|Abbate Primatist||Atlantis||Azimut Yachts|
|Bavaria Motor Boats||Bayliner||Beneteau|
|Fiart Mare||Jeanneau||ManÚ Marine|
|Rizzardi||Sanlorenzo||Sea Ray Boats|
|Sessa Marine||Sunseeker||Zodiac Italia|
In this article we explain first the theory of summer cooling and winter heating and then the available systems and finally a practical example of an installation
Nautica Magazine 420, April 1997
AIR CONDITIONING ON BOARDCruising is always a nice thing, but in summer the inside of the boat often gets too hot; We are already used to air-conditioning in our car, in offices, in hotels: why waste a nice day? Good air-conditioning can be a "do it yourself" installation. In this article we explain first the theory of summer cooling and winter heating and then the available systems and finally a practical example of an installation.
In the picture above, tools (not many nor specific tools (indeed) needed for the installation of a marine air-conditioner. In the picture below, some of the components used for the air distribution of the air-conditioning system.: flexible duct of different sizes, splitter plenums and distribution plenums, duct nipples and air grill in different shapes and sizes to match the cabin decor.
May be you still remember 'that July 199... when I could not sleep for an entire week because of heat, mosquitos, and marina noise'. There are an infinity of types and models of boats but all, even in different ways, have the same problems.
The capacity needed to air-condition a room is expressed in Btu/h. In order to calculate the value you must calculate the room surface of each cabin (drawing above) and consider is position in the boat. This table gives the capacity value expressed in btu/h from the surface value.
a) below deck cabin
When more rooms are to be conditioned, the addition of each
individual capacity gives the total capacity needed for the boat.
When more rooms are to be conditioned, see the paragraph
You do not need to go back to school, nor to look for the physics school book: with these tables and formulas you will know immediately the capacity you need. Our purpose is in fact clear your doubts and answer your questions. Air-conditioning is quite common already in any application, lets make it easy also for onboard air-conditioning. We find it already on even small cars, in houses it is more and more common, not to say of the offices which are widely air-conditioned for a better quality of life. Then we ask why a leisure boat, which is the long dreamed place to spend our vacations must be not livable in summer which is when we like to have holidays. This first part of the article deals with the evaluation of the boat characteristics and the needs, which will then be used to choose the correct system and model of air-conditioner more suitable to our boat.
What air-conditioning means
Btu/h: British Thermal Unit. The unit to measure the heat capacity. It is 1/4 of Calorie.
Calorie: Heat capacity measure. One calorie is the heat needed to increase of one degree C. one litre of water.
Reverse cycle: It is a technical way to modify the refrigeration circuit in order to produce heat.
Fan coil: It is a heat exchanger or evaporator equipped with a fan.
Evaporator: Heat exchanger between refrigerant and air or between refrigerant and water.
Heat exchanger: Technical component used to transfer heat from one fluid to another.
Climate control system: An air-conditioner with an automatic control which maintains the preset temperature.
Types of air-conditionersThere are three types of air-conditioners:
Cooling modeThe airconditioner, when used in cool mode (summer use), is a refrigerating unit which subtracts the heat from the room air (directly in the direct expansion systems, and indirectly with an intermediate fluid in case of 'chiller' systems. The heat removed together with the heat generated by the compressor working, must be then dissipated outside the air-conditioned space. The marine air-conditioner uses a special marine heat exchanger to dissipate the heat to the sea water, which is circulated by a pump.
Heating modeThe same airconditioner which produces 'cold' in summer, can produce heat in winter. In order to produce heat the air- conditioner must be equipped either by a "reverse cycle valve" or by an electric resistor. The reverse valve is special 4 ways valve which can "reverse" the refrigerating circuit so that the evaporator becomes a condenser and the condenser becomes an evaporator. In this way the heat is taken from the sea water (which is consequently cooled) and given to the room air which is heated. This heat is sufficient for Mediterranean climate, with mild winter temperature and, more important, sea water temperature above 0° C. The sea water temperature must be carefully considered as the air-conditioner efficiency drops dramatically if the sea water temperature drops below 10 c. If this happens the air-conditioner looses efficiency and it can no longer be used. In this case for cold seas it is advisable to install system equipped with electrical heating, which doesn't loose efficiency in cold waters. In the market are also available air-conditioners equipped with electrical heating.
Sea water cooling of the air-conditioner
The pictures show the use of the air distribution grills, their shape and some of the possible installations. As the cold air is heavier than warm air, the cold air falls therefore the cooled air should be dispersed across the deck head or at least upwards. This is achievable also by realigning the grill blades. The air grill has also a high impact on the inside decor.
SafetyThe marine air-conditioning has two aspects which must be well considered for safety reasons:
Air distribution - Recirculation and air exchange
The air-conditioning of a compartment may work only by treating the air of the room temperature. The majority of the air-conditioners work with recirculation only as the air-conditioner treats and delivers back to the ambient the same air taken from the room. The use of fresh air is not normal practice, as there is normally more than sufficient "natural" air exchange in the original yacht project, from ventilators, hatches, doors and generally "passage" to the external ambient for breathing and odour removal. The air exchange becomes a must for yachts above 25-30 metres and for boats designed for personnel carriers. When handling air (air-conditioning) it is necessary to keep in mind the following rules:
The diameter to be considered is the inside diameter
A. Steel spring
Air delivery grillsThe treated air must be delivered and diffused into the area to be air-conditioned, in such a way that it doesn't bother people by causing a draught and should be quiet, by avoid too high an air speed, and for this reason air grills have to be installed of a size adequate for the air-conditioner capacity. The market offers a variety of grills in metal, wood and plastic; it is also possible to make custom made grills incorporated in the yacht furniture. If well studied, grills can be aesthetically pleasing and matching the internal decor.
Intake grillThe air-conditioner or fan coil must take the air from the room to treat it. The space where the air-conditioner is installed must be in direct communication with the room to be conditioned. In this case it is not necessary for an intake grill as the air is drawn freely. The intake grill is needed for the decor purpose only, as the intake must be "masked" , but other solutions for the air intake can be found with improved appearance. When the treated air from an air-conditioner is delivered to several cabins, one must consider that the air from these cabin must return to the air- conditioner. Often cabin doors are not tight, but it must be checked that the air passage is enough, otherwise the air- conditioner will run at a reduced capacity due to a restricted return. A passage for the return air can sometimes be found through a locker which is common to both cabins.