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,

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

On Sun, 10 Jul 2005 17:10:56 GMT, 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,

A partially plugged condenser will not cause a freeze up

"hvactech2" wrote in message
...
On Sun, 10 Jul 2005 17:10:56 GMT, 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,

A partially plugged condenser will not cause a freeze up

This is Turtle.

The third NO in a row !

TURTLE

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

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

Art Todesco wrote:

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.

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



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