By Nigel Calder
Regardless of whether you are doing a minor wiring job or completely rewiring a boat, if the resulting installation is to be safe and reliable you have to understand how to choose and correctly size conductors, how to add terminals, where to add overcurrent protection devices (OCP, or OCPD – fuses and circuit breakers), how to size the OCPD, and certain key installation requirements and features. There are no shortcuts. Let’s start with the conductors themselves.
If the wiring on your boat looks like this, it is not just a mess; it is unsafe!
This boat needs complete rewiring, although there may be many salvageable parts.
Conductor Construction
Only copper conductors are used for wiring in boats. Solid conductors, which are common in household wiring, must never be used; with vibration, these conductors are liable to fracture, especially at connection points. Stranded conductors are always used.
Ideally, the individual strands in a conductor will be tinned. This substantially enhances long-term corrosion resistance.
Untinned (copper colored) and tinned (silver-colored) stranded conductors.
Insulation Properties and Labeling
Conductor insulation, and the sheath around multiple conductors in a cable, must consist of a fire-retardant material and be self-extinguishing. However, note that with sufficient heat, self-extinguishing insulation can still be set on fire (at which point the smoke will rapidly make a boat uninhabitable). The fire-retardant and self-extinguishing features simply mean that once the source of the fire is removed, the insulation will stop burning within a certain period of time.
