Tech Talk
Right tools, skills needed when electrical system fails
By
Roger Marshall, Technical Editor (Soundings)
In fact, a boat’s electrical system is the most common item to fail. Electrical failure takes many forms. It can be a light that simply doesn’t go on. It might be a radio with a lot of static. It could be a wire in contact with a metal part of the engine. You may not even notice the failure until the electrical current has dissolved your bronze propeller and the strut. When your electrical system gives up the ghost, can you fix it yourself? If you are reasonably competent and can understand a simple wiring diagram, you probably can. If you cut your finger every time you pick up a knife, rewiring your boat should be left to an expert. The basics If you do the work yourself, you’ll need a drawing of your boat’s electrical system. If you don’t have an electrical diagram for your boat, you can create one (see accompanying story). Even if you don’t do your own electrical work, the diagram will save a lot of time and money if you ever have to hire an electrician. (The chances are that with such a drawing you will never have to find an electrician.) When you have the finished drawing and have calculated the load in each circuit, you will know where you can add additional lights or other electronic equipment. If you find any burned-out wires while inspecting your breaker panel, determine whether they’re still in use. If they are not, remove them. If they are in use, replace them. “But before you correct the problem, correct the system,” advises Jeff Frazer, president of Jamestown (R.I.) Electronics. Find out why those wires are burned out before you rewire them. The existing wires may simply be too small for the load. If this is the case, you should calculate the load on the circuit and install a suitably sized wire. If the problem was caused by anything other than an overloaded circuit or if you cannot find the cause of the problem, have a qualified electrician check it out. Selecting the right wire Marine wires are specially treated to prevent oil and moisture penetration, which cause corrosion inside the sheathing. The common place for moisture to enter a wire or cable is where the ends are cut for attaching terminals or lugs. At this point you should cover the bare wire with heat-shrink tubing. Wire should be sized according to the length of the wire between the fuse or breaker panel and the electrical or electronic device and back to the breaker panel. For best performance you should get the lowest voltage drop over the system. For example, a thin wire absorbs more of the voltage flowing through the cable than a thicker wire. (This is similar to water flowing through a pipe. A smaller diameter pipe causes more friction and allows less water to flow through the pipe than does a larger diameter pipe.) You should use wires from the 3 percent voltage drop table for equipment that draws heavy loads, such as panel feeds, autopilots and motors, according to Frazer. Most lighting and electronics will still work when the voltage drops to about 10 volts, so using the 10 percent voltage drop table should suffice when wiring electronics. But if you use a wire with a 10 percent voltage drop, the equipment is only getting 10.8 volts. If a device fails to start properly, temporarily wire it close to the breaker panel to see if increased voltage will make it work. It is critical when sizing wiring to include the length of the wire both to and from the unit. In other words, double the distance from the panel to the electronic or electrical unit. Using the right tools You can get most of these tools at a hardware store. Purchase good quality ones; cheap tools may rust within a season or two. Stow your tools in a watertight toolbox with some rust-preventive material in the box. • Strippers — You’ll need strippers to remove the insulation on a cable before you attach a terminal end. Frankly, I would buy a cut, strip and crimp tool that does it all. These tools are available for under $20. • Terminal crimps — You can buy a separate set of crimping pliers that squeeze terminal ends onto the wire. However, the results you get from a combination tool are just as good. Cost for crimping pliers is under $20. • Battery cable stripper — If you are attaching cables to a battery, you might want to purchase a battery cable stripper that strips the heavy cable used for battery connections. Cost is about $25. • Coaxial cable stripper — If you are installing an antenna or want to expand your cable TV system, you might want to buy this stripper. It costs under $20 from Ancor. • Pliers — You will also need a pair of pliers to pull cable ties tight, grip terminals as you push them onto cables, and perform other minor jobs. I use different types depending on the job to be done — needle nose, square end, round nose, bent nose and others. Invest in an insulated square-ended pair to start with and buy others as you need them. • Screwdrivers — At a minimum, invest in two or three different sized flat-head types suitable for the screws you will be working on and one or two Phillips head screwdrivers. You should probably buy insulated drivers for electrical work, so your eyes don’t light up when you put them on a live terminal by accident. You can insulate the blades of your screwdrivers by sliding some shrink-wrap tubing down the blade and heating it gently. I leave about a half-inch of metal protruding from the shrink-wrap. This ensures that the metal of the screwdriver cannot touch a live end when I am doing electrical work. • Cleaning tools — A small wire brush will sufficiently clean terminals and connection points before crimping. Ancor Marine also offers a Marine Prep Pen that has retractable glass fibers for removing rust and corrosion. • Heat gun — A heat gun is used to shrink heat-shrink tubing, although the units can be expensive. With a little care, a mini butane torch will do the job. (The mini butane torch also can be used for light soldering.) In a pinch, you might want to try a hair dryer. • Soldering iron — If you have access to 110 volts, you can use a regular household soldering gun. But on a boat, especially a small boat, you may not have 110 volts, so you might want to invest in a propane-powered torch with a soldering iron tip. Typically, the cost of such a unit is $150 to $200. Installing a terminal end If the cable is small, terminals can be crimped directly onto the end of the cable (no heavier than 10 AWG, according to Ancor Marine). First, strip the cable for the length of the cup in the terminal. Next, put the heat-shrink tubing on the cable. If you forget, you might be unable to get the tubing over the terminal. Put the terminal on the cable and, using a crimping tool, squeeze gently to clamp the terminal to the cable. Slide the heat-shrink tubing over the connection and apply heat (carefully if you’re using a torch) until the insulation shrinks and seals the wire. To solder the cable, strip the cable and slide a length of heat-shrink tubing over the cable. Heat the stripped end. Make sure the cable end is very clean. Apply solder to the cable, not to the soldering iron. When the cable is hot enough, the solder will melt and run into the cable. Use a clean rag to wipe the end of the cable of extra solder. Heat the terminal end and apply solder to the inside faces of the terminal cup that will cover the cable. Flick excess solder out of the cup (not onto the cabin sole where it will burn the wood). With the cable end and the terminal cup heated, put the cable into the cup and crimp it. This will ensure that the cable cannot pull out of the terminal cup. Then apply solder to the cable until it runs out of the cup. Hold everything steady until the solder has hardened. If you move the soldered joint while the solder is still liquid you will get a “dry” joint that will fall apart fairly quickly. Then apply the heat-shrink tubing. Wiring electronics Figure out where your easiest cable run is while still keeping the cables hidden. If your boat has wires installed in conduit, your work will be much easier. You may find that you have to go into the overhead and down inside a stanchion or handrail to get the wires to the unit location. It doesn’t matter how you get the wires in place as long as they are large enough to carry the load. Check at the breaker panel that you have space for a new breaker or can attach the wires to an existing breaker easily. Make sure you have a suitable breaker, cable ties, terminals, tools and anything else you need before you start. When feeding wires, you will have to be aware of how and where wires can chafe. Boatbuilders who build to a price simply drill holes in frames to run wires. But fiberglass is hard, and boats tend to flex and to bounce around, causing the wires to chafe against the fiberglass. This can eventually cause short circuits and broken wires. To alleviate chafe problems, drill a slightly larger hole and feed flexible plastic conduit through the hole before inserting the wires. The conduit should be placed and caulked to prevent moisture from getting into the frame. If you cannot fit conduit, use a plastic bushing or even several layers of tape at each frame to prevent chafe. Another factor you should keep in mind is how wiring expands and shrinks when it is heated and cooled. Be sure to leave a small loop of extra wire to allow for the boat to flex or for the wire to expand. This extra loop also will help if you have to move equipment or pull it out for servicing. I try very hard not to cut wires extremely short. You never know when you might need an extra little bit. Feed the wires through the conduit or clamp them into place where you want them to go. Make the terminal ends at the unit and connect them up. Make a note of what each wire is connected to. Ideally, you should adhere to ABYC recommendations for cable colors and terminals, but you’re not bound by them. Go back to the breaker panel and attach the wires to the breaker. If you want to be sure that you got everything right, use a multimeter to check the circuits. Install the breaker in the breaker panel and turn it on. If you haven’t hooked it up right, you will notice the sparks traveling down the wire and a burning smell coming from the electronics. If nothing happens, turn on the unit and set it up. Wiring a bilge pump To install a bilge pump, take the pump terminals directly to a fused busbar mounted on a bulkhead on the battery side of the isolation switch. The fuse will help prevent an overload. When installing wiring to the bilge pump, make sure your wiring and the fused busbar will not get submerged when your sailboat heels or your powerboat trims up as it accelerates and water surges aft.
In the old days a sailor who fell asleep on watch might be wakened by “blowing the grampus.” That is, by having a bucket of cold water thrown over him. Today, nobody would dream of tossing a bucket of water around below deck because it might reach the electrical system and cause it to fail.
In a former life, I spent six years installing and designing electrical systems on boats and ships. Consequently, I have seen my share of wiring diagrams. Many leave a lot to be desired. In the typical design office, an engineer connects the electronic equipment to the switch panel with a computer-drawn line and it is left to those doing the work to determine the best wire size and to install the circuit in the best suitable way. This means that those workers need to know what they are doing.
Choosing the right wire is critical to the success and longevity of any wiring project. According to ABYC specifications, all wires should be at least 16 AWG (American Wire Gauge) except for cables inside a wiring panel, which may be 18 AWG. (The higher the AWG number, the smaller the wire.) You should use marine-grade, not automobile-grade, wires. Ancor Marine makes wires that are trademarked Marine-Grade. According to the company, these wires meet national and international standards for marine wires.
Having the right tools for working with electrical wiring is almost essential. Yes, I know. You think you can do the job with a single knife, using it both as a screwdriver and a stripping tool. However, stripping with a knife takes longer than with a stripping tool, and you’re likely to nick the conductor. With a stripping tool, a terminal crimper and heat-shrink tubing, the job is done faster and the finished work looks more attractive. Plus, it will probably last a lot longer.
Unless you are installing a battery terminal, you should not solder the cable to the terminal as your only connection. Solder tends to create a hard spot at the end of the cable, and if the cable has to flex at all it will eventually break just behind the soldered joint. Also, if a solder joint cracks the cable can fall out.
Suppose you want to add a depth sounder and a bilge pump to your boat’s electrical system. First, determine if there is enough space behind your navigation panel to flush-mount the electronics, including plugs and wires. If you do not have space, you will have to surface-mount the unit. Next, check to see that you can get wires from your breaker panel to the unit. Remember to check the other side of a bulkhead before you drill or screw through it.
Wiring a bilge pump that will operate when nobody is aboard your boat is a slightly different proposition. If you connect the bilge pump to your breaker panel it will go off when you turn the power off at the isolation switch. Consequently, you need to wire the bilge pump directly to your battery using a fused busbar. Be aware that if you do this and you get a lot of water in your boat, you could run the battery flat, and the bilge pump might stop working.
