SJ-Chris wrote:
Bobbo wrote:
SJ-Chris wrote:
This is one of the main things I'm trying to understand about the cooling unit operation while out of level. Assume for example the RV is parked on a steep driveway with the refrigerator on. What happens if the refrigerator is out of level and starting to overheat and the refrigerant cannot flow where it needs to flow. Then a thermostat cuts off the refrigerator power when the boiler temp hits 205*C and then turns it back on when it cools to 170*C and it just oscillates between 170*C and 205*C. Does any damage occur if left in this oscillating state for a few hours or even days? Would the refrigerant cool and harden and cause some incremental damage?
-Chris
Yes. The problem is when the refrigerator is running, it vaporizes the ammonia solution. That vapor then goes into the piping where being off level causes some of it to retain and solidify. It being subject to occasional shut offs doesn't prevent that. I am unsure if occasional shut downs would slow down the process because it is running less, or speed up the process because it has more cooling off periods for the ammonia to precipitate. It would definitely reduce the cooling efficiency inside the refrigerator.
I believe the only way to assuage your fear is to replace it with a compressor refrigerator.
I have been trying to learn/understand refrigerator operation more so that I can best protect from overheating. Correct me if I am wrong, but the only thing that should be in the coils (top of the fridge down towards the bottom) is ammonium and hydrogen. These do not "harden" as they cool. The ammonium is a liquid. In the boiler it turns into a vapor and rises and then starts its journey through the coils at the top of the fridge on down towards the bottom (speaking in simplified terms here...). During this process, it is cooled and turns back into a liquid (it doesn't harden). So I'm not sure this is an issue.
One significant thing (most important?) to avoid during operation is having the boiler get too hot and boiling the water that is inside. This can be avoided with a thermostat (or Fridge Defend). If the water did boil and the boiler got too hot, then the rust preventative solution inside the cooling unit can start to crystalize (...builds up over time). This can weaken the rust prevention protection and cause the metal tubing on the cooling unit to start to rust. This rust can cause a rupture/leak eventually. This crystalizing can also ultimately cause blockages in some of the tubing. Having a thermostat (or Fridge Defend) will prevent this from happening.
One additional concern is too much pressure in the cooling unit. During normal operation it is under pretty high pressure (350-400psi). If the boiler/system gets too hot the pressure increases. If there are weak spots (due to rust) in the system it will put more stress on those spots and increase the chance of a rupture or leak. A thermostat (or Fridge Defend) will prevent this excess pressure.
So far, from my still limited understanding, I feel like if a thermostat (or Fridge Defend) is installed and it prevents the boiler from getting over 220*C (...I will likely set it to 205*C) then all of the above issues can be avoided.
Thoughts?
Thanks!
Chris
Your thinking is correct except about the blocking process. When the liquid cannot go from gas to liquid due to incorrect gravity, the liquid "adheres" to the area of the cooling unit just below the freezer coils. The actual process has never been completely explained to me how this gets "HARD". It just happens. It starts out gradually and everytime you run off level it adds a little more to that blockage. One day, your refer does not cool as expected. It still cools but not as well as new and is harder to cool in hotter ambient temps. The blockage has been described to me by both Dometic and Norcold at Tech schools as harder than a weld. The ONLY way to rebuild a blocked cooling unit is to cut out the top of the coil and weld a replacement. Blockage, the freezer will still appear to freeze, but will not get below 10 degrees which is spec. This is how when people sell their RV with a bad refer, they always show the freezer as "cold". But cold is deceptive, 5 degrees to 32 degrees will seem the same. One of my trainers from 40 years ago explained blocking as like Heart disease. You are born with a clear functioning blood artery system. But gradually over your lifetime, by eating the wrong foods, your arteries become slowly clogged. Then one day, you have a Heart problem and you think it "just happened". Your arteries are partially clogged, not instantly, but over years. Doug
