Electrical Tips
1. Electrical wiring should be protected from moisture whenever possible. Moisture, through the effects of corrosion, robs wiring of the ability to carry loads. Once moisture finds an opening, it can creep underneath the insulation and corrode the copper wire far away from the point of intrusion. Extensive corrosion can severely reduce the circuit's ability to support the load, causing dangerous heat buildup, and even total load failure. Breaks in the wire insulation, which allow moisture to enter, can happen in many ways.
Chafing against chase passageways through bulkheads can wear a hole or cut in a wire. Always use double insulated boat cable where possible and install chafe protection at all entry and exit points through bulkheads, decks, masts, etc.
Sunlight can break down insulation causing it to crack, allowing moisture to enter the wire. Where possible exterior wiring should be covered , run through conduit or wrapped with shrink tubing or high grade electrical tape. Periodic inspections and recovering will be necessary to maintain wire integrity.
Wires run in wet areas below decks and in the engine room are more susceptible to moisture intrusion. All wire bundles should be run as high as possible within the boat , only entering the wet areas to attach to a load, such as a bilge pump.
All wire splices should be soldered with very few exceptions. Crimp splices should NEVER be used under any circumstances. Soldered connections should be shrink wrapped or wrapped with high quality electrical tape. ALL splice connections made to electronic gear and data carrying cables MUST BE SOLDERED without exception. Heavy battery cables which must be lengthened and cannot be replaced, should have appropriate terminal ends installed and the splice made on an approved insulated post, firmly anchored and covered to prevent accidental short circuit. Terminal blocks with approved ring terminals can be used when connections may need frequent disconnection or for testing purposes. Where possible all splices should be located in accessible areas for periodic inspections, and sealed with a spray coating, shrink tubing, electrical tape or silicon sealant.
Harness connections and special connectors for electronics should be inspected at least once a year, taken apart and sprayed with a non-conductive anti-corrosion type spray, and wrapped with a high grade electrical tape to keep moisture out.
2. When planning a new wiring installation or a refit, wire size is a very important consideration. All wiring tends to lose its capacity over time to carry the loads it was designed for. This degradation is primarily due to "creeping corrosion" from poorly sealed wires exposed to years of wet conditions. When considering the wire size to use in an installation, first consult the ABYC codes and then consider the following:
Within the normal lifespan of a yacht between refits, electrical equipment is upgraded and loads increased as new equipment is purchased and installed. This increases the wire size requirements as new loads are added. Increasing the wire size now, one gauge larger than needed, will help insure satisfactory performance in the later years from the additional loads.
As corrosion reduces the wires ability to carry designed loads, adding additional equipment will only compound the problem. Over sizing the wire bundles now will help offset the negative effects of corrosion years from now.
3. When buying wire stay with American made wire unless you are over sizing the wire needed for the installation. Some foreign made wire has a cross section measured in millimeters instead of inches, thus a 12 gauge foreign manufactured wire may not have the cross section of some American made 12 gauge wires. And even though the wire may be of excellent quality, it will not have the load carrying capacity.
4. When attaching your wires to loads, allow a few inches of slack for strain relief, and to allow for shortening the wire in the future to cut off a corroded connector. By putting a loop in the wire lower than the point you are connecting to, you provide a "drip loop" for moisture to collect and drip away from the equipment. Hopefully this will prevent some of the moisture from entering the equipment.
5. Do not attach all your grounding systems (ie. DC ground, AC ground, RF ground, and Bonding System grounds) to the same bolt on the engine block or ground plate. Should the attachment point become loose, you may find DC and AC grounding current pouring down your bonding system, overwhelming the zinc anode protective system, thus causing serious and potentially damaging stray current to your underwater metal fittings. By attaching each ground to a different bolt on the engine or ground plate, a loose connection will be more likely to show up as poor equipment performance on that circuit. This will tip you off to look for a problem before it creates another one.
Vic now maintains a home and office both in Hong Kong and Florida, please Visit his other site in Asia.