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
While there are a wide variety of crimp connectors available from the likes of auto and home improvement stores, the only terminals you should be using are the tinned marine connectors approved for marine use. So-called "captive" connectors, which are shaped like an "O" or ring, or can be shaped like a "U" if they have turned-up lugs on each end, are generally preferred. What this generally means is that you are better off buying them at a marine store.
Use a wire stripper that allows you to strip a pre-set length of wire. These are a little more expensive than the pliers-style strippers, but will save you time and money in the long run. While you're at it, buy a good quality ratcheting crimper, which does a better, more reliable job of crimping than pliers-style crimpers.
Inevitably, the question of whether to solder connections comes up. Some say that American Boat and Yacht Council (ABYC), which sets standards for marine electrical work, does not recommend soldering. What it actually says is that solder should not be the sole method of terminating a wire. The reason is that solder will run down a wire and form a hard spot that can cause the strands to break, while a crimped terminal will remain slightly flexible.
If you decide to solder your wires as well as crimp them, use a heat sink right behind the crimp connector to prevent solder from wicking past the connector. You can buy a heat sink at an electronics store where they are used to protect delicate components from the heat of a soldering iron. They look a little like a spring clip clothes pin. You can also use an old pair of medical hemostats. In either case, the heat sink is clamped around the bare wire next to the connector being soldered. The terminal is then heated with the soldering iron and the solder is fed in through the opening opposite the wire.
A popular method of terminating wires is to use a crimp connector with an attached piece of adhesive-lined, heat-shrink tubing. After the connection is crimped, a heat gun shrinks the tubing while activating the hot glue adhesive inside. The result is a strong waterproof connection that also affords some relief from strain for the wire and connector.
Often two wires will need to be connected. In a house, this type of connection is often made with a wire nut. But wire nuts should never be used aboard a boat. They will eventually work loose or short out. I prefer using a butt-connector with adhesive-lined shrink tubing. Properly crimped, with the tubing heat-shrunk and the adhesive activated, they provide a secure connection. You can even find "step-down" connectors with the wire one size on one side and a slightly different size on the other side.
As we discussed in the first part of our series, all wires should be labeled and logged on your wiring diagrams. To label wires, I use the standard book of wire tags found in most home improvement stores. These come in small adhesive strips with numbers or letters on them. I cover these markings with a short length of clear shrink tubing to protect the marking.
WIRING AIDS
The two most common wiring aids are bus bars and terminal strips. Bus bars allow you to connect multiple outputs to one source. A good example is a bus bar used for negative grounding. You will have a host of negative ground wires in your DC system. Instead of trying to connect 20 wires to a single ground, you install a bus bar. The 20 wires go to the bus bar and one, heavier gauge wire goes to the ground.
PAUL ESTERLEAnother handy option is a unit that has two bus bars mounted on a single mounting board. These dual bus bars come in five and ten conductor versions. On my 35-footer, I installed one these units on either side of the boat, aft of the v-berth. It allowed me to run a single duplex wire to the bus bar and then connect the lights and fans to that bus bar. It was far better than trying to run individual wires back to the electrical panel.
Terminal blocks are another handy device. These consist of an insulating molded strip with a series of conductors, with each end of a strip having a mounting screw. Wires can then be attached to either side, completing a circuit across the strip. This gives you a convenient place to disconnect things. One example would be the mast wiring. It's easier and better to loosen the wires and remove them from the terminal block rather than having to cut them. If you want to connect one wire to multiple wires using a terminal block, there are jumper strips available that will connect adjacent connectors to each other.
When installing either bus bars or terminal blocks, drip loops are often used. Because these systems are aboard boats, water does occasionally find its way aboard. A drip loop is a wire that loops down below the device and then back up to make the connection. The idea is that any water running down the wire will drip off the bottom of the loop instead of running into the bus bar or terminal block.
CIRCUIT PROTECTION
There are specific ABYC recommendations for circuit protection. They specify the rating of the protective device, as well as where that device should be located in the circuit. You can consult a book, such as Nigel Calder's Boatowner's Mechanical and Electrical Manual, to find out the standards that apply to your project. I would recommend having this book available from the start of your design process.
Circuit protection comes in the form of a fuse or a circuit breaker. Fuses come in a variety of styles. Small glass fuses are common. Automotive AATO/ANC type fuses are also starting to become common. There are also fuse styles designed for high current, heavy-duty applications such as battery connections and power to the windlass. Each of these heavy-duty fuses has an associated mounting block with studs for attaching wires.
Often your choice of distribution panel(s) will determine what style of circuit protection you have. Fuse style panels give you a wide choice of amperages simply by switching fuses. A panel with circuit breakers, on the other hand, will require the circuit breaker to be swapped out for one of a different rating.
DISTRIBUTION PANELS
Indeed, distribution panels are where a good deal of the wiring ends up. Power from the battery comes into a panel and goes out to the various items. These panels usually house the circuit protection – either fuses or circuit breakers – and can also include test meters for determining battery power levels, accessory sockets and other features. They range from simple panels with three or four fuses, to elaborate panels with two dozen or more. You can get an idea of what is available at Blue Sea Systems, though there are many other panel makers.
In some case, several panels might be required to get the combination of features and circuits you need. On one of my project boats, I used a main panel with three circuits, a test meter and an accessory socket, in combination with an auxiliary panel with eight fused circuits.
Many of these panel manufacturers also produce 120-volt AC panels. Keep in mind that AC electrical systems should be segregated from DC systems. If you are considering work on an AC system, I would recommend finding a competent marine electrician. A shock from an AC system can be fatal.
However, with proper planning and a little bit of study, DC projects are within the reach of most recreational boaters. The key is preparation. By mapping your boat's electrical system and producing diagrams, you are familiarizing yourself with what is onboard and how it works – and what needs to be upgraded.
By planning these projects thoroughly, taking care to buy marine-grade parts and following established boating standards, you are guarding against incidents now or out on the water.
While an article can only give you the high points when it comes to electrical work, there are a great many resources – from books to skilled marine electricians – out there to help you. Take your time, do your homework, follow the standards and you should do well.
Paul Esterle is Technical Editor for Small Craft Advisor Magazine, and his freelance work has appeared in Sail, BoatWorks, Voyaging and Good Old Boat magazines. He has produced a series of boating videos and lectures widely. He also works at West Marine and has written product reviews for the company.