AC problem - cools half a day then fails to cool


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Old 06-30-11, 08:02 PM
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AC problem - cools half a day then fails to cool

A little history:

Late this spring I had a problem, the house was being cooled about a half of the day. From early morning through about 2:00 in the afternoon, the ac seemed to be working fine. I could hold my hand about 3 feet above a vent and feel the cool air being blown. Then, around 2:00 (not always the same time), I could put my hand 3 inches above the same vent and barely feel any air coming from the vent. Although the air that barely came out did not do anything to cool the house, it was slightly cool. Okay, repairman called and suggested the bearings were going out of the fan... Replaced the fan, $400.00 and it has actually been "just a little" better since.

Currently:

Problem is back. For example, late this morning outdoor temperatures reached low 90's. Holding my hand about 3 foot above the vents, I could feel cold air and the house stayed cool as controlled by the thermostat. Later in the day, approximately 1:30 in the afternoon, outdoor temperatures reach in the high 90's. I stopped by my house and holding my hand about 3 feet above the vents, could feel cold air and the house felt very comfortable as it should. Then, later after work, I returned home at around 7:00 in the evening. The outdoor temperatures were between the upper 80's and low 90's. The house was very warm, not hot mind you, but uncomfortably warm. I placed my hand 3 "inches" above the vents and could barely feel air flow. However, the slight air flow that I did feel was cool...

Boy, I'm at a loss, not sure what to do. Number one, I don't want to keep throwing money at the problem with no results and number two, I can't afford to throw money at the problem without results.

Can anyone give my some advise? Possible troubleshooting steps?

Thanks!

Notes:
- I change my filter once a month in the forced air gas furnace unit.
- I have cleaned the outdoor ac unit three times this year counting 4 days ago.
- I have a very large venting fan in the attic that totally exchanges the attic air controlled by a thermostat.
-
 
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Old 06-30-11, 08:17 PM
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You need to find out the temperature of the cold air come out of the register, then minus from the room termperature at that time, the difference should be at least 16 degrees, if not, you have a problem (usually you should be able to feel the cold air by hand at least 6 to 8 feet away). Another simple check you can do is go to your outside condenser, hand touch the 2 copper lines. the small uninsulated one should be ambient temperature, feels a little warm. the large insulated line should be cold like a glass of ice water. If not, you have problem....(But I don't think the fan caused the problem, don't use this AC tech anymore, get someone else, could be just as simple as lack of freon..)
 
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Old 06-30-11, 08:34 PM
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Yes...I figured that out...about using a different tech.

I appreciate and will follow your steps and check. Right now, 11:30 PM, it is blowing out stronger and is, again a cool house (with the help of three fans in the windows blowing hot are out and cool air in)... I understand the idea of low freon, but why would I have the decrease in the air flow/force at the vents, no matter what the temperature is coming out? I'm not sure I understand what would cause that...

Originally Posted by clocert View Post
You need to find out the temperature of the cold air come out of the register, then minus from the room termperature at that time, the difference should be at least 16 degrees, if not, you have a problem (usually you should be able to feel the cold air by hand at least 6 to 8 feet away). Another simple check you can do is go to your outside condenser, hand touch the 2 copper lines. the small uninsulated one should be ambient temperature, feels a little warm. the large insulated line should be cold like a glass of ice water. If not, you have problem....(But I don't think the fan caused the problem, don't use this AC tech anymore, get someone else, could be just as simple as lack of freon..)
 
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Old 07-01-11, 04:08 AM
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very good chance your evap coil is slowly freezing up over the course of the day thats why you have good air flow for a fair amount of the day and then it gets weak. Typically a coil freezing up is caused by 2 conditions: 1 poor air flow 2 low refrigerant charge.
 
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Old 07-06-11, 06:56 PM
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Thought I'd close this thread... Evap coil was freezing up over the coarse of the day due to low charge. The system required 1 and 1/2 lbs of refrigerant to fill it up. AC has been performing great ever since. Thanks for the help, I appreciate the assistance!

Originally Posted by hvactechfw View Post
very good chance your evap coil is slowly freezing up over the course of the day thats why you have good air flow for a fair amount of the day and then it gets weak. Typically a coil freezing up is caused by 2 conditions: 1 poor air flow 2 low refrigerant charge.
 
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Old 07-06-11, 07:32 PM
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ok, so 1 1/2 lbs r22.... where did it go? its a sealed system and the system does not consume refrigerant. YOU HAVE A LEAK! Did the contractor look for the leak? Or mention anything about a leak?
 
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Old 07-08-11, 04:20 PM
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Yes he did mention it after I asked him, "Do I have a leak?" He said that he thinks that the last service tech, or whoever took these caps off, did not tighten the caps. After showing the caps to me, you could see oil on the inside threads, base of the caps, and on the line below the caps. I have no reason not to believe him, furthermore, he's hired my company to do some IT Networking at his company's office and shop...

* Here is my take on this whole situation: Last tech, the useless one, that over-charged me for a fan that I did not need, did not tighten the caps back on after checking the levels. I did watch him check and he said that I did not need r22, which I believed him at the time and still do. I think the reason my evaporator froze up initially was due to a completely clogged filter. Although I change the filter regularly, I had just sanded hard wood floors in one of the rooms in my house. The varnish-dust completely clogged the filter, and I new it did, but did not realize that an air flow problem could cause the evaporator to freeze up. I think the first tech took advantage of my lack of knowledge in this area... Then, the second tech discovered that the evaporator was frozen. He in turn, saw that the filter was clean, the outside unit was clean, then asked me to turn ac off and leave fan on. He left and returned a couple hours later. He removed some more sheet metal near the evaporator and checked that it was clean. Then, checked the r22 level which required adding refrigerant.

In the near future, I am having this same tech wrap my duct-work with insulation. I will get him to check the refrigerant again at that time, to see if there is any loss/leakage.

Originally Posted by hvactechfw View Post
ok, so 1 1/2 lbs r22.... where did it go? its a sealed system and the system does not consume refrigerant. YOU HAVE A LEAK! Did the contractor look for the leak? Or mention anything about a leak?
 
 

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