Quote:
Originally Posted by rick-l
Is the reason these form ice when they are low on charge is that the capillary tube (is that what this unit has?) doesn't flow enough liquid and the pressure in the evaporator goes down lowering the temperature?
Part of the coil has the latent heat of vaporization and the other is just sensible heat? The part with the liquid ices over?
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Close enough.
When low on charge, the back (suction) pressure drops. This results in a lower (below freezing) saturated refrigerant temperature. The ice on the coil starts right after the metering device (tx valve or cap tube). Once that part of the coil is frozen, the ice slowly starts to spread through the rest of the coil.
Good first line of defense is to make sure the filters and coils are clean. Second make sure the fan is running to speed and is not loaded with dirt/dust on a forward curved fan. Third make sure vents are not blocked on the discharge air side. Mind you if you have a tx valve system and see continual flash gas in the sight glass (not just at start up or high load conditions) you are most likely short of gas.