dougrainer wrote:
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
Good info. If that is the case, then it seems like anytime the refrigerator is far enough out of level and gravity flow cannot happen it has the risk of adding an incremental amount of blockage into the coils. Seems unavoidable. Does anyone know if blockage in these coils is a common (or rare) cause of cooling unit failures? What are the most common causes of failure? Holes/leakage? Blockage? (and if so, in which tubes?)
The question then becomes, "In a situation where the gravity flow through the coils is reduced or cannot happen because it is too far out of level, what effect does temperature (controlled by the boiler) have with respect to adding more incremental blockage?"
Would it be best to hold the boiler temp close to it's normal operation temperature of 180-190*C? Would it actually be BETTER to allow it to rise to 200-215*C to add pressure to the system and/or keep the ammonium mixture in a form that doesn't increase incremental blockage from happening? (I'm not sure if it works that way...) If the boiler temp got up to 205-210*C (indicating the fridge is off-level or there is some sort of blockage) would there be any advantage to the thermostat simply turning off the refrigerator until the boiler cools all the way down to 50*C (meaning the refrigerator (and boiler) would be off for probably 10-20 minutes)?
Sounds like having a thermostat on the boiler (Fridge Defend, or simple high temp thermostat) is a good thing to prevent the boiler from getting over 220*C and actually boiling the water and thus crystalizing the rust prevention solution, and also putting too much pressure in the system (thus reducing the chance of leaks or rupture). It would also prevent the boiler from getting up to 300*C, 400*C or however high it could get, thereby reducing the chance of a fire. But a thermostat would not do much/any good to prevent incremental blockage from happening if the gravity flow of vapor/liquid ammonium cannot flow properly through the coils.
-Chris
