Quote:
Originally Posted by cstreit
Why would a low freon charge cause the evap to freeze up like that?
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A low charge will as was already said flash from high pressure liquid (and gas mixed) to a low pressure saturated mixture after the expansion device (valve or capillary tube). Due to the lower operating pressure of a system short of refrigerant, the saturated temperature also drops. Under 60 psi with R-22 you end up treading close to the freezing mark.
As the system operates this way, a little ice will form where the refrigerant enters the evaporator. Over time it builds itself into a mini coil shaped igloo. Because the system is short of gas, the run time is longer so the igloo gets more and more time to build.
A quick way to check the charge in your home central a/c, after thawing, start it up and allow it to run for a while, grab onto the suction line. Should be cold. Grab onto the liquid line supplying the coil, should be warm to the touch, but not hot.
Short of gas? Do, or get someone to do a leak check with an electronic leak detector. It may be an easy fix. Another tip, look for oil on the system. If the oil is getting out, so is the refrigerant.