CLIMATE SELF-CONTAINED HVAC
PLANNING AN AIR CONDITIONING SYSTEM FOR YOUR BOAT In order to find the ideal air conditioning solution for your boat or yacht, you should consider the following six factors * :
1. Calculating the required system capacity To calculate the required A/C capacity, divide your boat into three areas:
3. The seawater cooling system This system consists of a through-hull fitting, a seacock (water valve), a seawater filter, a pump, a seawater discharge fitting, and a hose or pipe. Dometic recommends centrifugal seawater pumps because of their maximum efficiency and long service life. The ideal solution calls for all onboard air conditioning systems to use a single pump, which must of course have sufficient capacity. The basic rule for calculating the required capacity assumes a flow rate of 3 gal/min (11.3 L/min) per ton of air conditioning (1 ton = 12,000 BTU/h). See the table below for examples.
Below deck: Cabins where the hull slopes inward toward the keel with minimal port lights and hatches.
Mid-deck: Areas on the main deck with small or shaded windows.
Above deck: Areas with large glass surfaces and direct sunlight. Calculate the area of each space to be air-conditioned.
System Capacity
Seawater Flow Rate Through-Hull Inlet Size
12,000 BTU/h (3,517 W)
3 gal/min (11 L/min)
1/2 in (13 mm)
It is assumed that your boat has an average headroom of about 6.5 feet (2 metres). Next, multiply the area by its load factor to determine the required capacity in BTU/h. Use the table below to find the appropriate load factor for each space and for different locations.
24,000 BTU/h (7,034 W)
6 gal/min (23 L/min)
3/4 in (19 mm)
48,000 BTU/h (14,067 W)
12 gal/min (45 L/min)
1 in (25 mm)
4. Duct and grille sizes Cross-section and size are based on the air conditioning system’s capacity in BTU/h. (1 ton = 12,000 BTU/h). See the table below for examples.
Climate
Below Deck
Mid Deck
Above Deck
Load factor, BTU/h per ft 2
Temperate 1
60
90
120
System Capacity Duct Diameter
Supply-Air Grille Return-Air Grille
Tropical 2
90
120
150
6,000 BTU/h (1,758 W) 8,000 BTU/h (2,344 W) 10,000 BTU/h (2,931 W) 12,000 BTU/h (3,517 W) 16,000 BTU/h (4,689 W) 18,000 BTU/h (5,275 W) 27,000 BTU/h (7,913 W) 30,000 BTU/h (8,792 W)
Arabic Gulf 3
120
150
180
4 in (10.16 cm)
32 in 2 (206 cm 2 )
64 in 2 (413 cm 2 )
Load factor, BTU/h per m 2
5 in (12.7 cm)
48 in 2 (310 cm 2 )
80 in 2 (516 cm 2 )
Temperate 1
646
969
1,292
Tropical 2
969
1,292
1,615
6 in (15.2 cm)
60 in 2 (387 cm 2 )
100 in 2 (645 cm 2 )
Arabic Gulf 3
1,292
1,615
1,938
6 in (15.2 cm)
70 in 2 (452 cm 2 )
130 in 2 (839 cm 2 )
1. 95 °F (35 °C) air, 95 °F (35 °C) seawater, moderate humidity. 2. 105 °F (41 °C) air, 95 °F (35 °C) seawater, high humidity. 3. 122 °F (50 °C) air, 104 °F/40 °C seawater, 95% humidity.
7 in (17.8 cm)
80 in 2 (516 cm 2 )
160 in 2 (1,032 cm 2 )
7 in (17.8 cm)
100 in 2 (646 cm 2 )
200 in 2 (1,291 cm 2 )
2. The number of units needed and their location(s) Both are determined by the size and layout of the boat and space limitations for the installation of ducting and plumbing. Consider which areas require their own cabin control and which cabins will be supplied by ducting or a secondary air handler. Temperature control is then only possible by reducing the airflow with an adjustable grille or by controlling the fan speed. Please ensure that there is enough space around the unit for servicing and the installation of an air outlet duct to a high point in the cabin. When designing air distribution ductwork, it is important to keep note of air return and supply. Air must have a way to return to the air handler. Taking air from one room and ducting to another may cause negative and positive pressure issues. Negative spaces may become dangerous as make-up air may come from bilges or engine rooms.
8 in (20.4 cm)
140 in 2 (904 cm 2 )
240 in 2 (1,549 cm 2 )
2 × 6 in (2 × 15.2 cm)
150 in 2 (968 cm 2 )
250 in 2 (1,613 cm 2 )
5. Cabin Controls Dometic offers a complete line of cabin controls that can be found in the catalogue. 6. Electrical requirements All Dometic air conditioning systems are available in 50 Hz or 60 Hz versions and in all standard voltages. All electrical information is listed in the product data sheets. When at port, the power connection must also be dimensioned accordingly. For easy start-up with less current, see the SmartStart product later in the catalogue.
* These methods are for estimation only. Detailed heat load analysis is required for exact BTU/h requirements.
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