GRAVITY and RV REFRIGERATORS

Unlike your common household refrigerators that use a compressor motor to circulate the coolant (freon) through a cooling unit, an rv refrigerator has no motor or moving parts. An ammonia based rv refrigerator uses GRAVITY to circulate the coolant (ammonia) through the cooling unit. The cooling unit on a rv refrigerator uses a heat source to boil the ammonia solution. The vapor then travels to the top of the cooling unit, where is condenses and changes back into it's liquid form. The cold liquid ammonia must then rely on gravity to trickle down through the many bends in the evaporator tubes and back to the bottom of the cooling unit where the process starts over. For this reason, the cooling unit must be as close to perfectly level as possible. If not, the liquid ammonia will collect in the many bend and angles of the evaporator tubes. When this happens, the liquid level in boiler section of the cooling unit will begin to decrease, causing the temperature of the boiler to increase. This causes one of 2 things to happen.

1) The boiler will soon overheat and crack.

                                or

2) The sodium chromate in solution with the ammonia will begin to "cook" and solidify, plugging the small internal tubes of the cooling unit.

Either way, your cooling unit will no longer function properly, if at all.

For this reason, all ammonia based refrigerators (RV refrigerators) have to be level when stationary and turned on to any heat source. There are no exceptions to this. Not doing so will permanently damage the cooling unit. This condition can occur in a very short amount of time, often in a single camping trip.

         DOMETIC EVAPORATOR ASSEMBLY                                                            NORCOLD EVAPORATOR ASSEMBLY
 

The pictures above show the bends that I have referred to. First, let me say that the evaporators pictured are not level, but are just sitting on a table. As you can see, running a refrigerator even the slightest bit out of level will slow the flow of the ammonia. This causes the the ammonia to warm up before it reaches the bottom of the evaporator, making your refrigerator compartment warmer. It also reduces the liquid level available to the boiler assembly, causing it to run hot. This can lead to a partial blockage due to the sodium chromate solidifying as a result of the hotter temperatures, or a cracked boiler. Either way, you have ruined your cooling unit.

All refrigerators need to be leveled by placing a small bubble level in the freezer section or, if necessary, on the floor of the refrigerator. We recommend that the refrigerator be leveled to within 3 to 5 degrees side to side and front to back.

Traveling with the refrigerator on is acceptable, as the liquids in the cooling unit are sloshing around and not collecting in unwanted areas of the cooling unit.

Running a cooling unit out of level will void the warranty.

***********************************************************

*** NOW READ THIS ***

***********************************************************

The following is an explanation of a common “cure” for a refrigerator with the problems described above:

WHEN YOU HEAR OF SOMEONE “BURPING” THEIR REFRIGERATOR BY TURNING IT UPSIDE DOWN AND SIDEWAYS, YOU HAVE JUST SPOKEN TO A PERSON WITH A STOPPED UP COOLING UNIT. THE THEORY HERE IS THAT BY TURNING IT UPSIDE DOWN, THE SOLIDIFIED SODIUM CHROMATE CAN SOMETIMES DISLODGE ITSELF, RESTORING AT LEAST PARTIAL FLOW AND ALLOWING THE REFRIGERATOR TO WORK FOR A SHORT WHILE. HOWEVER, THE DAMAGE TO THE UNIT IS PERMANENT AS THE SODIUM WILL NOT TURN BACK INTO A LIQUID STATE ONCE THIS PROCESS STARTS. IT WILL CONTINUE TO SOLIDIFY UNIT THE ENTIRE UNIT IS IRREVERSIBLY PLUGGED. THE BOILER WILL THEN SUPERHEAT AND CRACK.

Send mail to admin@rvfridge.com with questions or comments about this web site.
Copyright © 2006 World Class RV Refrigeration, Inc.
Last modified: 07/01/09