Most motorhomes contain a fridge which is an essential item for storing milk and cold drinks. There are two types, the more common gas (or 3-way) fridge and the compressor fridge.
The three way fridge is a special type of refrigerator known as an absorption refrigerator and contains no moving parts. It requires heat energy to operate which can be provided from three sources:
Mains power usually provides the best performance. Because of the relatively high power consumption (approx. 100W), the 12V DC supply is normally connected through a split-charge relay which disconnects the fridge when the engine driven alternator is not charging the battery. Otherwise, the battery would discharge rapidly. The fridge requires ventilation to the outside to dissipate heat and disperse the products of combustion.
Usually, there is a small ice box which can be used to keep frozen items from defrosting.
The compressor fridge is a more efficient device than the absorption fridge. It operates in exactly the same manner as a normal household fridge except that the compressor operates on 12V DC rather than 240V AC. Typically, the mean power consumption is about 40W meaning that the fridge can run for a long time on the leisure battery without fear of discharging it completely. In contrast to the gas fridge which is completely silent the noise of the compressor may become irritating. A compressor fridge is usually more expensive to purchase.
A compressor fridge should be maintenance free. A three-way fridge, like any other gas burning appliance, will require periodic cleaning of the gas jet and possibly of the heat exchanger and flue also. It is advisable to have the entire gas system examined for safety by a qualified technician from time to time.
Absorption refrigerator on Wikipedia.
Dometic - fridge manufacturer.
WAECO - fridge manufacturer.