| With the growth in the number of berths, shore | | | | can have the use of electrically powered equipment |
| supplies of electricity are more readily available and | | | | both at sea and in harbour. To avoid having to run the |
| boatbuilders are responding by installing shore power | | | | generator all the time, a common arrangement is to |
| connections and shore power circuits into boats as a | | | | have an installation which can be connected to the |
| standard feature. There are obvious benefits in terms | | | | shore supply when in harbour and which can be |
| of bringing all the comforts of home on board, but | | | | powered by the generator when at sea or away from |
| there are considerable dangers if the system is poorly | | | | your home port where a shore supply may not be |
| installed. | | | | available. A changeover switch enables the onboard |
| Electricity and water should not mix, and if they do, | | | | circuits to be fed from either power source and |
| water will always win. With battery powered systems, | | | | prevents feed back from one to the other. |
| if water gets to any connections or fittings, then the | | | | Modern generators are mainly diesel powered |
| worst that can happen is that you have an inoperative | | | | generators, although the guiding rule here should be to |
| system and a flat battery. With shore supply voltages | | | | use the same fuel as the main engine. Diesel |
| the risks from water are much greater. The voltages | | | | generators tend to be noisier and produce more |
| used can be lethal, so a sound installation and care in | | | | vibration than their petrol counterparts, but are more |
| its use are vital. | | | | economical and last longer. However, noise and |
| The concept of having mains voltage on board opens | | | | vibration can be critical with marine gen sets, because |
| up the possibility of enjoying all the comforts of home - | | | | while you may be happy to put up with engine noise at |
| freezers, electric cookers, electric kettles, microwave | | | | sea, the noise of a generator running whilst stationary |
| ovens, washing machines, water heaters and television. | | | | can disturb a quiet anchorage or upset your |
| Some of these can be enjoyed by using 12 or 24 volt | | | | neighbours in a marina. |
| systems (refrigerators, television and microwave | | | | The problem of noise and vibration means that |
| ovens, for example) but unless the battery is being | | | | particular care has to be taken when installing boat |
| charged they can cause quite a heavy drain, which | | | | generators. Locating it as far as possible from the |
| can exhaust the battery fairly rapidly. For equipment | | | | accommodation will help, but the engine compartment |
| with heavier power requirements such as cookers and | | | | is often under the saloon or the cockpit, which are the |
| water heaters, there is no question of using the battery | | | | prime social areas on board. The normal engine |
| even when it is being charged because neither the | | | | compartment insulation will not absorb the noise, so it is |
| battery nor the charging system would cope. | | | | common practice to enclose the generator in a sound |
| The advantage of shore power lies mainly in its higher | | | | box to help damp out the noise. This box can turn the |
| voltage. The wattage of the equipment is the | | | | generator into quite a large package, so unless it has |
| determining factor; the following gives some idea of | | | | been designed in to the boat it can be very difficult to |
| the wattage of various items of equipment: | | | | find adequate space for a retrofit. The generator will |
| Boat Cookers 6000 watts | | | | need servicing just like the main engines, so leave |
| Boat Microwave ovens 1000 watts | | | | space for access to all parts. |
| Boat refrigerators 500 watts | | | | Marine generators should be flexibly mounted to |
| Water heaters 3000 watts | | | | reduce vibration, which involves introducing flexible |
| Hair dryers 1000 watts | | | | sections into all the connections such as fuel lines and |
| Watts = Amps x Volts, so if we have a 3000 watt | | | | exhaust. The exhaust is a difficult area for boat |
| water heater operating on 240 volts, this will require | | | | generators; it is generally taken outside the boat to |
| 12.5 amps. On 110 volts it will need just over twice that | | | | reduce the onboard noise, but it can prove offensive |
| amount, but if you tried to operate the water heater on | | | | to neighbours who have to suffer it. Silencers can help |
| 24 volts you would need a massive 125 amps-a load | | | | keep the noise levels down. Another alternative is to |
| which would drain the battery in under an hour and | | | | have the option of switching the exhaust to alternative |
| which would require heavy duty wiring the size of the | | | | outlets so that it can be directed away from |
| starter motor cables. Using 240 volts the load is | | | | neighbouring craft. |
| acceptable and the cable size reasonable, so if you | | | | Generators tend to be taken for granted, particularly |
| want the full home comforts on board, then either 240 | | | | when they are shut up in a soundproof box. Monitoring |
| or 115 volts is the route to follow. There are two main | | | | of their operation tends to be casual, so it is a sensible |
| ways of getting this voltage on board. | | | | precaution to fit them with alarms governing water |
| Shore power supply | | | | temperature, oil pressure and rpm, so that you will |
| This the easiest method because all you need is a | | | | receive warning before the engine has major |
| suitable cable connected to a power point on the | | | | problems. Keep the generator self-contained as far as |
| shore. The snag with such a system is, of course, that | | | | possible, including a separate fuel feed from the tank |
| you can't take it with you when you go to sea, but for | | | | and its own starter battery. The installation should be |
| many people this is acceptable; they simply fit dual | | | | up to the same standards as the main engines. Since |
| voltage refrigerators and microwave ovens to | | | | the generator could be left running when there is |
| overcome the lack of high voltage at sea, and | | | | no-one on board, an automatic shut down system |
| temporarily forgo the use of high power users like the | | | | should be considered if any of the monitored |
| cooker and water heater. On powerboats you can | | | | parameters such as pressure or temperature |
| retain the use of the water heater by having a water | | | | changes, so as to avoid expensive damage to the unit. |
| tank which can be heated by either the shore | | | | The size of the generator is decided in much the |
| electricity supply or from the engine cooling system. | | | | same way as for the DC battery system. Add up the |
| Shore power is fine so long as you operate from the | | | | wattage of all the equipment on board and this will give |
| same berth all the time or know that you can find a | | | | you the top consumption. Remember that there isn't a |
| plug-in point when cruising. There is now increasing | | | | battery in the system to compensate for any |
| standardisation of marina power points, so that | | | | temporary extra loading. Generators are normally |
| connection is easier when away from home, but going | | | | rated in kilowatts (kW), with one kilowatt being 1000 |
| abroad can bring its problems with different sockets | | | | watts. You are unlikely to have every device switched |
| and different voltages. | | | | on at once, so you can probably accept a generator |
| The cable linking the boat to the shore needs to be | | | | with a rating less than the total, but not too small |
| rugged to stand up to the treatment and exposure it | | | | otherwise you will have to go round switching |
| will receive and the current it will have to carry. It is | | | | equipment off before you can switch something else |
| possible to use a domestic wandering lead if it has | | | | on, or the generator will shut down because it is |
| suitable electric plugs and sockets, but this casual | | | | overloaded. |
| approach to high voltage electricity will get you into | | | | Another reason for having a higher rated generator is |
| trouble sooner or later. It also means having a hatch or | | | | that it will be better equipped to handle changes of |
| porthole open to bring the cable on board, so you | | | | loading. When you switch on new equipment, |
| won't want to leave the lead connected when the | | | | particularly with a high wattage, there can be a drop in |
| boat is unattended. The open hatch or port will also be | | | | voltage as the generator struggles to cope with the |
| a nuisance in rain and possibly a danger if water runs | | | | extra load. This is bound to be more of a problem with |
| down the lead and into the connection box. | | | | a smaller generator working near to capacity than a |
| There is a strong move towards the standardisation | | | | larger one. This extra loading can also be a problem |
| of power supply sockets both on boats and at the | | | | where the unit being switched on has a powerful |
| shore connection so that you can plug wherever you | | | | electric motor. With air conditioners, for example, when |
| are. However, different countries still have different | | | | the motor cuts in, the initial loading can be two or three |
| approaches to plugs and sockets although the US 60 | | | | times the normal running load, and this extra |
| amp push and twist plug with flat pins is becoming the | | | | consumption could be enough to make the generator |
| standard. In Britain BS 4343/ 16 amps and BS 4343/32 | | | | cut out if it is working to near capacity. |
| amps are still common and are quite suitable for the | | | | As far as generator controls are concerned there are |
| lower rated power supplies which are often all that is | | | | two main options, manual or automatic start. With |
| available at marinas. The US type plugs and sockets | | | | manual start you have to activate the starter switch |
| can handle higher ratings, and -though designed for 110 | | | | just like starting the main engines. With automatic start, |
| volts are adequate for 240 volt supplies. | | | | sensors detect when a switch has been closed and |
| Shore power cables should never have live pins. This | | | | automatically respond by starting the generator. This |
| means that the end of the cable you connect into your | | | | adds to the convenience of the system, but could |
| boat will be a socket, with the fixture on board being a | | | | result in the generator starting at night when a light is |
| plug. This may seem back to front, but the last thing | | | | switched on, to the annoyance of everyone on board. |
| you want is live pins on a plug exposed where you | | | | Manual starting is to be preferred in that you will check |
| might touch them. Even though they are protected | | | | the output voltage and running of the unit at start up. |
| from rain, the connections at each end of shore supply | | | | All modern generators produce AC, and all high |
| cables should be waterproof to reduce the chance of | | | | voltage equipment used on board will operate on AC. |
| corrosion and the risk of water running down the cable | | | | This is the same power as used at home. Much of the |
| on to connection. | | | | equipment like hair dryers, television sets, microwave |
| The shore power cable should be adequate, and well | | | | ovens and refrigerators will be identical to your home |
| protected, for the current it has to carry. For a 16 amp | | | | appliances. AC is current which switches back and |
| current a 2.5 sq mm wire is adequate and for 32 | | | | forth and it does this at a certain number of cycles per |
| amps, 4 sq mm. Heavy duty insulation will protect the | | | | second, normally 60. This cycling rate is carefully |
| cable where it might be trodden on on the marina | | | | controlled on shore at the generating station, but on |
| pontoons. The cable should be long enough so that | | | | board it is unlikely that the generator will be able to |
| with movement of the boat at the berth it is not | | | | produce the same accurate number of cycles per |
| inadvertently used as a mooring line. You can make it | | | | second, which explains why some equipment like |
| just the right size for your regular berth, but if you | | | | electric clocks and some types of tape and record |
| cruise a lot then a longer cable, say up to 25 metres, | | | | player will not operate satisfactorily on board when a |
| will enable you to connect up at most marinas where | | | | generator is providing the power. This matching of the |
| a supply is available. To cope with different types of | | | | cycles of AC is one of the reasons why shore power |
| connection you should take alternative plugs with you | | | | and on board generated power cannot be mixed in |
| for the shore end of the cable you connect into your | | | | the same circuits. It is almost impossible to get the |
| boat will be a socket, with the directly into the shore | | | | match perfect, and major damage could result. |
| end of your cable. | | | | Another point to watch with alternating current is the |
| The location of the shore power connection on board | | | | way the current flow switches from one way to the |
| is important. This should not be inside because you | | | | other. All shore supplies and marine gen sets will have |
| don't want to leave hatches or ports open, but even | | | | what is termed a sine wave curve, which means that |
| though it is a waterproof connection it will benefit from | | | | there is a gradual switch in the flow of each cycle. |
| being protected. On some boats it is fitted in a small | | | | From a peak in one direction, the flow diminishes and |
| locker in the cockpit, or in the transom where stern-to | | | | then steadily builds up in the other direction. The |
| mooring is common. Otherwise it is located in a | | | | alternative is the square wave flow, where there is a |
| semi-protected position in the cockpit. If the connection | | | | sudden transition from one direction to the other. This |
| is in the open, then it should be angled downwards so | | | | square wave current is produced by some convertors |
| that water will not run down the cable and into the | | | | of DC to AC, which we will examine later. Some |
| connection. | | | | equipment will not operate happily on square wave |
| Yacht Generators | | | | AC, mainly equipment such as microwave ovens, |
| A more flexible way of producing the higher shore | | | | television sets, computers and electronically controlled |
| power voltages is to have a generator on board. With | | | | battery chargers. |
| marine gen sets you are completely independent and | | | | |