I have lived in this house since it was new, 20 years ago. This past
week, during the late afternoon, I would get condensation coming from the
air outlet closest to the air handler and right after the coil. I
remember reading on this group that this is probably caused by icing of
the coil. remembering that low air movement across the coil could cause
this, I changed the filter and this time used a filter that would allow
more flow ( I had one of those super duper ones that wouldn't let any
pollen through). For the next day or so, that seemed to fix the problem.
Now today, It has started again. I turned the AC off for about an hour,
then turned it back on and no more condensation dripping from the outlet.
I know, however, that it will probably return in another couple of hours.
It is presently 100 degrees outside. The humidity is about 40%. Inside
the temp is 77 degrees with a humidity of about 33%.
This is the situation. The compressor is out side. Everything else is
inside in the attic. Over the life of the AC, the filters have NOT be
changed out on a regular basis. For the first 15 years or so, I used the
el-chepo filters. Usually, when I did remember to change them, they were
clogged up with dust. Last year I had someone come out to do a checkup.
This was the first time in about 10 years. He measured the flow from the
vents and used the gauges (I have no idea what the measurements were but
he said the readings all looked good). He also checked the temp of the
air coming out of the vents. All was good for the unit I had. He of
course tried to sell me a new high effency unit, but when we finished
talking, the payback would be after I was dead.
So now I'm thinking that one of two things is wrong. Either the coil is
clogged up and won't allow enough air to flow through the coil and it
therefore freezes up, or the freon level is low(?). There seems to be
good air flow coming from the vents and the air is cool, but can the air
get around the coil? Or is it possible that some of the coil is clogged
and that's where the ice starts to form, and then it just gets worse from
I know I'm going to have to call an AC guy out, but I'd like to have an
idea of what else the problem could be.
I have a 2000sf home but I am shutting down the vents in unused rooms
and have only 1400-1500sf to cool. The AC unit is scaled for 2000sf (4
ton unit). Does closing off the vents reduce the efficiency of the AC?
Will it cycle more and thereby use more power?
This is Turtle.
You really need to get the sizes of the duct your cutting off and get the C.F.M.
that your cutting off to get it right.
Now to a rule that may work or not but has been used for many years.
Never cut off more than 1/3 of the vents of your home. If you have 3 cut 1 , 6
cut 2 , 9 cut 3, 12 cut 4.
Now to the efficent operation of the equipment at this condition, Well your
cooling a lot less space and would seem to cost less. With 1/3 cut off I would
not think short cycling would become a factor.
Yes i cut vent off for a living.
Don't close the vents!!!!!
You won't save money and with the lowered air flow, there is a chance
you won't boil off all of the refrigerant in the evaporator coil. when
liquid refrigerant gets back to the compressor it can wash the oil out
of the bearings. It can also blow the valves apart as LIQUID
refrigerant is not compressable. doing anything to lower the air flow
will reduce the efficiency, may freeze the indoor coil and can daage
the compressor. letting your filter get dirty can have the same effect
as can using pleated or washable one inch filters.
By the way, my 2000 square foot house has a properly sized unit which
is 2-ton. I did a load calculation to determine what my house actually
needed instead of using a 50 year old rule of thumb. That rule of
thumb started when there was no insulation in the walls or ceilings and
single pane glass was the norm. Depending on where you are, your
system may be way oversized.
I made an assumption regarding the size of the AC unit and I was wrong.
I do have a new home with all the engery things and the AC unit is a 3
ton based on my research of the model number. I live in the Boise,
Idaho area and July and August are the hot months, high 90s and a few
100s. It does appear at this point it would be best not to close off
the vents. Thanks to all for your replies and suggestions.
It will definitely save you money on your power bill. A couple of
1. If you shut off too much of the house, then the inside coil will
2. The overpowered unit will not run long enough to dehumidify the
air so you may notice a cold muggy feeling in the house. And all the
other things that go with high humidity such as mold and mildew.
Since you obviously trying to save a buck, let me suggest something
that worked for me.
Although I have a nice Trane central air and heat, I purchased a
small 6,000 btu very high efficiency window unit (11eer) and placed
it on the wall in our master bedroom.
It does an excellent job of removing moisture from the house and also
keeps up comfortably cool while in the bedroom. My outside unit
hardly ever comes on except in the very hottest part of the day.
The best part is that my summer electric bill went from over $300 to
I cut down in a similar way by closing vents in unused rooms on a 4000 sf
houses upper AC unit and the blower motor failed ( cooked) the second year.
I attributed to the increased backpressure with so many vents closed .
Does this make sense ?
I cut down in a similar way by closing vents in unused rooms on a 4000
houses upper AC unit and the blower motor failed ( cooked) the second
I attributed to the increased backpressure with so many vents closed .
Does this make sense ?
Heat is usually the culprit in motor failure. When you reduce the air
flow, there is less air flowing over the motor to cool it. I have been
to many motor seminars and the manufacturers will tell you reducing the
air flow is a major cause of motor failure. The motor amps go down
slightly, but the cooling air flow is reduced more. The result is
premature motor failure. The backpressure is not a problem.
i was thinking like stretch , that to reduce air flow may cause
problems, closing off rooms for heating is different and can save money
and still work good. but max air flow over the evaporator while cooling
is important. lucas
Check your t-stat settings as well
When a unit stops working: say from the filter and someone will usally
turn the t-stat down thinking that will make the air colder. That will
also ice up the coil as well and since you changed the air filter it may
have started working again but now it is to low.
Just a thought
On My Way
Dave...first of all....ignore the comment about the stat being too
low...turning the stat too low on a properly charged system does NADA...the
system knows only on, or off, and going too low will NOT cause freezing on a
properly charged and operational unit in summer temps...PERIOD.
Now, you probably answered your own question, but its impossible to see it
from here, however, your lack of normal service is screaming clogged
coil....DO NOT LET YOUR AC GUY PUT ANY REFRIGERANT IN THE UNIT TILL HE
INSPECTS THE COIL!!!!
Most guys will come out, with only a manifold and a nice green tank and
start juicing the unit..they never go inside, never take a lineset temp,
never take a RH% reading indoors, never get a dew point...never do any of
that and start to overcharge the unit, and then, WITHOUT a scale, they start
to dump refrigerant into the unit and then, with NO WAY to know what they
put in the unit, they proudly proclaim its working, and charge you for 3lbs
of refrigerant that they got for next to nothing and charge you $45 a lb for
Low airflow across the coil, due to dirt, mold, etc, will cause the pressure
readings at the manifold to be, or appear low. (BTW, those pressures...mean
NOTHING to a trained tech...hes looking for temps anyway) A dirty blower
wheel will cause the same thing due to lack of airflow..lack of airflow,
means lack of heat being transfered to the coil, and thus, lower pressures.
IF the units not been serviced, its worth your while to get the evap
properly cleaned, the condensor properly cleaned, and THEN have the tech
look for the issue..chances are, if it is low, and the ONLY way hes gonna
know is to check the coils, clean the coils, and go inside and take temp
readings for starters...then its got a slow leak. Any legitimate company
will check the coils while they are servicing the unit for leaks..and use a
detector thats of decent quality...not soap unless its a question of
moisture setting the detector off..and if hes got a decent one, like CPS, or
LeBold, that wont happen anyway.
9 out of 10 leaks are at the service ports and can be repaired in seconds,
not hours normally.
Now...things you want to see..
1-Checking the evap coil, and cleaning if needed.
2-Taking temp readings of the suction line and return air temp indoors
BEFORE adding a damn drop of refrigerant.
3-a SCALE under that green refrigerant jug, so he knows EXACTLY how much he
4-a leak check if he adds any refrigerant.
You will want to ask him how hes gonna check the charge, and if he says, by
pressure, you can tell him to get on down the road..superheat, or subcool,
and HE wont know till he checks your metering device in the evap.
Now...if you want a gas-n-go.....then let him do whatever he wants, and dont
do anything but pay him whatever he asks...LOL
CY: Ignore, NADA, NOT..... three negatives.
CY: Impossbile, lack. two more negatives.
DO NOT LET YOUR AC GUY PUT ANY REFRIGERANT IN THE UNIT TILL HE
CY: More negative energy.
CY: Mind reading. And critizing the other workers. More negative energy.
they never go inside, never take a lineset temp,
CY: I read six negatives, here.
with NO WAY to know what they
CY: More mind reading. More criticizing the other guy.
CY: Ah, now some information. Shame the reader had to wade through so much
negative energy to get here. If anyone got this far. It's clear that your
main game is critizing others.
CY: More instruction. Shame you had to dump so much negative energy on
everyone to get here.
You should save this one as a template. Will save retyping it over and
over. Very thorough.
CY: Highly negative, and very insulting of every other tech. Why would
anyone want to repeat a bunch of insults and putdowns?
Here is a fourth in a hurry for ya Chris...what fucking brand of megger do
How do you check compressor windings?
Your own words were....you know nothing about those....and you claim to be a
You stupid incompetent moron....suggest you learn how to read....that wasnt
negative..this is....you are impossible to train...
Its negative to your type..the untrained, unwilling to learn kind that isnt
licenced....and has admitted to putting used parts on your so called
No...thats a fact, and I bet I nailed you on the head.
What brand and model scale do you use Chris?
I read that I just nailed how you charge a unit.
Whassa matter Chris? Really pisses you off that you have been called out
time and time again, and now, your charging techiques have been uncovered?
No...just putting the hacks out....get used to it bubba...
See Chris, the bad thing is that there are people out there like you....the
average homeowner has no clue the things that need to be done, so when
someone like you comes out, they think, wow, hes got it running...and all
you did was keep them stupid to what you did...need I remind you about your
Educate the homeowner, the hacks will find other avenues.
You learned something? Amazing.
Shame you continue to lie to everyone....more negative energy that I am
Another pro, (something you are not even close to) thinks its ok...deal with
Wait till the vid comes out that we are gonna offer...its got guys like you
that we taped working on units, and then it shows the RIGHT way to do what
they lied to the customer about.
BTW Chris..for someone that claims to be a Mormon..that sure was a very
un-moron..err..mormom post you made there..
Dont mind if I send it to the local Mormons in your area do you? Ill also
include your most recent post about how you cheated and admitted to us all
how you cheated a customer by installing used parts on his unit in the hopes
it would run, and how you KNEW you had a GUARANTEED return visit you could
BTW..glad you cross posted this to alt.hvac....the guys there will have a
field day with you...
Generally, people with jobs don't spend this much time on the computer. I
don't have the time to rebutt each and every accusation. Why don't you make
some more vicious accusations? You sure are revealing your true personality.
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