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Refrigeration on board


psygeioThe necessary complement for small and medium-length boats

In nowadays we cannot imagine a boat, from the smallest to the largest,  without the elementary luxury of an electric radiator. The old times when we were looking for ice on the islands is gone for good. The technology in the field of marine refrigeration has made many important steps in order to enjoy our trip in comfort.The refrigeration equipment manufacturing companies in the last 35 years have faced two main problems in the development of the electric fridge. The first is directly related to the power consumption of the batteries and the second with the performance of the refrigerator on high temperatures.

So the problem of the high consumption had to be solved so that the refrigerator to perform perfectly on the high temperatures during the summer months.

As expected, the level of the quality and the manufacturing of the refrigerators and refrigeration equipment is technologically superior to that of conventional domestic applications. Refrigerators that are placed on boats are divided in two categories.

 

  • In electric refrigerators 12/24V which have the cooling machine embedded or separated.
  • In ice refrigerators which are insulated cabinets(refrigerator box) and in these are installed cooling elements 12 & 24V.

The ice refrigerators are mostly common on sailing boats. In this article we will deal with the electric refrigerators 12 & 24V and the cooling machines 12 & 24V. Due to the consumption improvement of the fridges, we rarely encounter refrigerators with engine driven compressor which are driven by an impeller from the main engine of the vessel.

Several sailing boats work with this fridge type which in dialect has prevailed as “ Frigo”.

So, we start with the fridges 12-24V which must be adapted on the space of each boat.

In the market we can find many types of fridges from 30 to 200 litres. These fridges have air-cooled cooling elements mainly with Compressor Danfoss 35F. As for the construction of the cabin, is plastic and inner cooling element(evaporator) or stainless steel with an internal cooling element on the side walls. On the above photo you can see fridges and freezers of this type.

 


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So, all you have to do is looking on the dimensions of your available space you have for a refrigerator and choose one that meets these dimensions.

If you want to utilize all the space you have, you can also build a fridge based on the dimensions of your space(with the “scoop”).

Remarkable Italian companies in the field of marine refrigeration, and Greek manufacturers make refrigerators that will fit in your space. So let’s deal with the cooling elements of the ready refrigerators and the cooling elements used in the refrigerators which are manufactured according to the dimensions that we have on board.

 

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The electric cooling elements 12V and 24V DC can cool the cabins of the fridges, with a capacity of 20 to 350 litres, consuming about 40 Watt power. Now with the new generation compressors 12/24Volt Danfoss 35F we have electrical consumption 25% lower than with the old compressors, ranging incredibly low for reaching small refrigerator capacities  from 3 Amps to 12Volt and 1.5 Amps at function in 24Volt. Also a very great advantage is the regulated battery protection.

The Danfoss company in the late 1970’s presented on the market the electrical controller protection from excessive battery drain. This controller stops the operation of the fridge when it detects voltage below 10.6 Volt. Today, 30 years later, the battery protection system is adjustable to “cut” the refrigerator from voltage 9,6 to 11,3 Volt, when it comes to 12 Volt batteries and from 21,3 to 22,8 Volt when it comes to 24 Volt.

The second major advantage of the new Danfoss 35F is the possibility of regulating the speed(rpms). On this way we can achieve faster cooling the hours there is energy( e.g. operation of the engine) and we can save money & energy, by lowering the speed at overnight. The rounds per minute at which the compressor Danfoss 35F operates are four, 2000 rpms, 2500 rpms, 3000 rpms and 3500 rpms, as you can easily see in the figure below showing the electronic Danfoss controller  with speed controller of  Veco Frigoboat for selecting the four speeds of the compressor.

For example a frigde of capacity 42 litres can run 24hours with a battery 65-70 Ah, with no need to charge. We replenish the power consumption (in Ah) of the fridge apart from the alternator(dynamo) of the boat, in many other ways like the solar charger, the wind turbine and for larger vessels using the battery charger which is powered with 220V from the generator.

Electric  fridges are divided into two major categories.

  • The Air-cooled, eliminating the heat they absorb in the air and on the water-cooled eliminating the heat in sea water.
  • The Water-cooled electric refrigerators  are divided into two types of  water-cooled condensers.


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The first machine uses pump 12V or 24V of low consumption almost 1.0 Amp and the other uses a special, very small and of low dimensions condenser which is mounted on the hull of the boat to a point that is constantly below the waterline. This last way is the most modern and the most economical as far as the consumption in Amps of the batteries is concerned.

At this point it’s worth mentioning that the electrical fridges 12 & 24 Volt are installed in thousands of sailboats and motorboats with amazing performance results. It should be also noted that with the electric fridges we can have such powerful freezers as freezers used in our homes.


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Of course the more you work a refrigerator and mainly the freezer, to lower temperatures, both absorb energy by discharging the batteries on board.

In 2004 the company Veco Frigoboat presented in the market of the electrical fridges the Economy Energy, a device which measures the available battery voltage and selects the operation mode of the fridge by reducing 50% the consumption. Specifically it’s been for a control panel, dimensions 8 x 6 cm, that in the back incorporates an electronic card with electronic thermostat and sensor to measure the temperature inside the generator. In the Economy Energy the electronic board disables the heater radiator, putting into operation the electric thermostat of the system and allowing to rise the temperature to +10 C. Also automatically sets the operation at 2000 rpms, to avoid energy loss. These steps are made from Economy Energy when the batteries are not charged by the alternator or the charger and the voltage is below 12.2 V (24.4 Amps). The Economy Energy is compatible with the Danfoss compressors, is connected easily and reduces by 50% the consumption of the electric refrigerator.


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And if after all that secure the electric refrigerators, still you love Frigo, the following certainly interests you.

REFRIGERATOR CUMULATIVE WITHHOLDING COOLING PLATES(HOLDING PLATES)

Let’s go now to the dependents fridges of the engine coolers(engine driven), which traditionally have been implemented over 30 years in the marine area, mostly on sailboats that use little machine. These machines have the ability to store the cooling producing  in special stainless cumulative plates(holding plates). The cumulative plates can be frozen with 30 minutes operation of the compressor of the engine or the electric compressor and keep the ice for 12 whole hours. You realize the gain of the energy. In this case of course the performance is higher because it is used a multiple compressor horsepower than in the electric refrigerators 12V/ 24V.

In this application the Veco Frigoboat with years of experience in this field can provide the whole kit from the base of the machine(construction drawing plus the installation drawing), and the entire cooling circuit with quick connections, prefilled with freon so it can be fitted easily and quickly.

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Finally the big advantage of the refrigerator whose compressor is driven by the engine of the vessel, is that we have plenty of cooling without loss of energy from the batteries. In recent years, in vessels which have an electric generator, we find systems with compressors 220V in order to freeze the cumulative plates. 



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Once again the Veco Frigoboat, pioneer in the refrigeration-air conditioning field, uses a specific kit by a water-cooled cooling machine of 220V 50Hz, which is associated with one and more freezers. These cabins have a different temperature, e.g. maintenance and freezing. Each chamber can work autonomously thanks to the electromagnetic control system by Frigobat of two or more temperatures.



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Note that the improvement of living has brought in the field of marine refrigeration refrigerator-freezers, ice makers, portable refrigerators, water coolers and generally cooling elements for the full range of the applications.



source: ortsa.gr - skafos - naytiliaka eidh