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Marine Air Conditioning
Once thought to be impractical or extravagant, air conditioning
a single sleeping cabin or your entire vessel is easier than you
think. Our Climma marine air conditioning systems are manufactured
by Veco in Italy and their product range spans the requirements
of small cabin cruisers through to large megayachts. Veco product
engineering is second to none.
All systems feature marine grade
stainless steel chassis components and carry a full one year manufacturers
warranty from date of installation. We match the right size
AC Generator to power the system - too big a generator will often result in premature failure due to bore glazing. Smaller systems can be powered
by an Inverter/Charger which means that an AC generator set is not always required.
Board
Cruising 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.
 Everybody
who owns a boat with a small or medium-size cabin knows that the warmest place
of the boat in summer is probably the sleeping cabin, where the temperature
is always a few degrees higher than the external temperature on hot summer days:
The sensation of heat created by the warm still air increases if we are not
moving with air flow through the vessel which may be limited by small accesses
and hatches. It is obvious that as boats are made from different materials and
have different shapes and configurations, we can find more or less comfortable
cabins; another variable is the possibility of ventilation and therefore the
quantity, size and position of doors, hatches etc.
We have so far considered the problems of the summer season, but if you use
the boat in the cooler periods as well, even if the cabin feels slightly warmer
than outside, it will never reach a comfortable temperature if you do not install
a heating system. Many boat owners give up using their boat in the hottest or
coldest period of the year exactly for this reason. Or in summer they simply
cannot use the cabin as it is more comfortable staying outside. Cabins become
very uncomfortable when the sun shines and there is little or no natural ventilation.
Maybe 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.
Nowadays we can find in the market a wide choice of systems which will solve
this summer inconvenience satisfactorily. The market offers air-conditioning
units specifically designed for marine use. The range of these systems includes
units for any size of boat, with cabins of small, medium or large size. We will
deal here with the smaller units and boats, but it must be said that the same
manufacturers make very large units for very large vessels. The most interesting
thing, which is the good news of recent years, is that the 'small' systems are
quite easy to install and reasonably inexpensive. Considering the advantages
of the air-conditioning on a boat, the installation of an air-conditioning system
is quite simple and anybody with a bit of "do it yourself" experience
and a with few, non specific tools, will be capable of a successful installation
of a compact system. This article will give you all the necessary information
to complete your installation.
Capacity Requirements
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 and
consider its' position in the boat. This table gives the capacity value expressed
in btu/h from the surface area value for tropical conditions. When more rooms
are to be conditioned, the addition of each individual capacity gives the total
capacity needed for the boat.
The "K" factor used on the chart at right takes into account
the location of the cabin with respect to the anticipated heat load.
Cross reference the cabin area (in square metres) to the K-factor to
determine the BTU capacity required to cool the cabin. This chart uses
a differential temperature (Outside air temperature minus inside temperature) of 15 degrees which is a standard for tropical climates. For moderate climates, derate the resulting BTUs' by 33%.
K = 20-22
Owners cabin and guest cabins:
K= 28-30
Saloon or dinette without or limited window and glass area (sail yacht
or power "open" configuration):
K=35
Saloon or dinette with large glass area (power boat- Fly configuration):
K=40
Wheelhouse (power boat) with very large glass area:
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Below you will find a short theoretical chapter with tables, numbers and coefficients:
it is obvious that in order to air-condition a space, as each boat has different
sizes and characteristics, it is necessary to combine the different components
supplied by the manufacturers, and to do this, you need positive figures of
the requirement. 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 to 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 small cars, in houses
it is more and more common, and offices 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.
| Glossary |
| BTU (British Thermal Unit) |
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The unit to measure the heat capacity. It is 1/4 of Calorie. |
| Calorie: |
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Heat capacity measure. One calorie is the heat needed
to increase of one degree C. one litre of water. |
| Reverse cycle: |
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It is a technical way to modify the refrigeration circuit in order to
produce heat. |
| Fan coil |
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It is a heat exchanger or evaporator equipped with a fan. |
| Evaporator: |
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Heat exchanger between refrigerant and air or between refrigerant and
water. |
| Heat exchanger: |
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Technical component used to transfer heat from one fluid to another. |
| Climate control system: |
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An air-conditioner with an automatic control which maintains the preset
temperature. |
What air-conditioning means
Air-conditioning means to modify the temperature and humidity of a room in order
to achieve a more comfortable living condition. An air-conditioning system has
the capacity to take, treat and deliver the air of a room cooled and dehumidified
to the correct values. An air-conditioner has normally also the capacity to
heat the room when it is equipped either with the reverse cycle system or with
an electrical heater. an air-conditioner is also supplied with a room temperature
control (thermostat), a on/off switch and a fan speed control with multiple
speeds. If the air-conditioner has also the heat function, then the control
panel gives also gives the choice between cooling and heating. This choice can
also be automatically made, in such a way that once you set the desired temperature,
the air-conditioner control will choose automatically the functioning mode to
reach and maintain the set temperature. In this case the air-conditioner becomes
an environmental control system.
| Air ducting |
A. Saloon delivery grill
B. Owner's cabin delivery grill
C. Guest's cabin delivery grill
D. Air intake grills
E. Compact self-contained air conditioner,
installed under the seats of the dinette |
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| Independent Direct
Expansion Units |
| Independent direct expansion units are self contained
or two part units which are used to air-condition one or two rooms close
to one another.
The air-conditioner treats the room air and delivers the air back directly
to the room recirculation, through air ducting with sizes from 75 to 175
mm which avoids making complicated and long distribution systems.
The compact type combines the compressor, condenser and evaporator on
a single platform. Being fully self contained, the units are factory pre-charged
with gas and do not require a refrigeration mechanic for set-up and installation.
An interesting version of the independent unit is the split model which
is built in two parts: a compressor/condenser assembly and a separate
evaporator/fan assembly which can be installed several metres away from
the compressor, saving cabin space and permitting the air-conditioning
installation in boats where there is no space for both components in one
piece. The compressor/condenser set assembly might be mounted in the engine
room space.
The temperature control in both cases is made by stopping and running
the compressor and also by controlling the fan speed.
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Direct Expansion Compact Type
Direct Expansion Split Type
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| Central Direct
Expansion Units |
Central units with direct expansion circuit
to several evaporators (fan coils). These are very common units used in
land installations where they can be called 'multi-split'. In marine applications
there are some installations made with this configuration where one (large)
compressor cools several evaporators. Unfortunately this simplified configuration
makes the system inflexible and it tends to become unbalanced, particularly
when the thermal load is reduced at night and with the large compressor
balanced for the high load of the day, it becomes far in excess of the reduced
night load. This situation can cause an increase in the fan coil noise into
the cabins. In addition to this, the piping for the refrigerant connection
to each fan coil could become a weak point if not correctly designed and
installed: as any leak will stop the entire system and the repair could
be a real hassle. With this type of system it is not possible to connect
several compressors in parallel on the same circuit; each compressor must
have its independent circuit connected to its evaporators. The temperature
of each room is controlled by stopping the fan of that room or by stopping
the refrigerant flow to that fan coil. In either case again the system becomes
unbalanced if not properly designed as the compressor capacity is still
the same while the fan coil load is reduced.
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| Central Chilled
Water Systems |
Central systems use chilled (or heated) water distribution
to several fan coils each installed in the room to be air-conditioned.
In this case the central system, which can be made with one or more compressors,
cools (or heats) the water of a closed water circuit which is pumped to
each fan coil.
The main compressor equipment is usually mounted in the engin room equipment
space.
This type of unit has several advantages:
- the distribution system of the chilled (or heated) water has the same
characteristics as a heating circuit but instead of a boiler there are
one or more chiller compressors and at the place of the radiator in
each room there are the fan coils.
- Each fan coil is completely independent from the central unit, which
is set to keep the fresh water circuit temperature at a preset value
(normally +12C in summer mode and +40C in winter mode); all the fan
coils are connected in parallel to the fresh water circuit and the room
temperature.
- The system can be run at reduced capacity (maybe a single compressor)
to reduce load when connected to limited shore power systems.
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Central Chilled Water System
1 |
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CENTRAL CHILLER PLANT |
2 |
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FAN COIL |
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A - FAN COIL EV |
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B - FAN COIL FC |
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C - FAN COIL FCV |
3 |
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FRESH WATER PUMP |
4 |
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SEA WATER PUMP |
5 |
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EXPANSION TANK |
6 |
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FAN COIL MANIFOLD |
7 |
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FRESH WATER CIRCUIT HOUSES |
8 |
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FAN COIL CONTROL PANEL |
9 |
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SEA WATER INTAKE |
10 |
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SEA WATER STRAINER |
11 |
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CONDENSATE DRAIN |
12 |
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SEA WATER OUTLET |
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EV Type Fan Coil |
FC Type Fan Coil |
FCV Type Fan Coil |
Cooling mode
The 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 mode
The 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
cycle valve is a special 4 way 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 a 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.
| Air Grilles |
| 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.
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Sea water cooling of the air-conditioner
Because of the heat rejected overboard by an air-conditioner when cooling, and
the consequent problems in typical marine installations, all marine air-conditioners
are water cooled, in other words the air-conditioner dissipates the heat into
the sea water, using a special marine heat exchanger in which the sea water
is circulated by means of a pump. Of course a "land" air- conditioner
could also be installed but due to external noise and water ingress the result
will-hardly be satisfactory. The pump used to circulate the sea water should
be rated for continuous duty and built to-marine specifications. It is normal
to use a marine 240-volt centrifugal pump which is installed below the water
line as the standard centrifugal pump is not self priming.
Safety
The marine air-conditioning has two aspects which must be well considered for
safety reasons:
- The system is connected to mains supply (normally 230V) and it is essential
that the connections follow the safety rules.
- The air-conditioner unit (or its fan coils) must recirculate the cabin air
and possibly a small percentage of external air. The air intake should never
come from a contaminated compartment or even worse, from the engine or generator
room. In case of a problem in the exhaust system of the engine or generator,
the exhaust gas is lethal to man and if the air-conditioner takes and delivers
these gasses it will be extremely dangerous or even lethal to the people on
board.
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:
- Cold air is heavier than warm air and therefore always falls, and for this
reason, in order to achieve a good temperature distribution of the air-conditioned
space, it is advisable that the treated (cold) air is delivered towards the
ceiling, vertically or horizontally. This rule is valid particularly for the
spaces of the areas used during the day, such as the dinette and the saloon
and wheelhouse; as these areas suffer the maximum solar effect which increases
the heat load to be dissipated. In order to get a minimum temperature gradient,
the air is ideally delivered across the deck head or at least towards the
top of the space and therefore takes advantage of the natural convection which
pushes the cold air down and lifts the warm air.
- The winter heating typically needs less capacity than the summer cooling
and it is advisable to give a priority to the configuration for the cooling
effect rather than the heating which will be achieved without too much effort.
- Toilets and the galley space (if apart) are normally not conditioned and
it is good practice to keep them slightly depressurised by using an extractor
fan: in this way odours will be kept inside these spaces and the extractor
will take air from the other rooms which are conditioned. External air will
be therefore taken from the deck area (saloon), helping the fresh air exchange,
and the conditioned air will also cool toilets and the galley.
- The ducting of the conditioned air must be as simple as possible to reduce
the pressure drop; short and straight ducting is the rule, while elbows, bends
and generally "winding" paths are to be avoided. Complex "networks"
must be avoided as they cause pressure drop and reduce the air-conditioner
capacity and effectiveness dramatically.
- All the air-conditioners have a "nominal" capacity expressed in
Btus/h or Watts/h; however this maximum capacity is strictly related to the
air treated by the air-conditioner and drop at the same rate as the air flow.
Therefore we recommend that the air circuit is as short and simple as possible,
particularly if the maximum capacity of the air-conditioner is needed.
- The air intake for the air-conditioner is also important. Air intake must
be straight back to the air-conditioner through a grill or opening which does
not cause any pressure drop.
| Air Duct |
The diameter to be considered is the inside diameter
A. Steel spring
B. Inside duct: textile with PVC
C. Insulating material: rockwool
D. Outside skin: Craft paper |
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Air delivery grills
The 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 avoiding 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.
The 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 cabins 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.
Practical Example
| Having explained the theoretical
issue of onboard air-conditioning, we are now at the point to start a
practical installation, putting theory to practice. We will start from
the components needed for the installation, the heat load calculation
and finally the detailed installation of each component.
Air distribution accessories
The air supply grill is the item which is clearly visible on an air-conditioning
installation, but it is not the only one. The air-conditioner is usually
supplied with a duct adaptor of a specified diameter suitable for the capacity
determined by the air-conditioner. In order to connect the air outlet from
the air-conditioner to the delivery air grill (see drawing) the following
components are normally needed:
- flexible insulated duct
- duct adaptors
- splitter plenums (for installations with more than one grill)
- plenum chamber (to connect the duct and duct adaptor to the grill)
The only exceptions to this configuration are the direct expansion split
units and the chilled water fan coils of boxed type for horizontal or
vertical installation and direct air delivery, which do not need any accessory
other than the intake and supply air grills.
Air filtration
The treated air should be preferably filtered to stop dust and other particles
which can clog the finned air heat exchanger. Normally all the air handlers
and boxed fan coil are supplied with their air filter as a standard. or
as an alternative the air filter can be installed on the air intake grill.
Heat load calculation
This is the name of the formula which is used to find the capacity needed
to air-condition a room (cabin). The most simple formula needs the following
data:
S=The floor area of the room to be conditioned (see drawing).
Te= External temperature
Ti= Desired Inside temperature
K=Thermal coefficient of the room to be conditioned (there must be a K,
otherwise what formula is this?)
The formula is: Heat load = S x (Te-Ti) x K.
(Te - Ti) depends from the climate you want to consider: Mediterranean
uses 8-10 which is the difference you want to achieve between outside
and inside temperature. For tropical climates the standard used value
is 15.
Finally we get to K:
K value is determined by the solar gain, the quantity of people and the
use of the room.
In a very rough calculation these are the values:
Owners cabin and guest cabins: K = 20-22
Saloon or dinette without or limited window and glass area (sail yacht
or power "open" configuration): K= 28-30
Saloon or dinette with large glass area (power boat- Fly configuration):
K=35
Wheelhouse (power boat) with very large glass area: K=40
For example, suppose you have to air-condition a dinette in a "open"
power boat: its area is (3 x 2) = 6 sqM; the heat load is then:
Heat Load = 6sqM. x 30 (K) x 10 (Te-Ti)= 1,800 W/h.
This is a nice number which corresponds to the heat load to be extracted
by the air-conditioner in order to keep the inside temperature 10 °C
below the outside temperature which is a Mediterranean condition, all
expressed in W/h Most of the air-conditioners are given with a Btu/h capacity;
the rate between W/h and Btu/h is 3.4, therefore our magic number is now
1,800 x 3.4 which is 6,120 Btu/h.
Contemporary loads
Contemporary means that the cabins of the "night" area and the
rooms of the "day" area must be air-conditioned at the same
time. This normally is not requested; the heat load calculation considers
the maximum load for each room; in the day area it means that it is lunch
time and everybody is at table, the cook is cooking and the sun is at
its height. For the cabins the peak is reached in the first hours of the
night when there is still the heat of the day, and two people are in the
cabin. As you consider this situation, then you have to make the choice
if you want the 'night' area air-conditioned at the same time as the 'day'
area. This would mean that more capacity of air-conditioning has to be
installed.
We have choosen a power boat "open" type (no flybridge) 12
M. long. The plan of the boat (see drawing) shows a dinette with a galley,
one aft guest cabin connected to the dinette and a forward owner's cabin.
The heat load is the following:
Dinette: 6(S) x 30(K) x 10 (Te-Ti) x 3.4 (rate w/h-Btus/h) = 6,120 Btus/h
Owner's cabin: 4.5 (S) x 22 (K) x 10 (Te-Ti) x 3.4 = 3,336 Btus/h
Guest cabin : 4 (S) x 22 (K) x 10 (Te-Ti) x 3.4 = 2,992 Btus/h
Total heat load = 12,478 Btus/h
For the complete air-conditioning of this boat we need 12,478 Btus/h.
If the boat is equipped with a small diesel generator of 3.5 KW, we must
check that the air-conditioner will work properly with the available power
source. We have calculated the total load but it is necessary to consider
the "life" onboard. We can split the boat into two areas, as
we have already said, "day" area and "night" area.
The total load is a straight addition but the air-conditioning will be
requested by only one area per time.
From this consideration we can choose a unit capable of air-conditioning
the dinette during the day in the hottest hours, reducing or isolating
the cabin supply, which will need air-conditioning only in the night,
when the heat load of the dinette is much less. This consideration is
more valid for small and medium boats, as the air-conditioning of the
main area affects all of the cabins. In this case the most practical,
economical but not less effective solution is to install an independent
air-conditioner in the dinette under the sofa and make three air outlets:
one main grill for the dinette and two smaller closable grills for the
cabins.
As an alternative: 1 air-conditioner of 9,000 Btus/h for the dinette
and the guest cabin, plus another air-conditioner of 5,000 Btus/h for
the owner's cabin. This alternative is sometimes the only possibility
as it is not always possible to run a duct for the air distribution to
the forward cabin from the dinette; the second unit has however the advantage
to have an independent temperature regulation and also to have two independent
and smaller units which will start in sequence and reduce the start current
load on the generator. In fact the start current of two independent air-conditioners
is always lower than the start current of one only air-conditioner with
the same capacity.
Third alternative: central system with a small chiller unit (12,000 Btu/h)
installed in the engine room connected to a 9,000 Btu/h fan coil installed
in the dinette and a second fan coil of 4,500 Btu/h installed in the owner's
cabin. As to the configuration of the second alternative, the fan coil
installed in the dinette is also cooling the guest cabin where the temperature
is adjusted by means of a closable grill. This last solution is more expensive
but also more complete and flexible as a third fan coil for the guest
cabin can be added reaching a complete automatic control on all the cabins.
Each cabin can have therefore its independent automatic temperature control
not only on the fan speed as in the other solutions.
Installation
For the installation on this power boat of 12 M. we have chosen an air-conditioner
manufactured by Veco of Giussano (Italy), a Company well known not only
in Europe but almost world wide. Veco has reached the ISO 9002 certification
of its quality control in 1996. The drawing 2 of the air distribution
schematic shows the position of the Compact air-conditioner, installed
under the settee of the dinette; the air intake grill will be positioned
on the vertical side of the seat; the air delivery is made connecting
a flexible duct between the air outlet of the air-conditioner and a splitter
triangular three ways plenum (B); from the splitter plenum there are two
more ducts: one forward to the owner's cabin and one aft to reach the
guest cabin.
The most important leg is the forward one which will bring air to the
dinette and the forward cabin. For the distribution to the cabin and the
dinette, a plenum chamber is made on the top of the forward cabin locker,
where two outlets are cut, one to the dinette and one to the cabin, where
the dinette has priority.(drawing 5). In the drawings 3 and 4 it is shown
the sea water circuit schematic with the sea water pump in the engine
room and the piping to the unit and out.and also the electrical schematic
with the remote control panel. As the flexible insulated ducts must bring
different quantities of air, different diameters must be used in order
to avoid high pressure drops and also to balance the air distribution.
So the duct from the fan outlet to the splitter plenum is 125mm., from
the splitter to the aft cabin is 75mm. and from the splitter to the fwd
cabin and dinette is 100 mm. It is important to insist that the efficiency
of the unit and a good air-conditioning plant are properly linked to a
good air distribution layout. With a well detailed project, we will know
what is needed, the length and diameter of the ducts, the position of
the grills, and also choose the correct and better design as grills are
available in different sizes and materials. When we say "grill"
it means a specific type made for air distribution and not other types
of grills such as used for air vents. The design and orientation of the
grill fins are essential for a good air distribution.
The first step is to determine the location of each component of the
system, checking all the possibilities and watching that each component
is accessible for maintenance, taking into consideration the manufacturer's
specifications on service. The second step is to mark the position of
all the holes for the passage of flexible ducts and the grill openings.
Once the fan outlet position has been determined, and before installing
the air-conditioner, we can drill the holes and install the flexible duct
in the compartment next to the unit location; where we also install the
3 way splitter plenum connecting the duct as shown in picture 2. The intake
grill (picture 4) is located in the vertical wall in front of the unit.
In our case the air-conditioner intake is facing the intake grill, but
this is not important once there is enough space around the air-conditioner
and the intake air can run around it from the intake grill to the air-conditioner
intake.
In the aft cabin, we run a duct of 75 mm inside diameter, after making
the hole in the bulkhead between the dinette and the aft cabin. We make
two holes for the two round adjustable outlets (picture 5) which we install
on the back of the bulkhead which is accessible, the distribution plenum
is already connected to the duct by means of a duct adaptor of the correct
size. In areas with reduced accessibility this sequence is the rule (connect
first the duct to the plenum and then install the plenum) and so we are
sure that the duct is well fitted on to the duct adaptor. The duct is
fixed on the adaptor by means of screws, glue and/or silicon. It might
be difficult to fit the duct to its adaptor as the two measurements are
very close in order to ensure a good air seal.
From the first splitter plenum (picture 3) we have the duct to the aft
cabin and the other duct (10 cm. dia) which passes through the forward
bulkhead between the dinette and the forward cabin and enters the locker.
In this locker we have installed a panel in the top so as to make a custom
distribution plenum (drawing 5) which feeds the air to the dinette and
to the forward cabin. The distribution is made by means of a smaller grill
(picture 6) above the locker door for the cabin and a main grill (picture
7) in the forward bulkhead. This solution is very practical and saves
a lot of space. The possibility of simultaneously occurring loads is very
rare, and we have considered using a manual valve (details in picture
5) which permits to close the grill of the cabin and concentrates the
air-conditioning in the dinette during the day. This device must be studied
and adapted to the boat configuration but it is practical and inexpensive
solution when more cabins are conditioned by the same unit if the shape
or size of a closable grill available in the market doesn't fit to our
need.
Sea Water Circuit
As the air distribution circuit is finished we have now to install the
sea water cooling circuit (drawing 4). We need a scoop type intake port,
a manual valve, a strainer, a centrifugal pump, a discharge port and suitable
hoses (picture 8).
The centrifugal pump, supplied with the air-conditioner is equipped with
a stainless steel base with rubber vibration mounts (picture 9); the pump
must be installed at least 50 cm. below the water line. The intake through
hull fitting must be positioned possibly in the aft part of the boat.
This job needs the boat to be in dry dock. Make sure to check the position
both outside and inside the boat. The skin fitting must be accessible
from inside, as the manual valve is installed directly on the intake port.
The hole is easily drilled by a normal drill equipped by a special tool
(centre bit) of the correct diameter. Make sure that the hole corresponds
to the through hull fitting as it is quite difficult to increase the diameter
of an already drilled hole. The scoop type fitting must be installed with
the finned part (intake) towards the front, so that the speed will help
the flow and will drain the air out .
There is no risk in having a water circulation when cruising as the water
circuit is closed and will discharge outboard, but the positive pressure
at the intake will bleed air out of the circuit if the intake takes air
in high speed. Air locking in the circuit is the most common cause of
pump problems as the centrifugal pump is not self bleeding. A wrong installation
(facing astern) will prevent the water circulation even at low speed and
worsen the air lock. Install the through hull using the appropriate sealant
and screw it tight by means of the washer and nut; from the inside then
install the manual valve and its hose fitting. From the valve to the strainer
use a flexible hose I.D. 25 mm. as short as possible and the same size
from the strainer to the pump intake (in the centre of the pump body).
The intake leg from the through hull to the pump must be as short as possible.
For the outlet from the pump you can use a hose 16 I.D. straight to the
air-conditioner and then from the air-conditioner overboard. It is important
that the first 50 cm of the pump outlet is orientated upwards so that
any air entering the pump will have room to get out, leaving the pump
full of water. The water outlet must be above the water line but not high
(5-10 cm. are fine) so that it will be possible to check the water flow
and also not so high that will sink your or somebody's else tender. All
the hoses must be fastened using stainless steel clamps. The drawing 6
shows the characteristics of the ideal sea water circuit. In order to
avoid syphoning and give a good and even flow, try to keep all the hoses
as straight as possible and fix all the hoses to the walls and bulkheads.
Electrical circuit
It is mandatory to obey all of the safety rules and follow with extreme
care the manufacturer's instructions and specifications (by the way, clear
and very easy schematics). The electrical circuit includes the connections
of sea water pump control panel mains supply (see drawing 4 and electrical
schematic 7) Having cut a hole to the dimensions of the remote control
panel on the wall above the seat where the air-conditioner is installed,
insert the cable and the thermostat bulb and capillary pipe, and then
fasten the panel (picture 13). The cable and thermostat bulb must reach
the space where the air-conditioner is installed, where we will run also
the pump and mains supply cables. The Veco air-conditioner model Compact
12 RC (picture 14) is supplied on a wooden base for a better protection
during transportation, fixed by means of four stainless steel brackets
to be used to fasten it at final installation. In order to meet any configuration
the fan scroll can rotate from a upper discharge to a low discharge position,
by just undoing a few screws (picture 15). Remove the plastic cover from
the air filter: Before placing the air-filter in position (picture 16)
install the thermostat sensor on its bracket in front of the air intake
(picture 17). The air-conditioner is placed in its place under the seat
and fastened using the brackets supplied with it and self tapping screws
(picture 18). Then the water hoses are connected, taking care of in and
out sense; picture 19 shows the fastening of the water hose on the top
(out) connection using a stainless steel jubilee clamp; a very useful
system is to mark each tail of hose and cable with masking paper tape,
making it possible to write indications and marks. Then we connect the
panel cable to the electrical box: there is no way to make a mistake as
the cable terminal is a polarized plug. The sea water pump and mains wires
have their terminals in the electrical box (picture 21).
Condensate drain
Bear in mind that the air-conditioner, in high humidity conditions can
produce more than 1 litre of water per hour. For this reason the air-conditioner
is equipped with a condensate pan (picture 15) which has two discharge
ports for connection to the bilge (picture 3) or, better, to a small tank
with an independent drain pump. special pumps for lifting condensate are
also available. If the bilge solution is chosen, make sure that the limbers
are open and clean to enable the water to reach the bilge pump. If the
independent tank solution is chosen, then we suggest a small tank with
an automatic drain pump. The installation is now completed: just open
the sea cock and check that the sea water circuit is tight. Then power
the A.C. circuit and turn the new "Air.conditioning" circuit
breaker to "ON "position. The system is ready to run. First
push the "Cool" button on the remote control panel, then turn
the thermostat knob to the maximum heat (the compressor will not start)
so you have the time to check the sea water flow. As you push the button,
the pump and the fan must start. As you are happy with the sea water flow
and the air flow, you can finally turn the thermostat knob counter-clockwise
to adjust to mid range. The compressor will start, the air will become
cooler. Enjoy your new air-conditioner. One only recommendation: do not
regret too much of not having installed it before. |
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Picture 2: The three way splitter plenum is installed, following the procedure
to preconnect insulated flexible ducts. A splitter plenum is a manifold
chamber, preferably insulated, with one inlet and several outlets. A distribution
plenum is a chamber used to connect a duct to a delivery grill.
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Picture 3: The space under the seat where the air-conditioner and most
of the insulated ducts are to be installed. Ducts cannot be strangled
or run in sharp bends as air needs to flow freely.
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Picture 4: The intake grill must have a sufficient area, enough to feed
air to the air-conditioner. The intake of the air- conditioner doesn't
need to be oriented toward the intake, as the fan can take the air from
the entire space around it, but there must be enough clearance around
the air-conditioner to permit air to flow freely.
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Picture 5: As explained in the text, round closable grills are simply
installed by making a hole in the wall. On the opposite side of the wall,
a distribution plenum connects to the air duct.
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Picture 6: The air is ducted, through a connecting plenum to the owner's
cabin and to the dinette; the grill for the owner's cabin is just above
the locker door. You must remember that cold air falls and must be delivered
at a high level.
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Picture 7: Above figure shows the delivery grill for the dinette, installed
in the forward bulkhead; especially for the "day area" zones
it is important that air is supplied at deck head level.
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Picture 8: The picture shows the components of the sea water circuit: A
through hull "scoop" type intake, a manual valve, a centrifugal
pump, different diameters hoses, and jubilee clips of different sizes.
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Picture 9: The picture above shows the sea water pump installed on rubber
antivibration mounts. The sea water pump must be installed at least 50 cm.
under the water line. The skin fitting must be installed well under the
water line when the boat is in dry dock.
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Picture 10: The through hull intake installed in the aft section. The scoop
type intake oriented forward helps the flow and will clear the sea water
circuit of air if it gets into the circuit. If installed facing aft it will
prevent proper functioning of the pump as the circuit will be emptied while
cruising.
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Picture 11: The manual valve is installed directly on the through hull intake;
the sea water strainer is installed immediately after.
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Picture 12: The space under the seat (sofa) is where the unit will be installed.
In this space we install the two sea water hoses (in and out) and the electrical
connecting cables. The sea water out through hull fitting must be drilled
as low as possible just above the water line in order to reduce to a minimum
any noise from the falling water. (see drawing 6)
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Picture 13: The control panel position must be chosen considering ease of
use and also the inside decor. The connecting cable is 3m long.
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Picture 14: The air-conditioner Veco Climma Compact 12 RC comes on a wooden
base for transportation and protection. Air-conditioners are not light weight!
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Picture 15: A moment of the installation, when the fan scroll is oriented
downwards to fit into the restricted space. A few screws are enough to make
the change.
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Picture 16: The air filter taken out from its plastic bag and is installed
in the front of the air-conditioner after the thermostat bulb has been fixed
on its support. The thermostat senses the ambient temperature more effectively
if its sensing bulb is installed in the return air path.
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Picture 17: The bulb is installed on its support in the air intake section
of the air-conditioner.
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Picture 18: The air-conditioner is installed in its space and fastened by
means of four practical brackets in stainless steel.
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Picture 19: The in and out hoses are then connected to the air-conditioner,
taking care to respect the indication of the water flow direction. Care
must be taken in installing the Jubilee hose clips as a failure may flood
the vessel.
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Picture 20: The connection between control panel and electrical box. The
cable ends with a polarized plug: no hassles, but keep it dry!
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Picture 21: Mains cable and pump cable must be connected to the electrical
box. Make sure that each wire goes into its corresponding terminal and
that the fixing screw is tightened correctly. |
Above article courtesy of Veco Italy.
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