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         Selecting The Right Equipment

Selecting the right refrigeration system for your boat is important. What works for your friend’s boat may not work for you. Also, advertisements can mislead you. Such statements as: Chosen by more boat owners than any others; We build the World's leading refrigeration system; our system is rated #1; etc. All of these statements may contain some truth under certain applications but they can be misleading and lead to the installation of a system that will prove to be wholly inadequate for your needs.

The selection of a refrigeration system for an individual boat should be based on the following:

  • Size of the box to be converted
  • The amount and quality of insulation
  • The amount of cooling required per day -Do you just need a replacement for ice of 40-60 degrees or or do you need short or long term freezing?
  • The size of the freezer
  • Whether the boat will be used in the tropics or a more temperate climate
  • Whether the boat has a generator
  • The size of the alternator
  • The total available house battery
  • Whether the boat is used for week end jaunts, short vacations of 1-2 weeks or extended cruising or live-aboard
  • Your personal needs such as the need to cool a large amount of drinks per day for a charter, or do you need quick freezing for your fish catch.

Once you have the above questions answered, you will need to consider the types of boat refrigeration systems available. I’ve listed the main ones below.

  • The standard hermetic sealed 110 or 220 volt units that can be water or air cooled
  • The hermetic sealed 12-volt brushless compressor that is air-cooled only.
  • The hermetic sealed 12-volt brushless compressor that is water-cooled only.
  • An engine drive, belt driven system that is normally connected to holding plates.
  • A belt driven 12-volt unit or direct drive.
  • A hermetic sealed 12-volt unit with brushes.
  • Thermocycle electronic units are available but rarely used.
  • Gas and kerosene units are used on some small catamarans and houseboats.

Since all ice boxes have different amounts and quality of insulation and boats are used in all different climates, I have assumed, for the following examples on equipment selection, that the box has 3 inches of good quality insulation in the refrigerator and 4 inches in the freezer and that the boat will be operated in the tropics with 86 degree F seawater and  has a crew of two.

BOX A: Two boxes An 8 cubic foot refrigerator and a 4 cubic foot freezer with a 9000 BTU daily requirement.

RECOMMENDATIONS: There are a couple of options for this box.

  1. Three holding plates with a 110 volt 1/2 HP system. The boat would need to be equipped with a reliable auxiliary generator and the generator would need to run 2 hours per day.
  2. Three holding plates connected to an engine drive system. The engine would need to be run 2 hours per day even when connected to shore power.
  3. Although a 12-volt system could be used I would not recommend it as the daily energy drain would be too high. A small 12-volt unit would require 150 AMP per day and a belt-driven 12-volt unit would require 180 AMP per day.
  4. A combination of 1 & 2 connected to the same holding plates (plates would need dual coils) would give greater flexibility.

BOX B: A single 6 cubic foot box with a divider which allows for a 4 cubic foot refrigerator and a 2 cubic foot freezer. It would require 4800 BTU per day.

RECOMMENDATIONS: There are several options.

  1. A small 12-volt unit that uses a  Danfoss Compressor (If the lid opening is large enough) I would recommend the Adler/Barbour air-cooled Cold Machine. It would require 80 AMP hours per day. the boat should be equipped with the following:
  • At least 500 AMP hours of battery capacity
  • A high output alternator and smart generator
  • Some type of voltage monitor

The engine would need to be run   2-1/2 hours per day. For the live aboard at anchor, a wind generator could supply 30% of the energy requirement if in the tropics. For the more temperate climates it could supply almost 100% of the energy required.

   2. One or two holding plates connected to a 1/2 HP 110 volt system. I would only make this recommendation if the boat was equipped with a reliable auxiliary generator. The daily running time would be one hour.

   3.  One  holding plate could be connected to an engine drive system. The engine running time would be 1 hour per day.

   4.  A hybrid system that would use a 12-volt and an engine drive system connected to the same holding plates (dual coils needed). The engine drive would do the bulk of the work while the 12-volt would add supplemental cooling as desired. This would also add redundancy in case one system fails. I have had very good feedback on this type of system.

BOX C : a single box of 4 cubic feet or smaller and its daily BTU requirements would be 2400-3000

RECOMMENDATION: A small 12-volt Danfoss compressor such as the Adler/Barbour Cold Machine, if it will fit through the lid opening, which uses a large evaporator and requires 40-50 AMPs per day. The boat should also be equipped with at least a 70 AMP alternator, smart voltage regulator, and have a 400 AMP hour battery capacity and solar panels.

BOX D has two separate 4 cubic foot boxes, one as a freezer and the other as a refrigerator. It would require 7200 BTU per day.

RECOMMENDATION: One Danfoss unit for each box would provide adequate cooling The daily AMP hour requirement would be 120.

The boat should be equipped with at least a 100 AMP alternator and a smart regulator. The total battery capacity should be at least 500 AMP hour. Other options would be the addition of a wind generator or solar panel.