This article assumes a 12-volt negative-ground DC electrical system, which is the most common system found on todays production sailboats. It also assumes that all wiring is properly sized for the length (run) and load of the boats various electrical devices. The concepts described can be applied to most DC electrical systems but should be modified in some instances. The procedures discussed meet American Boat and Yacht Council (ABYC) standards; if in doubt about a specific situation aboard your boat, consult the ABYC standards.
The builder of my Pearson 40 in 1980 never imagined the incredible array of electronics and power-hungry gadgets that have since found their way onto todays sailboats. Consequently, the electrical system on an older boat needs constant upgrading to support its owners growing electrical demands. Increasing battery capacity and upgrading battery-charging systems are now common projects on older boats, but upgrading the electrical panel rarely gets attention. New equipment is often wired to existing circuit breakers (I use the word breaker to refer to either a circuit breaker or a standard fuse) on top of the original device the breaker services. What was originally a breaker for just a VHF radio may now end up controlling and protecting the VHF, the GPS, and the stereo because of the stacking of new equipment wiring onto existing breakers.
Stacking creates a number of problems. Breakers will trip when multiple devices are operating simultaneously, and it is harder to relate the source of a problem to a specific component. The most dangerous problem is the increased risk of electrical overload and fire. Every electrical device has a rated maximum current, usually specified in amps by the manufacturer. For a device to be properly and safely wired, it should be connected to its own properly sized breaker, and the wires connecting the device to the breaker (positive) and electrical-system ground (negative) must be sized according to the breaker trip current, the load of the device, and the length of the wire run.
Multiple low-load devices, such as a stereo drawing 10 amps, a VHF radio drawing 5 amps, and a GPS drawing 2 amps, can all be stacked on a 20-amp breaker and used concurrently without tripping the breaker. But safety issues can still arise in that an electrical problem with one device while the others are turned off could easily overload and overheat its wiring without tripping the high-amperage breaker. This can cause a fire. Adding new circuit breakers is the best way to install new equipment safely.
There are many ways to increase the number of breakers on a boat. You can simply add a new breaker panel near the existing panels if space permits, or you can add a new panel at a different location. As I upgraded my boats electrical system, I added a waterproof remote electrical panel in the cockpit for running lights and a third remote panel in the nav station for electronics.
If you prefer, you can replace the existing panel with a new and larger panel. One advantage to replacing a panel is that it enables you to add new features like an integrated digital ammeter and/or a voltmeter, backlighting for the switch labels, and a light indicating when a breaker is turned on. Deciding whether to add panels or completely replace an old one with an upgraded panel depends on your budget, the space available, and the interior aesthetics. Regardless of your choice, there are plenty of sources for new panels.
Here are some suggestions:
Thanks to the wide array of standard and customizable electrical panels now available, finding a new panel appropriate for new electrical equipment on almost all boats is a simple task. Installation can be accomplished by a competent DIY boat-owner with some electrical experience. If in doubt, hire a professional.