Mikhen, As per your request. This is the best way to try to explain how an RV refrigerator works. An RV refrigerator actually produces heat to cool. It is all done with science. The actual term for an RV refrigerator is a
gas absorption refrigeration system. An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling system. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, or where noise from the compressor is problematic.
On the Home Front Nearly all household refrigerators are powered by an electric pump. RV refrigerators, however, are often used in areas where there is no supply of electricity to draw from. Rather than depleting the RV battery to keep the food cold, RVs use a different type of system called a gas absorption refrigerator, which is powered by a propane burner.
Power Sources In order to maintain a constant temperature, 3-way RV refrigerators switch between power sources so that they are always on. They are called 3-way because they can operate on shore power, battery power or propane.
Changing Power Sources A sensor built in to the refrigerator alerts the appliance when a power source is removed, keying it to switch its draw to another source. There is an internal hierarchy that dictates which source it will try first, second and third. Most refrigerators also have a manual setting that allows you to choose the power source for the fridge.
Boiling the Ammonia The refrigeration process starts with the generator, a vessel with water containing dissolved ammonia inside. A burner heats the generator until it reaches the boiling point of ammonia. Since ammonia boils at a lower temperature than water does, the ammonia leaves the generator and wafts up into the condenser. In the condenser, the ammonia starts to cool and eventually forms liquid ammonia, now without water in it.
Cooling it Down The ammonia flows down from the condenser into a hydrogen-filled chamber called the evaporator. In this low-pressure chamber, the ammonia expands, cooling rapidly as it does. It is the evaporator that creates the cooling action of the refrigerator. A fan blows on the evaporator, cooling down the air as it blows past. This cold air is circulated through the refrigerator.
Back to the Beginning A device called the absorber sends water trickling through the evaporator. Ammonia dissolves easily in water, but hydrogen does not. The water trickles down with the dissolved ammonia in tow and flows back to the generator, starting the cycle all over again.
So there you have it in a nut shell, the cycles of a gas absorption refrigeration system. So for those of you who keep trying to 'hear' your RV refrigerator running, keep listening. You will be there for awhile, since there is no electric compressor to actually 'hear' running.
Safe Travels and Happy RVing!
