12 Volt Air Conditioner for Marine Use

Overview:

12 volt AC, like compact marine air conditioner, comes in three separate packages. Items required for a complete system are,

• 12 volt AC, which consists of a compressor, water cooled condenser, evaporator tubes and blower,

• water pump and tubes, and,

• ducts with duct accessories

Quite similar with other marine air conditioners.

However, this 12 volt AC has a unique variation. The flexibility of power supply.

Power supply for 12 volt air conditioner:

Batteries

You have to give a few consideration before sizing batteries for your 12 volt AC. These are,

• power consumed by the air conditioning unit, P_{12 volt air conditioner}, in Watts,

• power consumed by other equipment in the boat, P_{other electrical equipment}, in Watts,

• number of hours you would like to spend your time, away from main power supply, H_away

• the energy density of the battery, ED_battery, in Watts-hour/lb

The battery size in pounds that you would need is given by the formula:

pounds/hour

= [(P_{12 volt air conditioner} + P_{other electrical equipment}] X 1.7)] ÷ [ED_battery]

A combination of battery and engine alternator

This combination is most feasible for 12 volt air conditioner, as the life of the battery can be kept longer.

Items you should additionally consider when you’re using this option as power,

• power from the alternator, P_alternator,

• percentage of engine running time, %-age_{engine running}, throughout the entire period you’re away from land.

  If you’ll be using the AC for 24 hours, and you’re running the engine, for 4 hours, then the value should be 16.7%

You can size the battery weight accordingly:

pounds/hour

= [(P_{12 volt air conditioner} + P_{other electrical equipment}] X 1.7) – (P_alternator X %-age_{engine running})]

÷

[ED_battery]

Installation:

Generally, you need to carry out these main steps for complete installation,

1. locating a suitable space for the AC,

2. installing the AC unit and batteries,

3. installing the water pump unit, and its accessories,

4. wire the batteries (and alternator – if applicable) to the AC, and check for correct operation,

5. size and install the ducts

• scoop for sea water intake (for condenser cleaning) into hull section must face forward,

• must have a sea cock, or isolation valve between opening at the bottom of hull for water intake,

• pump filter must be installed, and it must be installed between pump, and scoop,

• please make sure that you apply marine sealant to external parts that come in constant contact with water or mist,

• pump and filter must be placed below water level, to provide positive pressure for pump priming,

• outlet water from condenser (discharge) must be higher than the suction,

• please make sure that you eliminate kinks.

  Use elbows where necessary, and make sure suction line and discharge line follows the sloping requirement from the manufacturer

Do you need it?

There are pros and cons of 12 volt air conditioner.

Pros are, it is compact, efficient, yet quite cheap in running costs, and you will not need a generator (which is costly).

Cons are, it is four times as expensive as normal marine air conditioners, and the supply is currently very limited.

However, if your boat size is quite small, and you go to the waters quite often, then 12 volt air conditioner would be a good choice for you.

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