Thirty or more years ago, it was a rarity to find vessels less than 40 feet that were equipped with shore power. Of those that did have it, it was often used for a limited number of devices, a battery charger, the occasional bulkhead-mounted receptacle and perhaps a light fixture. Generators were even less common, found only on large luxury yachts. The inverter as we know it today had yet to be invented. As frightening as it is to consider, most of these vessels were wired with common, solid Romex wiring and household circuit breakers. Today, however, the ubiquitous shore power cord is so common, even on the smallest of vessels, it is simply de rigueur. Generators and inverters have also become quite common. The latter is nearly as common as shore power itself.
Today’s voyaging vessel, even one that spends little time dockside, is certain to have at least a basic AC shore power system. In all likelihood, this includes a weatherproof, deck-mounted shore power receptacle, main AC electrical panel, some type of meyer system (volts, amps and perhaps cycles as well), main and branch circuit breakers, a galvanic isolator, battery charger/inverter, receptacles, hot water heater, and perhaps even reverse cycle heat and air conditioning. Larger vessels with greater demand, and more sophisticated electrical systems, may add to this list a generator and isolation transformer. All of this equipment will, or should, be interconnected with flexible type II or III (preferably the latter) stranded wire (type II no. 12 AWG wire has, for instance, 19 strands, type III no. 12 has 65), in all non-bonding applications, electrical cables and connections designed for use afloat. Additionally, the required safety equipment will include ground-fault circuit interrupters, reverse-polarity indicators and an extremely rugged grounding (that’s grounding, as opposed to grounded, more on this later) system. It’s clear to see, even from this brief comparison, that as the years have passed, the list of accessories and requirements has evolved considerably.
There is good reason for this leap in the popularity of shore power systems (120 and 240 VAC, or volts-alternating current, more on this later as well). Tools, appliances and equipment that operate on this higher voltage, and use AC, are more efficient and smaller. Most important of all, this gear is comparatively inexpensive because it is mass-produced. Virtually every home in America has a blender and coffee maker that operates on 120 VAC. When was the last time, however, you saw these devices on the shelves at your local department store in 12 kDC (volts direct current)? Not recently, if ever, I suspect. Of course, many household-type appliances are available in 12-volt versions (blenders, coffee makers and even microwave ovens); however, they are not readily available. Because of low production numbers, they are not often long-lived (unlike household gear, they’re not designed for everyday use), and they are more expensive than their 120 VAC cousins.
