This heat may require 'derating' to a larger wire size. (Note: If you're dealing with a foreign-built boat, color coding and conductor count may be a bit different than described here.)Īnother important issue has to do with AC cables routed through engine room spaces because of the potential for more heat. Again, the green grounding wire does not get counted.

In the case of 240-volt four-conductor cable, there are going to be three current-carrying wires per cable: two hot wires and a neutral. So a single piece of triplex cable has two current carrying conductors: the hot wire and the neutral, or the black and white wires. You only need to count normal current-carrying conductors. The green grounding conductor is not counted when considering bundle size. An additional concern is when multiple cables are bundled together, which increases the potential for even more heat.ĪC wiring is primarily what we call 'triplex' and sometimes 'four-conductor' cable. Sizing of individual conductors is based on three things: (1) how much amperage the circuit is going to have running through it, (2) whether the cable is routed through a hot engine room space, and (3) the temperature rating for the cable insulation. Again, with AC, our primary concern is heat buildup as cables get routed through your boat. Sizing for AC circuitsīecause AC circuit wire sizing is a bit simpler than DC, we'll start there. That said, because we are dealing with higher voltages and often higher amperage demands from the AC equipment in question, electrical resistance caused by loose, faulty connections and wiring that is too small for the job can generate significant, dangerous heat more quickly than a similar fault with a DC circuit. With shore power and the like, we're typically dealing with either 120- or 240-volts AC - much higher values - so a little loss has a less dramatic impact on equipment performance. With direct current (DC) circuits, one of the primary concerns is what we refer to as 'voltage drop.' Because we typically are dealing with either 12 or 24 volts - comparatively low values - we're concerned about any voltage loss due to electrical resistance. The criteria for determining wire gauge size is completely different depending on these power sources. The first thing you'll need to identify is whether the electrical circuit in question is running from DC battery power, a solar panel or wind generator, or supplied by AC shore power, a generator, or DC-to-AC inverter.

With these thoughts in mind, let's walk through the steps to selecting the correct size wiring for that new electrical gizmo you absolutely must have.

100 amp wire size chart