Evaporator freezing

I have a question for you hvac guys. Can a central AC A coil ice up from reduced air flow in the condenser (40-50% of the condenser matted up)? I know this can happen from low airflow in the evaporator. And I know it can happen when the freon is low. If yes, can you explain what happens to pressures when it happens? Thanks,
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No.
With a restricted condensor coil, head pressure will go up, cooling capacity and efficiency will go down, but the indoor coil will not freeze from that. If your indoor coil freezes, there is another problem.
Stretch
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wrote:

A partially plugged condenser will not cause a freeze up
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This is Turtle.
The third NO in a row !
TURTLE
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Art Todesco wrote:

Typically no, but it can happen, especially on window shakers. I suppose from the unanimity of the other responses that most techs would automatically assume either a solid restriction in the cap tube or filter, or a loss of charge as the cause. After having cleaned the thing up and rechecked it, and it is suddenly flying right, they naturally assume that the blockage has dislodged itself, problem solved. They might want to reconsider. Cap tubes don't typically clear themselves because soap and water met the outside of them :)
TXV's can also go into an excessive hunting mode causing evap icing. Excessive flashgas doesn't help matters.
I've seen both more than once, it doesn't get anymore straightforward than that. But it isn't exactly a common occurrence.
hvacrmedic
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Thanks. BTW, it was a bit low on freon. Also, this happened at night where I run the blower on a slower speed cut off a section of the house via a motor driven duct damper. It has been ok for some 10 or 15 years. The other factor is that the AC was turned on when the house was already very hot ... so it had to run longer than usual night time runs.
RP wrote:

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Art Todesco wrote:

The longer runtime, if it played any part, did nothing more than prevent the melting that would have occurred during the off cycle. Given that it was hotter inside, then this is that much more an incorrect assessment, since hotter air over the evaporator would tend to counter the real cause of the freezing.
There is no such thing as evaporator freezing due to excessive runtimes. If there is freezing, then any excessive runtime is a symptom of the problem and not the problem itself.
hvacrmedic

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