Selection Research
To select a means of refrigeration one must first understand the different types. There are three basic types of refrigeration used in portable fridge/freezers; thermoelectric refrigeration, absorption refrigeration, and refrigeration using reciprocating compressors.
Thermoelectric (TE) coolers work electronically without the use of Freon, compressors or evaporators. In a thermoelectric cooler, direct current is applied to a semiconductor which makes one side of it hot, and one side cold (which is known as the Peltier effect). Typically these units have the ability to either heat or cool.
Thermoelectric units draw a large amount of current (4.6 Amps) and can only cool to about 30 degrees below ambient temperature. Most units do not have the ability to freeze, or maintain a steady internal refrigerated temperature. Consequently they take many hours to cool a warm bottle of water.
They are very cheap – most retailing under $100, and light weight. They can be bought almost anywhere.
Absorption refrigeration units work by using ammonia as the coolant, water and hydrogen gas to create a continuous cycle for the ammonia. These coolers typically have no moving parts, and generally run on propane or gas.
Absorption refrigeration units have five major parts, a generator which produces ammonia gas, a separator which isolates ammonia gas from water, a condenser where hot ammonia gas is cooled and condensed to create liquid ammonia, an evaporator where liquid ammonia evaporates to create cold temperatures in side the cooler, and an absorber which absorbs the ammonia gas into water.
Heat is applied to the generator. The heat comes from burning something like gas, propane or kerosene. In the generator is a solution of ammonia and water. The heat raises the temperature of the solution to the boiling point of the ammonia. The boiling solution flows to the separator. In the separator, the water separates from the ammonia gas. The ammonia gas flows upward to the condenser. The condenser is composed of metal coils and fins that allow the ammonia gas to dissipate its heat and condense into a liquid. The liquid ammonia makes its way to the evaporator, where it mixes with hydrogen gas and evaporates, thus producing cold temperatures inside the refrigerator. The ammonia and hydrogen gases flow to the absorber. Here, the water that has collected in the separator is mixed with the ammonia and hydrogen gases. The ammonia forms a solution with the water and releases the hydrogen gas, which flows back to the evaporator. The ammonia-and-water solution flows toward the generator to repeat the cycle.
Through technological advances since their invention over 75 years ago, some fridges now incorporate a combination of thermoelectric and absorption technology, however these fridges are limited to level grounds and vibrations can harm the systems.
Aside from Engel, almost all reciprocating compressors are made in Germany by one company, Danfoss. Reciprocating compressors have many moving parts, and have much more that can go wrong. Some compressors cannot take the shock and vibrations that other compressors can take especially when running, so be careful. Reliability has always been a problem for reciprocating compressors, especially in vehicles, due to vibration intolerance.
The fridge/freezer unit selected for expedition use should be a compressor based unit. There are several brands currently available using compressors that are designed to handle the vibrations intolerances and have few moving parts: Waeco, ARB, Engel, and Norcold. The latter three are made by Sawafuji Products and incorporate a Swing Motor capable of operating at angles of up to 30° off level.
The Swing Motor is an electro-dynamic reciprocating device that connects directly to the piston of the compressor. The motor design and associated resonance characteristics achieve a very high power output. Since there is only one moving part, which is self lubricated, there is no maintenance needed. This offers advantages such as great economy, compact size, light weight, high efficiency due to the resonance phenomena, low friction losses and minimum power consumption. When combined with thermally efficient insulation, the result is a superior cooling performance.
Selection
There are numerous sizes of Fridge/Freezers to choose from to suit your expedition needs, from 14 quarts to 84 quarts. Each expedition will have different requirements for fridge/freezer selections. It is best to pick the unit that best suites your needs. The determining factors should be based upon capacity, weight, size and performance.
Accessories Research
Transit Bags. (Look for upcoming transit bag review ) Waeco, ARB, Engel, and Norcold offer transit bags, of which the latter three are interchangeable. Transit bags offer protection of your unit, by adding and extra layer of padding and insulation. Typical transit bags are made of a heavy duty canvas outside layer with a reflective layer on the inside. Transit bags should include proper ventilation for your specific fridge/freezer.
Thermometers. There are many solutions for monitoring the temperature inside your fridge/freezer. When selecting a thermometer ensure that it is rated to match the temperature range of your fridge/freezer.
Mounting Solutions. [See Below] There are numerous solutions to mounting a fridge/freezer. Units made by Sawafuji Products have two additional installation solutions produced by Engel, the Engel Slide, and the Engel Slide-Lok.
Expansion Options. TwoZone Manufacturing PTY LTD in Australia currently makes expansion units that add 21 or 40 Liters with out increasing the footprint of your fridge/freezer, by adding an extra compartment to the top of your unit.
Accessories. Engel has developed and hinge locking system to prevent the lid from accidentally sliding sideways when opening. This fits the Engel 35 and 45 models.
Installation / Mounting Solutions
Every expedition vehicle is different, and with that the mounting solutions are different. It is important to install the fridge/freezer in a location where it is clear of the elements, and easily accessible. Engel, ARB, and Norcold units have a few pre-manufactured mounting solutions available such as the Engel Slide, and the Engel Slide-Lok.
The Engel Slide is a strong low profile steel slide that extends out 80% allowing access to the Engel freezer in confined spaces. The fridge/freezer is placed on the slide and secured by attaching turnbuckles to the tabs attached behind the handles. The slide has sealed roller bearings, and a safety latch.
The Engel Slide-Lok is a simple mounting solution where the rubber feet of the fridge/freezer are replaced with included feet that attach to the Slide-Lok, thus locking your unit in place.
Custom installations. Of course there are many custom installation options.
(I hope to make it to at least half the places this bike has been)