The fan motor on my outside unit died last week. I took the fan motor
to a local appliance parts store and they gave me a new one. The new
one had a longer shaft but they said that did not matter. I replaced
the fan motor and it seems to work fine. The air is blowing up out of
the unit. However, when I run the air now the interior unit freezes
Any suggestions would be appreciated!!
Assuming the replacement fan is the correct rotation and RPM, the other
possible causes of evaporator freezing are that the system is low on
refrigerant or there is an airflow blockage (obstruction in the air
ducts, dirty air filter, or dirty evaporator coil).
Unfortunately I already discarded the old motor. I have tried raising
and lowering the fan blades. I tried moving the blades up to the top
of the unit as far as it will go. I have also tried moving it down
about 4 inches, and 2 different spots in between.
I'm no technician, but I don't see how the fan to
cool the condenser unit could have any affect on
icing up the evaporator unit. Others pointed out
the potential problems. So, the cause is either
unrelated to the condenser fan or you might have
caused a loss of coolant when you changed the fan
1- Did you replace the motor with the EXACT same HP and RPM? If you did not,
you have a problem.
2-did you put the fan back EXACTLY where it was located in relation to
height? if not, you have a problem.
If you have too much airflow over the condensor now, you have changed the
operational characteristics of the unit, and while you can correct it with
the proper tools and knowhow, I would suggest that either you had an issue
in addition to the fan motor, or, you have put a fan motor on that is too
high of an RPM now, and thus, created a charge issue with the unit.
Are you talking about a home unit? If so, I don't
believe it. My condenser unit couldn't blow any
harder. If it doesn't blow enough, that is
obviously a problem. Besides the OP indicated the
motor only differs by having a longer shaft.
Blowing too much, if possible, would have less
effect than the normal changes in outside
temperature. How in the hell could any hp change
or motor speed adversely affect the condenser as
long as it is keeping the coils cooled? Unless,
of course, some one has some cobbled up design
that involves electronic control of the blower
motor that is supposed to save energy.
Excessive condenser airflow will simulate a lower ambient. If ambient is
in the mid to low 70's as the OP states, then with a larger and thus
slightly faster motor the unit will *percieve* an ambient in the mid to
upper 60's, in which case a piston evap coil can easily freeze up,
especially if it was a bit undercharged to begin with. The new motor can
very well be the difference between evap freezing vs not freezing. This
can also occur even if the motor specs are identical. How? Well let's
get this out of the way too. If the old motor wasn't running up to speed
and the refrigerant charge was adjusted under those conditions, then it
will have actually been left undercharged. The result is the same as
installing a higher HP motor.
In this case the OP said that he also cleaned the condenser coil. This
could very be the only thing that caused the evap to start freezing up.
I'm astounded. If what you say is true, then some
engineer should come forward with a new design or
at least a new control system that would put all
the others out of business. Further, homeowners
would be constantly experience problems for which
there was no remedy because they would be due to
environmental changes. And the units on autos
would be virtually useless.
I think you are reaching. If the charge is wrong
it is wrong. Sure it may not show up under some
conditions and new changes could make it show up,
but the problem is the charge.
My home unit works in all kinds of weather and all
reasonable temperature and humidities and I have
never experienced any kind of freezing up (of
course I don't run it when the temperature is 20
degrees, in fact, it never run when the ambient
temperature is below 75 degrees.)
My automobile units work in more drastic
conditions since my truck AC works in any
temperature at some setting and it never fails to
This is Turtle.
George , Richard put the correct words in his writting as the system
could be slightly under charged in most all his cases which left the
door open to cause of low on freon to freeze it up. Richard covered his
ass with correct writting but the one you should be talking to is
CBHVAC for he is the one that put his foot in his mouth here by fully
stating the a fast running condenser fan motor will freeze up a
evaperator coil, period.
This is Turtle.
DUUUUUAAAA! I can tell the diffence of who is writting on the post by
the names above them. You need to go back and read the last line and
the O.P. was having a problem of the evaperator freezing up and CB was
giving causes. He better get Paul to delete that post for CB to get him
out of it.
What you read and what i read must be two different thing. Richard you
do need to talk for him here for it's not a matter for him to talk
Hey speedy, I didn't say there was a problem with the motor, did I? This
was just a description of how the unit could have gone from not freezing
up to freezing up by changing the motor and/or cleaning the condenser coil.
The only real problems are that, no.1 he's running the unit when he
should have the windows cracked. Truth be known, and this is no.2, he
probably either needs a new air filter or the evaporator coil is
plastered with years of his own filth from not changing the filter
regularly. Adding refrigerant may indeed be the only fix required, no.3,
but this isn't what you asked about numbnuts. You specifically asked how
increasing condenser airflow could lead to a freeze-up condition. If you
don't understand your own narrative then you should think about forgoing
the reading of anyone else's.
I agree with most of your statement Slick. But I
didn't really ask a question about how it could
freeze up, I indicated incredulity at your
statement about the "perceived" lower ambient
temperature. And, I pointed out that it would
really be a problem with the coolant and not the
This is Turtle
George you will never be answered by anybody about your statements
above because it is a cover up of someone bullshitting and got cought
doing so. CB said it and Richard covering it up. this is the end of it
for being caught bullshitting you have to forget about it and move on.
this is Turtle.
the last line you wrote above here about a problem such as the op that
the unit will freeze up with the condender fan blowing too much air. In
40 something years in the HVAC/R business have i ever heard of moving
too much air across a condenser coil will freeze up the evaperator coil
if it is properly charged.
Now you need to rethink what you stated it here about a faster
condenser fan motor speed will freezer the evaperator coil up with a
properly freon charge of the system.
That only proves that over that 40 years you weren't paying attention.
Do you recall the reply that I made to you about retrofitting a 13 SEER
condenser to a 10 SEER air handler and evaporator coil? You can add
refrigerant in order to get the suction pressure back up, and the
superheat to where it is supposed to be, but just changing a motor out
never added a drop of 22 to a system did it? Even if you go back and fix
the homeowner's fuck-up by adding 22, the suction pressure will still
run a bit lower than before at the same superheat because the subcool
will run much higher than before.
This ios Turtle.
i never said to CB anything as to the effect of the system not running
right but ONLY that a properly charged system and to put a big ass fan
on the condender will not cause the evaperator to freeze up . All that
your speaking about here is freon related problems and not fan speed
problem with nothing else in the picture. Your bring in freon charge
being off or not right to cause a problem when speeding up the fan but
you have to have a freon problem and not just a fan problem.
All that you spoke to me about was a freon level being off or different
and needed to be changhed.
So if you have a properly charged hvac syustem moving more air throught
the condenser coil will NEVER cause the evaperator to freeze up. you
was right in your words but CB was wrong big time. Go back and read
what CB wrote and see.
Every word of CB's post was spot on. You can never adjust the charge
correctly on this system after the condenser airflow has been increased
over its engineered value, unless you make a few other modifications.
One of those is the piston size, just in case you don't remember that
post that I spoke to you about. With the old piston and higher condenser
airflow the system is mismatched. The subcool will run too high and the
superheat will never correspond to the superheat chart over the range of
ambient temps that the unit runs under. Moreover the system will be
easier to freeze up, i.e. it will do so at a higher ambient than it did
before. Even when you change the piston out, the indoor air volume will
now be a tad too low since by increasing the condenser airflow the
capacity of the unit will be a tad greater than before. Now don't get
me wrong, the system will work, but it will never work as it was
engineered to work. Put a TXV on the evap coil and you have yourself a
blanket fix to all of these potential problems.
Now there's the issue of the under-loaded condenser fan motor and
premature failure due to overheating. This can be fixed by selective
capacitor sizing as a hack fix, but it isn't supported by the motor
manufactures unless you have the trip-saver, but I'm not even going to
go into any of this with you since you already have enough to digest for
one night :)
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