As our absorption refrigerator coils age, do they build up cold spots in them? If so, is there a way to restore them to complete function? —Donald
The tubing in the cooling unit of your absorption refrigerator will not build up “cold spots” with age. Rather, it can develop blockage if it is run in an unlevel condition.
How an absorption refrigerator works
The typical absorption refrigerator has a boiler vessel that contains a mixture of hydrogen, ammonia, water, and sodium chromate. The heat source, a flame when in LP mode and a heating element when in 120-volt mode, heats the mixture to a boil, which sends it up to the evaporator fins.
As you can see in this Dometic diagram, there is a chemical reaction and the components separate and travel back to the boiler vessel in a zigzag pattern by gravity only. Both Dometic and Norcold recommend the unit be level with a reference of 3 degrees side to side, 6 degrees front to back. This will allow the solution to flow and not “pool” at one of the bends in the tubing. Sometimes it’s hard to tell what is 3 degrees and 6 degrees, so they provide a bubble level that should be placed on the base of the freezer section.
If the bubble is halfway in the circle, it is good to use. Otherwise, the solution gets stuck or pools at the corner and will get hotter and eventually flake and cause a blockage. This prevents the solution from flowing and sometimes you will hear a gurgling sound as it hits the blockage and flows back the opposite direction.
Don’t park on a slanted driveway and run absorption fridge
This is a common issue with absorption refrigerators as owners bring their rig home and park in a driveway to plug it in and get ready for a trip. Most driveways are slanted for rain runoff. Since they are not sleeping in it, they may not realize it is out of level. Then they run the refrigerator for a couple of days to cool it down before leaving.
It is hard to determine how fast the flaking will start and how severe it will get. It depends on the temperature and how often the cooling unit cycles and the severity of the angle. However, the more you bring the unit to the house and run it while parked on the driveway, the more often you create the situation until it gets blocked and does not run efficiently.
Signs an absorption refrigerator may be experiencing blockage
We have done extensive work on a 1992 Norcold in an Itasca Suncruiser for The RV Repair Club, and that unit looks like it is brand-new. A telltale sign of a cooling unit that is experiencing a partial blockage is discoloration of the tubing or rusting. This is due to the extreme heat generated in an area and the powder coated paint peeling off.
Another sign is extreme heat, as the cooling unit typically will run at 250-300 degrees. When there is a blockage it can reach 800 degrees or even more. This unit had no discoloration and no extreme temperatures as it has always been stored and prepped for a trip inside a level building. The photo above shows the unit as we pulled it out to test.
So the best thing you can do to prolong the life of your absorption refrigerator is to make sure it is in a level position any time you run it.
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
Read more from Dave here.
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