.
- Heavy-duty switches are used in conjunction with high-current fuses for larger load circuits.
- High-current DC circuit breakers provide circuit protection and disconnect in one device.
TIPS
- Bilge pumps should be fed directly from the house bank(s) so the main battery switch can’t inadvertently disconnect them.
INSTALLATION
Fundamentals of DC electrical systems and a complete electrical toolbox are required for panel and over-current protective device installations.
Toolbox
- Screwdriver
- Drill and bits
- Bolts, nuts, and washers
- Soldering iron if required for connectors
- Multi-meter
- Wire ties and clips
- Tin-plated wire
- Terminal connectors
- Wire stripper/cutter/crimper
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