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:


Art Todesco wrote:

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,


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