Sooner or later, every boat owner wants to install something that requires electrical power. Whether it's a new weather station at the helm, a fuel meter in the engine compartment or simply adding an outlet to the galley, many projects require some knowledge of your boat's electrical system.
While there is certainly work that should be left to a licensed marine electrician – particularly work on the AC electrical system – many boaters can safely carry out simple DC rewiring and small additions. In the first part of our Wired series, we discussed how to investigate the wiring on your boat, create a functional diagram of that wiring, map the boat's major electrical features and determine the parts needed for the job. Today, we will focus on how to buy the correct parts and carry out an installation.
Whether you are replacing all of your boat's wiring, the wiring to a certain portion of the boat (such as a cabin) or simply installing a piece of new gear, many of the rules and procedures are the same. You'll want to use marine-grade materials, follow standards set by organizations like the American Boat and Yacht Council (ABYC), and document what you did so you can refer back to it.
Above all else, think about your own safety before you begin. Disconnect your boat's shore power cable and turn everything off at the breaker panel before working on the system. Electrical shocks can be fatal, so take all the necessary precautions.
PROPER WIRE
Buying the right wire is essential – and not all wire is created equal. Once you have determined the proper gage and how much wire you need, topics covered in the first part of our series (see link below), you will want to shop for wire that is marine-grade, stranded and tinned. Why? Marine wiring is subject to a great deal of vibration, more so than wires in a house, for example. Stranded wire is flexible and will stand up to that vibration without fatiguing and breaking.
Tinned wire resists corrosion. Take a look at old, non-marine wire installed on a boat and you will see green or black gunk where the wire is exposed. This corrosion is especially dangerous around connectors because it gradually raises the resistance. The result can be a loss of conductivity, extra heat build-up and even fire.
Marine wire is available in most marine stores, as well as online. It comes in a wide variety of colors to match the ABYC recommendations, which were also covered in the first part of the series (see link below).
One option is duplex safety wire – or triplex for AC applications. Duplex has two conductors carried inside an outer protective sheath. It will have a red and yellow wire to match the recommendation that DC negative conductors be yellow.
Duplex wire is a good choice if you're running the wire in an open chase or in area where a chase or conduit is impractical. You will have to forego color coded wire, because it is generally only available in the red/yellow combination, but it often allows you to pull one wire instead of two.
CHASES AND CONDUITS
Cable chases or conduits are a great way to organize and protect wiring, whether you add them to the boat or build them in. Often, you can take advantage of existing features on the boat.
In my 35-foot project boat, the toe rail is bolted to the hull-to-deck flange every six inches and the bolts were excessively long. Using this to my benefit, I was able to convert the space between the hull and the row of bolts into a cable chase. I used the extended bolts to fasten nylon wire clips, and then enclosed the wires in plastic spiral wrap to protect them from chafe. It was stable, out of the way and had the added benefit of it being high in the hull and therefore far away from bilge water.
Conduits are another option. They can be as simple as PVC pipe and pipe connectors, or you can use the low-cost corrugated conduit that is sold at hardware stores in a variety of sizes. My 20-foot sloop had an inner liner glassed to the exterior hull and cabin, leaving no room to install wiring between the two. I ended up putting together a simple conduit system using off-the-shelf PVC pipe and connectors.
Any conduit should have drain holes on the bottom to prevent standing water and be supported throughout its length. The same goes for wire, which should be supported at least every 18 inches when outside of a conduit.
If your work involves adding or moving batteries, thought should be given to how they are housed and mounted as well. Batteries are a compact source of energy. As such, there are a host of ABYC recommendations about proper placement, protection, ventilation and security.
Batteries need to be securely fastened so they don't shift and contact other conducting items. Battery boxes are one good way of accomplishing this, as long as they are securely lashed down. A covered battery box will prevent inadvertent contact with the battery terminals, something sure to ruin your day. Because batteries can produce hydrogen, proper ventilation is also a necessity.
WIRE TERMINATION AND MARKING
The wires you install will need to be connected to a distribution panel or a ground on one end and to some kind of bus bar or DC device on the other. The integrity of those terminations will determine a great deal about the reliability of your installation and there are marine standards for these connections that should be taken seriously.
PAUL ESTERLE
