The evaporator coil on my home A/C was turning into a block of ice.
The cure was to recharge the freon? Can't argue with success but it sure is confusing.
My guess is that there was a leak and the lower pressure freon would get colder easier. Putting more pressure in the line by adding freon would increase the temperature and decrease the boiling point.
if you want more info, I found a decent website here:
http://www.longviewweb.com/r22.htm
Basically its as Wyoming(BTW "W" welcome) stated... Resaon is most refergerants boil around -20*F. The pressure and amount of freon in the system keep the boiling point somewhere above 32*F(usually around 40* but it all depends on outside temp and amount of airflow on the condenser and evaporator).
For some reason my old central is doing exceptionally well this year. Possibly I recharged it a little too much last year when I topped it off(haven't touched it this year). Probably ought to take some pressure readings to see what makes it so happy...
The little $70 window unit in my bedroom ices up if I turn the t-stat up too far. My room is tiny, so the A/C, I think, actually runs out of air to cool.
Yay! I knew 4.5 years of going to school to become a Mechanical Engineer would pay off! I guess I can retire now. :D
Ok, if I go into a semi-trance and squint real hard I can almost visualize it.
Freon is a liquid under high pressure and a gas at atmospheric pressure. If released from pressure into the atmosphere, as it gasifies, it can absorb enough heat to drive the temperature down to -20 something degrees.
So pressure on the "low" side of the A/C system has to be low enough to allow the freon to gasify but high enough to keep the temp above freezing.
Yep! And I didnt even have to get out my Thermodynamics book... :headbang: