What is a Marine Air Conditioner

The principle behind air conditioning is the movement of heat. An air conditioner pulls the heat from the air by transferring the heat in the cabin to the refrigerant gas within the air conditioner. A marine air conditioner then transfers the heat from the refrigerant gas to the sea water. The process can also be reversed, the air conditioner can pull heat from the sea water and transfer that heat to the cabin. This is called reverse cycle air conditioning.

Types of Air Conditioners

There are three basic types of marine air conditioners. Self Contained Direct Expansion Systems (DX), Remote Systems (Split Gas), and Tempered Water Systems (Chilled Water). Use the size and layout of the boat to determine which system is right for you.

  • Self Contained DX systems are typically the best choice for boats up to 40 feet, due to their lower cost and ease of installation. A single unit can cool one or multiple areas with ducting and wyes to save space and cost. The unit itself is larger however due to the air handler and cooling unit being on one “skid”. Also, since the compressor is mounted on the same unit these systems are somewhat noisier than Split Gas or Chilled Water Systems.
  • Split Gas are often seen on boats up to 80 feet. The condensing unit of a remote system is generally installed in an engine room while the air handlers are mounted in the areas needing cooling. The air handlers are connected to the condensing unit with copper lines. The maximum distance of the line is 50 feet. Remote systems usually cost more to install due to high component costs and the requirement that a certified technician must “charge” the refrigerant system. The advantage to a remote system is that the units take up less space in living areas and are more quite because the compressor is mounted remotely where it is less likely to be heard.
  • For larger boats, a Chilled Water System uses the refrigerant to chill coolant water which is then pumped throughout the boat to air handlers to distribute cool air. There is no limitation to the size a vessel this type of system is used on or the length of run between the cooling unit and the air handler. Tempered Water Systems have the added benefits of flexible load management and often reduced peak electrical load.

Many factors are involved when choosing the right air conditioner for a particular boat. The boat’s size, insulation, and available electrical supply are all considerations that need to be taken into account. Where the owner intends to take the boat is also a factor. An air conditioner that is too small will run continuously and still not cool the area adequately. Too large of an air conditioner will draw unnecessary power and cycle excessively.

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