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Old 07-26-2012, 08:15 PM   #1
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no cold air, no solid airflow from AC


Hey all,

Sorry for the layman talk. I have an AC unit in my attic which is attached to the outside unit. We live in GA and it's been around 90 during the day.

All units are original from 1998.

This unit cools my upstairs. I crank it down to 60 and turn the fan on at the thermostat.

Only coolish air comes out - and very slowly - like hardly there. I took a thermometer and put it right on the vent - it only goes to 77 after running for an hour.

I checked the filter - clean - it's new anyway. I checked the lines and outside unit for frost. None. No debris around it outside.

Back in the attic, I inspected the unit. I saw no signs of icing, and the AC appeared to be running. My wife then turned the fan off/on - and I confirmed it got running.

I did notice that the brass/copper line running next to the insulated line into the unit was really, really hot. Maybe that's normal.

So I don't know what's going on. Maybe I'm low on freon. Yet at the same time - why would so little air come out of the vents? I even shut a bunch off to see if I could get more flow out of a few - nothing - just a tiny little breeze - hardly there. Could I have a double-whammy and the fan is somehow shot too?

Any ideas?

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Old 07-26-2012, 08:33 PM   #2
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no cold air, no solid airflow from AC


Check the temperature right after you turn it on. If it's low on freon it will be very cold and then the air flow will become restricted due to icing on the coil. Can you open it up and look at the coil?

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Old 07-26-2012, 09:11 PM   #3
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no cold air, no solid airflow from AC


is your outside unit running? if so can you see ice on any piping iside the unit or at the larger insulated copper line? This line will only freeze where ther is no insulation.
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Old 07-27-2012, 08:33 AM   #4
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Hey all - there is no ice outside or inside or on any of the lines near or under the insulated tubes. There are zero signs from the PVC overflow pipe that even a trickle of water has come out. There was no ice on the coil.

As an update - I left the fan on and temp set to 60. Two hours later, it was down to about 76. The thermometer has a magnet and was stuck to the vent. I let it run all night. This AM - it was 73 at that point, but still 80 in the room. Again, no ice, and everything outwardly looks and sounds fine.

But still - just a trickle of airflow.

I've heard that some systems can only lower the temp 15-20 degrees from the outside temp. It's been 90 outside. So my room should be 70-75? Instead, every room upstairs is about 86-87. Even so - the temp right at the vent should be "true" - and it's still not even close to the thermostat.
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Old 07-27-2012, 08:48 AM   #5
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no cold air, no solid airflow from AC


Ideally the differential between the intake and supply air should be between 15 and 20 degrees. You said a trickle of airflow? Clogged filters, blower failing, clogged coil and restricted return air are all reasons for this condition to exist.
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Old 07-27-2012, 10:39 AM   #6
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no cold air, no solid airflow from AC


need to wash the condenser inside out nozzle "DON't blast it..." easy hosing works.you'll need to shut the disconnect out on the condenser,shut the stat and remove the top off to the side condenser wires limit it off to the side hose the condenser top to bottom 360 degrees around...redo everything and runit check that thin copper line right out of the condenser see if it is cooled down 85F body temp..range.air inside the house verify HI fan at the stat with fan ONLY no cooling call.. should be the same in the cooling mode..filter is good squirrel cage rounds are clean...can the return hold a sheet of newspaper up ceiling or wall mounted it should..
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Old 07-27-2012, 03:08 PM   #7
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Not sure if this is related to what you all have said...but...

The temp in my attic is insane. It must be 120 degrees or more - a true sauna. There is no roof insulation, but there is heavy, deep loose insulation on the attic floor. I have ridge vents. There was originally a roof fan (wires still there) but the previous owner removed it when he had a new roof put on.

None of the air in the attic actually gets into the unit. The returns (and vents) are all in the ceiling of my second floor so all the air is from the living area.

Still - could such insane heat up there perhaps be heating up the insulated ducts or unit itself causing problems?
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Old 07-27-2012, 03:32 PM   #8
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no cold air, no solid airflow from AC


I am going through the same heat in NC and have a similar setup. Good venting and AC airflow.

Is your ductwork insulated?

Is there a chance that your unit is a heat pump? This could definitely make a difference to the approach.
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Old 07-27-2012, 06:29 PM   #9
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no cold air, no solid airflow from AC


Burning hot liquid line(the uninsulated copper) is either low on refrigerant or the outside coils are dirty. Follow the directions biggles posted and clean those condensing coils .
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Old 07-27-2012, 10:47 PM   #10
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you may have several problem but if you don't have much air flow the unit is frozen, will freeze or has very low refrigerant charge
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Old 07-28-2012, 05:45 AM   #11
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no cold air, no solid airflow from AC


I too think it would be a good idea to wash the condenser, but a clear water flush is not sufficient. You need to use a chemical to remove the organics and other embedded dirts and such. Follow the label directions, and be sure to turn the power OFF to the unit.

Quote:
check that thin copper line right out of the condenser see if it is cooled down 85F body temp
That's just wrong information. There is no way to know what liquid line temperature you should be looking for unless we know several other factors. If you don't have a method to check the refrigerant pressure, then the best thing you can do is call a professional to do this for you.
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Old 07-28-2012, 07:28 AM   #12
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no cold air, no solid airflow from AC


Check your indoor coil, it may be dirty. may have a weak capacitor, or a blower motor failing.
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Old 07-28-2012, 08:47 PM   #13
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if motor is failing or coil is dirty why is it not freezing? If anything is wrong with your air flow and the outside unit is running and charged with refrigerant you will freeze the indoor coil. Can't see any way around it. If you have air flow problem with no freezing problem then you have multiple problems.
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Old 07-30-2012, 08:56 AM   #14
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no cold air, no solid airflow from AC


How much airflow should be coming out of the vents? Our downstairs vents (on separate system) - they are enough to move the curtains. Upstairs - it's barely enough to move the hair on your head.

So is there just a fan in-line in the loop? Is this the same fan that would be sucking air for the return?

Because if I'm getting no solid output from vents - it must not be taking anything in from the returns.
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Old 07-30-2012, 09:27 AM   #15
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no cold air, no solid airflow from AC


Quote:
How much airflow should be coming out of the vents?
Not to be condescending, but "enough" Seriously, you should have enough air from each vent to cool the space that vent is intended to cool. That could be 50 cfm for one space, and 250 cfm for another space.

Your air handler or furnace supplies the air movement. There's a blower installed in that appliance that comes on in heating or cooling, and that's what (a) blows the air out of the supply vents and (b) sucks air back from the return vents. In most cases, there are no other fans involved, although some systems (very few) have "booster" fans installed.

If you're not getting a sufficient volume of air through your ducts then all we can give you is the same advice as before: dirty coil/filter/blower, defective motor/cap. You'll have to go through that list and see which applies to your situation. In some cases you can do these yourself, but if you're not confident with doing these things you should hire someone to take care of these for you.

If you ARE getting sufficient volume, but the space is not being cooled adequately, then other factors may come into play. If that's the case, let us know. Given that you report the small copper line is "very hot", I'd say at the very least you need a good chemical cleaning on the outdoor unit.

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