Confused about the different types of fridges you should buy?
It is important to know the difference and what type of refrigerator / freezer is best suited to your application.
There are three types of refrigerator / freezer designs; compressor, thermo-electric and heat exchanger.
Compressor refrigerator / freezer
The most widley used refrigerator / freezer uses compressors. The best compressor refrigerator / freezer run on both 12 VDC and 120 VAC, 60Hz without an additional power supply. Because they are controlled by an adjustable thermostat, current draw is more efficient maintaining the fridge and its contents at a temperature controlled by a knob. Some designs have a thermometer. The colder the setting, the higher the current consumption both in attaining the desired temperature and maintaining it.
Compressor refrigerators / freezers are ideally suited where high efficiency, low power consumption and lower freezer temperatures are required.
Thermo-electric refrigerators work electronically without the use of freon, compressors or evaporators. Thermo-electric refrigerators run on the Peltier principle that if a current is passed through a special metal element it becomes cold and if the current direction is reversed the element gets hot. So thermo-electric can also be used to warm up food. Apart from a small fan, thermo-electric refrigerators are solid state and relatively quiet but will not freeze, slow to cool, and cannot keep a steady internal temperature unlike compressor type refrigerators that have a thermostat to control and cycle the compressor on and off maintaining steady internal temperatures - independent of the outside temperature.
Thermo-electric coolers can only cool to about 30 degrees below ambient. They cannot freeze, or maintain a steady internal refrigerated temperature. Consequently they take many hours to cool a warm soda for example. In contrast, compressor type refrigerator can cool to any temperature in less than 20 minutes. In freezer mode they can get below freezing in about 1/2 hour.
Thermo-electric units typically are less efficient and draw more current than compressor type refrigerators, which can be a consideration when running of 12V battery. They are generally best used only when running the engine to keep the battery charged.
The main advantage of thermo-electric type refrigerators / coolers is that they can cool as well as warm and are very cheap to purchase.
Heat Exchange Refrigerator / freezer
Powered by LP gas and by 12-volts and 120-volts, heat-exchange fridges are inefficient when run off 12-volts, fairly efficient off 120-volts and highly efficient running on gas or paraffin.
The versatility of power source means that in situations where they remain in one location for a long period when battery charging is not possible or practical, they keep working. In a vehicle they must, for safety reasons, work off 12-volts. However, when in a moving vehicle or trailer under electric power they do lose efficiency and depending on outside influences, may not freeze. When set up in a fixed location they must be levelled, the flame centred, the regulator set and a yearly cleaning. They have no thermostat so when working off 12-volts the current draw, which averages 7-8 amps is not controlled ( i.e. it runs 24-hours a day). This makes them hugely inefficient on 12-volts.
The Northern Fridge Team