Negotiating With Foreign Power - Text-only Version

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Whether you intend to make a one-time passage to Europe, the Caribbean or some other far-off location, or you’re planning to become a full-time trawler globetrotter, it’s difficult to deny that shorepower is a necessary evil. When reaching foreign locales, however, you may be faced with unfamiliar dockside power receptacles, voltages and frequencies. This is true in most of the world outside of North America and even as close as many Caribbean islands.

In spite of the fact that most modern trawlers and ocean cruisers are generator equipped, extended use of this power source is often impractical or, as is increasingly becoming the case in many U.S. and European marinas, simply prohibited. Thus, plugging into shorepower is the most convenient method of maintaining your vessel’s onboard AC and DC electrical needs. But how does one do this when arriving in an electrically unfamiliar land? The following guidelines will help you achieve dockside electrical equilibrium, both at home and abroad. You will want to pay particular attention to this material if you plan to take part in one of the upcoming overseas rallies, such as the Grand Banks Grand Tour 2005: Northern Europe, scheduled for next summer.

SAFETY FIRST

During summers between college semesters, I worked as an apprentice for a commercial electrical contractor. I remember well the bumper stickers found on each one of the company’s trucks: “Wiring Is Not A Hobby—Call A Licensed Electrician.” Admittedly, there may have been some element of self-serving interest in this warning, but the sentiment could not have been more true. All electrical wiring, AC shorepower wiring in particular, poses a potential risk to you and your crew, through either electrocution or fire. Unless you are experienced in the installation of marine electrical systems and familiar with the relevant American Boat and Yacht Council (ABYC, Edgewater, MD, abycinc.org, 410.956.1050) guidelines, leave the wiring to a professional marine electrician.

SHOREPOWER 101

In the United States, Canada and parts of Mexico (referred to as North America or NA for the remainder of this article), alternating current, or AC, shorepower typically consists of 120/240 volts alternating current (VAC), 30-amp or 50-amp, 60Hz, single-phase, polarized power. Even larger shorepower services are available for the megayacht crowd: 100 amps, three-phase and 480 volts for instance. In Europe and many other parts of the world, however, shorepower is considerably different and, in its native state, incompatible with vessels built to NA specifications. Common European dockside power is 230 volts AC, 16- or 32-ampere, 50Hz, single-phase and often unpolarized. (Electricity standards for the EU’s 26 member nations, although they exist, are not universally adhered to, and thus variations often are encountered from country to country.)

The Caribbean presents an equally diverse array of shorepower supplies. Antigua, for instance, uses 230 volts and 60Hz, while Guadeloupe, only 45 miles away, employs 230 volts and 50Hz. What does all this mean, and how does it apply to your boat’s electrical system?

Without getting too technical, deciphering the above terms will serve as an aid to understanding the similarities and dissimilarities between North American and foreign shorepower systems. The most common NA shorepower configuration, one or two 120VAC, 30-amp receptacles and cord sets, provide onboard AC appliances—battery charger, refrigeration, air conditioning, water heater, etc.—with voltage similar to that found in your home. Hertz, abbreviated Hz, or cycles, refers to the number of times per second the voltage oscillates, hence the designation “alternating current.” In NA and several foreign countries, this frequency is 60Hz.

Beneath the familiar yellow jacket of the 30-amp, 120-volt cord set reside three wires, a hot wire, which is black, a neutral (sometimes referred to as the “grounded”) conductor, which is white, and a green safety grounding (not to be confused with “grounded”) conductor. Because this power utilizes a single hot conductor, it’s referred to as single-pole. In NA, this shorepower arrangement is, or should always be, polarized. That is, the hot wire is always black and the neutral white. In a reverse-polarity scenario, grounded items such as tanks, engine blocks and the water surrounding the boat may become energized with 120 volts. This could lead to electrocution of a crewmember or swimmer; thus, with few exceptions, a reverse-polarity indicator should be standard equipment aboard every shorepowerequipped vessel. In some countries, polarity is not observed, and its absence could present a problem aboard. The solution to this problem will be discussed below.

Larger North American vessels that require more power may be equipped with 50- amp, 240-volt service. This cord set is similar to the 30-amp version; however, it incorporates an additional hot conductor, which is typically color-coded red. If you were to test the voltage on this cord set, you’d find 120 volts between the white and black or between the white and red conductors, and 240 volts between the black and the red conductors. Thus, 120/240 volt, 50-amp systems are capable of supplying both voltages to a vessel’s electrical system simultaneously. Many vessels are equipped in this fashion, even if no 240-volt appliances are found aboard, simply for the capacity offered by the dual poles. The two-pole nature of this service is similar to having two 30-amp, 120-volt shorepower cords, except that the additional amperage available on each pole, or leg, of the 240-volt, 50-amp service, is 50 amps, not 30.

In either system, one cord set, or leg, may power the vessel’s air conditioning, while the other supplies power to the remaining AC loads and appliances. Most vessels that are wired with dual 30-amp service inlets are capable of some load sharing. That is, if only one 30-amp dockside receptacle is available, select loads from each leg may be used, provided they do not exceed the capacity of the single receptacle.

In European and other foreign shorepower systems, the average dockside power may consist of 230- volt AC (250-volt in some Eastern Mediterranean ports), 16- or 32-amp, single-pole, sometimes-polarized service. The conductors in this cord consist of a hot, a neutral and a safety ground, much like 120-volt service in NA. Color coding for Europe and many other areas may vary; however, it is typically brown for hot, blue for neutral and green with a yellow stripe for safety ground.

The greatest difference between the two shorepower systems lies in the hertz, or cycles. Europe and much of the rest of the world operates on 50Hz, as opposed to North America’s 60Hz. This becomes a factor when using cycle-sensitive equipment such as motors, fans, and air conditioning and refrigeration compressors, as well as timers, clock circuits, and some transformers, battery chargers and inverters. Incandescent lights and other resistive loads are usually unaffected by varying frequency.

Even if the voltage is converted, as discussed below, you may have difficulty operating some equipment unless it is designed for dual-frequency use. A word of caution: Just because a particular piece of gear operates on 50Hz doesn’t mean it’s designed for this frequency. Motors not designed for 50/60Hz use that are used on 50Hz power may overheat or die prematurely. In addition, some battery chargers and inverters are designed for 50Hz use, while others are not. Xantrex’s Prosine 2.0 inverter can charge with 40–70 Hz, and the new XC series chargers are designed for “worldwide” service, operating from 90–256 volts and 50 or 60Hz. Other inverters and chargers, however, may not operate properly or safely on 50Hz. Typically, even for 60Hz gear rated for 50/60Hz use, output must often be derated by approximately 18% when used with 50Hz service. This may be further complicated for items such as the variable-speed fans found in air conditioning units. Check with the manufacturer of any gear that is not clearly and specifically labeled for its frequency requirement.

Phase and amperage play their own roles in shorepower service, here and abroad. Most shorepower, other than the aforementioned megayacht supplies, is single phase. Again, without getting too technical, this means there are one or two hot conductors, the previously mentioned black and red hot wires. Three-phase power, used on very large vessels and industrial applications, utilizes three hot conductors.

Amps, or amperage, on the other hand, is simply a function of how much work a given voltage can do. The receptacles in your home are capable of delivering 15 amps at 120 volts, while the shorepower receptacle for your trawler will, depending upon its configuration, provide between 30 and 50 amps at 120 or 240 volts. Two 16,000-Btu air conditioning units will run nicely on the 50 amp service but not for very long, if at all, on the 30 amp service.

An interesting—and important, for the purposes of this discussion—interrelation exists between voltage and amperage. As voltage is increased, amperage decreases proportionately. Thus, an appliance that operates at 120VAC and 10 amps will require only 5 amps when operated on 230VAC. However, this is simply an example and doesn’t mean any device will operate on either voltage. Many motor devices are designed to operate on either 120 or 230–240VAC, although their internal wiring must be appropriately wired in order to accommodate the given voltage supply.

The result of this equation directly affects the wire size required for 120 and 230–240VAC shorepower systems. Because the amperage an appliance requires directly drives the size of wire it must use, 230VAC appliances typically use much smaller wires. Thus, when you first arrive in a foreign port where the service is 230VAC, you will notice that the shorepower cables will look more like extension cords than the cables you may be accustomed to seeing. It is for this reason that European and many other 230-volt, single-pole, foreign shorepower supplies are of the 16- and 32-amp (and often less) variety, rather than NA’s 30- and 50-amp service.

SOLUTIONS

Full Voltage And Frequency Conversion

There are several approaches to solving the problem of variable shorepower availability. The sophistication of your solution will often be dependent upon the needs of your vessel and her crew, as well as the amount of time you intend to spend abroad. If you’d like to be able to plug in seamlessly anywhere in the world for an extended duration, then full conversion capacity that mirrors domestic use, utilizing frequency and voltage conversion, is called for. These systems will essentially take widely varying dockside voltage and frequency and turn them into power that is virtually indistinguishable from North American domestic shorepower. This voltage- and frequency-conversion gear is comparatively large (smaller-capacity units are about the size of a dishwasher), heavy and costly; however, they work well, converting the world’s power supplies to standard 120/240-volt, 60Hz, AC power, while protecting sensitive onboard electrical equipment from spikes, surges and low-voltage situations. Although they may be installed on or retrofitted to nearly any vessel, they are intended primarily for larger, 50-foot-plus ocean-going yachts that are capable of accommodating equipment of this bulk.

Finally, voltage/frequency converters typically provide the equipped vessel with full galvanic isolation. The advantages of this feature will be discussed in detail below.

The Transformer Approach

If your vessel’s needs are less demanding and frequency conversion isn’t a necessity, as is often the case, then a less sophisticated approach may be used to accommodate the foreign connection. This shorepower conversion uses a straightforward transformer arrangement that simply steps voltage down from 250 or 230 volts (or other voltages depending upon its design) to 120 volts. These transformers may also be used to convert 250-, 240- or 230-volt, single-pole power to U.S. specification two-pole, 120/240 (50-amp) service through selectively accessing or tapping transformer windings.

For vessels whose onboard equipment isn’t cycle sensitive, this is an ideal approach that will provide power virtually identical to domestic dockside voltage, with the exception of the frequency and a slightly different amperage. For example, 32 amps at 230 volts will provide 65 amps at 120 volts. This is roughly comparable to twin 30- amp power inlets in NA, but somewhat less than the two 50-amp legs provided by NA’s 240VAC service.

Some isolation transformers, such as the 12I series from Charles Industries, provide a special, voltagederated tap for motor loads. This tap reduces the voltage output from 120VAC to 104VAC, which is more appropriate for 60Hz motors running on 50Hz service. Select loads such as air conditioning and refrigeration compressors as well as other AC motors could be wired to this tap for proper operation.

Isolation transformers offer several additional attributes beyond shorepower voltage conversion. (Look for a future article from PMM’s Technical Editor on isolation transformers, including their varied uses and installation protocols.) Most significantly, isolation transformers completely isolate your vessel, electrically, from shorepower. Power is passed from shore to your boat’s electrical system through the transformer using magnetic induction. As a result, the potential for externally induced galvanic corrosion is significantly reduced, if not entirely eliminated. Because the shorepower cable’s green grounding wire is no longer connected to your vessel’s grounding system, harmful galvanic currents can no longer make their way aboard.

Additionally, from the standpoint of power production, an isolation transformer operates much like an inverter or generator; it essentially behaves like a power source as far as your boat’s electrical system is concerned. As a result, all power “produced” by the isolation transformer must return to the isolation transformer, much like a generator or inverter. Thus, vessels equipped with isolation transformers, unlike those without this equipment, are virtually incapable of leaking current into the surrounding water and thereby electrocuting swimmers or divers.

Vessels using twin 120VAC, 30-amp receptacles will require dual 3.8kVA (an abbreviation for kilovolt-amperes, a measure of a transformer’s or other electrical device’s capacity, arrived at by multiplying volts and amps) isolation transformers, while a 50-amp, 240VAC vessel service requires only a single isolation transformer with a 12kVA rating.

Another advantage of isolation transformers is their inherent ability to establish permanent onboard voltage polarity. In simple terms, this means that regardless of the polarity of the dockside voltage supply, the isolation transformer’s output remains at the correct polarity established during its installation. This feature exempts isolation transformer-equipped vessels from the requirement for reverse-polarity indicators and galvanic isolators.

A few issues for isolation transformers are worth repeating or emphasizing. Primarily, they do not convert frequency, so frequencysensitive devices will not be compatible with this type of installation (particularly pertinent for motors, compressors, fans, etc., which are known collectively as inductive loads). Additionally, some isolation transformer installations include a series of receptacles that are connected to the primary supply wiring. That is, these receptacles are wired upstream of the transformer and therefore provide “native power” for locally acquired appliances. While this practice is useful, it introduces some risk in that the power for these devices is not, thanks to the transformers decoupling capability, referenced to the vessel’s ground. This means a short to a metallic device such as a tank, engine block or rail may not trip a circuit breaker or fuse, which could lead to a shock hazard. Technically speaking, this is tantamount to cutting the green safety ground on a conventional shorepower system, which would be a violation of ABYC guidelines. Thus, a native power supply aboard an isolation transformer-equipped vessel that is wired in this fashion is not recommended.

A safer, albeit more costly, alternative to this approach would involve wiring a smaller 120VACto- 230VAC transformer on the output or secondary side of the main isolation transformer, which would provide a properly grounded native power supply.

With the exception of their inability to convert frequency, there is much to recommend isolation transformer installations, even for vessels that don’t intend to leave the NA power grid. The windings of an isolation transformer may be configured for oneto- one power supply, meaning that while cruising in NA, the output and input voltages are the same, and thorough galvanic and electrocution protection is still provided. Incidentally, the galvanic corrosion protection afforded by an isolation transformer is considerably more effective than that of a galvanic isolator.

Some manufacturers, Olsun Electrics Corporation of Richmond, Illinois, for instance, offer switchequipped units that allow the user to select input voltage (120 volts for NA, 230 and 250 volts for other parts of the world), while other manufacturers offer auto-switch gear that automatically recognizes shorepower voltage and switches transformer inputs accordingly. The latter installation is somewhat safer and is therefore ideal for forgetful crews who may neglect to check voltage before plugging in.

If you choose the isolation transformer route, the transformer you choose should be UL-Listed, and, ideally, that listing should carry the “Marine UL” amendment. Although few transformers are able to meet it, the high standard set forth by ABYC’s section E-11 ensures a product that is safe and reliable. Whichever unit you choose, its installation and integration into your vessel’s electrical system are a somewhat complicated affair. If you are undertaking this challenge yourself, ensure that you thoroughly understand all of the details of the installation (there are several options for grounding of the transformer case and shield alone), or call on an experienced, ABYC-certified marine electrician to assist with or carry out the installation.

The Inverter Option

With the advent of larger, more reliable, true sinewave inverters, there remains a final option for North American vessels seeking a foreign power connection. As most cruisers know, inverters provide power much like shorepower, albeit at a lesser capacity. Thus, an inverter, or a series of “stacked” inverters as needed, could conceivably provide for all of a vessel’s onboard electrical needs. As most cruisers also know, inverters are infamous for the prodigious amounts of battery power they consume. Recharging your house bank during inverter operation using the main propulsion engine or generator isn’t a viable option for the reasons detailed in the opening lines of this article—smoke, noise, wear and tear, and marina regulations—and it fails to take advantage of the host country’s shorepower.

The other half of the equation addresses this problem, the battery consumption and recharging issue, by calling on multivoltage, multifrequency battery chargers. Thus, a vessel equipped with one or more inverters and one or more of these battery chargers can, using local shorepower, replace battery power as quickly as it is consumed. The newest of these chargers, such as the XC series from Xantrex, will operate on voltages between 90 and 265 volts at 50 or 60Hz. Additionally, these chargers offer most of the features a cruiser could want: equalization, temperature compensation, deadbattery charging (many modern chargers will not charge a completely dead battery) and the ability to charge different battery chemistries simultaneously.

A vessel equipped with this inverter/charger arrangement would utilize one or two shorepower cords wired for 230VAC operation, connected to single or multiple chargers that are appropriately sized for the house battery bank. The battery bank would also have to be appropriately sized for anticipated inverter use, which may, in all likelihood, be heavy, in light of the fact that it will essentially be handling all of the vessel’s shorepower needs.

Although an isolation transformer could be used to separate the vessel’s electrical system (connected only to the chargers in this case; however, the green safety grounds between shore and vessel must be connected) from shorepower, for galvanic and electrocution prevention purposes, this setup— although desirable—is optional and unnecessary for voltage conversion. The selected charger should be of the auto-voltage-ranging variety, preventing the need for rewiring upon arrival at the foreign port. The beauty of this system is that it can be used for either North American or foreign power supplies because the chargers will automatically recognize available voltage. Alternatively, it may remain dormant when the vessel is traveling on the NA power grid, where the conventional shorepower hookup will be used.

Provisions for native power can be made using a small 230VAC output inverter, which would provide native voltage from the vessel’s own batteries in the same way as the main inverter bank. This inverter could be wired to selected “foreign” outlets in the galley, engine room and saloon. This approach helps cruisers avoid all of the aforementioned potential problems of using the host country’s shorepower.

MORE FOREIGN POWER CONSIDERATIONS

Reports indicate that some or all of the European Union member nations have instituted, or intend to institute, a requirement for all vessels using shorepower to include the installation of a residual current device, or RCD. This is essentially a wholeboat ground fault circuit interrupter (GFCI). These are available in two trip amperages: 30 milliamps for protection against shock or electrocution of the crew, and 100 milliamps for protection against short circuits and the potential for a resulting fire. The isolation transformer installations I have performed have included an RCD, and I endorse its use for obvious reasons.

The ability to monitor voltage, amperage and to some extent frequency is desirable when using any shorepower connection. However, this is particularly so when going the foreign route. Low voltage can damage some equipment, especially motors, whether you are cruising at home or abroad. Incorrect frequency, as mentioned earlier, is also a problem for certain gear. The ability to check voltage before energizing any onboard circuits is critical, and thus, your voltmeter or meters must be wired in such a way that this is practicable.

Once you arrive in a foreign port, one of your first shorepower challenges will be obtaining the correct electrical connector or plug. Even in NA, there are several options (30-amp 120, 50-amp 120, 50-amp 120/240 etc.), but the number of foreign countries and even ports within these countries you visit will multiply this. Be prepared to purchase the necessary connectors upon your arrival. The more locales you visit, the more your shorepower connector collection will grow.

The second challenge you will face, after obtaining the correct connector, is adapting it to your shorepower cable. Depending on your level of electrical sophistication, you may have to call on local assistance for this step. Isolation transformerequipped vessels need not be concerned with polarity, so a mixup may not necessarily have dire consequences. Nevertheless, the fewer mistakes made in this realm, the better. Remember, you can be electrocuted by shorepower (or inverters, generators or isolation transformer outputs), so use due caution. Never work on an energized cable or on a cable that is plugged into a receptacle, even if you are certain the power is off.

Finally, foreign shorepower receptacles are, in some ports, sparsely located. It is therefore advisable to carry extra lengths of shorepower cable in order to bridge these distances. The larger gauge of NA cables (remember, the equivalent of NA 30-amp service is 16-amp service for 230 volts; thus, smallergauge cable is required outside NA) will work in your favor in this case, mitigating the voltage drops created by extended runs.

Thanks to modern and compact onboard electrical gear, shorepower in various parts of the world is now a realistic and affordable possibility.

Steve C. D’Antonio is PMM’s technical editor and the vice president of operations at Zimmerman Marine, located on Mobjack Bay in Cardinal, Virginia.

Reprinted with permission. Copyright 2004 © Dominion Enterprises (888.487.2953) www.passagemaker.com

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